Parallel.cs source code in C# .NET

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Code:

/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / clr / src / BCL / System / Threading / Tasks / Parallel.cs / 1305376 / Parallel.cs

                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// Parallel.cs 
//
// [....] 
//
// A helper class that contains parallel versions of various looping constructs.  This
// internally uses the task parallel library, but takes care to expose very little
// evidence of this infrastructure being used. 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 
 
using System;
using System.Diagnostics; 
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Security.Permissions;
using System.Threading; 
using System.Threading.Tasks;
using System.Diagnostics.Contracts; 
 

namespace System.Threading.Tasks 
{
    /// 
    /// Stores options that configure the operation of methods on the
    /// Parallel class. 
    /// 
    ///  
    /// By default, methods on the Parallel class attempt to utilize all available processors, are non-cancelable, and target 
    /// the default TaskScheduler (TaskScheduler.Default).  enables
    /// overriding these defaults. 
    /// 
    public class ParallelOptions
    {
        private TaskScheduler m_scheduler; 
        private int m_maxDegreeOfParallelism;
        private CancellationToken m_cancellationToken; 
 
        /// 
        /// Initializes a new instance of the  class. 
        /// 
        /// 
        /// This constructor initializes the instance with default values.  
        /// is initialized to -1, signifying that there is no upper bound set on how much parallelism should 
        /// be employed.   is initialized to a non-cancelable token,
        /// and  is initialized to the default scheduler (TaskScheduler.Default). 
        /// All of these defaults may be overwritten using the property set accessors on the instance. 
        /// 
        public ParallelOptions() 
        {
            m_scheduler = TaskScheduler.Default;
            m_maxDegreeOfParallelism = -1;
            m_cancellationToken = CancellationToken.None; 
        }
 
        ///  
        /// Gets or sets the TaskScheduler
        /// associated with this  instance. Setting this property to null 
        /// indicates that the current scheduler should be used.
        /// 
        public TaskScheduler TaskScheduler
        { 
            get { return m_scheduler; }
            set { m_scheduler = value; } 
        } 

        // Convenience property used by TPL logic 
        internal TaskScheduler EffectiveTaskScheduler
        {
            get
            { 
                if (m_scheduler == null) return TaskScheduler.Current;
                else return m_scheduler; 
            } 
        }
 
        /// 
        /// Gets or sets the maximum degree of parallelism enabled by this ParallelOptions instance.
        /// 
        ///  
        /// The  limits the number of concurrent operations run by Parallel method calls that are passed this 
        /// ParallelOptions instance to the set value, if it is positive. If  is -1, then there is no limit placed on the number of concurrently
        /// running operations. 
        /// 
        /// 
        /// The exception that is thrown when this  is set to 0 or some
        /// value less than -1. 
        /// 
        public int MaxDegreeOfParallelism 
        { 
            get { return m_maxDegreeOfParallelism; }
            set 
            {
                if ((value == 0) || (value < -1))
                    throw new ArgumentOutOfRangeException("MaxDegreeOfParallelism");
                m_maxDegreeOfParallelism = value; 
            }
        } 
 
        /// 
        /// Gets or sets the CancellationToken 
        /// associated with this  instance.
        /// 
        /// 
        /// Providing a CancellationToken 
        /// to a Parallel method enables the operation to be
        /// exited early. Code external to the operation may cancel the token, and if the operation observes the 
        /// token being set, it may exit early by throwing an 
        /// .
        ///  
        public CancellationToken CancellationToken
        {
            get { return m_cancellationToken; }
            set 
            {
                if (value == null) 
                    throw new ArgumentNullException("CancellationToken"); 
                m_cancellationToken = value;
            } 
        }

        internal int EffectiveMaxConcurrencyLevel
        { 
            get
            { 
                int rval = MaxDegreeOfParallelism; 
                int schedulerMax = EffectiveTaskScheduler.MaximumConcurrencyLevel;
                if ((schedulerMax > 0) && (schedulerMax != Int32.MaxValue)) 
                {
                    rval = (rval == -1) ? schedulerMax : Math.Min(schedulerMax, rval);
                }
                return rval; 
            }
        } 
    } 

    ///  
    /// Provides support for parallel loops and regions.
    /// 
    /// 
    /// The  class provides library-based data parallel replacements 
    /// for common operations such as for loops, for each loops, and execution of a set of statements.
    ///  
    [HostProtection(Synchronization = true, ExternalThreading = true)] 
    public static class Parallel
    { 
#if !FEATURE_PAL    // PAL doesn't support  eventing
        // static counter for generating unique Fork/Join Context IDs to be used in ETW events
        internal static int s_forkJoinContextID;
#endif 

        // We use a stride for loops to amortize the frequency of interlocked operations. 
        internal const int DEFAULT_LOOP_STRIDE = 16; // @ 

        // Static variable to hold default parallel options 
        internal static ParallelOptions s_defaultParallelOptions = new ParallelOptions();

        /// 
        /// Executes each of the provided actions, possibly in parallel. 
        /// 
        /// An array of Actions to execute. 
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        ///  array contains a null element.
        /// The exception that is thrown when any
        /// action in the  array throws an exception.
        ///  
        /// This method can be used to execute a set of operations, potentially in parallel.
        /// No guarantees are made about the order in which the operations execute or whether 
        /// they execute in parallel.  This method does not return until each of the 
        /// provided operations has completed, regardless of whether completion
        /// occurs due to normal or exceptional termination. 
        /// 
        public static void Invoke(params Action[] actions)
        {
            Invoke(s_defaultParallelOptions, actions); 
        }
 
        ///  
        /// Executes each of the provided actions, possibly in parallel.
        ///  
        /// A ParallelOptions
        /// instance that configures the behavior of this operation.
        /// An array of Actions to execute.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  array contains a null element. 
        /// The exception that is thrown when
        /// the CancellationToken in the
        ///  is set.
        /// The exception that is thrown when any 
        /// action in the  array throws an exception.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed. 
        /// 
        /// This method can be used to execute a set of operations, potentially in parallel.
        /// No guarantees are made about the order in which the operations execute or whether
        /// the they execute in parallel.  This method does not return until each of the 
        /// provided operations has completed, regardless of whether completion
        /// occurs due to normal or exceptional termination. 
        ///  
        public static void Invoke(ParallelOptions parallelOptions, params Action[] actions)
        { 
            if (actions == null)
            {
                throw new ArgumentNullException("actions");
            } 
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions"); 
            }
 
            // Throw an ODE if we're passed a disposed CancellationToken.
            if(parallelOptions.CancellationToken.CanBeCanceled)
                parallelOptions.CancellationToken.ThrowIfSourceDisposed();
 
            // Quit early if we're already canceled -- avoid a bunch of work.
            if (parallelOptions.CancellationToken.IsCancellationRequested) 
                throw new OperationCanceledException(parallelOptions.CancellationToken); 

            // We must validate that the actions array contains no null elements, and also 
            // make a defensive copy of the actions array.
            Action[] actionsCopy = new Action[actions.Length];
            for (int i = 0; i < actionsCopy.Length; i++)
            { 
                actionsCopy[i] = actions[i];
                if (actionsCopy[i] == null) 
                { 
                    throw new ArgumentException(Environment.GetResourceString("Parallel_Invoke_ActionNull"));
                } 
            }

#if !FEATURE_PAL    // PAL doesn't support  eventing
            // ETW event for Parallel Invoke Begin 
            int forkJoinContextID = 0;
            Task callerTask = null; 
            if (TplEtwProvider.Log.IsEnabled()) 
            {
                forkJoinContextID = Interlocked.Increment(ref s_forkJoinContextID); 
                callerTask = Task.InternalCurrent;
                TplEtwProvider.Log.ParallelInvokeBegin((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0),
                                                     forkJoinContextID, TplEtwProvider.ForkJoinOperationType.ParallelInvoke,
                                                     actionsCopy.Length); 
            }
#endif 
 
#if DEBUG
            actions = null; // Ensure we don't accidentally use this below. 
#endif

            // If we have no work to do, we are done.
            if (actionsCopy.Length < 1) return; 

            // In the algorithm below, if the number of actions is greater than this, we automatically 
            // use Parallel.For() to handle the actions, rather than the Task-per-Action strategy. 
            const int SMALL_ACTIONCOUNT_LIMIT = 10;
 
            try
            {
                // If we've gotten this far, it's time to process the actions.
                if ((actionsCopy.Length > SMALL_ACTIONCOUNT_LIMIT) || 
                     (parallelOptions.MaxDegreeOfParallelism != -1 && parallelOptions.MaxDegreeOfParallelism < actionsCopy.Length))
                { 
                    // Used to hold any exceptions encountered during action processing 
                    ConcurrentQueue exceptionQ = null; // will be lazily initialized if necessary
 
                    // This is more efficient for a large number of actions, or for enforcing MaxDegreeOfParallelism.
                    try
                    {
                        // Launch a self-replicating task to handle the execution of all actions. 
                        // The use of a self-replicating task allows us to use as many cores
                        // as are available, and no more.  The exception to this rule is 
                        // that, in the case of a blocked action, the ThreadPool may inject 
                        // extra threads, which means extra tasks can run.
                        int actionIndex = 0; 
                        ParallelForReplicatingTask rootTask = new ParallelForReplicatingTask(parallelOptions, delegate
                        {
                            // Each for-task will pull an action at a time from the list
                            int myIndex = Interlocked.Increment(ref actionIndex); // = index to use + 1 
                            while(myIndex <= actionsCopy.Length)
                            { 
                                // Catch and store any exceptions.  If we don't catch them, the self-replicating 
                                // task will exit, and that may cause other SR-tasks to exit.
                                // And (absent cancellation) we want all actions to execute. 
                                try
                                {
                                    actionsCopy[myIndex - 1]();
                                } 
                                catch (Exception e)
                                { 
                                    LazyInitializer.EnsureInitialized>(ref exceptionQ, () => { return new ConcurrentQueue(); }); 
                                    exceptionQ.Enqueue(e);
                                } 

                                // Check for cancellation.  If it is encountered, then exit the delegate.
                                if (parallelOptions.CancellationToken.IsCancellationRequested)
                                    throw new OperationCanceledException(parallelOptions.CancellationToken); 

                                // You're still in the game.  Grab your next action index. 
                                myIndex = Interlocked.Increment(ref actionIndex); 
                            }
                        }, TaskCreationOptions.None, InternalTaskOptions.SelfReplicating); 

                        rootTask.RunSynchronously(parallelOptions.EffectiveTaskScheduler);
                        rootTask.Wait();
                    } 
                    catch (Exception e)
                    { 
                        LazyInitializer.EnsureInitialized>(ref exceptionQ, () => { return new ConcurrentQueue(); }); 

                        // Since we're consuming all action exceptions, there are very few reasons that 
                        // we would see an exception here.  Two that come to mind:
                        //   (1) An OCE thrown by one or more actions (AggregateException thrown)
                        //   (2) An exception thrown from the ParallelForReplicatingTask constructor
                        //       (regular exception thrown). 
                        // We'll need to cover them both.
                        AggregateException ae = e as AggregateException; 
                        if (ae != null) 
                        {
                            // Strip off outer container of an AggregateException, because downstream 
                            // logic needs OCEs to be at the top level.
                            foreach (Exception exc in ae.InnerExceptions) exceptionQ.Enqueue(exc);
                        }
                        else 
                        {
                            exceptionQ.Enqueue(e); 
                        } 
                    }
 
                    // If we have encountered any exceptions, then throw.
                    if ((exceptionQ != null) && (exceptionQ.Count > 0))
                    {
                        ThrowIfReducableToSingleOCE(exceptionQ, parallelOptions.CancellationToken); 
                        throw new AggregateException(exceptionQ);
                    } 
                } 
                else
                { 
                    // This is more efficient for a small number of actions and no DOP support

