mcs/class/System.Core/System.Linq.Parallel/ParallelQueryEnumerator.cs

   1 //
   2 // ParallelEnumerator.cs
   3 //
   4 // Author:
   5 //       Jérémie "Garuma" Laval <jeremie.laval@gmail.com>
   6 //
   7 // Copyright (c) 2010 Jérémie "Garuma" Laval
   8 //
   9 // Permission is hereby granted, free of charge, to any person obtaining a copy
  10 // of this software and associated documentation files (the "Software"), to deal
  11 // in the Software without restriction, including without limitation the rights
  12 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13 // copies of the Software, and to permit persons to whom the Software is
  14 // furnished to do so, subject to the following conditions:
  15 //
  16 // The above copyright notice and this permission notice shall be included in
  17 // all copies or substantial portions of the Software.
  18 //
  19 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25 // THE SOFTWARE.
  26
  27 #if NET_4_0 || MOBILE
  28 using System;
  29 using System.Threading;
  30 using System.Collections;
  31 using System.Collections.Generic;
  32 using System.Collections.Concurrent;
  33 using System.Linq.Parallel.QueryNodes;
  34
  35 namespace System.Linq.Parallel
  36 {
  37         internal class ParallelQueryEnumerator<T> : IEnumerator<T>
  38         {
  39                 readonly int DefaultBufferSize = ParallelExecuter.GetBestWorkerNumber () * 50;
  40
  41                 BlockingCollection<T> buffer;
  42                 IEnumerator<T> loader;
  43                 QueryOptions options;
  44                 OrderingEnumerator<T> ordEnumerator;
  45
  46                 T current;
  47
  48                 Action waitAction;
  49
  50                 internal ParallelQueryEnumerator (QueryBaseNode<T> node)
  51                 {
  52                         this.options = ParallelExecuter.CheckQuery (node);
  53
  54                         if (options.ShouldBeSequential && options.Mode != ParallelExecutionMode.ForceParallelism) {
  55                                 IEnumerable<T> buffer = node.GetSequential ();
  56                                 loader = buffer.GetEnumerator ();
  57                         } else {
  58                                 Setup ();
  59
  60                                 // Launch adding to the buffer asynchronously via Tasks
  61                                 if (options.BehindOrderGuard.Value) {
  62                                         waitAction = ParallelExecuter.ProcessAndCallback (node,
  63                                                                                           ordEnumerator.Add,
  64                                                                                           ordEnumerator.EndParticipation,
  65                                                                                           ordEnumerator.Stop,
  66                                                                                           options);
  67                                 } else {
  68                                         waitAction = ParallelExecuter.ProcessAndCallback (node,
  69                                                                                           buffer.Add,
  70                                                                                           buffer.CompleteAdding,
  71                                                                                           options);
  72                                 }
  73
  74                                 if (options.Options.HasValue && options.Options.Value == ParallelMergeOptions.FullyBuffered)
  75                                         waitAction ();
  76                         }
  77                 }
  78
  79                 void Setup ()
  80                 {
  81                         if (!options.BehindOrderGuard.Value) {
  82                                 if (options.Options.HasValue && (options.Options.Value == ParallelMergeOptions.NotBuffered
  83                                                                  || options.Options.Value == ParallelMergeOptions.FullyBuffered)) {
  84                                         buffer = new BlockingCollection<T> ();
  85                                 } else {
  86                                         buffer = new BlockingCollection<T> (DefaultBufferSize);
  87                                 }
  88
  89                                 IEnumerable<T> source = buffer.GetConsumingEnumerable (options.MergedToken);
  90                                 loader = source.GetEnumerator ();
  91                         } else {
  92                                 loader = ordEnumerator = new OrderingEnumerator<T> (options.PartitionCount, options.MergedToken);
  93                         }
  94                 }
  95
  96                 public void Dispose ()
  97                 {
  98
  99                 }
 100
 101                 public void Reset ()
 102                 {
 103                         throw new NotSupportedException ();
 104                 }
 105
 106                 public bool MoveNext ()
 107                 {
 108                         // If there are no stuff in the buffer
 109                         // but CompleteAdding hasn't been called,
 110                         // MoveNext blocks until further results are produced
 111                         if (!loader.MoveNext ())
 112                                 return false;
 113
 114                         current = loader.Current;
 115                         return true;
 116                 }
 117
 118                 public T Current {
 119                         get {
 120                                 return current;
 121                         }
 122                 }
 123
 124                 object IEnumerator.Current {
 125                         get {
 126                                 return current;
 127                         }
 128                 }
 129         }
 130 }
 131 #endif