ParallelLoopState.Break ParallelLoopState.Break ParallelLoopState.Break ParallelLoopState.Break Method

Definizione

Comunica che il ciclo Parallel deve interrompere l'esecuzione delle iterazioni dopo l'iterazione corrente non appena il sistema lo richiede.Communicates that the Parallel loop should cease execution of iterations beyond the current iteration at the system's earliest convenience.

public:
 void Break();
public void Break ();
member this.Break : unit -> unit
Public Sub Break ()

Eccezioni

Il metodo Stop() è stato chiamato precedentemente.The Stop() method was previously called. Break() e Stop() non possono essere utilizzati in combinazione da iterazioni dello stesso ciclo.Break() and Stop() may not be used in combination by iterations of the same loop.

Esempi

Nell'esempio seguente vengono eseguite fino a 100 iterazioni di un ciclo in parallelo.The following example executes up to 100 iterations of a loop in parallel. Ogni iterazione viene sospesa per un intervallo casuale compreso tra 1 e 1.000 millisecondi.Each iteration pauses for a random interval from 1 to 1,000 milliseconds. Un valore generato in modo casuale determina in quale iterazione del ciclo Break viene chiamato il metodo.A randomly generated value determines on which iteration of the loop the Break method is called. Come illustrato nell'output dell'esempio, nessuna iterazione il cui indice è maggiore del valore LowestBreakIteration della proprietà inizia dopo la chiamata Break al metodo.As the output from the example shows, no iterations whose index is greater than the LowestBreakIteration property value start after the call to the Break method.

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

Poiché le iterazioni del ciclo possono comunque essere eseguite quando viene chiamato il Break metodo, ogni iterazione chiama la ShouldExitCurrentIteration proprietà per verificare se un'altra iterazione ha chiamato il Break metodo.Because iterations of the loop are still likely to be executing when the Break method is called, each iteration calls the ShouldExitCurrentIteration property to check whether another iteration has called the Break method. Se il valore della proprietà trueè, l'iterazione controlla il valore LowestBreakIteration della proprietà e, se è maggiore del valore di indice dell'iterazione corrente, viene restituito immediatamente.If the property value is true, the iteration checks the value of the LowestBreakIteration property and, if it is greater than the current iteration's index value, returns immediately.

Commenti

Breakindica che non deve essere eseguita alcuna iterazione dopo l'iterazione corrente.Break indicates that no iterations after the current iteration should be run. Annulla effettivamente eventuali iterazioni aggiuntive del ciclo.It effectively cancels any additional iterations of the loop. Tuttavia, non interrompe alcuna iterazione che ha già iniziato l'esecuzione.However, it does not stop any iterations that have already begun execution. Se Break , ad esempio, viene chiamato dalla centesima iterazione di un ciclo parallelo che scorre da 0 a 1.000, tutte le iterazioni inferiori a 100 devono comunque essere eseguite, ma le iterazioni da 101 a 1000 che non sono ancora state avviate non vengono eseguite.For example, if Break is called from the 100th iteration of a parallel loop iterating from 0 to 1,000, all iterations less than 100 should still be run, but the iterations from 101 through to 1000 that have not yet started are not executed.

Per le iterazioni con esecuzione prolungata che potrebbero essere già Break in esecuzione LowestBreakIteration , imposta la proprietà sull'indice dell'iterazione corrente se l'indice corrente è minore del valore LowestBreakIterationcorrente di.For long-running iterations that may already be executing, Break sets the LowestBreakIteration property to the current iteration's index if the current index is less than the current value of LowestBreakIteration. Per arrestare le iterazioni il cui indice è maggiore dell'iterazione di interruzione più bassa dall'esecuzione in competizione, è necessario eseguire le operazioni seguenti:To stop iterations whose index is greater than the lowest break iteration from competing execution, you should do the following:

  1. Controllare se la ShouldExitCurrentIteration proprietà è true.Check whether the ShouldExitCurrentIteration property is true.

  2. Uscire dall'iterazione se l'indice è maggiore del valore LowestBreakIteration della proprietà.Exit from the iteration if its index is greater than the LowestBreakIteration property value.

Nell'esempio viene illustrata una situazione di questo tipo.The example provides an illustration.

Breakviene in genere utilizzato negli algoritmi basati sulla ricerca in cui è presente un ordinamento nell'origine dati.Break is typically employed in search-based algorithms where an ordering is present in the data source.

Si applica a

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