                    // Initialize our array of tasks, one per action.
                    Task[] tasks = new Task[actionsCopy.Length]; 

                    // One more check before we begin... 
                    if (parallelOptions.CancellationToken.IsCancellationRequested) 
                        throw new OperationCanceledException(parallelOptions.CancellationToken);
 
                    // Launch all actions as tasks
                    for (int i = 0; i < tasks.Length; i++)
                    {
                        tasks[i] = Task.Factory.StartNew(actionsCopy[i], parallelOptions.CancellationToken, TaskCreationOptions.None, 
                                                            InternalTaskOptions.None, parallelOptions.EffectiveTaskScheduler);
                    } 
 
                    // Now wait for the tasks to complete.  This will not unblock until all of
                    // them complete, and it will throw an exception if one or more of them also 
                    // threw an exception.  We let such exceptions go completely unhandled.
                    try
                    {
                        if (tasks.Length <= 4) 
                        {
                            // for 4 or less tasks, the sequential waitall version is faster 
                            Task.FastWaitAll(tasks); 
                        }
                        else 
                        {
                            // otherwise we revert to the regular WaitAll which delegates the multiple wait to the cooperative event.
                            Task.WaitAll(tasks);
                        } 
                    }
                    catch (AggregateException aggExp) 
                    { 
                        // see if we can combine it into a single OCE. If not propagate the original exception
                        ThrowIfReducableToSingleOCE(aggExp.InnerExceptions, parallelOptions.CancellationToken); 
                        throw;
                    }
                    finally
                    { 
                        for (int i = 0; i < tasks.Length; i++)
                        { 
                            if(tasks[i].IsCompleted) tasks[i].Dispose(); 
                        }
                    } 
                }
            }
            finally
            { 
#if !FEATURE_PAL    // PAL doesn't support  eventing
                // ETW event for Parallel Invoke End 
                if (TplEtwProvider.Log.IsEnabled()) 
                {
                    TplEtwProvider.Log.ParallelInvokeEnd((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0), 
                                                         forkJoinContextID);
                }
#endif
            } 
        }
 
        ///  
        /// Executes a for loop in which iterations may run in parallel.
        ///  
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// The  delegate is invoked once for each value in the iteration range:
        /// [fromInclusive, toExclusive).  It is provided with the iteration count (an Int32) as a parameter.
        ///  
        public static ParallelLoopResult For(int fromInclusive, int toExclusive, Action body)
        { 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }

            return ForWorker(
                fromInclusive, toExclusive, 
                s_defaultParallelOptions,
                body, null, null, null, null); 
        } 

        ///  
        /// Executes a for loop in which iterations may run in parallel.
        /// 
        /// The start index, inclusive.
        /// The end index, exclusive. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the iteration count (an Int64) as a parameter.
        ///  
        public static ParallelLoopResult For(long fromInclusive, long toExclusive, Action body) 
        {
            if (body == null) 
            {
                throw new ArgumentNullException("body");
            }
 
            return ForWorker64(
                fromInclusive, toExclusive, s_defaultParallelOptions, 
                body, null, null, null, null); 
        }
 
        /// 
        /// Executes a for loop in which iterations may run in parallel.
        /// 
        /// The start index, inclusive. 
        /// The end index, exclusive.
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set. 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the iteration count (an Int32) as a parameter.
        ///  
        public static ParallelLoopResult For(int fromInclusive, int toExclusive, ParallelOptions parallelOptions, Action body)
        {
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            } 
            if (parallelOptions == null) 
            {
                throw new ArgumentNullException("parallelOptions"); 
            }

            return ForWorker(
                fromInclusive, toExclusive, parallelOptions, 
                body, null, null, null, null);
        } 
 
        /// 
        /// Executes a for loop in which iterations may run in parallel. 
        /// 
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the
        /// CancellationToken in the 
        /// argument is set. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the 
        ///  has been disposed.
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        ///  
        /// The  delegate is invoked once for each value in the iteration range:
        /// [fromInclusive, toExclusive).  It is provided with the iteration count (an Int64) as a parameter. 
        ///  
        public static ParallelLoopResult For(long fromInclusive, long toExclusive, ParallelOptions parallelOptions, Action body)
        { 
            if (body == null)
            {
                throw new ArgumentNullException("body");
            } 
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions"); 
            }
 
            return ForWorker64(
                fromInclusive, toExclusive, parallelOptions,
                body, null, null, null, null);
        } 

        ///  
        /// Executes a for loop in which iterations may run in parallel. 
        /// 
        /// The start index, inclusive. 
        /// The end index, exclusive.
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// 
        /// The  delegate is invoked once for each value in the iteration range:
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int32),
        /// and a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely.
        ///  
        ///  
        /// Calling ParallelLoopState.Break()
        /// informs the For operation that iterations after the current one need not 
        /// execute.  However, all iterations before the current one will still need to be executed if they have not already.
        /// Therefore, calling Break is similar to using a break operation within a
        /// conventional for loop in a language like C#, but it is not a perfect substitute: for example, there is no guarantee that iterations
        /// after the current one will definitely not execute. 
        /// 
        ///  
        /// If executing all iterations before the current one is not necessary, 
        /// ParallelLoopState.Stop()
        /// should be preferred to using Break.  Calling Stop informs the For loop that it may abandon all remaining 
        /// iterations, regardless of whether they're for interations above or below the current,
        /// since all required work has already been completed.  As with Break, however, there are no guarantees regarding
        /// which other iterations will not execute.
        ///  
        /// 
        /// When a loop is ended prematurely, the  that's returned will contain 
        /// relevant information about the loop's completion. 
        /// 
        ///  
        public static ParallelLoopResult For(int fromInclusive, int toExclusive, Action body)
        {
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            } 
 
            return ForWorker(
                fromInclusive, toExclusive, s_defaultParallelOptions, 
                null, body, null, null, null);
        }

        ///  
        /// Executes a for loop in which iterations may run in parallel.
        ///  
        /// The start index, inclusive. 
        /// The end index, exclusive.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        ///  
        /// The  delegate is invoked once for each value in the iteration range:
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int64), 
        /// and a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely.
        /// 
        public static ParallelLoopResult For(long fromInclusive, long toExclusive, Action body) 
        {
            if (body == null) 
            { 
                throw new ArgumentNullException("body");
            } 

            return ForWorker64(
                fromInclusive, toExclusive, s_defaultParallelOptions,
                null, body, null, null, null); 
        }
 
        ///  
        /// Executes a for loop in which iterations may run in parallel.
        ///  
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the 
        /// argument is set.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int32),
        /// and a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely. 
        /// 
        public static ParallelLoopResult For(int fromInclusive, int toExclusive, ParallelOptions parallelOptions, Action body) 
        {
            if (body == null)
            {
                throw new ArgumentNullException("body"); 
            }
            if (parallelOptions == null) 
            { 
                throw new ArgumentNullException("parallelOptions");
            } 

            return ForWorker(
                fromInclusive, toExclusive, parallelOptions,
                null, body, null, null, null); 
        }
 
        ///  
        /// Executes a for loop in which iterations may run in parallel.
        ///  
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the 
        /// argument is set.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int64),
        /// and a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely. 
        /// 
        public static ParallelLoopResult For(long fromInclusive, long toExclusive, ParallelOptions parallelOptions, 
            Action body)
        {
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            } 
            if (parallelOptions == null) 
            {
                throw new ArgumentNullException("parallelOptions"); 
            }

            return ForWorker64(
                fromInclusive, toExclusive, parallelOptions, 
                null, body, null, null, null);
        } 
 
        /// 
        /// Executes a for loop in which iterations may run in parallel. 
        /// 
        /// The type of the thread-local data.
        /// The start index, inclusive.
        /// The end index, exclusive. 
        /// The function delegate that returns the initial state of the local data
        /// for each thread. 
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        /// 
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int32),
        /// a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations 
        /// that execute on the same thread.
        ///  
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final 
        /// action on each thread's local state. 
        /// 
        ///  
        public static ParallelLoopResult For(
            int fromInclusive, int toExclusive,
            Func localInit,
            Func body, 
            Action localFinally)
        { 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            { 
                throw new ArgumentNullException("localFinally");
            } 

            return ForWorker(
                fromInclusive, toExclusive, s_defaultParallelOptions,
                null, null, body, localInit, localFinally); 
        }
 
        ///  
        /// Executes a for loop in which iterations may run in parallel.  Supports 64-bit indices.
        ///  
        /// The type of the thread-local data.
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// The function delegate that returns the initial state of the local data 
        /// for each thread.
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each 
        /// thread.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// 
        /// The  delegate is invoked once for each value in the iteration range:
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int64), 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations 
        /// that execute on the same thread. 
        /// 
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value 
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state. 
        ///  
        /// 
        public static ParallelLoopResult For( 
            long fromInclusive, long toExclusive,
            Func localInit,
            Func body,
            Action localFinally) 
        {
            if (body == null) 
            { 
                throw new ArgumentNullException("body");
            } 
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit");
            } 
            if (localFinally == null)
            { 
                throw new ArgumentNullException("localFinally"); 
            }
 
            return ForWorker64(
                fromInclusive, toExclusive, s_defaultParallelOptions,
                null, null, body, localInit, localFinally);
        } 

        ///  
        /// Executes a for loop in which iterations may run in parallel. 
        /// 
        /// The type of the thread-local data. 
        /// The start index, inclusive.
        /// The end index, exclusive.
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The function delegate that returns the initial state of the local data
        /// for each thread. 
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set.
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the 
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        /// 
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int32),
        /// a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations 
        /// that execute on the same thread.
        ///  
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final 
        /// action on each thread's local state. 
        /// 
        ///  
        public static ParallelLoopResult For(
            int fromInclusive, int toExclusive, ParallelOptions parallelOptions,
            Func localInit,
            Func body, 
            Action localFinally)
        { 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            { 
                throw new ArgumentNullException("localFinally");
            } 
            if (parallelOptions == null)
            {
                throw new ArgumentNullException("parallelOptions");
            } 

            return ForWorker( 
                fromInclusive, toExclusive, parallelOptions, 
                null, null, body, localInit, localFinally);
        } 

        /// 
        /// Executes a for loop in which iterations may run in parallel.
        ///  
        /// The type of the thread-local data.
        /// The start index, inclusive. 
        /// The end index, exclusive. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The function delegate that returns the initial state of the local data
        /// for each thread.
        /// The delegate that is invoked once per iteration.
        /// The delegate that performs a final action on the local state of each 
        /// thread.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the  
        /// argument is set. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        ///  
        /// 
        /// The  delegate is invoked once for each value in the iteration range: 
        /// [fromInclusive, toExclusive).  It is provided with the following parameters: the iteration count (an Int64),
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations
        /// that execute on the same thread. 
        /// 
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state.
        ///  
        /// 
        public static ParallelLoopResult For( 
            long fromInclusive, long toExclusive, ParallelOptions parallelOptions, 
            Func localInit,
            Func body, 
            Action localFinally)
        {
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            } 
            if (localInit == null) 
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null)
            {
                throw new ArgumentNullException("localFinally"); 
            }
            if (parallelOptions == null) 
            { 
                throw new ArgumentNullException("parallelOptions");
            } 


            return ForWorker64(
                fromInclusive, toExclusive, parallelOptions, 
                null, null, body, localInit, localFinally);
        } 
 

 



