Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Inlined / NullableLongAverageAggregationOperator.cs / 1305376 / NullableLongAverageAggregationOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // NullableLongAverageAggregationOperator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics.Contracts; using System.Threading; namespace System.Linq.Parallel { ////// An inlined average aggregation operator and its enumerator, for Nullable longs. /// internal sealed class NullableLongAverageAggregationOperator : InlinedAggregationOperator, double?> { //---------------------------------------------------------------------------------------- // Constructs a new instance of an average associative operator. // internal NullableLongAverageAggregationOperator(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)) { // If the sequence was empty, return null right away. if (!enumerator.MoveNext()) { return null; } Pair result = enumerator.Current; // Simply add together the sums and totals. while (enumerator.MoveNext()) { checked { result.First += enumerator.Current.First; result.Second += enumerator.Current.Second; } } // And divide the sum by the total to obtain the final result. return (double)result.First / result.Second; } } //--------------------------------------------------------------------------------------- // Creates an enumerator that is used internally for the final aggregation step. // protected override QueryOperatorEnumerator , int> CreateEnumerator ( int index, int count, QueryOperatorEnumerator source, object sharedData, CancellationToken cancellationToken) { return new NullableLongAverageAggregationOperatorEnumerator (source, index, cancellationToken); } //--------------------------------------------------------------------------------------- // This enumerator type encapsulates the intermediary aggregation over the underlying // (possibly partitioned) data source. // private class NullableLongAverageAggregationOperatorEnumerator : InlinedAggregationOperatorEnumerator > { private QueryOperatorEnumerator m_source; // The source data. //---------------------------------------------------------------------------------------- // Instantiates a new aggregation operator. // internal NullableLongAverageAggregationOperatorEnumerator(QueryOperatorEnumerator source, int partitionIndex, CancellationToken cancellationToken) : base(partitionIndex, cancellationToken) { Contract.Assert(source != null); m_source = source; } //--------------------------------------------------------------------------------------- // Tallies up the average of the underlying data source, walking the entire thing the first // time MoveNext is called on this object. // protected override bool MoveNextCore(ref Pair currentElement) { // The temporary result contains the running sum and count, respectively. long sum = 0; long count = 0; QueryOperatorEnumerator source = m_source; long? current = default(long?); TKey keyUnused = default(TKey); int i = 0; while (source.MoveNext(ref current, ref keyUnused)) { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); if (current.HasValue) { sum += current.GetValueOrDefault(); count++; } } currentElement = new Pair (sum, count); return count > 0; } //---------------------------------------------------------------------------------------- // 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.
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- HtmlAnchor.cs
- WebSysDisplayNameAttribute.cs
- PersonalizablePropertyEntry.cs
- SqlVisitor.cs
- MetadataUtilsSmi.cs
- _SingleItemRequestCache.cs
- XPathDocumentNavigator.cs
- Matrix.cs
- CmsInterop.cs
- UserControl.cs
- DropSource.cs
- ObjectSecurity.cs
- DataRecord.cs
- TextClipboardData.cs
- DelegatedStream.cs
- Byte.cs
- ValidatorCollection.cs
- TemplatedWizardStep.cs
- SafePEFileHandle.cs
- ZoneLinkButton.cs
- FontResourceCache.cs
- PublisherIdentityPermission.cs
- PageParserFilter.cs
- StdRegProviderWrapper.cs
- GeneralTransform2DTo3D.cs
- WindowsToolbar.cs
- MappingMetadataHelper.cs
- ErrorTableItemStyle.cs
- DataSet.cs
- DoubleStorage.cs
- MailSettingsSection.cs
- HttpCachePolicyBase.cs
- DataFieldEditor.cs
- ValidationSummary.cs
- FieldTemplateFactory.cs
- SQLInt16Storage.cs
- RegisteredDisposeScript.cs
- TableProviderWrapper.cs
- XmlNodeComparer.cs
- DataComponentMethodGenerator.cs
- SiteMapHierarchicalDataSourceView.cs
- ProtocolsSection.cs
- CmsUtils.cs
- GrammarBuilderDictation.cs
- ControllableStoryboardAction.cs
- ActiveXHelper.cs
- IFlowDocumentViewer.cs
- BuildResult.cs
- EqualityArray.cs
- Rotation3DAnimationBase.cs
- InstanceContext.cs
- ReadingWritingEntityEventArgs.cs
- Utils.cs
- ActivitySurrogateSelector.cs
- CodeEntryPointMethod.cs
- iisPickupDirectory.cs
- ProxyDataContractResolver.cs
- smtpconnection.cs
- Hex.cs
- TableCell.cs
- XmlValidatingReader.cs
- DecimalAnimationUsingKeyFrames.cs
- MetadataPropertyvalue.cs
- TokenBasedSetEnumerator.cs
- Parallel.cs
- EntityConnectionStringBuilder.cs
- NativeWindow.cs
- CodeExpressionCollection.cs
- IntSecurity.cs
- RewritingPass.cs
- SqlConnectionString.cs
- MethodCallConverter.cs
- IIS7WorkerRequest.cs
- COM2EnumConverter.cs
- MessageVersionConverter.cs
- Label.cs
- ToolStripProgressBar.cs
- SoapHeaderAttribute.cs
- BooleanAnimationBase.cs
- WebColorConverter.cs
- SystemMulticastIPAddressInformation.cs
- Viewport3DVisual.cs
- DateTimeOffset.cs
- AccessDataSourceDesigner.cs
- WebColorConverter.cs
- ConfigurationLockCollection.cs
- ReservationNotFoundException.cs
- LocalizableResourceBuilder.cs
- ListItemCollection.cs
- Compilation.cs
- ProfilePropertySettings.cs
- GB18030Encoding.cs
- Journal.cs
- FlowDocumentScrollViewer.cs
- ToolStripSettings.cs
- MouseButtonEventArgs.cs
- DataBoundControlHelper.cs
- ComAwareEventInfo.cs
- AppDomainShutdownMonitor.cs
- DefaultValueTypeConverter.cs