mcs/class/referencesource/System.Core/System/Linq/Parallel/QueryOperators/Inlined/FloatSumAggregationOperator.cs

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   7 //
   8 // FloatSumAggregationOperator.cs
   9 //
  10 // <OWNER>[....]</OWNER>
  11 //
  12 // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
  13
  14 using System.Collections.Generic;
  15 using System.Diagnostics.Contracts;
  16 using System.Threading;
  17 #if SILVERLIGHT
  18 using System.Core; // for System.Core.SR
  19 #endif
  20
  21 namespace System.Linq.Parallel
  22 {
  23     /// <summary>
  24     /// An inlined sum aggregation and its enumerator, for floats.
  25     /// </summary>
  26     internal sealed class FloatSumAggregationOperator : InlinedAggregationOperator<float, double, float>
  27     {
  28
  29         //---------------------------------------------------------------------------------------
  30         // Constructs a new instance of a sum associative operator.
  31         //
  32
  33         internal FloatSumAggregationOperator(IEnumerable<float> child) : base(child)
  34         {
  35         }
  36
  37         //---------------------------------------------------------------------------------------
  38         // Executes the entire query tree, and aggregates the intermediate results into the
  39         // final result based on the binary operators and final reduction.
  40         //
  41         // Return Value:
  42         //     The single result of aggregation.
  43         //
  44
  45         protected override float InternalAggregate(ref Exception singularExceptionToThrow)
  46         {
  47             // Because the final reduction is typically much cheaper than the intermediate
  48             // reductions over the individual partitions, and because each parallel partition
  49             // will do a lot of work to produce a single output element, we prefer to turn off
  50             // pipelining, and process the final reductions serially.
  51             using (IEnumerator<double> enumerator = GetEnumerator(ParallelMergeOptions.FullyBuffered, true))
  52             {
  53                 // We just reduce the elements in each output partition.
  54                 double sum = 0.0;
  55                 while (enumerator.MoveNext())
  56                 {
  57                     checked
  58                     {
  59                         sum += enumerator.Current;
  60                     }
  61                 }
  62
  63                 return (float)sum;
  64             }
  65         }
  66
  67         //---------------------------------------------------------------------------------------
  68         // Creates an enumerator that is used internally for the final aggregation step.
  69         //
  70
  71         protected override QueryOperatorEnumerator<double,int> CreateEnumerator<TKey>(
  72             int index, int count, QueryOperatorEnumerator<float, TKey> source, object sharedData,
  73             CancellationToken cancellationToken)
  74         {
  75             return new FloatSumAggregationOperatorEnumerator<TKey>(source, index, cancellationToken);
  76         }
  77
  78         //---------------------------------------------------------------------------------------
  79         // This enumerator type encapsulates the intermediary aggregation over the underlying
  80         // (possibly partitioned) data source.
  81         //
  82
  83         private class FloatSumAggregationOperatorEnumerator<TKey> : InlinedAggregationOperatorEnumerator<double>
  84         {
  85             private readonly QueryOperatorEnumerator<float, TKey> m_source; // The source data.
  86
  87             //---------------------------------------------------------------------------------------
  88             // Instantiates a new aggregation operator.
  89             //
  90
  91             internal FloatSumAggregationOperatorEnumerator(QueryOperatorEnumerator<float, TKey> source, int partitionIndex,
  92                 CancellationToken cancellationToken) :
  93                 base(partitionIndex, cancellationToken)
  94             {
  95                 Contract.Assert(source != null);
  96                 m_source = source;
  97             }
  98
  99             //---------------------------------------------------------------------------------------
 100             // Tallies up the sum of the underlying data source, walking the entire thing the first
 101             // time MoveNext is called on this object.
 102             //
 103
 104             protected override bool MoveNextCore(ref double currentElement)
 105             {
 106                 float element = default(float);
 107                 TKey keyUnused = default(TKey);
 108
 109                 QueryOperatorEnumerator<float, TKey> source = m_source;
 110                 if (source.MoveNext(ref element, ref keyUnused))
 111                 {
 112                     // We just scroll through the enumerator and accumulate the sum.
 113                     double tempSum = 0.0f;
 114                     int i = 0;
 115                     do
 116                     {
 117                         if ((i++ & CancellationState.POLL_INTERVAL) == 0)
 118                             CancellationState.ThrowIfCanceled(m_cancellationToken);
 119
 120                         tempSum += element;
 121                     }
 122                     while (source.MoveNext(ref element, ref keyUnused));
 123
 124                     // The sum has been calculated. Now just return.
 125                     currentElement = tempSum;
 126                     return true;
 127                 }
 128
 129                 return false;
 130             }
 131
 132             //---------------------------------------------------------------------------------------
 133             // Dispose of resources associated with the underlying enumerator.
 134             //
 135
 136             protected override void Dispose(bool disposing)
 137             {
 138                 Contract.Assert(m_source != null);
 139                 m_source.Dispose();
 140             }
 141         }
 142     }
 143 }