DoubleSumAggregationOperator.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Inlined / DoubleSumAggregationOperator.cs / 1305376 / DoubleSumAggregationOperator.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// DoubleSumAggregationOperator.cs 
//
// [....] 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

using System.Collections.Generic; 
using System.Diagnostics.Contracts;
using System.Threading; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// An inlined sum aggregation and its enumerator, for doubles.
    /// 
    internal sealed class DoubleSumAggregationOperator : InlinedAggregationOperator 
    {
 
        //---------------------------------------------------------------------------------------- 
        // Constructs a new instance of a sum associative operator.
        // 

        internal DoubleSumAggregationOperator(IEnumerable child) : base(child)
        {
        } 

        //--------------------------------------------------------------------------------------- 
        // Executes the entire query tree, and aggregates the intermediate results into the 
        // final result based on the binary operators and final reduction.
        // 
        // Return Value:
        //     The single result of aggregation.
        //
 
        protected override double InternalAggregate(ref Exception singularExceptionToThrow)
        { 
            // Because the final reduction is typically much cheaper than the intermediate 
            // reductions over the individual partitions, and because each parallel partition
            // will do a lot of work to produce a single output element, we prefer to turn off 
            // pipelining, and process the final reductions serially.
            using (IEnumerator enumerator = GetEnumerator(ParallelMergeOptions.FullyBuffered, true))
            {
                // We just reduce the elements in each output partition. 
                double sum = 0.0;
                while (enumerator.MoveNext()) 
                { 
                    checked
                    { 
                        sum += enumerator.Current;
                    }
                }
 
                return sum;
            } 
        } 

        //--------------------------------------------------------------------------------------- 
        // Creates an enumerator that is used internally for the final aggregation step.
        //

        protected override QueryOperatorEnumerator CreateEnumerator( 
            int index, int count, QueryOperatorEnumerator source, object sharedData, CancellationToken cancellationToken)
        { 
            return new DoubleSumAggregationOperatorEnumerator(source, index, cancellationToken); 
        }
 
        //---------------------------------------------------------------------------------------
        // This enumerator type encapsulates the intermediary aggregation over the underlying
        // (possibly partitioned) data source.
        // 

        private class DoubleSumAggregationOperatorEnumerator : InlinedAggregationOperatorEnumerator 
        { 
            private readonly QueryOperatorEnumerator m_source; // The source data.
 
            //----------------------------------------------------------------------------------------
            // Instantiates a new aggregation operator.
            //
 
            internal DoubleSumAggregationOperatorEnumerator(QueryOperatorEnumerator source, int partitionIndex,
                CancellationToken cancellationToken) : 
                base(partitionIndex, cancellationToken) 
            {
                Contract.Assert(source != null); 
                m_source = source;
            }

            //--------------------------------------------------------------------------------------- 
            // Tallies up the sum of the underlying data source, walking the entire thing the first
            // time MoveNext is called on this object. 
            // 

            protected override bool MoveNextCore(ref double currentElement) 
            {
                double element = default(double);
                TKey keyUnused = default(TKey);
 
                QueryOperatorEnumerator source = m_source;
                if (source.MoveNext(ref element, ref keyUnused)) 
                { 
                    // We just scroll through the enumerator and accumulate the sum.
                    double tempSum = 0.0; 
                    int i = 0;
                    do
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0) 
                            CancellationState.ThrowIfCanceled(m_cancellationToken);
                        tempSum += element; 
                    } 
                    while (source.MoveNext(ref element, ref keyUnused));
 
                    // The sum has been calculated. Now just return.
                    currentElement = tempSum;
                    return true;
                } 

                return false; 
            } 

            //---------------------------------------------------------------------------------------- 
            // Dispose of resources associated with the underlying enumerator.
            //

            protected override void Dispose(bool disposing) 
            {
                Contract.Assert(m_source != null); 
                m_source.Dispose(); 
            }
        } 
    }
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.

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