Parallel.For 方法

定义

执行 for 循环,其中可能会并行运行迭代。

重载

For(Int32, Int32, Action<Int32,ParallelLoopState>)

执行 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

For(Int32, Int32, Action<Int32>)

执行 for 循环,其中可能会并行运行迭代。

For(Int64, Int64, Action<Int64,ParallelLoopState>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

For(Int64, Int64, Action<Int64>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

For(Int32, Int32, ParallelOptions, Action<Int32,ParallelLoopState>)

执行 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

For(Int32, Int32, ParallelOptions, Action<Int32>)

执行 for 循环,其中可能会并行运行迭代,而且可以配置循环选项。

For(Int64, Int64, ParallelOptions, Action<Int64,ParallelLoopState>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

For(Int64, Int64, ParallelOptions, Action<Int64>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项。

For<TLocal>(Int64, Int64, ParallelOptions, Func<TLocal>, Func<Int64,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有 64 位索引和线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

For<TLocal>(Int32, Int32, ParallelOptions, Func<TLocal>, Func<Int32,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

For<TLocal>(Int32, Int32, Func<TLocal>, Func<Int32,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

For<TLocal>(Int64, Int64, Func<TLocal>, Func<Int64,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有 64 位索引和线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

For(Int32, Int32, Action<Int32,ParallelLoopState>)

执行 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

public:
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, Action<int, System::Threading::Tasks::ParallelLoopState ^> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (int fromInclusive, int toExclusive, Action<int,System.Threading.Tasks.ParallelLoopState> body);
static member For : int * int * Action<int, System.Threading.Tasks.ParallelLoopState> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Integer, toExclusive As Integer, body As Action(Of Integer, ParallelLoopState)) As ParallelLoopResult

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

body
Action<Int32,ParallelLoopState>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

包含在所有线程上引发的全部单个异常的异常。

示例

以下示例并行执行循环的最多 100 次迭代。 每次迭代将随机间隔从 1 到 1,000 毫秒暂停。 随机生成的值确定调用该方法的循环 ParallelLoopState.Break 的迭代。 如示例中的输出所示,其索引大于 ParallelLoopState.LowestBreakIteration 属性值的迭代在调用 ParallelLoopState.Break 方法后开始。

using System;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
    public static void Main()
    {
        var rnd = new Random();
        int breakIndex = rnd.Next(1, 11);

        Console.WriteLine($"Will call Break at iteration {breakIndex}\n");

        var result = Parallel.For(1, 101, (i, state) => 
        {
            Console.WriteLine($"Beginning iteration {i}");
            int delay;
            lock (rnd)
                delay = rnd.Next(1, 1001);
            Thread.Sleep(delay);

            if (state.ShouldExitCurrentIteration)
            {
                if (state.LowestBreakIteration < i)
                    return;
            }

            if (i == breakIndex)
            {
                Console.WriteLine($"Break in iteration {i}");
                state.Break();
            }

            Console.WriteLine($"Completed iteration {i}");
        });

        if (result.LowestBreakIteration.HasValue)
            Console.WriteLine($"\nLowest Break Iteration: {result.LowestBreakIteration}");
        else
            Console.WriteLine($"\nNo lowest break iteration.");
    }
}
// The example displays output like the following:
//       Will call Break at iteration 8
//
//       Beginning iteration 1
//       Beginning iteration 13
//       Beginning iteration 97
//       Beginning iteration 25
//       Beginning iteration 49
//       Beginning iteration 37
//       Beginning iteration 85
//       Beginning iteration 73
//       Beginning iteration 61
//       Completed iteration 85
//       Beginning iteration 86
//       Completed iteration 61
//       Beginning iteration 62
//       Completed iteration 86
//       Beginning iteration 87
//       Completed iteration 37
//       Beginning iteration 38
//       Completed iteration 38
//       Beginning iteration 39
//       Completed iteration 25
//       Beginning iteration 26
//       Completed iteration 26
//       Beginning iteration 27
//       Completed iteration 73
//       Beginning iteration 74
//       Completed iteration 62
//       Beginning iteration 63
//       Completed iteration 39
//       Beginning iteration 40
//       Completed iteration 40
//       Beginning iteration 41
//       Completed iteration 13
//       Beginning iteration 14
//       Completed iteration 1
//       Beginning iteration 2
//       Completed iteration 97
//       Beginning iteration 98
//       Completed iteration 49
//       Beginning iteration 50
//       Completed iteration 87
//       Completed iteration 27
//       Beginning iteration 28
//       Completed iteration 50
//       Beginning iteration 51
//       Beginning iteration 88
//       Completed iteration 14
//       Beginning iteration 15
//       Completed iteration 15
//       Completed iteration 2
//       Beginning iteration 3
//       Beginning iteration 16
//       Completed iteration 63
//       Beginning iteration 64
//       Completed iteration 74
//       Beginning iteration 75
//       Completed iteration 41
//       Beginning iteration 42
//       Completed iteration 28
//       Beginning iteration 29
//       Completed iteration 29
//       Beginning iteration 30
//       Completed iteration 98
//       Beginning iteration 99
//       Completed iteration 64
//       Beginning iteration 65
//       Completed iteration 42
//       Beginning iteration 43
//       Completed iteration 88
//       Beginning iteration 89
//       Completed iteration 51
//       Beginning iteration 52
//       Completed iteration 16
//       Beginning iteration 17
//       Completed iteration 43
//       Beginning iteration 44
//       Completed iteration 44
//       Beginning iteration 45
//       Completed iteration 99
//       Beginning iteration 4
//       Completed iteration 3
//       Beginning iteration 8
//       Completed iteration 4
//       Beginning iteration 5
//       Completed iteration 52
//       Beginning iteration 53
//       Completed iteration 75
//       Beginning iteration 76
//       Completed iteration 76
//       Beginning iteration 77
//       Completed iteration 65
//       Beginning iteration 66
//       Completed iteration 5
//       Beginning iteration 6
//       Completed iteration 89
//       Beginning iteration 90
//       Completed iteration 30
//       Beginning iteration 31
//       Break in iteration 8
//       Completed iteration 8
//       Completed iteration 6
//       Beginning iteration 7
//       Completed iteration 7
//
//       Lowest Break Iteration: 8
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim breakIndex As Integer = rnd.Next(1, 11)
      Dim lowest As New Nullable(Of Long)()

