ParallelLoopState.LowestBreakIteration プロパティ

定義

Break() を呼び出したループのイテレーションのうち、最下位のイテレーションを取得します。Gets the lowest iteration of the loop from which Break() was called.

public:
 property Nullable<long> LowestBreakIteration { Nullable<long> get(); };
public Nullable<long> LowestBreakIteration { get; }
member this.LowestBreakIteration : Nullable<int64>
Public ReadOnly Property LowestBreakIteration As Nullable(Of Long)

プロパティ値

Break() を呼び出したイテレーションのうち、最下位のイテレーション。The lowest iteration from which Break() was called. ForEach<TSource>(Partitioner<TSource>, Action<TSource>) ループの場合、値は内部的に生成されたインデックスに基づきます。In the case of a ForEach<TSource>(Partitioner<TSource>, Action<TSource>) loop, the value is based on an internally-generated index.

次の例では、ループの最大100の反復処理を並列実行します。The following example executes up to 100 iterations of a loop in parallel. 各イテレーションは、1 ~ 1000 ミリ秒のランダムな間隔で一時停止します。Each iteration pauses for a random interval from 1 to 1,000 milliseconds. ランダムに生成された値によって、Break メソッドが呼び出されるループの反復処理が決定されます。A randomly generated value determines on which iteration of the loop the Break method is called. これにより、インデックスが LowestBreakIteration プロパティ値よりも大きいイテレーションは、Break メソッドの呼び出しの後から開始されますが、実行を開始したイテレーションには影響しません。This prevents iterations whose index is greater than the LowestBreakIteration property value from starting after the call to the Break method, but it does not affect any iterations that have already begun executing. これらの処理が完了しないようにするために、各イテレーションは ShouldExitCurrentIteration メソッドを呼び出して、別のイテレーションが Break メソッドを呼び出したかどうかを確認します。To prevent these from completing, each iteration calls the ShouldExitCurrentIteration method to check whether another iteration has called the Break method. その場合は、反復処理によって LowestBreakIteration プロパティの値がチェックされ、現在のイテレーションのインデックス値より大きい場合はが直ちに返されます。If so, the iteration checks the value of the LowestBreakIteration property and, if it is greater than the current iteration's index value, returns immediately.

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);
      Nullable<long> lowest = new Nullable<long>();

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

      var result = Parallel.For(1, 101, (i, state) => {
                                            Console.WriteLine("Beginning iteration {0}", i);
                                            int delay;
                                            Monitor.Enter(rnd);
                                               delay = rnd.Next(1, 1001);
                                            Monitor.Exit(rnd);
                                            Thread.Sleep(delay);
                                            
                                            if (state.ShouldExitCurrentIteration) {
                                               if (state.LowestBreakIteration < i)
                                                  return;
                                            }

                                            if (i == breakIndex) {
                                               Console.WriteLine("Break in iteration {0}", i);
                                               state.Break();
                                               if (state.LowestBreakIteration.HasValue)
                                                  if (lowest < state.LowestBreakIteration)
                                                     lowest = state.LowestBreakIteration;
                                                  else
                                                     lowest = state.LowestBreakIteration;
                                            }

                                            Console.WriteLine("Completed iteration {0}", i);
                                       });
         if (lowest.HasValue)
            Console.WriteLine("\nLowest Break Iteration: {0}", lowest);
         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

LowestBreakIteration 値は並列ループの外側ではスコープ外であるため、値を保持する場合は、ループの外部から参照できる変数に割り当てる必要があります。Note that, because the LowestBreakIteration value is out of scope outside of the parallel loop, you must assign it to a variable that is visible outside of the loop if you want to preserve its value.

注釈

並列ループの複数の反復処理によって、Break メソッドを呼び出すことができます。It is possible for multiple iterations of a parallel loop to call the Break method. 指定されている場合、この値は Breakを呼び出したイテレーションの最小インデックスです。If they do, this value is the smallest index of an iteration that called Break. Break呼び出されたループの反復がない場合、このプロパティは nullを返します。If no iteration of the loop called Break, this property returns null. プロパティ値は、Stop メソッドを呼び出すことによって影響を受けないことに注意してください。Note that the property value is unaffected by calls to the Stop method.

Break メソッドを呼び出すイテレーション後のすべてのイテレーションが実行されない必要がある、実行時間の長いイテレーションでは、LowestBreakIteration プロパティを使用して、Break メソッドの呼び出しの前に実行を開始したイテレーションを終了します。In long-running iterations in which all iterations after the iteration that calls the Break method need not run, the LowestBreakIteration property is used to terminate iterations that began execution before the call to the Break method. インデックスが競合している実行の最小のブレークイテレーションよりも大きいイテレーションを停止するには、次の手順を実行します。To stop iterations whose index is greater than the lowest break iteration from competing execution, you should do the following:

  1. ShouldExitCurrentIteration プロパティが trueかどうかを確認します。Check whether the ShouldExitCurrentIteration property is true.

  2. インデックスが LowestBreakIteration プロパティ値よりも大きい場合は、イテレーションから終了します。Exit from the iteration if its index is greater than the LowestBreakIteration property value.

具体的な例を次に示します。The example provides an illustration.

適用対象

こちらもご覧ください