 
        /// 
        /// Performs the major work of the parallel for loop. It assumes that argument validation has already 
        /// been performed by the caller. This function's whole purpose in life is to enable as much reuse of 
        /// common implementation details for the various For overloads we offer. Without it, we'd end up
        /// with lots of duplicate code. It handles: (1) simple for loops, (2) for loops that depend on 
        /// ParallelState, and (3) for loops with thread local data.
        ///
        /// @
 

 
 

 



 

 
 

 
        private static ParallelLoopResult ForWorker(
            int fromInclusive, int toExclusive,
            ParallelOptions parallelOptions,
            Action body, 
            Action bodyWithState,
            Func bodyWithLocal, 
            Func localInit, Action localFinally) 
        {
            Contract.Assert(((body == null ? 0 : 1) + (bodyWithState == null ? 0 : 1) + (bodyWithLocal == null ? 0 : 1)) == 1, 
                "expected exactly one body function to be supplied");
            Contract.Assert(bodyWithLocal != null || (localInit == null && localFinally == null),
                "thread local functions should only be supplied for loops w/ thread local bodies");
 
            // Instantiate our result.  Specifics will be filled in later.
            ParallelLoopResult result = new ParallelLoopResult(); 
 
            // We just return immediately if 'to' is smaller (or equal to) 'from'.
            if (toExclusive <= fromInclusive) 
            {
                result.m_completed = true;
                return result;
            } 

            long sharedIndex64 = fromInclusive; 
 
            // For all loops we need a shared flag even though we don't have a body with state,
            // because the shared flag contains the exceptional bool, which triggers other workers 
            // to exit their loops if one worker catches an exception
            ParallelLoopStateFlags32 sharedPStateFlags = new ParallelLoopStateFlags32();

            TaskCreationOptions creationOptions = TaskCreationOptions.None; 
            InternalTaskOptions internalOptions = InternalTaskOptions.SelfReplicating;
 
            // Before getting started, do a quick peek to see if we have been canceled already 
            if (parallelOptions.CancellationToken.IsCancellationRequested)
            { 
                throw new OperationCanceledException(parallelOptions.CancellationToken);
            }

            // initialize ranges with passed in loop arguments and expected number of workers 
            int numExpectedWorkers = (parallelOptions.EffectiveMaxConcurrencyLevel == -1) ?
                Environment.ProcessorCount : 
                parallelOptions.EffectiveMaxConcurrencyLevel; 
            RangeManager rangeManager = new RangeManager(fromInclusive, toExclusive, 1, numExpectedWorkers);
 
            // Keep track of any cancellations
            OperationCanceledException oce = null;

            CancellationTokenRegistration ctr = new CancellationTokenRegistration(); 

            // if cancellation is enabled, we need to register a callback to stop the loop when it gets signaled 
            if (parallelOptions.CancellationToken.CanBeCanceled) 
            {
                ctr = parallelOptions.CancellationToken.InternalRegisterWithoutEC((o) => 
                {
                    // Cause processing to stop
                    sharedPStateFlags.Cancel();
                    // Record our cancellation 
                    oce = new OperationCanceledException(parallelOptions.CancellationToken);
                }, null); 
            } 

#if !FEATURE_PAL    // PAL doesn't support  eventing 
            // ETW event for Parallel For begin
            int forkJoinContextID = 0;
            Task callingTask = null;
            if (TplEtwProvider.Log.IsEnabled()) 
            {
                forkJoinContextID = Interlocked.Increment(ref s_forkJoinContextID); 
                callingTask = Task.InternalCurrent; 
                TplEtwProvider.Log.ParallelLoopBegin((callingTask != null ? callingTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callingTask != null ? callingTask.Id : 0),
                                                     forkJoinContextID,TplEtwProvider.ForkJoinOperationType.ParallelFor, 
                                                     fromInclusive, toExclusive);
            }
#endif
 
            ParallelForReplicatingTask rootTask = null; // eliminates "Use of unassigned local variable" compiler bug below.
 
            try 
            {
                // this needs to be in try-block because it can throw in BuggyScheduler.MaxConcurrencyLevel 
                rootTask = new ParallelForReplicatingTask(
                    parallelOptions,
                    delegate
                    { 
                        //
                        // first thing we do upon enterying the task is to register as a new "RangeWorker" with the 
                        // shared RangeManager instance. 
                        //
                        // If this call returns a RangeWorker struct which wraps the state needed by this task 
                        //
                        // We need to call FindNewWork32() on it to see whether there's a chunk available.
                        //
 

                        // Cache some information about the current task 
                        Task currentWorkerTask = Task.InternalCurrent; 
                        bool bIsRootTask = (currentWorkerTask == rootTask);
 
                        RangeWorker currentWorker = new RangeWorker();
                        Object savedStateFromPreviousReplica = currentWorkerTask.SavedStateFromPreviousReplica;

                        if (savedStateFromPreviousReplica is RangeWorker) 
                            currentWorker = (RangeWorker)savedStateFromPreviousReplica;
                        else 
                            currentWorker = rangeManager.RegisterNewWorker(); 

 

                        // These are the local index values to be used in the sequential loop.
                        // Their values filled in by FindNewWork32
                        int nFromInclusiveLocal; 
                        int nToExclusiveLocal;
 
                        if (currentWorker.FindNewWork32(out nFromInclusiveLocal, out nToExclusiveLocal) == false || 
                            sharedPStateFlags.ShouldExitLoop(nFromInclusiveLocal) == true)
                        { 
                            return; // no need to run
                        }

#if !FEATURE_PAL    // PAL doesn't support  eventing 
                        // ETW event for ParallelFor Worker Fork
                        if (TplEtwProvider.Log.IsEnabled()) 
                        { 
                            TplEtwProvider.Log.ParallelFork((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                             forkJoinContextID); 
                        }
#endif

                        TLocal localValue = default(TLocal); 
                        bool bLocalValueInitialized = false; // Tracks whether localInit ran without exceptions, so that we can skip localFinally if it wasn't
 
                        try 
                        {
                            // Create a new state object that references the shared "stopped" and "exceptional" flags 
                            // If needed, it will contain a new instance of thread-local state by invoking the selector.
                            ParallelLoopState32 state = null;

                            if (bodyWithState != null) 
                            {
                                Contract.Assert(sharedPStateFlags != null); 
                                state = new ParallelLoopState32(sharedPStateFlags); 
                            }
                            else if (bodyWithLocal != null) 
                            {
                                Contract.Assert(sharedPStateFlags != null);
                                state = new ParallelLoopState32(sharedPStateFlags);
                                if (localInit != null) 
                                {
                                    localValue = localInit(); 
                                    bLocalValueInitialized = true; 
                                }
                            } 

                            // initialize a loop timer which will help us decide whether we should exit early
                            LoopTimer loopTimer = new LoopTimer(rootTask.ActiveChildCount);
 
                            // Now perform the loop itself.
                            do 
                            { 
                                if (body != null)
                                { 
                                    for (int j = nFromInclusiveLocal;
                                         j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline
                                                                   || !sharedPStateFlags.ShouldExitLoop()); // the no-arg version is used since we have no state
                                         j += 1) 
                                    {
 
                                        body(j); 
                                    }
                                } 
                                else if (bodyWithState != null)
                                {
                                    for (int j = nFromInclusiveLocal;
                                        j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline 
                                                                   || !sharedPStateFlags.ShouldExitLoop(j));
                                        j += 1) 
                                    { 

                                        state.CurrentIteration = j; 
                                        bodyWithState(j, state);
                                    }
                                }
                                else 
                                {
                                    for (int j = nFromInclusiveLocal; 
                                        j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline 
                                                                   || !sharedPStateFlags.ShouldExitLoop(j));
                                        j += 1) 
                                    {
                                        state.CurrentIteration = j;
                                        localValue = bodyWithLocal(j, state, localValue);
                                    } 
                                }
 
                                // Cooperative multitasking hack for AppDomain fairness. 
                                // Check if allowed loop time is exceeded, if so save current state and return. The self replicating task logic
                                // will detect this, and queue up a replacement task. Note that we don't do this on the root task. 
                                if ( !bIsRootTask && loopTimer.LimitExceeded())
                                {
                                    currentWorkerTask.SavedStateForNextReplica = (object)currentWorker;
                                    break; 
                                }
 
                            } 
                            // Exit if we can't find new work, or if the loop was stoppped.
                            while (currentWorker.FindNewWork32(out nFromInclusiveLocal, out nToExclusiveLocal) && 
                                    ((sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE) ||
                                      !sharedPStateFlags.ShouldExitLoop(nFromInclusiveLocal)));
                        }
                        catch 
                        {
                            // if we catch an exception in a worker, we signal the other workers to exit the loop, and we rethrow 
                            sharedPStateFlags.SetExceptional(); 
                            throw;
                        } 
                        finally
                        {
                            // If a cleanup function was specified, call it. Otherwise, if the type is
                            // IDisposable, we will invoke Dispose on behalf of the user. 
                            if (localFinally != null && bLocalValueInitialized)
                            { 
                                localFinally(localValue); 
                            }
 
#if !FEATURE_PAL    // PAL doesn't support  eventing
                            // ETW event for ParallelFor Worker Join
                            if (TplEtwProvider.Log.IsEnabled())
                            { 
                                TplEtwProvider.Log.ParallelJoin((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                                 forkJoinContextID); 
                            } 
#endif
                        } 
                    },
                    creationOptions, internalOptions);

                rootTask.RunSynchronously(parallelOptions.EffectiveTaskScheduler); // might throw TSE 
                rootTask.Wait();
 
                // If we made a cancellation registration, we need to clean it up now before observing the OCE 
                // Otherwise we could be caught in the middle of a callback, and observe PLS_STOPPED, but oce = null
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                {
                    ctr.Dispose();
                }
 
                // If we got through that with no exceptions, and we were canceled, then
                // throw our cancellation exception 
                if (oce != null) throw oce; 
            }
            catch (AggregateException aggExp) 
            {
                // if we made a cancellation registration, and rootTask.Wait threw, we need to clean it up here
                if (parallelOptions.CancellationToken.CanBeCanceled)
                { 
                    ctr.Dispose();
                } 
 
                // see if we can combine it into a single OCE. If not propagate the original exception
                ThrowIfReducableToSingleOCE(aggExp.InnerExceptions, parallelOptions.CancellationToken); 
                throw;
            }
            catch (TaskSchedulerException)
            { 
                // if we made a cancellation registration, and rootTask.RunSynchronously threw, we need to clean it up here
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                { 
                    ctr.Dispose();
                } 
                throw;
            }
            finally
            { 
                int sb_status = sharedPStateFlags.LoopStateFlags;
                result.m_completed = (sb_status == ParallelLoopStateFlags.PLS_NONE); 
                if ((sb_status & ParallelLoopStateFlags.PLS_BROKEN) != 0) 
                {
                    result.m_lowestBreakIteration = sharedPStateFlags.LowestBreakIteration; 
                }

                if( (rootTask != null) && rootTask.IsCompleted) rootTask.Dispose();
 

#if !FEATURE_PAL    // PAL doesn't support  eventing 
                // ETW event for Parallel For End 
                if (TplEtwProvider.Log.IsEnabled())
                { 
                    int nTotalIterations = 0;

                    // calculate how many iterations we ran in total
                    if (sb_status == ParallelLoopStateFlags.PLS_NONE) 
                        nTotalIterations = toExclusive - fromInclusive;
                    else if ((sb_status & ParallelLoopStateFlags.PLS_BROKEN) != 0) 
                        nTotalIterations = sharedPStateFlags.LowestBreakIteration - fromInclusive; 
                    else
                        nTotalIterations = -1; //PLS_STOPPED! We can't determine this if we were stopped.. 