      Console.WriteLine("Will call Break at iteration {0}", breakIndex)
      Console.WriteLine()

      Dim result = Parallel.For(1, 101, Sub(i, state)
                                            Console.WriteLine("Beginning iteration {0}", i)
                                            Dim delay As Integer
                                            Monitor.Enter(rnd)
                                               delay = rnd.Next(1, 1001)
                                            Monitor.Exit(rnd)
                                            Thread.Sleep(delay)

                                            If state.ShouldExitCurrentIteration Then
                                               If state.LowestBreakIteration < i Then
                                                  Return
                                               End If
                                            End If

                                            If i = breakIndex Then
                                               Console.WriteLine("Break in iteration {0}", i)
                                               state.Break()
                                               If state.LowestBreakIteration.HasValue Then
                                                  If lowest < state.LowestBreakIteration Then
                                                     lowest = state.LowestBreakIteration
                                                  Else
                                                     lowest = state.LowestBreakIteration
                                                  End If
                                               End If
                                            End If

                                            Console.WriteLine("Completed iteration {0}", i)
                                       End Sub )
         Console.WriteLine()
         If lowest.HasValue Then
            Console.WriteLine("Lowest Break Iteration: {0}", lowest)
         Else
            Console.WriteLine("No lowest break iteration.")
         End If
   End Sub
End Module
' The example displays output like the following:
'       Will call Break at iteration 8
'
'       Beginning iteration 1
'       Beginning iteration 13
'       Beginning iteration 97
'       Beginning iteration 25
'       Beginning iteration 49
'       Beginning iteration 37
'       Beginning iteration 85
'       Beginning iteration 73
'       Beginning iteration 61
'       Completed iteration 85
'       Beginning iteration 86
'       Completed iteration 61
'       Beginning iteration 62
'       Completed iteration 86
'       Beginning iteration 87
'       Completed iteration 37
'       Beginning iteration 38
'       Completed iteration 38
'       Beginning iteration 39
'       Completed iteration 25
'       Beginning iteration 26
'       Completed iteration 26
'       Beginning iteration 27
'       Completed iteration 73
'       Beginning iteration 74
'       Completed iteration 62
'       Beginning iteration 63
'       Completed iteration 39
'       Beginning iteration 40
'       Completed iteration 40
'       Beginning iteration 41
'       Completed iteration 13
'       Beginning iteration 14
'       Completed iteration 1
'       Beginning iteration 2
'       Completed iteration 97
'       Beginning iteration 98
'       Completed iteration 49
'       Beginning iteration 50
'       Completed iteration 87
'       Completed iteration 27
'       Beginning iteration 28
'       Completed iteration 50
'       Beginning iteration 51
'       Beginning iteration 88
'       Completed iteration 14
'       Beginning iteration 15
'       Completed iteration 15
'       Completed iteration 2
'       Beginning iteration 3
'       Beginning iteration 16
'       Completed iteration 63
'       Beginning iteration 64
'       Completed iteration 74
'       Beginning iteration 75
'       Completed iteration 41
'       Beginning iteration 42
'       Completed iteration 28
'       Beginning iteration 29
'       Completed iteration 29
'       Beginning iteration 30
'       Completed iteration 98
'       Beginning iteration 99
'       Completed iteration 64
'       Beginning iteration 65
'       Completed iteration 42
'       Beginning iteration 43
'       Completed iteration 88
'       Beginning iteration 89
'       Completed iteration 51
'       Beginning iteration 52
'       Completed iteration 16
'       Beginning iteration 17
'       Completed iteration 43
'       Beginning iteration 44
'       Completed iteration 44
'       Beginning iteration 45
'       Completed iteration 99
'       Beginning iteration 4
'       Completed iteration 3
'       Beginning iteration 8
'       Completed iteration 4
'       Beginning iteration 5
'       Completed iteration 52
'       Beginning iteration 53
'       Completed iteration 75
'       Beginning iteration 76
'       Completed iteration 76
'       Beginning iteration 77
'       Completed iteration 65
'       Beginning iteration 66
'       Completed iteration 5
'       Beginning iteration 6
'       Completed iteration 89
'       Beginning iteration 90
'       Completed iteration 30
'       Beginning iteration 31
'       Break in iteration 8
'       Completed iteration 8
'       Completed iteration 6
'       Beginning iteration 7
'       Completed iteration 7
'
'       Lowest Break Iteration: 8

由于调用该方法时 ParallelLoopState.Break 循环迭代仍可能执行,因此每次迭代都会调用 ParallelLoopState.ShouldExitCurrentIteration 该属性来检查另一次迭代是否调用 ParallelLoopState.Break 了该方法。 如果属性值为 true,迭代将检查属性的值 ParallelLoopState.LowestBreakIteration ,如果该值大于当前迭代的索引值,则立即返回。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供两个参数:

Break调用该方法会for通知操作,即在当前迭代之后,无需执行迭代。 但是,如果当前迭代尚未执行,则仍需执行当前迭代之前的所有迭代。

因此,调用 Break 类似于在 C# 等语言中使用传统 for 循环中的中断操作,但它不是完美的替代方法:例如,无法保证当前循环之后的迭代绝对不会执行。

如果在不需要当前迭代之前执行所有迭代,请使用 Stop 该方法而不是使用 Break。 调用 Stopfor 通知循环,它可能会放弃所有剩余迭代,无论它们是在当前迭代之前还是之后,因为所有必需的工作都已完成。 但是,与上一 Break样,无法保证其他迭代不会执行。

如果循环过早结束, ParallelLoopResult 则返回的结构将包含有关循环完成的相关信息。

如果 fromInclusive 大于或等于 toExclusive,该方法将立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int32, Int32, Action<Int32>)

执行 for 循环,其中可能会并行运行迭代。

public:
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, Action<int> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (int fromInclusive, int toExclusive, Action<int> body);
static member For : int * int * Action<int> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Integer, toExclusive As Integer, body As Action(Of Integer)) As ParallelLoopResult

