Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Inlined / NullableIntAverageAggregationOperator.cs / 1305376 / NullableIntAverageAggregationOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // NullableIntAverageAggregationOperator.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 ints. /// internal sealed class NullableIntAverageAggregationOperator : InlinedAggregationOperator, double?> { //---------------------------------------------------------------------------------------- // Constructs a new instance of an average associative operator. // internal NullableIntAverageAggregationOperator(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 NullableIntAverageAggregationOperatorEnumerator (source, index, cancellationToken); } //--------------------------------------------------------------------------------------- // This enumerator type encapsulates the intermediary aggregation over the underlying // (possibly partitioned) data source. // private class NullableIntAverageAggregationOperatorEnumerator : InlinedAggregationOperatorEnumerator > { private QueryOperatorEnumerator m_source; // The source data. //---------------------------------------------------------------------------------------- // Instantiates a new aggregation operator. // internal NullableIntAverageAggregationOperatorEnumerator(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; int? current = default(int?); 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
- TextBoxView.cs
- MultipartIdentifier.cs
- Profiler.cs
- WebPartVerbCollection.cs
- ControlFilterExpression.cs
- BookmarkEventArgs.cs
- ApplicationDirectoryMembershipCondition.cs
- AppDomainGrammarProxy.cs
- UnsafeNetInfoNativeMethods.cs
- DocobjHost.cs
- DesignerDataTableBase.cs
- XmlReflectionImporter.cs
- ReflectionHelper.cs
- CapabilitiesPattern.cs
- TableCellCollection.cs
- UnsafeNativeMethods.cs
- DictionaryEntry.cs
- TextSelection.cs
- NotSupportedException.cs
- StreamGeometry.cs
- UpdatePanelTrigger.cs
- MobileContainerDesigner.cs
- ApplicationInfo.cs
- CallbackHandler.cs
- HandlerFactoryCache.cs
- Evidence.cs
- DataQuery.cs
- ManageRequest.cs
- TileBrush.cs
- DrawingState.cs
- SqlRetyper.cs
- ZipIOExtraFieldPaddingElement.cs
- FederatedMessageSecurityOverHttpElement.cs
- SynchronizedRandom.cs
- IRCollection.cs
- ContextMarshalException.cs
- ActivityExecutorOperation.cs
- FilterQueryOptionExpression.cs
- BaseContextMenu.cs
- unsafenativemethodstextservices.cs
- FontDialog.cs
- ResourceDictionary.cs
- AstTree.cs
- DesignerTextBoxAdapter.cs
- CancellationHandler.cs
- FormatConvertedBitmap.cs
- ConfigurationManagerInternalFactory.cs
- DefaultEvaluationContext.cs
- CharEnumerator.cs
- HttpStreamMessage.cs
- RegexTree.cs
- ClientSideQueueItem.cs
- WCFServiceClientProxyGenerator.cs
- DesignBindingConverter.cs
- KeyGestureValueSerializer.cs
- FileFormatException.cs
- HideDisabledControlAdapter.cs
- DCSafeHandle.cs
- FrameworkElementAutomationPeer.cs
- Debug.cs
- CompilerWrapper.cs
- IndexOutOfRangeException.cs
- IIS7UserPrincipal.cs
- SqlTopReducer.cs
- QueryPageSettingsEventArgs.cs
- ColorBlend.cs
- WebControl.cs
- XmlWriterTraceListener.cs
- FragmentQueryKB.cs
- FieldDescriptor.cs
- Equal.cs
- DataRecordInternal.cs
- HtmlFormWrapper.cs
- RootBrowserWindowProxy.cs
- DynamicResourceExtension.cs
- SafeRightsManagementHandle.cs
- XPathDocumentNavigator.cs
- CharStorage.cs
- Math.cs
- ObjectViewListener.cs
- DefaultTraceListener.cs
- Latin1Encoding.cs
- EntityTemplateUserControl.cs
- LightweightCodeGenerator.cs
- LogSwitch.cs
- FileDialog_Vista_Interop.cs
- WindowsListViewScroll.cs
- MessageBox.cs
- DefaultHttpHandler.cs
- InputLanguage.cs
- ParameterEditorUserControl.cs
- PerformanceCounterCategory.cs
- TextAnchor.cs
- ModelEditingScope.cs
- XmlElementAttributes.cs
- DataContractJsonSerializer.cs
- HandoffBehavior.cs
- ToolbarAUtomationPeer.cs
- Int32CollectionConverter.cs
- EmptyQuery.cs