Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Inlined / NullableDoubleAverageAggregationOperator.cs / 1305376 / NullableDoubleAverageAggregationOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // NullableDoubleAverageAggregationOperator.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 doubles. /// internal sealed class NullableDoubleAverageAggregationOperator : InlinedAggregationOperator, double?> { //---------------------------------------------------------------------------------------- // Constructs a new instance of an average associative operator. // internal NullableDoubleAverageAggregationOperator(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 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 NullableDoubleAverageAggregationOperatorEnumerator (source, index, cancellationToken); } //--------------------------------------------------------------------------------------- // This enumerator type encapsulates the intermediary aggregation over the underlying // (possibly partitioned) data source. // private class NullableDoubleAverageAggregationOperatorEnumerator : InlinedAggregationOperatorEnumerator > { private QueryOperatorEnumerator m_source; // The source data. //---------------------------------------------------------------------------------------- // Instantiates a new aggregation operator. // internal NullableDoubleAverageAggregationOperatorEnumerator(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. double sum = 0.0; long count = 0; QueryOperatorEnumerator source = m_source; double? current = default(double?); TKey keyUnused = default(TKey); int i = 0; while (source.MoveNext(ref current, ref keyUnused)) { if (current.HasValue) { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); 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
- DataGridRelationshipRow.cs
- TableLayoutStyleCollection.cs
- ConfigViewGenerator.cs
- COM2PropertyPageUITypeConverter.cs
- Control.cs
- NumberAction.cs
- UrlPath.cs
- GorillaCodec.cs
- PassportPrincipal.cs
- HandlerFactoryWrapper.cs
- DoubleKeyFrameCollection.cs
- SecondaryIndex.cs
- RtfFormatStack.cs
- CollectionBuilder.cs
- TypeElementCollection.cs
- WorkflowTransactionOptions.cs
- ActivitySurrogate.cs
- ArrayHelper.cs
- OperatorExpressions.cs
- AuthenticationServiceManager.cs
- RefType.cs
- PerspectiveCamera.cs
- TableItemProviderWrapper.cs
- XmlSchemaImport.cs
- UDPClient.cs
- SqlRemoveConstantOrderBy.cs
- Latin1Encoding.cs
- DataGridColumnCollectionEditor.cs
- Guid.cs
- VectorAnimationUsingKeyFrames.cs
- MarkupCompiler.cs
- DynamicRendererThreadManager.cs
- WorkflowDesignerColors.cs
- WindowsIdentity.cs
- DbConnectionPool.cs
- DigestTraceRecordHelper.cs
- CompiledRegexRunnerFactory.cs
- AuthenticationConfig.cs
- RegexCode.cs
- InputLangChangeEvent.cs
- Queue.cs
- JsonSerializer.cs
- ModelTreeEnumerator.cs
- DynamicActionMessageFilter.cs
- TimeSpanSecondsConverter.cs
- StrictModeSecurityHeaderElementInferenceEngine.cs
- WebServiceMethodData.cs
- EventLevel.cs
- Trace.cs
- UniformGrid.cs
- SubclassTypeValidatorAttribute.cs
- Point3D.cs
- WizardStepBase.cs
- AnnotationElement.cs
- ProxyFragment.cs
- BlockExpression.cs
- LicenseContext.cs
- ConstrainedDataObject.cs
- SubpageParagraph.cs
- RawStylusSystemGestureInputReport.cs
- SqlMethodTransformer.cs
- SqlDataSourceView.cs
- sqlser.cs
- SettingsContext.cs
- VectorValueSerializer.cs
- Win32SafeHandles.cs
- DataGridViewMethods.cs
- BindingContext.cs
- DataRowExtensions.cs
- FlowDocumentPage.cs
- HttpProfileBase.cs
- XmlILConstructAnalyzer.cs
- InternalControlCollection.cs
- DesignerSerializerAttribute.cs
- CatalogZone.cs
- sqlpipe.cs
- UserPersonalizationStateInfo.cs
- SystemInformation.cs
- SqlCharStream.cs
- Decoder.cs
- RoleService.cs
- _ShellExpression.cs
- XhtmlBasicValidationSummaryAdapter.cs
- Stroke.cs
- CodeIterationStatement.cs
- AsyncOperationManager.cs
- IsolatedStoragePermission.cs
- DoubleLinkList.cs
- LocalsItemDescription.cs
- AssemblyResolver.cs
- ArgumentValidation.cs
- PipelineComponent.cs
- UIElement3DAutomationPeer.cs
- InteropAutomationProvider.cs
- EntityDataSourceState.cs
- documentsequencetextview.cs
- WeakReferenceList.cs
- StateBag.cs
- CategoryAttribute.cs
- SimpleTypeResolver.cs