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

body
Action<Int32>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

包含在所有线程上引发的全部单个异常的异常。

示例

以下示例使用 For 方法调用生成随机字节值的委托的 100 次调用,并计算其总和。

using System;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      ParallelLoopResult result = Parallel.For(0, 100, ctr => { Random rnd = new Random(ctr * 100000);
                                                                Byte[] bytes = new Byte[100];
                                                                rnd.NextBytes(bytes);
                                                                int sum = 0;
                                                                foreach(var byt in bytes)
                                                                    sum += byt;
                                                                Console.WriteLine("Iteration {0,2}: {1:N0}", ctr, sum);
                                                              });
      Console.WriteLine("Result: {0}", result.IsCompleted ? "Completed Normally" : 
                                                             String.Format("Completed to {0}", result.LowestBreakIteration));
   }
}
// The following is a portion of the output displayed by the example:
//       Iteration  0: 12,509
//       Iteration 50: 12,823
//       Iteration 51: 11,275
//       Iteration 52: 12,531
//       Iteration  1: 13,007
//       Iteration 53: 13,799
//       Iteration  4: 12,945
//       Iteration  2: 13,246
//       Iteration 54: 13,008
//       Iteration 55: 12,727
//       Iteration 56: 13,223
//       Iteration 57: 13,717
//       Iteration  5: 12,679
//       Iteration  3: 12,455
//       Iteration 58: 12,669
//       Iteration 59: 11,882
//       Iteration  6: 13,167
//       ...
//       Iteration 92: 12,275
//       Iteration 93: 13,282
//       Iteration 94: 12,745
//       Iteration 95: 11,957
//       Iteration 96: 12,455
//       Result: Completed Normally
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      Dim result As ParallelLoopResult = Parallel.For(0, 100, Sub(ctr)
                                                                 Dim rnd As New Random(ctr * 100000)
                                                                 Dim bytes(99) As Byte
                                                                 rnd.NextBytes(bytes)
                                                                 Dim sum As Integer
                                                                 For Each byt In bytes
                                                                    sum += byt
                                                                 Next
                                                                 Console.WriteLine("Iteration {0,2}: {1:N0}", ctr, sum)
                                                              End Sub)
      Console.WriteLine("Result: {0}", If(result.IsCompleted, "Completed Normally", 
                                                             String.Format("Completed to {0}", result.LowestBreakIteration)))
   End Sub
End Module
' The following is a portion of the output displayed by the example:
'       Iteration  0: 12,509
'       Iteration 50: 12,823
'       Iteration 51: 11,275
'       Iteration 52: 12,531
'       Iteration  1: 13,007
'       Iteration 53: 13,799
'       Iteration  4: 12,945
'       Iteration  2: 13,246
'       Iteration 54: 13,008
'       Iteration 55: 12,727
'       Iteration 56: 13,223
'       Iteration 57: 13,717
'       Iteration  5: 12,679
'       Iteration  3: 12,455
'       Iteration 58: 12,669
'       Iteration 59: 11,882
'       Iteration  6: 13,167
'       ...
'       Iteration 92: 12,275
'       Iteration 93: 13,282
'       Iteration 94: 12,745
'       Iteration 95: 11,957
'       Iteration 96: 12,455
'       Result: Completed Normally

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它以参数的形式 Int32 提供迭代计数 () 。

如果 fromInclusive 大于或等于 toExclusive,该方法将立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int64, Int64, Action<Int64,ParallelLoopState>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

public:
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, Action<long, System::Threading::Tasks::ParallelLoopState ^> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (long fromInclusive, long toExclusive, Action<long,System.Threading.Tasks.ParallelLoopState> body);
static member For : int64 * int64 * Action<int64, System.Threading.Tasks.ParallelLoopState> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Long, toExclusive As Long, body As Action(Of Long, ParallelLoopState)) As ParallelLoopResult

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

body
Action<Int64,ParallelLoopState>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

一个 ParallelLoopResult 结构,其中包含有关已完成的循环部分的信息。

例外

body 参数为 null

包含在所有线程上引发的全部单个异常的异常。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int64) ,以及 ParallelLoopState 可用于过早中断循环的实例。

Break调用该方法会for通知操作,即当前迭代之后不必执行迭代,而是当前迭代之前的所有迭代。

因此,调用 Break 类似于在 C# 等语言中使用传统 for 循环中的中断操作,但它不是完美的替代项:例如,无法保证当前循环之后的迭代绝对不会执行。

如果在不需要当前迭代之前执行所有迭代,请使用 Stop 该方法而不是使用 Break。 调用 Stopfor 通知循环,它可能会放弃所有剩余迭代,无论它们是在当前迭代之前还是之后,因为所有必需的工作都已完成。 但是,与上一 Break样,无法保证其他迭代不会执行。

如果循环过早结束, ParallelLoopResult 则返回的结构将包含有关循环完成的相关信息。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int64, Int64, Action<Int64>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

public:
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, Action<long> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (long fromInclusive, long toExclusive, Action<long> body);
static member For : int64 * int64 * Action<int64> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Long, toExclusive As Long, body As Action(Of Long)) As ParallelLoopResult

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

body
Action<Int64>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

包含在所有线程上引发的全部单个异常的异常。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它以参数的形式 Int64 提供迭代计数 () 。

如果 fromInclusive 大于或等于 toExclusive,该方法将立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int32, Int32, ParallelOptions, Action<Int32,ParallelLoopState>)

执行 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

public:
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Action<int, System::Threading::Tasks::ParallelLoopState ^> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (int fromInclusive, int toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Action<int,System.Threading.Tasks.ParallelLoopState> body);
static member For : int * int * System.Threading.Tasks.ParallelOptions * Action<int, System.Threading.Tasks.ParallelLoopState> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Integer, toExclusive As Integer, parallelOptions As ParallelOptions, body As Action(Of Integer, ParallelLoopState)) As ParallelLoopResult

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

body
Action<Int32,ParallelLoopState>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

parallelOptions 取消的 CancellationToken 参数。

body 参数为 null

  • 或 - parallelOptions 参数为 null

包含在所有线程上引发的全部单个异常的异常。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int32) ,以及 ParallelLoopState 可用于过早中断循环的实例。