                    TplEtwProvider.Log.ParallelLoopEnd((callingTask != null ? callingTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callingTask != null ? callingTask.Id : 0),
                                                         forkJoinContextID, nTotalIterations);
                } 
#endif
            } 
 
            return result;
        } 

        /// 
        /// Performs the major work of the 64-bit parallel for loop. It assumes that argument validation has already
        /// been performed by the caller. This function's whole purpose in life is to enable as much reuse of 
        /// common implementation details for the various For overloads we offer. Without it, we'd end up
        /// with lots of duplicate code. It handles: (1) simple for loops, (2) for loops that depend on 
        /// ParallelState, and (3) for loops with thread local data. 
        ///
        /// @ 



 

 
 

 



 

 
        private static ParallelLoopResult ForWorker64( 
            long fromInclusive, long toExclusive,
            ParallelOptions parallelOptions, 
            Action body,
            Action bodyWithState,
            Func bodyWithLocal,
            Func localInit, Action localFinally) 
        {
            Contract.Assert(((body == null ? 0 : 1) + (bodyWithState == null ? 0 : 1) + (bodyWithLocal == null ? 0 : 1)) == 1, 
                "expected exactly one body function to be supplied"); 
            Contract.Assert(bodyWithLocal != null || (localInit == null && localFinally == null),
                "thread local functions should only be supplied for loops w/ thread local bodies"); 

            // Instantiate our result.  Specifics will be filled in later.
            ParallelLoopResult result = new ParallelLoopResult();
 
            // We just return immediately if 'to' is smaller (or equal to) 'from'.
            if (toExclusive <= fromInclusive) 
            { 
                result.m_completed = true;
                return result; 
            }

            long sharedIndex = fromInclusive;
 
            // For all loops we need a shared flag even though we don't have a body with state,
            // because the shared flag contains the exceptional bool, which triggers other workers 
            // to exit their loops if one worker catches an exception 
            ParallelLoopStateFlags64 sharedPStateFlags = new ParallelLoopStateFlags64();
 
            TaskCreationOptions creationOptions = TaskCreationOptions.None;
            InternalTaskOptions internalOptions = InternalTaskOptions.SelfReplicating;

            // Before getting started, do a quick peek to see if we have been canceled already 
            if (parallelOptions.CancellationToken.IsCancellationRequested)
            { 
                throw new OperationCanceledException(parallelOptions.CancellationToken); 
            }
 
            // initialize ranges with passed in loop arguments and expected number of workers
            int numExpectedWorkers = (parallelOptions.EffectiveMaxConcurrencyLevel == -1) ?
                Environment.ProcessorCount :
                parallelOptions.EffectiveMaxConcurrencyLevel; 
            RangeManager rangeManager = new RangeManager(fromInclusive, toExclusive, 1, numExpectedWorkers);
 
            // Keep track of any cancellations 
            OperationCanceledException oce = null;
 
            CancellationTokenRegistration ctr = new CancellationTokenRegistration();

            // if cancellation is enabled, we need to register a callback to stop the loop when it gets signaled
            if (parallelOptions.CancellationToken.CanBeCanceled) 
            {
                ctr = parallelOptions.CancellationToken.InternalRegisterWithoutEC((o) => 
                { 
                    // Cause processing to stop
                    sharedPStateFlags.Cancel(); 
                    // Record our cancellation
                    oce = new OperationCanceledException(parallelOptions.CancellationToken);
                }, null);
            } 

#if !FEATURE_PAL    // PAL doesn't support  eventing 
            // ETW event for Parallel For begin 
            Task callerTask = null;
            int forkJoinContextID = 0; 
            if (TplEtwProvider.Log.IsEnabled())
            {
                forkJoinContextID = Interlocked.Increment(ref s_forkJoinContextID);
                callerTask = Task.InternalCurrent; 
                TplEtwProvider.Log.ParallelLoopBegin((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0),
                                                     forkJoinContextID, TplEtwProvider.ForkJoinOperationType.ParallelFor, 
                                                     fromInclusive, toExclusive); 
            }
#endif 


            ParallelForReplicatingTask rootTask = null; // eliminates "Use of unassigned local variable" compiler bug below.
 
            try
            { 
                // this needs to be in try-block because it can throw in BuggyScheduler.MaxConcurrencyLevel 
                rootTask = new ParallelForReplicatingTask(
                parallelOptions, 
                delegate
                {
                    //
                    // first thing we do upon enterying the task is to register as a new "RangeWorker" with the 
                    // shared RangeManager instance.
                    // 
                    // If this call returns a RangeWorker struct which wraps the state needed by this task 
                    //
                    // We need to call FindNewWork() on it to see whether there's a chunk available. 
                    //

                    // Cache some information about the current task
                    Task currentWorkerTask = Task.InternalCurrent; 
                    bool bIsRootTask = (currentWorkerTask == rootTask);
 
                    RangeWorker currentWorker = new RangeWorker(); 
                    Object savedStateFromPreviousReplica = currentWorkerTask.SavedStateFromPreviousReplica;
 
                    if (savedStateFromPreviousReplica is RangeWorker)
                        currentWorker = (RangeWorker)savedStateFromPreviousReplica;
                    else
                        currentWorker = rangeManager.RegisterNewWorker(); 

 
                    // These are the local index values to be used in the sequential loop. 
                    // Their values filled in by FindNewWork
                    long nFromInclusiveLocal; 
                    long nToExclusiveLocal;

                    if (currentWorker.FindNewWork(out nFromInclusiveLocal, out nToExclusiveLocal) == false ||
                        sharedPStateFlags.ShouldExitLoop(nFromInclusiveLocal) == true) 
                    {
                        return; // no need to run 
                    } 

 
#if !FEATURE_PAL    // PAL doesn't support  eventing
                    // ETW event for ParallelFor Worker Fork
                    if (TplEtwProvider.Log.IsEnabled())
                    { 
                        TplEtwProvider.Log.ParallelFork((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                         forkJoinContextID); 
                    } 
#endif
 

                    TLocal localValue = default(TLocal);
                    bool bLocalValueInitialized = false; // Tracks whether localInit ran without exceptions, so that we can skip localFinally if it wasn't
 
                    try
                    { 
 
                        // Create a new state object that references the shared "stopped" and "exceptional" flags
                        // If needed, it will contain a new instance of thread-local state by invoking the selector. 
                        ParallelLoopState64 state = null;

                        if (bodyWithState != null)
                        { 
                            Contract.Assert(sharedPStateFlags != null);
                            state = new ParallelLoopState64(sharedPStateFlags); 
                        } 
                        else if (bodyWithLocal != null)
                        { 
                            Contract.Assert(sharedPStateFlags != null);
                            state = new ParallelLoopState64(sharedPStateFlags);

                            // If a thread-local selector was supplied, invoke it. Otherwise, use the default. 
                            if (localInit != null)
                            { 
                                localValue = localInit(); 
                                bLocalValueInitialized = true;
                            } 
                        }

                        // initialize a loop timer which will help us decide whether we should exit early
                        LoopTimer loopTimer = new LoopTimer(rootTask.ActiveChildCount); 

                        // Now perform the loop itself. 
                        do 
                        {
                            if (body != null) 
                            {
                                for (long j = nFromInclusiveLocal;
                                     j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline
                                                               || !sharedPStateFlags.ShouldExitLoop()); // the no-arg version is used since we have no state 
                                     j += 1)
                                { 
                                    body(j); 
                                }
                            } 
                            else if (bodyWithState != null)
                            {
                                for (long j = nFromInclusiveLocal;
                                     j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline 
                                                               || !sharedPStateFlags.ShouldExitLoop(j));
                                     j += 1) 
                                { 
                                    state.CurrentIteration = j;
                                    bodyWithState(j, state); 
                                }
                            }
                            else
                            { 
                                for (long j = nFromInclusiveLocal;
                                     j < nToExclusiveLocal && (sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE  // fast path check as SEL() doesn't inline 
                                                               || !sharedPStateFlags.ShouldExitLoop(j)); 
                                     j += 1)
                                { 
                                    state.CurrentIteration = j;
                                    localValue = bodyWithLocal(j, state, localValue);
                                }
                            } 

                            // Cooperative multitasking hack for AppDomain fairness. 
                            // Check if allowed loop time is exceeded, if so save current state and return. The self replicating task logic 
                            // will detect this, and queue up a replacement task. Note that we don't do this on the root task.
                            if (!bIsRootTask && loopTimer.LimitExceeded()) 
                            {
                                currentWorkerTask.SavedStateForNextReplica = (object)currentWorker;
                                break;
                            } 
                        }
                        // Exit if we can't find new work, or if the loop was stoppped. 
                        while (currentWorker.FindNewWork(out nFromInclusiveLocal, out nToExclusiveLocal) && 
                                  ((sharedPStateFlags.LoopStateFlags == ParallelLoopStateFlags.PLS_NONE) ||
                                    !sharedPStateFlags.ShouldExitLoop(nFromInclusiveLocal))); 
                    }
                    catch
                    {
                        // if we catch an exception in a worker, we signal the other workers to exit the loop, and we rethrow 
                        sharedPStateFlags.SetExceptional();
                        throw; 
                    } 
                    finally
                    { 
                        // If a cleanup function was specified, call it. Otherwise, if the type is
                        // IDisposable, we will invoke Dispose on behalf of the user.
                        if (localFinally != null && bLocalValueInitialized)
                        { 
                            localFinally(localValue);
                        } 
 
#if !FEATURE_PAL        // PAL doesn't support  eventing
                        // ETW event for ParallelFor Worker Join 
                        if (TplEtwProvider.Log.IsEnabled())
                        {
                            TplEtwProvider.Log.ParallelJoin((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                             forkJoinContextID); 
                        }
#endif 
                    } 
                },
                creationOptions, internalOptions); 

                rootTask.RunSynchronously(parallelOptions.EffectiveTaskScheduler); // might throw TSE
                rootTask.Wait();
 
                // If we made a cancellation registration, we need to clean it up now before observing the OCE
                // Otherwise we could be caught in the middle of a callback, and observe PLS_STOPPED, but oce = null 
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                {
                    ctr.Dispose(); 
                }

                // If we got through that with no exceptions, and we were canceled, then
                // throw our cancellation exception 
                if (oce != null) throw oce;
            } 
            catch (AggregateException aggExp) 
            {
                // if we made a cancellation registration, and rootTask.Wait threw, we need to clean it up here 
                if (parallelOptions.CancellationToken.CanBeCanceled)
                {
                    ctr.Dispose();
                } 

                // see if we can combine it into a single OCE. If not propagate the original exception 
                ThrowIfReducableToSingleOCE(aggExp.InnerExceptions, parallelOptions.CancellationToken); 
                throw;
            } 
            catch (TaskSchedulerException)
            {
                // if we made a cancellation registration, and rootTask.RunSynchronously threw, we need to clean it up here
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                {
                    ctr.Dispose(); 
                } 
                throw;
            } 
            finally
            {
                int sb_status = sharedPStateFlags.LoopStateFlags;
                result.m_completed = (sb_status == ParallelLoopStateFlags.PLS_NONE); 
                if ((sb_status & ParallelLoopStateFlags.PLS_BROKEN) != 0)
                { 
                    result.m_lowestBreakIteration = sharedPStateFlags.LowestBreakIteration; 
                }
 
                if( (rootTask != null) && rootTask.IsCompleted) rootTask.Dispose();

#if !FEATURE_PAL    // PAL doesn't support  eventing
                // ETW event for Parallel For End 
                if (TplEtwProvider.Log.IsEnabled())
                { 
                    long nTotalIterations = 0; 

                    // calculate how many iterations we ran in total 
                    if (sb_status == ParallelLoopStateFlags.PLS_NONE)
                        nTotalIterations = toExclusive - fromInclusive;
                    else if ((sb_status & ParallelLoopStateFlags.PLS_BROKEN) != 0)
                        nTotalIterations = sharedPStateFlags.LowestBreakIteration - fromInclusive; 
                    else
                        nTotalIterations = -1; //PLS_STOPPED! We can't determine this if we were stopped.. 
 
