code.grnet.gr Git - pithos-ms-client/blob - trunk/Libraries/ParallelExtensionsExtras/ParallelAlgorithms/ParallelAlgorithms_SpeculativeFor.cs

   1 //--------------------------------------------------------------------------
   2 //
   3 //  Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 //  File: ParallelAlgorithms_SpeculativeFor.cs
   6 //
   7 //--------------------------------------------------------------------------
   8
   9 using System.Collections.Generic;
  10 using System.Threading.Tasks;
  11
  12 namespace System.Threading.Algorithms
  13 {
  14     public static partial class ParallelAlgorithms
  15     {
  16         /// <summary>Executes a function for each value in a range, returning the first result achieved and ceasing execution.</summary>
  17         /// <typeparam name="TResult">The type of the data returned.</typeparam>
  18         /// <param name="fromInclusive">The start of the range, inclusive.</param>
  19         /// <param name="toExclusive">The end of the range, exclusive.</param>
  20         /// <param name="options">The options to use for processing the loop.</param>
  21         /// <param name="body">The function to execute for each element.</param>
  22         /// <returns>The result computed.</returns>
  23         public static TResult SpeculativeFor<TResult>(
  24             int fromInclusive, int toExclusive, Func<int, TResult> body)
  25         {
  26             return SpeculativeFor(fromInclusive, toExclusive, s_defaultParallelOptions, body);
  27         }
  28
  29         /// <summary>Executes a function for each value in a range, returning the first result achieved and ceasing execution.</summary>
  30         /// <typeparam name="TResult">The type of the data returned.</typeparam>
  31         /// <param name="fromInclusive">The start of the range, inclusive.</param>
  32         /// <param name="toExclusive">The end of the range, exclusive.</param>
  33         /// <param name="options">The options to use for processing the loop.</param>
  34         /// <param name="body">The function to execute for each element.</param>
  35         /// <returns>The result computed.</returns>
  36         public static TResult SpeculativeFor<TResult>(
  37             int fromInclusive, int toExclusive, ParallelOptions options, Func<int, TResult> body)
  38         {
  39             // Validate parameters; the Parallel.For we delegate to will validate the rest
  40             if (body == null) throw new ArgumentNullException("body");
  41
  42             // Store one result.  We box it if it's a value type to avoid torn writes and enable
  43             // CompareExchange even for value types.
  44             object result = null;
  45
  46             // Run all bodies in parallel, stopping as soon as one has completed.
  47             Parallel.For(fromInclusive, toExclusive, options, (i, loopState) =>
  48             {
  49                 // Run an iteration.  When it completes, store (box)
  50                 // the result, and cancel the rest
  51                 Interlocked.CompareExchange(ref result, (object)body(i), null);
  52                 loopState.Stop();
  53             });
  54
  55             // Return the computed result
  56             return (TResult)result;
  57         }
  58     }
  59 }