如果 fromInclusive 大于或等于 toExclusive,该方法将立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int32, Int32, ParallelOptions, Action<Int32>)

执行 for 循环,其中可能会并行运行迭代,而且可以配置循环选项。

public:
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Action<int> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (int fromInclusive, int toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Action<int> body);
static member For : int * int * System.Threading.Tasks.ParallelOptions * Action<int> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Integer, toExclusive As Integer, parallelOptions As ParallelOptions, body As Action(Of Integer)) As ParallelLoopResult

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

body
Action<Int32>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

parallelOptions 取消的 CancellationToken 参数。

body 参数为 null

  • 或 - parallelOptions 参数为 null

包含在所有线程上引发的全部单个异常的异常。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

示例

以下示例演示如何取消并行循环:


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class ParallelForCancellation
{
    // Demonstrated features:
    //		CancellationTokenSource
    // 		Parallel.For()
    //		ParallelOptions
    //		ParallelLoopResult
    // Expected results:
    // 		An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
    //		The order of execution of the iterations is undefined.
    //		The iteration when i=2 cancels the loop.
    //		Some iterations may bail out or not start at all; because they are temporally executed in unpredictable order, 
    //          it is impossible to say which will start/complete and which won't.
    //		At the end, an OperationCancelledException is surfaced.
    // Documentation:
    //		http://msdn.microsoft.com/library/system.threading.cancellationtokensource(VS.100).aspx
    static void CancelDemo()
    {
        CancellationTokenSource cancellationSource = new CancellationTokenSource();
        ParallelOptions options = new ParallelOptions();
        options.CancellationToken = cancellationSource.Token;

        try
        {
            ParallelLoopResult loopResult = Parallel.For(
                    0,
                    10,
                    options,
                    (i, loopState) =>
                    {
                        Console.WriteLine("Start Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i);

                        // Simulate a cancellation of the loop when i=2
                        if (i == 2)
                        {
                            cancellationSource.Cancel();
                        }

                        // Simulates a long execution
                        for (int j = 0; j < 10; j++)
                        {
                            Thread.Sleep(1 * 200);

                            // check to see whether or not to continue
                            if (loopState.ShouldExitCurrentIteration) return;
                        }

                        Console.WriteLine("Finish Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i);
                    }
                );

            if (loopResult.IsCompleted)
            {
                Console.WriteLine("All iterations completed successfully. THIS WAS NOT EXPECTED.");
            }
        }
        // No exception is expected in this example, but if one is still thrown from a task,
        // it will be wrapped in AggregateException and propagated to the main thread.
        catch (AggregateException e)
        {
            Console.WriteLine("Parallel.For has thrown an AggregateException. THIS WAS NOT EXPECTED.\n{0}", e);
        }
        // Catching the cancellation exception
        catch (OperationCanceledException e)
        {
            Console.WriteLine("An iteration has triggered a cancellation. THIS WAS EXPECTED.\n{0}", e.ToString());
        }
        finally
        {
           cancellationSource.Dispose();
        }
    }
}
Imports System.Threading
Imports System.Threading.Tasks

Module LoopCancellation
    ' Demonstrated features:
    '   CancellationTokenSource
    '   Parallel.For()
    '   ParallelOptions
    '   ParallelLoopResult
    ' Expected results:
    '   An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
    '   The order of execution of the iterations is undefined.
    '   The iteration when i=2 cancels the loop.
    '   Some iterations may bail out or not start at all; because they are temporally executed in unpredictable order, 
    '      it is impossible to say which will start/complete and which won't.
    '   At the end, an OperationCancelledException is surfaced.
    ' Documentation:
    '   http://msdn.microsoft.com/library/system.threading.cancellationtokensource(VS.100).aspx
    Private Sub Main()
        Dim cancellationSource As New CancellationTokenSource()
        Dim options As New ParallelOptions()
        options.CancellationToken = cancellationSource.Token

        Try
            Dim loopResult As ParallelLoopResult = _
                Parallel.For(0, 10, options, Sub(i, loopState)
                                                 Console.WriteLine("Start Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)

                                                 ' Simulate a cancellation of the loop when i=2
                                                 If i = 2 Then
                                                     cancellationSource.Cancel()
                                                 End If

                                                 ' Simulates a long execution
                                                 For j As Integer = 0 To 9
                                                     Thread.Sleep(1 * 200)

                                                     ' check to see whether or not to continue
                                                     If loopState.ShouldExitCurrentIteration Then
                                                         Exit Sub
                                                     End If
                                                 Next

                                                 Console.WriteLine("Finish Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)
                                             End Sub)

            If loopResult.IsCompleted Then
                Console.WriteLine("All iterations completed successfully. THIS WAS NOT EXPECTED.")
            End If
        Catch e As AggregateException
            ' No exception is expected in this example, but if one is still thrown from a task,
            ' it will be wrapped in AggregateException and propagated to the main thread.
            Console.WriteLine("An action has thrown an AggregateException. THIS WAS NOT EXPECTED." & vbLf & "{0}", e)
        Catch e As OperationCanceledException
            ' Catching the cancellation exception
            Console.WriteLine("An iteration has triggered a cancellation. THIS WAS EXPECTED." & vbLf & "{0}", e)
        Finally
            cancellationSource.Dispose()
        End Try
    End Sub
End Module

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它以参数的形式 Int32 提供迭代计数 () 。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int64, Int64, ParallelOptions, Action<Int64,ParallelLoopState>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

public:
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Action<long, System::Threading::Tasks::ParallelLoopState ^> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (long fromInclusive, long toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Action<long,System.Threading.Tasks.ParallelLoopState> body);
static member For : int64 * int64 * System.Threading.Tasks.ParallelOptions * Action<int64, System.Threading.Tasks.ParallelLoopState> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Long, toExclusive As Long, parallelOptions As ParallelOptions, body As Action(Of Long, ParallelLoopState)) As ParallelLoopResult