                    TplEtwProvider.Log.ParallelLoopEnd((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0),
                                                         forkJoinContextID, nTotalIterations); 
                }
#endif
            }
 
            return result;
        } 
 

        ///  
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel.
        /// 
        /// The type of the data in the source. 
        /// An enumerable data source.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the current element as a parameter.
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, Action body)
        {
            if (source == null)
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }

            return ForEachWorker(
                source, s_defaultParallelOptions, body, null, null, null, null, null, null); 
        }
 
        ///  
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source.
        /// An enumerable data source.
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the current element as a parameter.
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, ParallelOptions parallelOptions, Action body)
        {
            if (source == null)
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (parallelOptions == null)
            {
                throw new ArgumentNullException("parallelOptions"); 
            }
 
            return ForEachWorker( 
                source, parallelOptions, body, null, null, null, null, null, null);
        } 

        /// 
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source. 
        /// An enumerable data source. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed. 
        /// 
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the following parameters: the current element,
        /// and a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely.
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, Action body)
        { 
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            }
            if (body == null)
            {
                throw new ArgumentNullException("body"); 
            }
 
            return ForEachWorker( 
                source, s_defaultParallelOptions, null, body, null, null, null, null, null);
        } 

        /// 
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source. 
        /// An enumerable data source. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the  
        /// argument is set
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the 
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// The  delegate is invoked once for each element in the 
        /// enumerable.  It is provided with the following parameters: the current element,
        /// and a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely.
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, ParallelOptions parallelOptions, Action body) 
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source");
            }
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            } 
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions");
            }

            return ForEachWorker( 
                source, parallelOptions, null, body, null, null, null, null, null);
        } 
 
        /// 
        /// Executes a for each operation on an  
        /// in which iterations may run in parallel.
        /// 
        /// The type of the data in the source.
        /// An enumerable data source. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and the current element's index (an Int64). 
        /// 
        public static ParallelLoopResult ForEach(IEnumerable source, Action body)
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            }

            return ForEachWorker( 
                source, s_defaultParallelOptions, null, null, body, null, null, null, null);
        } 
 
        /// 
        /// Executes a for each operation on an  
        /// in which iterations may run in parallel.
        /// 
        /// The type of the data in the source.
        /// An enumerable data source. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the  
        /// argument is set 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        ///  
        /// The  delegate is invoked once for each element in the 
        /// enumerable.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and the current element's index (an Int64).
        /// 
        public static ParallelLoopResult ForEach(IEnumerable source, ParallelOptions parallelOptions, Action body) 
        {
            if (source == null) 
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null)
            {
                throw new ArgumentNullException("body");
            } 
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions"); 
            }
 
            return ForEachWorker(
                source, parallelOptions, null, null, body, null, null, null, null);
        }
 
        /// 
        /// Executes a for each operation on an  
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source. 
        /// The type of the thread-local data.
        /// An enumerable data source.
        /// The function delegate that returns the initial state of the local data
        /// for each thread. 
        /// The delegate that is invoked once per iteration.
        /// The delegate that performs a final action on the local state of each 
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        /// 
        /// 
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations 
        /// that execute on the same thread.
        ///  
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final 
        /// action on each thread's local state. 
        /// 
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, Func localInit,
            Func body, Action localFinally)
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            }
            if (localInit == null)
            { 
                throw new ArgumentNullException("localInit");
            } 
            if (localFinally == null) 
            {
                throw new ArgumentNullException("localFinally"); 
            }

            return ForEachWorker(
                source, s_defaultParallelOptions, null, null, null, body, null, localInit, localFinally); 
        }
 
        ///  
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source.
        /// The type of the thread-local data.
        /// An enumerable data source. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The function delegate that returns the initial state of the local data 
        /// for each thread.
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        ///  
        /// The  delegate is invoked once for each element in the 
        /// enumerable.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations
        /// that execute on the same thread.
        ///  
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first 
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value 
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state.
        /// 
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source,
            ParallelOptions parallelOptions, Func localInit, 
            Func body, Action localFinally) 
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source");
            }
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            } 
            if (localInit == null)
            { 
                throw new ArgumentNullException("localInit");
            }
            if (localFinally == null)
            { 
                throw new ArgumentNullException("localFinally");
            } 
            if (parallelOptions == null) 
            {
                throw new ArgumentNullException("parallelOptions"); 
            }

            return ForEachWorker(
                source, parallelOptions, null, null, null, body, null, localInit, localFinally); 
        }
 
        ///  
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel. 
        /// 
        /// The type of the data in the source.
        /// The type of the thread-local data.
        /// An enumerable data source. 
        /// The function delegate that returns the initial state of the local data
        /// for each thread. 
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        ///  
        /// 
        /// The  delegate is invoked once for each element in the  
        /// enumerable.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, the current element's index (an Int64), and some local 
        /// state that may be shared amongst iterations that execute on the same thread.
        /// 
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value 
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state. 
        /// 
        /// 
        public static ParallelLoopResult ForEach(IEnumerable source, Func localInit,
            Func body, Action localFinally) 
        {
            if (source == null) 
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null)
            {
                throw new ArgumentNullException("body");
            } 
            if (localInit == null)
            { 
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            {
                throw new ArgumentNullException("localFinally");
            }
 
            return ForEachWorker(
                source, s_defaultParallelOptions, null, null, null, null, body, localInit, localFinally); 
        } 

        ///  
        /// Executes a for each operation on an 
        /// in which iterations may run in parallel.
        /// 
        /// The type of the data in the source. 
        /// The type of the thread-local data.
        /// An enumerable data source. 
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation.
        /// The function delegate that returns the initial state of the local data 
        /// for each thread.
        /// The delegate that is invoked once per iteration.
        /// The delegate that performs a final action on the local state of each
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the  
        /// argument is set
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the 
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed. 
        /// 
        ///  
        /// The  delegate is invoked once for each element in the 
        /// enumerable.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, the current element's index (an Int64), and some local 
        /// state that may be shared amongst iterations that execute on the same thread.
        ///  
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first 
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state. 
        /// 
        ///  
        public static ParallelLoopResult ForEach(IEnumerable source, ParallelOptions parallelOptions, Func localInit, 
            Func body, Action localFinally)
        { 
            if (source == null)
            {
                throw new ArgumentNullException("source");
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null) 
            {
                throw new ArgumentNullException("localInit");
            }
            if (localFinally == null) 
            {
                throw new ArgumentNullException("localFinally"); 
            } 
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions");
            }

            return ForEachWorker( 
                source, parallelOptions, null, null, null, null, body, localInit, localFinally);
        } 
 

        ///  
        /// Performs the major work of the parallel foreach loop. It assumes that argument validation has
        /// already been performed by the caller. This function's whole purpose in life is to enable as much
        /// reuse of common implementation details for the various For overloads we offer. Without it, we'd
        /// end up with lots of duplicate code. It handles: (1) simple foreach loops, (2) foreach loops that 
        /// depend on ParallelState, and (3) foreach loops that access indices, (4) foreach loops with thread
        /// local data, and any necessary permutations thereof. 
        /// 
        /// @
 



 

 
 

 



 

 
 
        private static ParallelLoopResult ForEachWorker(
            IEnumerable source, 
            ParallelOptions parallelOptions,
            Action body,
            Action bodyWithState,
            Action bodyWithStateAndIndex, 
            Func bodyWithStateAndLocal,
            Func bodyWithEverything, 
            Func localInit, Action localFinally) 
        {
            Contract.Assert(((body == null ? 0 : 1) + (bodyWithState == null ? 0 : 1) + 
                (bodyWithStateAndIndex == null ? 0 : 1) + (bodyWithStateAndLocal == null ? 0 : 1) + (bodyWithEverything == null ? 0 : 1)) == 1,
                "expected exactly one body function to be supplied");
            Contract.Assert((bodyWithStateAndLocal != null) || (bodyWithEverything != null) || (localInit == null && localFinally == null),
                "thread local functions should only be supplied for loops w/ thread local bodies"); 

            // Before getting started, do a quick peek to see if we have been canceled already 
            if (parallelOptions.CancellationToken.IsCancellationRequested) 
            {
                throw new OperationCanceledException(parallelOptions.CancellationToken); 
            }

            // If it's an array, we can use a fast-path that uses ldelems in the IL.
            TSource[] sourceAsArray = source as TSource[]; 
            if (sourceAsArray != null)
            { 
                return ForEachWorker( 
                    sourceAsArray, parallelOptions, body, bodyWithState, bodyWithStateAndIndex, bodyWithStateAndLocal,
                    bodyWithEverything, localInit, localFinally); 
            }

            // If we can index into the list, we can use a faster code-path that doesn't result in
            // contention for the single, shared enumerator object. 
            IList sourceAsList = source as IList;
            if (sourceAsList != null) 
            { 
                return ForEachWorker(
                    sourceAsList, parallelOptions, body, bodyWithState, bodyWithStateAndIndex, bodyWithStateAndLocal, 
                    bodyWithEverything, localInit, localFinally);
            }

            // This is an honest-to-goodness IEnumerable.  Wrap it in a Partitioner and defer to our 
            // ForEach(Partitioner) logic.
            return PartitionerForEachWorker(Partitioner.Create(source), parallelOptions, body, bodyWithState, 
                bodyWithStateAndIndex, bodyWithStateAndLocal, bodyWithEverything, localInit, localFinally); 

        } 

        /// 
        /// A fast path for the more general ForEachWorker method above. This uses ldelem instructions to
        /// access the individual elements of the array, which will be faster. 
        /// 
        /// The type of the source data. 
        /// The type of the local data. 
        /// An array data source.
        /// The options to use for execution. 
        /// The simple loop body.
        /// The loop body for ParallelState overloads.
        /// The loop body for indexed/ParallelLoopState overloads.
        /// The loop body for local/ParallelLoopState overloads. 
        /// The loop body for the most generic overload.
        /// A selector function that returns new thread local state. 
        /// A cleanup function to destroy thread local state. 
        /// A  structure.
        private static ParallelLoopResult ForEachWorker( 
            TSource[] array,
            ParallelOptions parallelOptions,
            Action body,
            Action bodyWithState, 
            Action bodyWithStateAndIndex,
            Func bodyWithStateAndLocal, 
            Func bodyWithEverything, 
            Func localInit, Action localFinally)
        { 
            Contract.Assert(array != null);
            Contract.Assert(parallelOptions != null, "ForEachWorker(array): parallelOptions is null");

            int from = array.GetLowerBound(0); 
            int to = array.GetUpperBound(0) + 1;
 
            if (body != null) 
            {
                return ForWorker( 
                    from, to, parallelOptions, (i) => body(array[i]), null, null, null, null);
            }
            else if (bodyWithState != null)
            { 
                return ForWorker(
                    from, to, parallelOptions, null, (i, state) => bodyWithState(array[i], state), null, null, null); 
            } 
            else if (bodyWithStateAndIndex != null)
            { 
                return ForWorker(
                    from, to, parallelOptions, null, (i, state) => bodyWithStateAndIndex(array[i], state, i), null, null, null);
            }
            else if (bodyWithStateAndLocal != null) 
            {
                return ForWorker( 
                    from, to, parallelOptions, null, null, (i, state, local) => bodyWithStateAndLocal(array[i], state, local), localInit, localFinally); 
            }
            else 
            {
                return ForWorker(
                    from, to, parallelOptions, null, null, (i, state, local) => bodyWithEverything(array[i], state, i, local), localInit, localFinally);
            } 
        }
 
