Code:
/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Unary / AnyAllSearchOperator.cs / 1305376 / AnyAllSearchOperator.cs
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// AnyAllSearchOperator.cs
//
// [....]
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Threading;
namespace System.Linq.Parallel
{
///
/// The any/all operators work the same way. They search for the occurrence of a predicate
/// value in the data source, and upon the first occurrence of such a value, yield a
/// particular value. Specifically:
///
/// - Any returns true if the predicate for any element evaluates to true.
/// - All returns false if the predicate for any element evaluates to false.
///
/// This uniformity is used to apply a general purpose algorithm. Both sentences above
/// take the form of "returns XXX if the predicate for any element evaluates to XXX."
/// Therefore, we just parameterize on XXX, called the qualifciation below, and if we
/// ever find an occurrence of XXX in the input data source, we also return XXX. Otherwise,
/// we return !XXX. Obviously, XXX in this case is a bool.
///
/// This is a search algorithm. So once any single partition finds an element, it will
/// return so that execution can stop. This is done with a "cancelation" flag that is
/// polled by all parallel workers. The first worker to find an answer sets it, and all
/// other workers notice it and quit as quickly as possible.
///
/// : UnaryQueryOperator
{
private readonly Func m_predicate; // The predicate used to test membership.
private readonly bool m_qualification; // Whether we're looking for true (any) or false (all).
//----------------------------------------------------------------------------------------
// Constructs a new instance of an any/all search operator.
//
// Arguments:
// child - the child tree to enumerate.
// qualification - the predicate value we require for an element to be considered
// a member of the set; for any this is true, for all it is false.
//
internal AnyAllSearchOperator(IEnumerable child, bool qualification, Func predicate)
:base(child)
{
Contract.Assert(child != null, "child data source cannot be null");
Contract.Assert(predicate != null, "need a predicate function");
m_qualification = qualification;
m_predicate = predicate;
}
//---------------------------------------------------------------------------------------
// Executes the entire query tree, and aggregates the individual partition results to
// form an overall answer to the search operation.
//
internal bool Aggregate()
{
// Because the final reduction is typically much cheaper than the intermediate
// reductions over the individual partitions, and because each parallel partition
// could 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))
{
// Any value equal to our qualification means that we've found an element matching
// the condition, and so we return the qualification without looking in subsequent
// partitions.
while (enumerator.MoveNext())
{
if (enumerator.Current == m_qualification)
{
return m_qualification;
}
}
}
return !m_qualification;
}
//---------------------------------------------------------------------------------------
// Just opens the current operator, including opening the child and wrapping it with
// partitions as needed.
//
internal override QueryResults Open(
QuerySettings settings, bool preferStriping)
{
// We just open the child operator.
QueryResults childQueryResults = Child.Open(settings, preferStriping);
return new UnaryQueryOperatorResults(childQueryResults, this, settings, preferStriping);
}
internal override void WrapPartitionedStream(
PartitionedStream inputStream, IPartitionedStreamRecipient recipient, bool preferStriping, QuerySettings settings)
{
// Create a shared cancelation variable and then return a possibly wrapped new enumerator.
Shared resultFoundFlag = new Shared(false);
int partitionCount = inputStream.PartitionCount;
PartitionedStream outputStream = new PartitionedStream(
partitionCount, Util.GetDefaultComparer(), OrdinalIndexState.Correct);
for (int i = 0; i < partitionCount; i++)
{
outputStream[i] = new AnyAllSearchOperatorEnumerator(inputStream[i], m_qualification, m_predicate, i, resultFoundFlag,
settings.CancellationState.MergedCancellationToken);
}
recipient.Receive(outputStream);
}
//---------------------------------------------------------------------------------------
// Returns an enumerable that represents the query executing sequentially.
//
internal override IEnumerable AsSequentialQuery(CancellationToken token)
{
Contract.Assert(false, "This method should never be called as it is an ending operator with LimitsParallelism=false.");
throw new NotSupportedException();
}
//----------------------------------------------------------------------------------------
// Whether this operator performs a premature merge.
//
internal override bool LimitsParallelism
{
get { return false; }
}
//---------------------------------------------------------------------------------------
// This enumerator performs the search over its input data source. It also cancels peer
// enumerators when an answer was found, and polls this cancelation flag to stop when
// requested.