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

body
Action<Int64,ParallelLoopState>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

parallelOptions 取消的 CancellationToken 参数。

body 参数为 null

  • 或 - parallelOptions 参数为 null

包含在所有线程上引发的全部单个异常的异常。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

示例

以下示例演示如何 Parallel.For 将方法与对象一 ParallelOptions 起使用:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class ParallelOptionsDemo
{
    // Demonstrated features:
    // 		Parallel.For()
    //		ParallelOptions
    // Expected results:
    // 		An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
    //		The order of execution of the iterations is undefined.
    //		Verify that no more than two threads have been used for the iterations.
    // Documentation:
    //		http://msdn.microsoft.com/library/system.threading.tasks.parallel.for(VS.100).aspx
    static void Main()
    {
        ParallelOptions options = new ParallelOptions();
        options.MaxDegreeOfParallelism = 2; // -1 is for unlimited. 1 is for sequential.

        try
        {
            Parallel.For(
                    0,
                    9,
                    options,
                    (i) =>
                    {
                        Console.WriteLine("Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i);
                    }
                );
        }
        // No exception is expected in this example, but if one is still thrown from a task,
        // it will be wrapped in AggregateException and propagated to the main thread.
        catch (AggregateException e)
        {
            Console.WriteLine("Parallel.For has thrown the following (unexpected) exception:\n{0}", e);
        }
    }
}
Imports System.Threading
Imports System.Threading.Tasks


Module ParallelForDemo

    ' Demonstrated features:
    '   Parallel.For()
    '   ParallelOptions
    ' Expected results:
    '   An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
    '   The order of execution of the iterations is undefined.
    '   Verify that no more than two threads have been used for the iterations.
    ' Documentation:
    '   http://msdn.microsoft.com/library/system.threading.tasks.parallel.for(VS.100).aspx
    Sub Main()
        Dim options As New ParallelOptions()
        options.MaxDegreeOfParallelism = 2 ' -1 is for unlimited. 1 is for sequential.
        Try
            Parallel.For(0, 9, options, Sub(i)
                                            Console.WriteLine("Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)

                                        End Sub)
        Catch e As AggregateException
            ' No exception is expected in this example, but if one is still thrown from a task,
            ' it will be wrapped in AggregateException and propagated to the main thread.
            Console.WriteLine("Parallel.For has thrown the following (unexpected) exception:" & vbLf & "{0}", e)
        End Try
    End Sub

End Module

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int64) ,以及 ParallelLoopState 可用于过早中断循环的实例。

如果 fromInclusive 大于或等于 toExclusive,该方法将立即返回,而无需执行任何迭代。

另请参阅

适用于

For(Int64, Int64, ParallelOptions, Action<Int64>)

执行具有 64 位索引的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项。

public:
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Action<long> ^ body);
public static System.Threading.Tasks.ParallelLoopResult For (long fromInclusive, long toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Action<long> body);
static member For : int64 * int64 * System.Threading.Tasks.ParallelOptions * Action<int64> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For (fromInclusive As Long, toExclusive As Long, parallelOptions As ParallelOptions, body As Action(Of Long)) As ParallelLoopResult

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

body
Action<Int64>

将为每个迭代调用一次的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

parallelOptions 取消的 CancellationToken 参数。

body 参数为 null

  • 或 - parallelOptions 参数为 null

包含在所有线程上引发的全部单个异常的异常。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

示例

以下示例演示如何用于 ParallelOptions 指定自定义任务计划程序:

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class ParallelSchedulerDemo2
{
        // Demonstrated features:
        //		TaskScheduler
        //      BlockingCollection
        // 		Parallel.For()
        //		ParallelOptions
        // Expected results:
        // 		An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
        //		The TwoThreadTaskScheduler employs 2 threads on which iterations may be executed in a random order.
        //		Thus a scheduler thread may execute multiple iterations.
        // Documentation:
        //		http://msdn.microsoft.com/library/system.threading.tasks.taskscheduler(VS.100).aspx
        //		http://msdn.microsoft.com/library/dd997413(VS.100).aspx
        // More information:
        //		http://blogs.msdn.com/pfxteam/archive/2009/09/22/9898090.aspx
        static void Main()
        {
            ParallelOptions options = new ParallelOptions();

            // Construct and associate a custom task scheduler
            options.TaskScheduler = new TwoThreadTaskScheduler();

            try
            {
                Parallel.For(
                        0,
                        10,
                        options,
                        (i, localState) =>
                        {
                            Console.WriteLine("i={0}, Task={1}, Thread={2}", i, Task.CurrentId, Thread.CurrentThread.ManagedThreadId);
                        }
                    );
            }
            // No exception is expected in this example, but if one is still thrown from a task,
            // it will be wrapped in AggregateException and propagated to the main thread.
            catch (AggregateException e)
            {
                Console.WriteLine("An iteration has thrown an exception. THIS WAS NOT EXPECTED.\n{0}", e);
            }
        }

        // This scheduler schedules all tasks on (at most) two threads
        sealed class TwoThreadTaskScheduler : TaskScheduler, IDisposable
        {
            // The runtime decides how many tasks to create for the given set of iterations, loop options, and scheduler's max concurrency level.
            // Tasks will be queued in this collection
            private BlockingCollection<Task> _tasks = new BlockingCollection<Task>();

            // Maintain an array of threads. (Feel free to bump up _n.)
            private readonly int _n = 2;
            private Thread[] _threads;

            public TwoThreadTaskScheduler()
            {
                _threads = new Thread[_n];

                // Create unstarted threads based on the same inline delegate
                for (int i = 0; i < _n; i++)
                {
                    _threads[i] = new Thread(() =>
                    {
                        // The following loop blocks until items become available in the blocking collection.
                        // Then one thread is unblocked to consume that item.
                        foreach (var task in _tasks.GetConsumingEnumerable())
                        {
                            TryExecuteTask(task);
                        }
                    });

                    // Start each thread
                    _threads[i].IsBackground = true;
                    _threads[i].Start();
                }
            }

            // This method is invoked by the runtime to schedule a task
            protected override void QueueTask(Task task)
            {
                _tasks.Add(task);
            }

            // The runtime will probe if a task can be executed in the current thread.
            // By returning false, we direct all tasks to be queued up.
            protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)
            {
                return false;
            }

            public override int MaximumConcurrencyLevel { get { return _n; } }

            protected override IEnumerable<Task> GetScheduledTasks()
            {
                return _tasks.ToArray();
            }