        ///  
        /// A fast path for the more general ForEachWorker method above. This uses IList<T>'s indexer
        /// capabilities to access the individual elements of the list rather than an enumerator. 
        /// 
        /// The type of the source data.
        /// The type of the local data.
        /// A list data source. 
        /// The options to use for execution.
        /// The simple loop body. 
        /// The loop body for ParallelState overloads. 
        /// The loop body for indexed/ParallelLoopState overloads.
        /// The loop body for local/ParallelLoopState overloads. 
        /// The loop body for the most generic overload.
        /// A selector function that returns new thread local state.
        /// A cleanup function to destroy thread local state.
        /// A  structure. 
        private static ParallelLoopResult ForEachWorker(
            IList list, 
            ParallelOptions parallelOptions, 
            Action body,
            Action bodyWithState, 
            Action bodyWithStateAndIndex,
            Func bodyWithStateAndLocal,
            Func bodyWithEverything,
            Func localInit, Action localFinally) 
        {
            Contract.Assert(list != null); 
            Contract.Assert(parallelOptions != null, "ForEachWorker(list): parallelOptions is null"); 

            if (body != null) 
            {
                return ForWorker(
                    0, list.Count, parallelOptions, (i) => body(list[i]), null, null, null, null);
            } 
            else if (bodyWithState != null)
            { 
                return ForWorker( 
                    0, list.Count, parallelOptions, null, (i, state) => bodyWithState(list[i], state), null, null, null);
            } 
            else if (bodyWithStateAndIndex != null)
            {
                return ForWorker(
                    0, list.Count, parallelOptions, null, (i, state) => bodyWithStateAndIndex(list[i], state, i), null, null, null); 
            }
            else if (bodyWithStateAndLocal != null) 
            { 
                return ForWorker(
                    0, list.Count, parallelOptions, null, null, (i, state, local) => bodyWithStateAndLocal(list[i], state, local), localInit, localFinally); 
            }
            else
            {
                return ForWorker( 
                    0, list.Count, parallelOptions, null, null, (i, state, local) => bodyWithEverything(list[i], state, i, local), localInit, localFinally);
            } 
        } 

 

        // @

 
        /// 
        /// Executes a for each operation on a  
        /// Partitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in . 
        /// The Partitioner that contains the original data source.
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false. 
        /// The exception that is thrown when any
        /// methods in the  Partitioner return null.
        /// The exception that is thrown when the
        /// GetPartitions() method in the  Partitioner does not return 
        /// the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner returns an IList 
        /// with at least one null value.
        /// The exception that is thrown when the 
        /// GetDynamicPartitions() method in the  Partitioner returns an
        /// IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        ///  
        /// 
        /// The Partitioner is used to retrieve 
        /// the elements to be processed, in place of the original data source.  If the current element's
        /// index is desired, the source must be an 
        /// OrderablePartitioner.
        ///  
        /// 
        /// The  delegate is invoked once for each element in the  
        /// Partitioner.  It is provided with the current element as a parameter. 
        /// 
        ///  
        public static ParallelLoopResult ForEach(
            Partitioner source,
            Action body)
        { 
            if (source == null)
            { 
                throw new ArgumentNullException("source"); 
            }
            if (body == null) 
            {
                throw new ArgumentNullException("body");
            }
 
            return PartitionerForEachWorker(source, s_defaultParallelOptions, body, null, null, null, null, null, null);
        } 
 
        /// 
        /// Executes a for each operation on a  
        /// Partitioner in which iterations may run in parallel.
        /// 
        /// The type of the elements in .
        /// The Partitioner that contains the original data source. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false.
        /// The exception that is thrown when any 
        /// methods in the  Partitioner return null.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner does not return 
        /// the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner returns an IList
        /// with at least one null value.
        /// The exception that is thrown when the
        /// GetDynamicPartitions() method in the  Partitioner returns an 
        /// IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// 
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's 
        /// index is desired, the source must be an 
        /// OrderablePartitioner. 
        ///  
        /// 
        /// The  delegate is invoked once for each element in the  
        /// Partitioner.  It is provided with the following parameters: the current element,
        /// and a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely.
        ///  
        /// 
        public static ParallelLoopResult ForEach( 
            Partitioner source, 
            Action body)
        { 
            if (source == null)
            {
                throw new ArgumentNullException("source");
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body"); 
            }
 
            return PartitionerForEachWorker(source, s_defaultParallelOptions, null, body, null, null, null, null, null);
        }

        ///  
        /// Executes a for each operation on a 
        /// OrderablePartitioner in which iterations may run in parallel. 
        ///  
        /// The type of the elements in .
        /// The OrderablePartitioner that contains the original data source. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        /// SupportsDynamicPartitions property in the  OrderablePartitioner returns 
        /// false.
        /// The exception that is thrown when the 
        /// KeysNormalized property in the  OrderablePartitioner returns
        /// false.
        /// The exception that is thrown when any
        /// methods in the  OrderablePartitioner return null. 
        /// The exception that is thrown when the
        /// GetPartitions() or GetOrderablePartitions() methods in the  
        /// OrderablePartitioner do not return the correct number of partitions. 
        /// The exception that is thrown when the
        /// GetPartitions() or GetOrderablePartitions() methods in the  
        /// OrderablePartitioner return an IList with at least one null value.
        /// The exception that is thrown when the
        /// GetDynamicPartitions() or GetDynamicOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IEnumerable whose GetEnumerator() method returns null. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// 
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's
        /// index is desired, the source must be an  
        /// OrderablePartitioner.
        ///  
        ///  
        /// The  delegate is invoked once for each element in the 
        /// Partitioner.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and the current element's index (an Int64).
        /// 
        ///  
        public static ParallelLoopResult ForEach(
            OrderablePartitioner source, 
            Action body) 
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source");
            }
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            } 

            if (!source.KeysNormalized) 
            {
                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_OrderedPartitionerKeysNotNormalized"));
            }
 
            return PartitionerForEachWorker(source, s_defaultParallelOptions, null, null, body, null, null, null, null);
        } 
 
        /// 
        /// Executes a for each operation on a  
        /// Partitioner in which iterations may run in parallel.
        /// 
        /// The type of the elements in .
        /// The type of the thread-local data. 
        /// The Partitioner that contains the original data source.
        /// The function delegate that returns the initial state of the local data 
        /// for each thread. 
        /// The delegate that is invoked once per iteration.
        /// The delegate that performs a final action on the local state of each 
        /// thread.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false.
        /// The exception that is thrown when any 
        /// methods in the  Partitioner return null.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner does not return 
        /// the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner returns an IList
        /// with at least one null value.
        /// The exception that is thrown when the
        /// GetDynamicPartitions() method in the  Partitioner returns an 
        /// IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// 
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's 
        /// index is desired, the source must be an 
        /// OrderablePartitioner. 
        ///  
        /// 
        /// The  delegate is invoked once for each element in the  
        /// Partitioner.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations
        /// that execute on the same thread. 
        /// 
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state.
        ///  
        /// 
        public static ParallelLoopResult ForEach( 
            Partitioner source, 
            Func localInit,
            Func body, 
            Action localFinally)
        {
            if (source == null)
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            { 
                throw new ArgumentNullException("localFinally");
            } 

            return PartitionerForEachWorker(source, s_defaultParallelOptions, null, null, null, body, null, localInit, localFinally);
        }
 
        /// 
        /// Executes a for each operation on a  
        /// OrderablePartitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in . 
        /// The type of the thread-local data.
        /// The OrderablePartitioner that contains the original data source.
        /// The function delegate that returns the initial state of the local data
        /// for each thread. 
        /// The delegate that is invoked once per iteration.
        /// The delegate that performs a final action on the local state of each 
        /// thread. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the 
        /// SupportsDynamicPartitions property in the  OrderablePartitioner returns
        /// false. 
        /// The exception that is thrown when the
        /// KeysNormalized property in the  OrderablePartitioner returns
        /// false.
        /// The exception that is thrown when any 
        /// methods in the  OrderablePartitioner return null.
        /// The exception that is thrown when the 
        /// GetPartitions() or GetOrderablePartitions() methods in the  
        /// OrderablePartitioner do not return the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() or GetOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IList with at least one null value.
        /// The exception that is thrown when the
        /// GetDynamicPartitions() or GetDynamicOrderablePartitions() methods in the  
        /// OrderablePartitioner return an IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        /// 
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's 
        /// index is desired, the source must be an 
        /// OrderablePartitioner. 
        ///  
        /// 
        /// The  delegate is invoked once for each element in the  
        /// Partitioner.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, the current element's index (an Int64), and some local
        /// state that may be shared amongst iterations that execute on the same thread. 
        /// 
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly 
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state.
        ///  
        /// 
        public static ParallelLoopResult ForEach( 
            OrderablePartitioner source, 
            Func localInit,
            Func body, 
            Action localFinally)
        {
            if (source == null)
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            { 
                throw new ArgumentNullException("localFinally");
            } 

            if (!source.KeysNormalized)
            {
                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_OrderedPartitionerKeysNotNormalized")); 
            }
 
            return PartitionerForEachWorker(source, s_defaultParallelOptions, null, null, null, null, body, localInit, localFinally); 
        }
 
        /// 
        /// Executes a for each operation on a 
        /// Partitioner in which iterations may run in parallel.
        ///  
        /// The type of the elements in .
        /// The Partitioner that contains the original data source. 
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set 
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false.
        /// The exception that is thrown when any 
        /// methods in the  Partitioner return null.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner does not return 
        /// the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner returns an IList
        /// with at least one null value.
        /// The exception that is thrown when the
        /// GetDynamicPartitions() method in the  Partitioner returns an 
        /// IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed.
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed. 
        /// 
        ///  
        /// The Partitioner is used to retrieve 
        /// the elements to be processed, in place of the original data source.  If the current element's
        /// index is desired, the source must be an  
        /// OrderablePartitioner.
        /// 
        /// 
        /// The  delegate is invoked once for each element in the  
        /// Partitioner.  It is provided with the current element as a parameter.
        ///  
        ///  
        public static ParallelLoopResult ForEach(
            Partitioner source, 
            ParallelOptions parallelOptions,
            Action body)
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            }
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions");
            } 
 
            return PartitionerForEachWorker(source, parallelOptions, body, null, null, null, null, null, null);
        } 

        /// 
        /// Executes a for each operation on a 
        /// Partitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in . 
        /// The Partitioner that contains the original data source. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The delegate that is invoked once per iteration.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the  
        /// argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the  
        /// argument is set
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false. 
        /// The exception that is thrown when any
        /// methods in the  Partitioner return null. 
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner does not return
        /// the correct number of partitions. 
        /// The exception that is thrown when the
        /// GetPartitions() method in the  Partitioner returns an IList
        /// with at least one null value.
        /// The exception that is thrown when the 
        /// GetDynamicPartitions() method in the  Partitioner returns an
        /// IEnumerable whose GetEnumerator() method returns null. 
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the
        /// the CancellationToken in the
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        ///  
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's 
        /// index is desired, the source must be an 
        /// OrderablePartitioner.
        /// 
        ///  
        /// The  delegate is invoked once for each element in the 
        /// Partitioner.  It is provided with the following parameters: the current element, 
        /// and a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely.
        ///  
        /// 
        public static ParallelLoopResult ForEach(
            Partitioner source,
            ParallelOptions parallelOptions, 
            Action body)
        { 
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            }
            if (body == null)
            {
                throw new ArgumentNullException("body"); 
            }
            if (parallelOptions == null) 
            { 
                throw new ArgumentNullException("parallelOptions");
            } 

            return PartitionerForEachWorker(source, parallelOptions, null, body, null, null, null, null, null);
        }
 
