// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // NullableDoubleSumAggregationOperator.cs // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics; using System.Threading; namespace System.Linq.Parallel { /// <summary> /// An inlined sum aggregation and its enumerator, for nullable doubles. /// </summary> internal sealed class NullableDoubleSumAggregationOperator : InlinedAggregationOperator<double?, double?, double?> { //--------------------------------------------------------------------------------------- // Constructs a new instance of a sum associative operator. // internal NullableDoubleSumAggregationOperator(IEnumerable<double?> 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<double?> enumerator = GetEnumerator(ParallelMergeOptions.FullyBuffered, true)) { // We just reduce the elements in each output partition. double sum = 0.0; while (enumerator.MoveNext()) { sum += enumerator.Current.GetValueOrDefault(); } return sum; } } //--------------------------------------------------------------------------------------- // Creates an enumerator that is used internally for the final aggregation step. // protected override QueryOperatorEnumerator<double?, int> CreateEnumerator<TKey>( int index, int count, QueryOperatorEnumerator<double?, TKey> source, object? sharedData, CancellationToken cancellationToken) { return new NullableDoubleSumAggregationOperatorEnumerator<TKey>(source, index, cancellationToken); } //--------------------------------------------------------------------------------------- // This enumerator type encapsulates the intermediary aggregation over the underlying // (possibly partitioned) data source. // private sealed class NullableDoubleSumAggregationOperatorEnumerator<TKey> : InlinedAggregationOperatorEnumerator<double?> { private readonly QueryOperatorEnumerator<double?, TKey> _source; // The source data. //--------------------------------------------------------------------------------------- // Instantiates a new aggregation operator. // internal NullableDoubleSumAggregationOperatorEnumerator(QueryOperatorEnumerator<double?, TKey> source, int partitionIndex, CancellationToken cancellationToken) : base(partitionIndex, cancellationToken) { Debug.Assert(source != null); _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<double?, TKey> source = _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) _cancellationToken.ThrowIfCancellationRequested(); tempSum += element.GetValueOrDefault(); } 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) { Debug.Assert(_source != null); _source.Dispose(); } } } } |