            // Dispose is not thread-safe with other members.
            // It may only be used when no more tasks will be queued
            // to the scheduler.  This implementation will block
            // until all previously queued tasks have completed.
            public void Dispose()
            {
                if (_threads != null)
                {
                    _tasks.CompleteAdding();

                    for (int i = 0; i < _n; i++)
                    {
                        _threads[i].Join();
                        _threads[i] = null;
                    }
                    _threads = null;
                    _tasks.Dispose();
                    _tasks = null;
                }
            }
    }
}
Imports System.Collections.Concurrent
Imports System.Threading
Imports System.Threading.Tasks

Module SchedulerDemo
    ' Demonstrated features:
    '   TaskScheduler
    '   BlockingCollection
    '   Parallel.For()
    '   ParallelOptions
    ' Expected results:
    '   An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
    '   The TwoThreadTaskScheduler employs 2 threads on which iterations may be executed in a random order.
    '   A task is internally created for each thread of the task scheduler (plus an aditional internal task).
    '	Thus a scheduler thread may execute multiple iterations.
    ' Documentation:
    '   http://msdn.microsoft.com/library/system.threading.tasks.taskscheduler(VS.100).aspx
    '   http://msdn.microsoft.com/library/dd997413(VS.100).aspx
    ' More information:
    '   http://blogs.msdn.com/pfxteam/archive/2009/09/22/9898090.aspx
    Sub Main()
        Dim options As New ParallelOptions()

        ' Construct and associate a custom task scheduler
        options.TaskScheduler = New TwoThreadTaskScheduler()

        Try
            Parallel.For(0, 10, options, Sub(i, localState)
                                             Console.WriteLine("i={0}, Task={1}, Thread={2}", i, Task.CurrentId, Thread.CurrentThread.ManagedThreadId)

                                         End Sub)
        Catch e As AggregateException
            ' No exception is expected in this example, but if one is still thrown from a task,
            ' it will be wrapped in AggregateException and propagated to the main thread.
            Console.WriteLine("An iteration has thrown an exception. THIS WAS NOT EXPECTED." & vbLf & "{0}", e)
        End Try
    End Sub

    ' This scheduler schedules all tasks on (at most) two threads
    Private NotInheritable Class TwoThreadTaskScheduler
        Inherits TaskScheduler
        Implements IDisposable
        ' The runtime decides how many tasks to create for the given set of iterations, loop options, and scheduler's max concurrency level.
        ' Tasks will be queued in this collection
        Private _tasks As New BlockingCollection(Of Task)()

        ' Maintain an array of threads. (Feel free to bump up _n.)
        Private ReadOnly _n As Integer = 2
        Private _threads As Thread()

        Public Sub New()
            _threads = New Thread(_n - 1) {}

            ' Create unstarted threads based on the same inline delegate
            For i As Integer = 0 To _n - 1
                _threads(i) = New Thread(Sub()
                                             ' The following loop blocks until items become available in the blocking collection.
                                             ' Then one thread is unblocked to consume that item.
                                             For Each task In _tasks.GetConsumingEnumerable()
                                                 TryExecuteTask(task)
                                             Next
                                         End Sub)

                ' Start each thread
                _threads(i).IsBackground = True
                _threads(i).Start()
            Next
        End Sub

        ' This method is invoked by the runtime to schedule a task
        Protected Overloads Overrides Sub QueueTask(ByVal task As Task)
            _tasks.Add(task)
        End Sub

        ' The runtime will probe if a task can be executed in the current thread.
        ' By returning false, we direct all tasks to be queued up.
        Protected Overloads Overrides Function TryExecuteTaskInline(ByVal task As Task, ByVal taskWasPreviouslyQueued As Boolean) As Boolean
            Return False
        End Function

        Public Overloads Overrides ReadOnly Property MaximumConcurrencyLevel() As Integer
            Get
                Return _n
            End Get
        End Property

        Protected Overloads Overrides Function GetScheduledTasks() As IEnumerable(Of Task)
            Return _tasks.ToArray()
        End Function

        ' Dispose is not thread-safe with other members.
        ' It may only be used when no more tasks will be queued
        ' to the scheduler. This implementation will block
        ' until all previously queued tasks have completed.
        Public Sub Dispose() Implements IDisposable.Dispose
            If _threads IsNot Nothing Then
                _tasks.CompleteAdding()

                For i As Integer = 0 To _n - 1
                    _threads(i).Join()
                    _threads(i) = Nothing
                Next
                _threads = Nothing
                _tasks.Dispose()
                _tasks = Nothing
            End If
        End Sub
    End Class

End Module

注解

支持 64 位索引。 对 body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它以参数的形式 Int64 提供迭代计数 () 。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

另请参阅

适用于

For<TLocal>(Int64, Int64, ParallelOptions, Func<TLocal>, Func<Int64,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有 64 位索引和线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

public:
generic <typename TLocal>
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Func<TLocal> ^ localInit, Func<long, System::Threading::Tasks::ParallelLoopState ^, TLocal, TLocal> ^ body, Action<TLocal> ^ localFinally);
public static System.Threading.Tasks.ParallelLoopResult For<TLocal> (long fromInclusive, long toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Func<TLocal> localInit, Func<long,System.Threading.Tasks.ParallelLoopState,TLocal,TLocal> body, Action<TLocal> localFinally);
static member For : int64 * int64 * System.Threading.Tasks.ParallelOptions * Func<'Local> * Func<int64, System.Threading.Tasks.ParallelLoopState, 'Local, 'Local> * Action<'Local> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For(Of TLocal) (fromInclusive As Long, toExclusive As Long, parallelOptions As ParallelOptions, localInit As Func(Of TLocal), body As Func(Of Long, ParallelLoopState, TLocal, TLocal), localFinally As Action(Of TLocal)) As ParallelLoopResult

类型参数

TLocal

线程本地数据的类型。

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

localInit
Func<TLocal>

用于返回每个线程的本地数据的初始状态的函数委托。

body
Func<Int64,ParallelLoopState,TLocal,TLocal>

将为每个迭代调用一次的委托。

localFinally
Action<TLocal>

用于对每个线程的本地状态执行一个最终操作的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

  • 或 - localInit 参数为 null

  • 或 - localFinally 参数为 null

  • 或 - parallelOptions 参数为 null

parallelOptions 取消的 CancellationToken 参数。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