        /// 
        /// Executes a for each operation on a  
        /// OrderablePartitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in . 
        /// The OrderablePartitioner that contains the original data source.
        /// A ParallelOptions
        /// instance that configures the behavior of this operation.
        /// The delegate that is invoked once per iteration. 
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the
        /// CancellationToken in the 
        /// argument is set 
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  OrderablePartitioner returns 
        /// false. 
        /// The exception that is thrown when the
        /// KeysNormalized property in the  OrderablePartitioner returns 
        /// false.
        /// The exception that is thrown when any
        /// methods in the  OrderablePartitioner return null.
        /// The exception that is thrown when the 
        /// GetPartitions() or GetOrderablePartitions() methods in the 
        /// OrderablePartitioner do not return the correct number of partitions. 
        /// The exception that is thrown when the 
        /// GetPartitions() or GetOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IList with at least one null value. 
        /// The exception that is thrown when the
        /// GetDynamicPartitions() or GetDynamicOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception 
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the 
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure
        /// that contains information on what portion of the loop completed.
        /// 
        ///  
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's 
        /// index is desired, the source must be an  
        /// OrderablePartitioner.
        ///  
        /// 
        /// The  delegate is invoked once for each element in the 
        /// Partitioner.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be 
        /// used to break out of the loop prematurely, and the current element's index (an Int64).
        ///  
        ///  
        public static ParallelLoopResult ForEach(
            OrderablePartitioner source, 
            ParallelOptions parallelOptions,
            Action body)
        {
            if (source == null) 
            {
                throw new ArgumentNullException("source"); 
            } 
            if (body == null)
            { 
                throw new ArgumentNullException("body");
            }
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions");
            } 
 
            if (!source.KeysNormalized)
            { 
                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_OrderedPartitionerKeysNotNormalized"));
            }

            return PartitionerForEachWorker(source, parallelOptions, null, null, body, null, null, null, null); 
        }
 
        ///  
        /// Executes a for each operation on a 
        /// Partitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in .
        /// The type of the thread-local data.
        /// The Partitioner that contains the original data source. 
        /// A ParallelOptions
        /// instance that configures the behavior of this operation. 
        /// The function delegate that returns the initial state of the local data 
        /// for each thread.
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread.
        /// The exception that is thrown when the 
        /// argument is null. 
        /// The exception that is thrown when the
        ///  argument is null. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the
        ///  argument is null.
        /// The exception that is thrown when the 
        /// CancellationToken in the 
        /// argument is set 
        /// The exception that is thrown when the 
        /// SupportsDynamicPartitions property in the  Partitioner returns
        /// false. 
        /// The exception that is thrown when any
        /// methods in the  Partitioner return null.
        /// The exception that is thrown when the
        /// GetPartitions() method in the  Partitioner does not return 
        /// the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() method in the  Partitioner returns an IList 
        /// with at least one null value.
        /// The exception that is thrown when the 
        /// GetDynamicPartitions() method in the  Partitioner returns an
        /// IEnumerable whose GetEnumerator() method returns null.
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates. 
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the 
        ///  has been disposed.
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        /// 
        /// 
        /// The Partitioner is used to retrieve 
        /// the elements to be processed, in place of the original data source.  If the current element's
        /// index is desired, the source must be an  
        /// OrderablePartitioner. 
        /// 
        ///  
        /// The  delegate is invoked once for each element in the 
        /// Partitioner.  It is provided with the following parameters: the current element,
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, and some local state that may be shared amongst iterations 
        /// that execute on the same thread.
        ///  
        ///  
        /// The  delegate is invoked once for each thread that participates in the loop's
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first 
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state. 
        /// 
        ///  
        public static ParallelLoopResult ForEach( 
            Partitioner source,
            ParallelOptions parallelOptions, 
            Func localInit,
            Func body,
            Action localFinally)
        { 
            if (source == null)
            { 
                throw new ArgumentNullException("source"); 
            }
            if (body == null) 
            {
                throw new ArgumentNullException("body");
            }
            if (localInit == null) 
            {
                throw new ArgumentNullException("localInit"); 
            } 
            if (localFinally == null)
            { 
                throw new ArgumentNullException("localFinally");
            }
            if (parallelOptions == null)
            { 
                throw new ArgumentNullException("parallelOptions");
            } 
 
            return PartitionerForEachWorker(source, parallelOptions, null, null, null, body, null, localInit, localFinally);
        } 

        /// 
        /// Executes a for each operation on a 
        /// OrderablePartitioner in which iterations may run in parallel. 
        /// 
        /// The type of the elements in . 
        /// The type of the thread-local data. 
        /// The OrderablePartitioner that contains the original data source.
        /// A ParallelOptions 
        /// instance that configures the behavior of this operation.
        /// The function delegate that returns the initial state of the local data
        /// for each thread.
        /// The delegate that is invoked once per iteration. 
        /// The delegate that performs a final action on the local state of each
        /// thread. 
        /// The exception that is thrown when the  
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        /// argument is null.
        /// The exception that is thrown when the 
        ///  argument is null.
        /// The exception that is thrown when the 
        ///  argument is null. 
        /// The exception that is thrown when the
        /// CancellationToken in the  
        /// argument is set
        /// The exception that is thrown when the
        /// SupportsDynamicPartitions property in the  OrderablePartitioner returns
        /// false. 
        /// The exception that is thrown when the
        /// KeysNormalized property in the  OrderablePartitioner returns 
        /// false. 
        /// The exception that is thrown when any
        /// methods in the  OrderablePartitioner return null. 
        /// The exception that is thrown when the
        /// GetPartitions() or GetOrderablePartitions() methods in the 
        /// OrderablePartitioner do not return the correct number of partitions.
        /// The exception that is thrown when the 
        /// GetPartitions() or GetOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IList with at least one null value. 
        /// The exception that is thrown when the 
        /// GetDynamicPartitions() or GetDynamicOrderablePartitions() methods in the 
        /// OrderablePartitioner return an IEnumerable whose GetEnumerator() method returns null. 
        /// The exception that is thrown to contain an exception
        /// thrown from one of the specified delegates.
        /// The exception that is thrown when the
        /// the CancellationTokenSource associated with the 
        /// the CancellationToken in the
        ///  has been disposed. 
        /// A ParallelLoopResult structure 
        /// that contains information on what portion of the loop completed.
        ///  
        /// 
        /// The Partitioner is used to retrieve
        /// the elements to be processed, in place of the original data source.  If the current element's
        /// index is desired, the source must be an  
        /// OrderablePartitioner.
        ///  
        ///  
        /// The  delegate is invoked once for each element in the 
        /// Partitioner.  It is provided with the following parameters: the current element, 
        /// a ParallelLoopState instance that may be
        /// used to break out of the loop prematurely, the current element's index (an Int64), and some local
        /// state that may be shared amongst iterations that execute on the same thread.
        ///  
        /// 
        /// The  delegate is invoked once for each thread that participates in the loop's 
        /// execution and returns the initial local state for each of those threads.  These initial states are passed to the first 
        ///  invocations on each thread.  Then, every subsequent body invocation returns a possibly
        /// modified state value that is passed to the next body invocation.  Finally, the last body invocation on each thread returns a state value 
        /// that is passed to the  delegate.  The localFinally delegate is invoked once per thread to perform a final
        /// action on each thread's local state.
        /// 
        ///  
        public static ParallelLoopResult ForEach(
            OrderablePartitioner source, 
            ParallelOptions parallelOptions, 
            Func localInit,
            Func body, 
            Action localFinally)
        {
            if (source == null)
            { 
                throw new ArgumentNullException("source");
            } 
            if (body == null) 
            {
                throw new ArgumentNullException("body"); 
            }
            if (localInit == null)
            {
                throw new ArgumentNullException("localInit"); 
            }
            if (localFinally == null) 
            { 
                throw new ArgumentNullException("localFinally");
            } 
            if (parallelOptions == null)
            {
                throw new ArgumentNullException("parallelOptions");
            } 

            if (!source.KeysNormalized) 
            { 
                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_OrderedPartitionerKeysNotNormalized"));
            } 

            return PartitionerForEachWorker(source, parallelOptions, null, null, null, null, body, localInit, localFinally);
        }
 
        // Main worker method for Parallel.ForEach() calls w/ Partitioners.
        private static ParallelLoopResult PartitionerForEachWorker( 
            Partitioner source, // Might be OrderablePartitioner 
            ParallelOptions parallelOptions,
            Action simpleBody, 
            Action bodyWithState,
            Action bodyWithStateAndIndex,
            Func bodyWithStateAndLocal,
            Func bodyWithEverything, 
            Func localInit,
            Action localFinally) 
        { 
            Contract.Assert(((simpleBody == null ? 0 : 1) + (bodyWithState == null ? 0 : 1) +
                (bodyWithStateAndIndex == null ? 0 : 1) + (bodyWithStateAndLocal == null ? 0 : 1) + (bodyWithEverything == null ? 0 : 1)) == 1, 
                "PartitionForEach: expected exactly one body function to be supplied");
            Contract.Assert((bodyWithStateAndLocal != null) || (bodyWithEverything != null) || (localInit == null && localFinally == null),
                "PartitionForEach: thread local functions should only be supplied for loops w/ thread local bodies");
 
            OrderablePartitioner orderedSource = source as OrderablePartitioner;
            Contract.Assert((orderedSource != null) || (bodyWithStateAndIndex == null && bodyWithEverything == null), 
                "PartitionForEach: bodies with indices are only allowable for OrderablePartitioner"); 

            if (!source.SupportsDynamicPartitions) 
            {
                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_PartitionerNotDynamic"));
            }
 
            // Before getting started, do a quick peek to see if we have been canceled already
            if (parallelOptions.CancellationToken.IsCancellationRequested) 
            { 
                throw new OperationCanceledException(parallelOptions.CancellationToken);
            } 

#if !FEATURE_PAL    // PAL doesn't support  eventing
            // ETW event for Parallel For begin
            int forkJoinContextID = 0; 
            Task callerTask = null;
            if (TplEtwProvider.Log.IsEnabled()) 
            { 
                forkJoinContextID = Interlocked.Increment(ref s_forkJoinContextID);
                callerTask = Task.InternalCurrent; 
                TplEtwProvider.Log.ParallelLoopBegin((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0),
                                                     forkJoinContextID, TplEtwProvider.ForkJoinOperationType.ParallelForEach,
                                                     0, 0);
            } 
#endif
 
            // For all loops we need a shared flag even though we don't have a body with state, 
            // because the shared flag contains the exceptional bool, which triggers other workers
            // to exit their loops if one worker catches an exception 
            ParallelLoopStateFlags64 sharedPStateFlags = new ParallelLoopStateFlags64();

            // Instantiate our result.  Specifics will be filled in later.
            ParallelLoopResult result = new ParallelLoopResult(); 

            // Keep track of any cancellations 
            OperationCanceledException oce = null; 

            CancellationTokenRegistration ctr = new CancellationTokenRegistration(); 

            // if cancellation is enabled, we need to register a callback to stop the loop when it gets signaled
            if (parallelOptions.CancellationToken.CanBeCanceled)
            { 
                ctr = parallelOptions.CancellationToken.InternalRegisterWithoutEC((o) =>
                { 
                    // Cause processing to stop 
                    sharedPStateFlags.Cancel();
                    // Record our cancellation 
                    oce = new OperationCanceledException(parallelOptions.CancellationToken);
                }, null);
            }
 