//
private class AnyAllSearchOperatorEnumerator : QueryOperatorEnumerator
{
private readonly QueryOperatorEnumerator m_source; // The source data.
private readonly Func m_predicate; // The predicate.
private readonly bool m_qualification; // Whether this is an any (true) or all (false) operator.
private readonly int m_partitionIndex; // The partition's index.
private readonly Shared m_resultFoundFlag; // Whether to cancel the search for elements.
private readonly CancellationToken m_cancellationToken;
//----------------------------------------------------------------------------------------
// Instantiates a new any/all search operator.
//
internal AnyAllSearchOperatorEnumerator(QueryOperatorEnumerator source, bool qualification,
Func predicate, int partitionIndex, Shared resultFoundFlag,
CancellationToken cancellationToken)
{
Contract.Assert(source != null);
Contract.Assert(predicate != null);
Contract.Assert(resultFoundFlag != null);
m_source = source;
m_qualification = qualification;
m_predicate = predicate;
m_partitionIndex = partitionIndex;
m_resultFoundFlag = resultFoundFlag;
m_cancellationToken = cancellationToken;
}
//----------------------------------------------------------------------------------------
// This enumerates the entire input source to perform the search. If another peer
// partition finds an answer before us, we will voluntarily return (propagating the
// peer's result).
//
internal override bool MoveNext(ref bool currentElement, ref int currentKey)
{
Contract.Assert(m_predicate != null);
// Avoid enumerating if we've already found an answer.
if (m_resultFoundFlag.Value)
return false;
// We just scroll through the enumerator and accumulate the result.
TInput element = default(TInput);
TKey keyUnused = default(TKey);
if (m_source.MoveNext(ref element, ref keyUnused))
{
currentElement = !m_qualification;
currentKey = m_partitionIndex;
int i = 0;
// Continue walking the data so long as we haven't found an item that satisfies
// the condition we are searching for.
do
{
if ((i++ & CancellationState.POLL_INTERVAL) == 0)
CancellationState.ThrowIfCanceled(m_cancellationToken);
if (m_resultFoundFlag.Value)
{
// If cancelation occurred, it's because a successful answer was found.
return false;
}
if (m_predicate(element) == m_qualification)
{
// We have found an item that satisfies the search. Tell other
// workers that are concurrently searching, and return.
m_resultFoundFlag.Value = true;
currentElement = m_qualification;
break;
}
}
while (m_source.MoveNext(ref element, ref keyUnused));
return true;
}
return false;
}
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.
// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// AnyAllSearchOperator.cs
//
// [....]
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Threading;
namespace System.Linq.Parallel
{
///
/// The any/all operators work the same way. They search for the occurrence of a predicate
/// value in the data source, and upon the first occurrence of such a value, yield a
/// particular value. Specifically:
///
/// - Any returns true if the predicate for any element evaluates to true.
/// - All returns false if the predicate for any element evaluates to false.
///
/// This uniformity is used to apply a general purpose algorithm. Both sentences above
/// take the form of "returns XXX if the predicate for any element evaluates to XXX."
/// Therefore, we just parameterize on XXX, called the qualifciation below, and if we
/// ever find an occurrence of XXX in the input data source, we also return XXX. Otherwise,
/// we return !XXX. Obviously, XXX in this case is a bool.
///
/// This is a search algorithm. So once any single partition finds an element, it will
/// return so that execution can stop. This is done with a "cancelation" flag that is
/// polled by all parallel workers. The first worker to find an answer sets it, and all
/// other workers notice it and quit as quickly as possible.
///
/// : UnaryQueryOperator
{
private readonly Func m_predicate; // The predicate used to test membership.
private readonly bool m_qualification; // Whether we're looking for true (any) or false (all).
//----------------------------------------------------------------------------------------
// Constructs a new instance of an any/all search operator.
//
// Arguments:
// child - the child tree to enumerate.
// qualification - the predicate value we require for an element to be considered
// a member of the set; for any this is true, for all it is false.
//
internal AnyAllSearchOperator(IEnumerable child, bool qualification, Func predicate)
:base(child)
{
Contract.Assert(child != null, "child data source cannot be null");
Contract.Assert(predicate != null, "need a predicate function");
m_qualification = qualification;
m_predicate = predicate;
}
//---------------------------------------------------------------------------------------
// Executes the entire query tree, and aggregates the individual partition results to
// form an overall answer to the search operation.