包含在所有线程上引发的全部单个异常的异常。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int64) ,一个实例,可用于提前突破循环,以及一些本地状态,这些状态可能在在同一 ParallelLoopState 线程上执行的迭代之间共享。

localInit对于参与循环执行的每个线程调用委托一次,并返回每个线程的初始本地状态。 这些初始状态将传递到每个线程上的第一个 body 调用。 然后,每个后续的正文调用都会返回一个可能修改的状态值,该值传递给下一个正文调用。 最后,每个线程上的最后一个正文调用返回传递给 localFinally 委托的状态值。 每个 localFinally 线程调用一次委托,对每个线程的本地状态执行最终操作。 可以在多个线程上并发调用此委托;因此,必须同步对任何共享变量的访问。

当现有任务完成并替换为新任务时,该方法 Parallel.For 可能在其执行生存期内使用线程数更多的任务。 这样,基础 TaskScheduler 对象就有机会添加、更改或删除服务循环的线程。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

另请参阅

适用于

For<TLocal>(Int32, Int32, ParallelOptions, Func<TLocal>, Func<Int32,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以配置循环选项,可以监视和操作循环的状态。

public:
generic <typename TLocal>
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, System::Threading::Tasks::ParallelOptions ^ parallelOptions, Func<TLocal> ^ localInit, Func<int, System::Threading::Tasks::ParallelLoopState ^, TLocal, TLocal> ^ body, Action<TLocal> ^ localFinally);
public static System.Threading.Tasks.ParallelLoopResult For<TLocal> (int fromInclusive, int toExclusive, System.Threading.Tasks.ParallelOptions parallelOptions, Func<TLocal> localInit, Func<int,System.Threading.Tasks.ParallelLoopState,TLocal,TLocal> body, Action<TLocal> localFinally);
static member For : int * int * System.Threading.Tasks.ParallelOptions * Func<'Local> * Func<int, System.Threading.Tasks.ParallelLoopState, 'Local, 'Local> * Action<'Local> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For(Of TLocal) (fromInclusive As Integer, toExclusive As Integer, parallelOptions As ParallelOptions, localInit As Func(Of TLocal), body As Func(Of Integer, ParallelLoopState, TLocal, TLocal), localFinally As Action(Of TLocal)) As ParallelLoopResult

类型参数

TLocal

线程本地数据的类型。

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

parallelOptions
ParallelOptions

一个对象,用于配置此操作的行为。

localInit
Func<TLocal>

用于返回每个任务的本地数据的初始状态的函数委托。

body
Func<Int32,ParallelLoopState,TLocal,TLocal>

将为每个迭代调用一次的委托。

localFinally
Action<TLocal>

用于对每个任务的本地状态执行一个最终操作的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

  • 或 - localInit 参数为 null

  • 或 - localFinally 参数为 null

  • 或 - parallelOptions 参数为 null

parallelOptions 取消的 CancellationToken 参数。

parallelOptions 中与 CancellationTokenSource 关联的 CancellationToken 已被释放。

包含在所有线程上引发的全部单个异常的异常。

示例

以下示例使用线程局部变量来计算许多长时间操作的结果的总和。 本示例将并行度限制为 4。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

class ThreadLocalForWithOptions
{
   // The number of parallel iterations to perform.
   const int N = 1000000;

   static void Main()
   {
      // The result of all thread-local computations.
      int result = 0;

      // This example limits the degree of parallelism to four.
      // You might limit the degree of parallelism when your algorithm
      // does not scale beyond a certain number of cores or when you 
      // enforce a particular quality of service in your application.

      Parallel.For(0, N, new ParallelOptions { MaxDegreeOfParallelism = 4 },
         // Initialize the local states
         () => 0,
         // Accumulate the thread-local computations in the loop body
         (i, loop, localState) =>
         {
            return localState + Compute(i);
         },
         // Combine all local states
         localState => Interlocked.Add(ref result, localState)
      );

      // Print the actual and expected results.
      Console.WriteLine("Actual result: {0}. Expected 1000000.", result);
   }

   // Simulates a lengthy operation.
   private static int Compute(int n)
   {
      for (int i = 0; i < 10000; i++) ;
      return 1;
   }
}
Imports System.Threading
Imports System.Threading.Tasks

Module ThreadLocalForWithOptions

   ' The number of parallel iterations to perform.
   Const N As Integer = 1000000

   Sub Main()
      ' The result of all thread-local computations.
      Dim result As Integer = 0

      ' This example limits the degree of parallelism to four.
      ' You might limit the degree of parallelism when your algorithm
      ' does not scale beyond a certain number of cores or when you 
      ' enforce a particular quality of service in your application.

      Parallel.For(0, N, New ParallelOptions With {.MaxDegreeOfParallelism = 4},
         Function()
            ' Initialize the local states 
            Return 0
         End Function,
         Function(i, loopState, localState)
            ' Accumulate the thread-local computations in the loop body
            Return localState + Compute(i)
         End Function,
         Sub(localState)
            ' Combine all local states
            Interlocked.Add(result, localState)
         End Sub
      )

      ' Print the actual and expected results.
      Console.WriteLine("Actual result: {0}. Expected 1000000.", result)
   End Sub

   ' Simulates a lengthy operation.
   Function Compute(ByVal n As Integer) As Integer
      For i As Integer = 0 To 10000
      Next
      Return 1
   End Function
End Module

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int32) ,一个实例,可用于提前突破循环,以及一些本地状态,这些状态可能在执行同一 ParallelLoopState 任务的迭代之间共享。

localInit对于参与循环执行的每个任务调用委托一次,并返回每个任务的初始本地状态。 这些初始状态将传递到每个任务的第一个 body 调用。 然后,每个后续的正文调用都会返回一个可能修改的状态值,该值传递给下一个正文调用。 最后,每个任务的最后一个正文调用返回传递给 localFinally 委托的状态值。 每个 localFinally 任务调用一次委托,对每个任务的本地状态执行最终操作。 可以在多个线程上并发调用此委托;因此,必须同步对任何共享变量的访问。

