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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / Enumerables / RangeEnumerable.cs / 1305376 / RangeEnumerable.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // RangeEnumerable.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; namespace System.Linq.Parallel { ////// A simple enumerable type that implements the range algorithm. It also supports /// partitioning of the indices by implementing an interface that PLINQ recognizes. /// internal class RangeEnumerable : ParallelQuery, IParallelPartitionable { private int m_from; // Lowest index to include. private int m_count; // Number of indices to include. //------------------------------------------------------------------------------------ // Constructs a new range enumerable object for the specified range. // internal RangeEnumerable(int from, int count) :base(QuerySettings.Empty) { // Transform the from and to indices into low and highs. m_from = from; m_count = count; } //----------------------------------------------------------------------------------- // Retrieves 'count' partitions, each of which uses a non-overlapping set of indices. // public QueryOperatorEnumerator [] GetPartitions(int partitionCount) { // Calculate a stride size, avoiding overflow if m_count is large int stride = m_count / partitionCount; int biggerPartitionCount = m_count % partitionCount; // Create individual partitions, carefully avoiding overflow int doneCount = 0; QueryOperatorEnumerator [] partitions = new QueryOperatorEnumerator [partitionCount]; for (int i = 0; i < partitionCount; i++) { int partitionSize = (i < biggerPartitionCount) ? stride + 1 : stride; partitions[i] = new RangeEnumerator( m_from + doneCount, partitionSize, doneCount); doneCount += partitionSize; } return partitions; } //----------------------------------------------------------------------------------- // Basic IEnumerator method implementations. // public override IEnumerator GetEnumerator() { return new RangeEnumerator(m_from, m_count, 0).AsClassicEnumerator(); } //----------------------------------------------------------------------------------- // The actual enumerator that walks over the specified range. // class RangeEnumerator : QueryOperatorEnumerator { private readonly int m_from; // The initial value. private readonly int m_count; // How many values to yield. private readonly int m_initialIndex; // The ordinal index of the first value in the range. private Shared m_currentCount; // The 0-based index of the current value. [allocate in moveNext to avoid false-sharing] //------------------------------------------------------------------------------------ // Creates a new enumerator. // internal RangeEnumerator(int from, int count, int initialIndex) { m_from = from; m_count = count; m_initialIndex = initialIndex; } //----------------------------------------------------------------------------------- // Basic enumeration method. This implements the logic to walk the desired // range, using the step specified at construction time. // internal override bool MoveNext(ref int currentElement, ref int currentKey) { if( m_currentCount == null) m_currentCount = new Shared (-1); // Calculate the next index and ensure it falls within our range. int nextCount = m_currentCount.Value + 1; if (nextCount < m_count) { m_currentCount.Value = nextCount; currentElement = nextCount + m_from; currentKey = nextCount + m_initialIndex; return true; } return false; } internal override void Reset() { // We set the current value such that the next addition of step // results in the 1st real value in the range. m_currentCount = null; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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