            // Get our dynamic partitioner -- depends on whether source is castable to OrderablePartitioner
            // Also, do some error checking. 
            IEnumerable partitionerSource = null; 
            IEnumerable> orderablePartitionerSource = null;
            if (orderedSource != null) 
            {
                orderablePartitionerSource = orderedSource.GetOrderableDynamicPartitions();
                if (orderablePartitionerSource == null)
                { 
                    throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_PartitionerReturnedNull"));
                } 
            } 
            else
            { 
                partitionerSource = source.GetDynamicPartitions();
                if (partitionerSource == null)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_PartitionerReturnedNull")); 
                }
            } 
 
            ParallelForReplicatingTask rootTask = null;
 
            // This is the action that will be run by each replicable task.
            Action partitionAction = delegate
            {
                Task currentWorkerTask = Task.InternalCurrent; 

#if !FEATURE_PAL    // PAL doesn't support  eventing 
                // ETW event for ParallelForEach Worker Fork 
                if (TplEtwProvider.Log.IsEnabled())
                { 
                    TplEtwProvider.Log.ParallelFork((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                    forkJoinContextID);
                }
#endif 

                TLocal localValue = default(TLocal); 
                bool bLocalValueInitialized = false; // Tracks whether localInit ran without exceptions, so that we can skip localFinally if it wasn't 

                try 
                {
                    // Create a new state object that references the shared "stopped" and "exceptional" flags.
                    // If needed, it will contain a new instance of thread-local state by invoking the selector.
                    ParallelLoopState64 state = null; 

                    if (bodyWithState != null || bodyWithStateAndIndex != null) 
                    { 
                        state = new ParallelLoopState64(sharedPStateFlags);
                    } 
                    else if (bodyWithStateAndLocal != null || bodyWithEverything != null)
                    {
                        state = new ParallelLoopState64(sharedPStateFlags);
                        // If a thread-local selector was supplied, invoke it. Otherwise, stick with the default. 
                        if (localInit != null)
                        { 
                            localValue = localInit(); 
                            bLocalValueInitialized = true;
                        } 
                    }


                    bool bIsRootTask = (rootTask == currentWorkerTask); 

                    // initialize a loop timer which will help us decide whether we should exit early 
                    LoopTimer loopTimer = new LoopTimer(rootTask.ActiveChildCount); 

                    if (orderedSource != null) 
                    {
                        // Use this path for OrderablePartitioner

 
                        // first check if there's saved state from a previous replica that we might be replacing.
                        // the only state to be passed down in such a transition is the enumerator 
                        IEnumerator> myPartition = currentWorkerTask.SavedStateFromPreviousReplica as IEnumerator>; 
                        if (myPartition == null)
                        { 
                            // apparently we're a brand new replica, get a fresh enumerator from the partitioner
                            myPartition = orderablePartitionerSource.GetEnumerator();
                            if (myPartition == null)
                            { 
                                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_NullEnumerator"));
                            } 
                        } 

                        while (myPartition.MoveNext()) 
                        {
                            KeyValuePair kvp = myPartition.Current;
                            long index = kvp.Key;
                            TSource value = kvp.Value; 

                            // Update our iteration index 
                            if (state != null) state.CurrentIteration = index; 

                            if (simpleBody != null) 
                                simpleBody(value);
                            else if (bodyWithState != null)
                                bodyWithState(value, state);
                            else if (bodyWithStateAndIndex != null) 
                                bodyWithStateAndIndex(value, state, index);
                            else if (bodyWithStateAndLocal != null) 
                                localValue = bodyWithStateAndLocal(value, state, localValue); 
                            else
                                localValue = bodyWithEverything(value, state, index, localValue); 

                            if (sharedPStateFlags.ShouldExitLoop(index)) break;

                            // Cooperative multitasking hack for AppDomain fairness. 
                            // Check if allowed loop time is exceeded, if so save current state and return. The self replicating task logic
                            // will detect this, and queue up a replacement task. Note that we don't do this on the root task. 
                            if (!bIsRootTask && loopTimer.LimitExceeded()) 
                            {
                                currentWorkerTask.SavedStateForNextReplica = myPartition; 
                                break;
                            }
                        }
                    } 
                    else
                    { 
                        // Use this path for Partitioner that is not OrderablePartitioner 

                        // first check if there's saved state from a previous replica that we might be replacing. 
                        // the only state to be passed down in such a transition is the enumerator
                        IEnumerator myPartition = currentWorkerTask.SavedStateFromPreviousReplica as IEnumerator;
                        if (myPartition == null)
                        { 
                            // apparently we're a brand new replica, get a fresh enumerator from the partitioner
                            myPartition = partitionerSource.GetEnumerator(); 
                            if (myPartition == null) 
                            {
                                throw new InvalidOperationException(Environment.GetResourceString("Parallel_ForEach_NullEnumerator")); 
                            }
                        }

                        // I'm not going to try to maintain this 
                        if (state != null)
                            state.CurrentIteration = 0; 
 
                        while (myPartition.MoveNext())
                        { 
                            TSource t = myPartition.Current;

                            if (simpleBody != null)
                                simpleBody(t); 
                            else if (bodyWithState != null)
                                bodyWithState(t, state); 
                            else if (bodyWithStateAndLocal != null) 
                                localValue = bodyWithStateAndLocal(t, state, localValue);
                            else 
                                Contract.Assert(false, "PartitionerForEach: illegal body type in Partitioner handler");


                            // Any break, stop or exception causes us to halt 
                            // We don't have the global indexing information to discriminate whether or not
                            // we are before or after a break point. 
                            if (sharedPStateFlags.LoopStateFlags != ParallelLoopStateFlags.PLS_NONE) 
                                break;
 
                            // Cooperative multitasking hack for AppDomain fairness.
                            // Check if allowed loop time is exceeded, if so save current state and return. The self replicating task logic
                            // will detect this, and queue up a replacement task. Note that we don't do this on the root task.
                            if (!bIsRootTask && loopTimer.LimitExceeded()) 
                            {
                                currentWorkerTask.SavedStateForNextReplica = myPartition; 
                                break; 
                            }
                        } 
                    }
                }
                catch
                { 
                    // Inform other tasks of the exception, then rethrow
                    sharedPStateFlags.SetExceptional(); 
                    throw; 
                }
                finally 
                {
                    if (localFinally != null && bLocalValueInitialized)
                    {
                        localFinally(localValue); 
                    }
 
#if !FEATURE_PAL    // PAL doesn't support  eventing 
                    // ETW event for ParallelFor Worker Join
                    if (TplEtwProvider.Log.IsEnabled()) 
                    {
                        TplEtwProvider.Log.ParallelJoin((currentWorkerTask != null ? currentWorkerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (currentWorkerTask != null ? currentWorkerTask.Id : 0),
                                                         forkJoinContextID);
                    } 
#endif
                } 
            }; 

            try 
            {
                // Create and start the self-replicating task.
                // This needs to be in try-block because it can throw in BuggyScheduler.MaxConcurrencyLevel
                rootTask = new ParallelForReplicatingTask(parallelOptions, partitionAction, TaskCreationOptions.None, 
                                                          InternalTaskOptions.SelfReplicating);
 
                // And process it's completion... 
                // Moved inside try{} block because faulty scheduler may throw here.
                rootTask.RunSynchronously(parallelOptions.EffectiveTaskScheduler); 

                rootTask.Wait();

                // If we made a cancellation registration, we need to clean it up now before observing the OCE 
                // Otherwise we could be caught in the middle of a callback, and observe PLS_STOPPED, but oce = null
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                { 
                    ctr.Dispose();
                } 

                // If we got through that with no exceptions, and we were canceled, then
                // throw our cancellation exception
                if (oce != null) throw oce; 
            }
            catch (AggregateException aggExp) 
            { 
                // if we made a cancellation registration, and rootTask.Wait threw, we need to clean it up here
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                {
                    ctr.Dispose();
                }
 
                // see if we can combine it into a single OCE. If not propagate the original exception
                ThrowIfReducableToSingleOCE(aggExp.InnerExceptions, parallelOptions.CancellationToken); 
                throw; 
            }
            catch (TaskSchedulerException) 
            {
                // if we made a cancellation registration, and either we threw an exception constructing rootTask or
                // rootTask.RunSynchronously threw, we need to clean it up here.
                if (parallelOptions.CancellationToken.CanBeCanceled) 
                {
                    ctr.Dispose(); 
                } 
                throw;
            } 
            finally
            {
                int sb_status = sharedPStateFlags.LoopStateFlags;
                result.m_completed = (sb_status == ParallelLoopStateFlags.PLS_NONE); 
                if ((sb_status & ParallelLoopStateFlags.PLS_BROKEN) != 0)
                { 
                    result.m_lowestBreakIteration = sharedPStateFlags.LowestBreakIteration; 
                }
 
                if( (rootTask != null) && rootTask.IsCompleted) rootTask.Dispose();

                //dispose the partitioner source if it implements IDisposable
                IDisposable d = null; 
                if (orderablePartitionerSource != null)
                { 
                    d = orderablePartitionerSource as IDisposable; 
                }
                else 
                {
                    d = partitionerSource as IDisposable;
                }
 
                if (d != null)
                { 
                    d.Dispose(); 
                }
 

#if !FEATURE_PAL    // PAL doesn't support  eventing
                // ETW event for Parallel For End
                if (TplEtwProvider.Log.IsEnabled()) 
                {
                    TplEtwProvider.Log.ParallelLoopEnd((callerTask != null ? callerTask.m_taskScheduler.Id : TaskScheduler.Current.Id), (callerTask != null ? callerTask.Id : 0), 
                                                         forkJoinContextID, 0); 
                }
#endif 
            }

            return result;
        } 

        ///  
        /// Internal utility function that implements the OCE filtering behavior for all Parallel.* APIs. 
        /// Throws a single OperationCancelledException object with the token if the Exception collection only contains
        /// OperationCancelledExceptions with the given CancellationToken. 
        ///
        /// 
        ///  The exception collection to filter
        ///  The CancellationToken expected on all inner exceptions 
        /// 
        internal static void ThrowIfReducableToSingleOCE(IEnumerable excCollection, CancellationToken ct) 
        { 
            bool bCollectionNotZeroLength = false;
            if (ct.IsCancellationRequested) 
            {
                foreach(Exception e in excCollection)
                {
                    bCollectionNotZeroLength = true; 
                    OperationCanceledException oce = e as OperationCanceledException;
                    if (oce == null || oce.CancellationToken != ct) 
                    { 
                        // mismatch found
                        return; 
                    }
                }

                // all exceptions are OCEs with this token, let's throw it 
                if(bCollectionNotZeroLength) throw new OperationCanceledException(ct);
            } 
        } 

        internal struct LoopTimer 
        {
            public LoopTimer(int nWorkerTaskIndex)
            {
                // This logic ensures that we have a diversity of timeouts across worker tasks (100, 150, 200, 250, 100, etc) 
                // Otherwise all worker will try to timeout at precisely the same point, which is bad if the work is just about to finish
                int timeOut = s_BaseNotifyPeriodMS + (nWorkerTaskIndex % Environment.ProcessorCount) * s_NotifyPeriodIncrementMS; 
 
                m_timeLimit = Environment.TickCount + timeOut;
            } 

            public bool LimitExceeded()
            {
                Contract.Assert(m_timeLimit != 0, "Probably the default initializer for LoopTimer was used somewhere"); 

                // comparing against the next expected time saves an addition operation here 
                // Also we omit the comparison for wrap around here. The only side effect is one extra early yield every 38 days. 
                return (Environment.TickCount > m_timeLimit);
            } 

            const int s_BaseNotifyPeriodMS = 100;
            const int s_NotifyPeriodIncrementMS = 50;
 
            private int m_timeLimit;
        } 
 
    }
 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

                        

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