当现有任务完成并替换为新任务时,该方法 Parallel.For 可能在其执行生存期内使用线程数更多的任务。 这样,基础 TaskScheduler 对象就有机会添加、更改或删除服务循环的线程。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

另请参阅

适用于

For<TLocal>(Int32, Int32, Func<TLocal>, Func<Int32,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

public:
generic <typename TLocal>
 static System::Threading::Tasks::ParallelLoopResult For(int fromInclusive, int toExclusive, Func<TLocal> ^ localInit, Func<int, System::Threading::Tasks::ParallelLoopState ^, TLocal, TLocal> ^ body, Action<TLocal> ^ localFinally);
public static System.Threading.Tasks.ParallelLoopResult For<TLocal> (int fromInclusive, int toExclusive, Func<TLocal> localInit, Func<int,System.Threading.Tasks.ParallelLoopState,TLocal,TLocal> body, Action<TLocal> localFinally);
static member For : int * int * Func<'Local> * Func<int, System.Threading.Tasks.ParallelLoopState, 'Local, 'Local> * Action<'Local> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For(Of TLocal) (fromInclusive As Integer, toExclusive As Integer, localInit As Func(Of TLocal), body As Func(Of Integer, ParallelLoopState, TLocal, TLocal), localFinally As Action(Of TLocal)) As ParallelLoopResult

类型参数

TLocal

线程本地数据的类型。

参数

fromInclusive
Int32

开始索引(含)。

toExclusive
Int32

结束索引(不含)。

localInit
Func<TLocal>

用于返回每个任务的本地数据的初始状态的函数委托。

body
Func<Int32,ParallelLoopState,TLocal,TLocal>

将为每个迭代调用一次的委托。

localFinally
Action<TLocal>

用于对每个任务的本地状态执行一个最终操作的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

  • 或 - localInit 参数为 null

  • 或 - localFinally 参数为 null

包含在所有线程上引发的全部单个异常的异常。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int32) ,一个实例,可用于提前突破循环,以及一些本地状态,这些状态可能在在同一 ParallelLoopState 线程上执行的迭代之间共享。

localInit对于参与循环执行的每个任务调用委托一次,并返回每个任务的初始本地状态。 这些初始状态将传递到每个任务的第一个 body 调用。 然后,每个后续的正文调用都会返回一个可能修改的状态值,该值传递给下一个正文调用。 最后,每个任务的最后一个正文调用返回传递给 localFinally 委托的状态值。 每个 localFinally 任务调用一次委托,对每个任务的本地状态执行最终操作。 此委托可能会在多个任务上并发调用;因此,必须同步对任何共享变量的访问。

当现有任务完成并替换为新任务时,该方法 Parallel.For 可能在其执行生存期内使用线程数更多的任务。 这样,基础 TaskScheduler 对象就有机会添加、更改或删除服务循环的线程。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

有关使用此方法的示例,请参阅 How to: Write a Parallel.For Loop with Thread-Local Variables

另请参阅

适用于

For<TLocal>(Int64, Int64, Func<TLocal>, Func<Int64,ParallelLoopState,TLocal,TLocal>, Action<TLocal>)

执行具有 64 位索引和线程本地数据的 for 循环,其中可能会并行运行迭代,而且可以监视和操作循环的状态。

public:
generic <typename TLocal>
 static System::Threading::Tasks::ParallelLoopResult For(long fromInclusive, long toExclusive, Func<TLocal> ^ localInit, Func<long, System::Threading::Tasks::ParallelLoopState ^, TLocal, TLocal> ^ body, Action<TLocal> ^ localFinally);
public static System.Threading.Tasks.ParallelLoopResult For<TLocal> (long fromInclusive, long toExclusive, Func<TLocal> localInit, Func<long,System.Threading.Tasks.ParallelLoopState,TLocal,TLocal> body, Action<TLocal> localFinally);
static member For : int64 * int64 * Func<'Local> * Func<int64, System.Threading.Tasks.ParallelLoopState, 'Local, 'Local> * Action<'Local> -> System.Threading.Tasks.ParallelLoopResult
Public Shared Function For(Of TLocal) (fromInclusive As Long, toExclusive As Long, localInit As Func(Of TLocal), body As Func(Of Long, ParallelLoopState, TLocal, TLocal), localFinally As Action(Of TLocal)) As ParallelLoopResult

类型参数

TLocal

线程本地数据的类型。

参数

fromInclusive
Int64

开始索引(含)。

toExclusive
Int64

结束索引(不含)。

localInit
Func<TLocal>

用于返回每个任务的本地数据的初始状态的函数委托。

body
Func<Int64,ParallelLoopState,TLocal,TLocal>

将为每个迭代调用一次的委托。

localFinally
Action<TLocal>

用于对每个任务的本地状态执行一个最终操作的委托。

返回

ParallelLoopResult

包含有关已完成的循环部分的信息的结构。

例外

body 参数为 null

  • 或 - localInit 参数为 null

  • 或 - localFinally 参数为 null

包含在所有线程上引发的全部单个异常的异常。

注解

body 迭代范围中的每个值调用委托一次, (fromInclusivetoExclusive) 。 它提供以下参数:迭代计数 (Int64) ,一个实例,可用于提前突破循环,以及一些本地状态,这些状态可能在执行同一 ParallelLoopState 任务的迭代之间共享。

localInit对于参与循环执行的每个任务调用委托一次,并返回每个任务的初始本地状态。 这些初始状态将传递到每个任务的第一个 body 调用。 然后,每个后续的正文调用都会返回一个可能修改的状态值,该值传递给下一个正文调用。 最后,每个任务的最后一个正文调用返回传递给 localFinally 委托的状态值。 每个 localFinally 任务调用一次委托,对每个任务的本地状态执行最终操作。 此委托可能会在多个任务上并发调用;因此,必须同步对任何共享变量的访问。

当现有任务完成并替换为新任务时,该方法 Parallel.For 可能在其执行生存期内使用线程数更多的任务。 这样,基础 TaskScheduler 对象就有机会添加、更改或删除服务循环的线程。

如果 fromInclusive 大于或等于 toExclusive,则该方法会立即返回,而无需执行任何迭代。

有关使用此方法的示例,请参阅 How to: Write a Parallel.For Loop with Thread-Local Variables

另请参阅

适用于