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

   1 // ==++==
   2 //
   3 //   Copyright (c) Microsoft Corporation.  All rights reserved.
   4 //
   5 // ==--==
   6 // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   7 //
   8 // LongSumAggregationOperator.cs
   9 //
  10 // <OWNER>Microsoft</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 longs.
  25     /// </summary>
  26     internal sealed class LongSumAggregationOperator : InlinedAggregationOperator<long, long, long>
  27     {
  28
  29         //---------------------------------------------------------------------------------------
  30         // Constructs a new instance of a sum associative operator.
  31         //
  32
  33         internal LongSumAggregationOperator(IEnumerable<long> 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 long 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<long> enumerator = GetEnumerator(ParallelMergeOptions.FullyBuffered, true))
  52             {
  53                 // We just reduce the elements in each output partition.
  54                 long sum = 0L;
  55                 while (enumerator.MoveNext())
  56                 {
  57                     checked
  58                     {
  59                         sum += enumerator.Current;
  60                     }
  61                 }
  62
  63                 return sum;
  64             }
  65         }
  66
  67         //---------------------------------------------------------------------------------------
  68         // Creates an enumerator that is used internally for the final aggregation step.
  69         //
  70
  71         protected override QueryOperatorEnumerator<long,int> CreateEnumerator<TKey>(
  72             int index, int count, QueryOperatorEnumerator<long, TKey> source, object sharedData, CancellationToken cancellationToken)
  73         {
  74             return new LongSumAggregationOperatorEnumerator<TKey>(source, index, cancellationToken);
  75         }
  76
  77         //---------------------------------------------------------------------------------------
  78         // This enumerator type encapsulates the intermediary aggregation over the underlying
  79         // (possibly partitioned) data source.
  80         //
  81
  82         private class LongSumAggregationOperatorEnumerator<TKey> : InlinedAggregationOperatorEnumerator<long>
  83         {
  84             private readonly QueryOperatorEnumerator<long, TKey> m_source; // The source data.
  85
  86             //---------------------------------------------------------------------------------------
  87             // Instantiates a new aggregation operator.
  88             //
  89
  90             internal LongSumAggregationOperatorEnumerator(QueryOperatorEnumerator<long, TKey> source, int partitionIndex,
  91                 CancellationToken cancellationToken) :
  92                 base(partitionIndex, cancellationToken)
  93             {
  94                 Contract.Assert(source != null);
  95                 m_source = source;
  96             }
  97
  98             //---------------------------------------------------------------------------------------
  99             // Tallies up the sum of the underlying data source, walking the entire thing the first
 100             // time MoveNext is called on this object.
 101             //
 102
 103             protected override bool MoveNextCore(ref long currentElement)
 104             {
 105                 long element = default(long);
 106                 TKey keyUnused = default(TKey);
 107
 108                 QueryOperatorEnumerator<long, TKey> source = m_source;
 109                 if (source.MoveNext(ref element, ref keyUnused))
 110                 {
 111                     // We just scroll through the enumerator and accumulate the sum.
 112                     long tempSum = 0L;
 113                     int i = 0;
 114                     do
 115                     {
 116                         if ((i++ & CancellationState.POLL_INTERVAL) == 0)
 117                             CancellationState.ThrowIfCanceled(m_cancellationToken);
 118
 119                         checked
 120                         {
 121                             tempSum += element;
 122                         }
 123                     }
 124                     while (source.MoveNext(ref element, ref keyUnused));
 125
 126                     // The sum has been calculated. Now just return.
 127                     currentElement = tempSum;
 128                     return true;
 129                 }
 130
 131                 return false;
 132             }
 133
 134             //---------------------------------------------------------------------------------------
 135             // Dispose of resources associated with the underlying enumerator.
 136             //
 137
 138             protected override void Dispose(bool disposing)
 139             {
 140                 Contract.Assert(m_source != null);
 141                 m_source.Dispose();
 142             }
 143         }
 144     }
 145 }