//
internal bool Aggregate()
{
// Because the final reduction is typically much cheaper than the intermediate
// reductions over the individual partitions, and because each parallel partition
// could 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))
{
// Any value equal to our qualification means that we've found an element matching
// the condition, and so we return the qualification without looking in subsequent
// partitions.
while (enumerator.MoveNext())
{
if (enumerator.Current == m_qualification)
{
return m_qualification;
}
}
}
return !m_qualification;
}
//---------------------------------------------------------------------------------------
// Just opens the current operator, including opening the child and wrapping it with
// partitions as needed.
//
internal override QueryResults Open(
QuerySettings settings, bool preferStriping)
{
// We just open the child operator.
QueryResults childQueryResults = Child.Open(settings, preferStriping);
return new UnaryQueryOperatorResults(childQueryResults, this, settings, preferStriping);
}
internal override void WrapPartitionedStream(
PartitionedStream inputStream, IPartitionedStreamRecipient recipient, bool preferStriping, QuerySettings settings)
{
// Create a shared cancelation variable and then return a possibly wrapped new enumerator.
Shared resultFoundFlag = new Shared(false);
int partitionCount = inputStream.PartitionCount;
PartitionedStream outputStream = new PartitionedStream(
partitionCount, Util.GetDefaultComparer(), OrdinalIndexState.Correct);
for (int i = 0; i < partitionCount; i++)
{
outputStream[i] = new AnyAllSearchOperatorEnumerator(inputStream[i], m_qualification, m_predicate, i, resultFoundFlag,
settings.CancellationState.MergedCancellationToken);
}
recipient.Receive(outputStream);
}
//---------------------------------------------------------------------------------------
// Returns an enumerable that represents the query executing sequentially.
//
internal override IEnumerable AsSequentialQuery(CancellationToken token)
{
Contract.Assert(false, "This method should never be called as it is an ending operator with LimitsParallelism=false.");
throw new NotSupportedException();
}
//----------------------------------------------------------------------------------------
// Whether this operator performs a premature merge.
//
internal override bool LimitsParallelism
{
get { return false; }
}
//---------------------------------------------------------------------------------------
// This enumerator performs the search over its input data source. It also cancels peer
// enumerators when an answer was found, and polls this cancelation flag to stop when
// requested.
//
private class AnyAllSearchOperatorEnumerator : QueryOperatorEnumerator
{
private readonly QueryOperatorEnumerator m_source; // The source data.
private readonly Func m_predicate; // The predicate.
private readonly bool m_qualification; // Whether this is an any (true) or all (false) operator.
private readonly int m_partitionIndex; // The partition's index.
private readonly Shared m_resultFoundFlag; // Whether to cancel the search for elements.
private readonly CancellationToken m_cancellationToken;
//----------------------------------------------------------------------------------------
// Instantiates a new any/all search operator.
//
internal AnyAllSearchOperatorEnumerator(QueryOperatorEnumerator source, bool qualification,
Func predicate, int partitionIndex, Shared resultFoundFlag,
CancellationToken cancellationToken)
{
Contract.Assert(source != null);
Contract.Assert(predicate != null);
Contract.Assert(resultFoundFlag != null);
m_source = source;
m_qualification = qualification;
m_predicate = predicate;
m_partitionIndex = partitionIndex;
m_resultFoundFlag = resultFoundFlag;
m_cancellationToken = cancellationToken;
}
//----------------------------------------------------------------------------------------
// This enumerates the entire input source to perform the search. If another peer
// partition finds an answer before us, we will voluntarily return (propagating the
// peer's result).
//
internal override bool MoveNext(ref bool currentElement, ref int currentKey)
{
Contract.Assert(m_predicate != null);
// Avoid enumerating if we've already found an answer.
if (m_resultFoundFlag.Value)
return false;
// We just scroll through the enumerator and accumulate the result.
TInput element = default(TInput);
TKey keyUnused = default(TKey);
if (m_source.MoveNext(ref element, ref keyUnused))
{
currentElement = !m_qualification;
currentKey = m_partitionIndex;
int i = 0;
// Continue walking the data so long as we haven't found an item that satisfies
// the condition we are searching for.
do
{
if ((i++ & CancellationState.POLL_INTERVAL) == 0)
CancellationState.ThrowIfCanceled(m_cancellationToken);
if (m_resultFoundFlag.Value)
{
// If cancelation occurred, it's because a successful answer was found.
return false;
}
if (m_predicate(element) == m_qualification)
{
// We have found an item that satisfies the search. Tell other
// workers that are concurrently searching, and return.
m_resultFoundFlag.Value = true;
currentElement = m_qualification;
break;
}
}
while (m_source.MoveNext(ref element, ref keyUnused));
return true;
}
return false;
}
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.
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