Partitioner<TSource> Class
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Represents a particular manner of splitting a data source into multiple partitions.
generic <typename TSource>
public ref class Partitioner abstractpublic abstract class Partitioner<TSource>type Partitioner<'Source> = classPublic MustInherit Class Partitioner(Of TSource)Type Parameters
- TSource
Type of the elements in the collection.
- Inheritance
-
Partitioner<TSource>
- Derived
Examples
The following example shows how to implement a partitioner that returns a single element at a time:
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks;
namespace PartitionerDemo
{
// Simple partitioner that will extract one item at a time, in a thread-safe fashion,
// from the underlying collection.
class SingleElementPartitioner<T> : Partitioner<T>
{
// The collection being wrapped by this Partitioner
IEnumerable<T> m_referenceEnumerable;
// Internal class that serves as a shared enumerable for the
// underlying collection.
private class InternalEnumerable : IEnumerable<T>, IDisposable
{
IEnumerator<T> m_reader;
bool m_disposed = false;
// These two are used to implement Dispose() when static partitioning is being performed
int m_activeEnumerators;
bool m_downcountEnumerators;
// "downcountEnumerators" will be true for static partitioning, false for
// dynamic partitioning.
public InternalEnumerable(IEnumerator<T> reader, bool downcountEnumerators)
{
m_reader = reader;
m_activeEnumerators = 0;
m_downcountEnumerators = downcountEnumerators;
}
public IEnumerator<T> GetEnumerator()
{
if (m_disposed)
throw new ObjectDisposedException("InternalEnumerable: Can't call GetEnumerator() after disposing");
// For static partitioning, keep track of the number of active enumerators.
if (m_downcountEnumerators) Interlocked.Increment(ref m_activeEnumerators);
return new InternalEnumerator(m_reader, this);
}
IEnumerator IEnumerable.GetEnumerator()
{
return ((IEnumerable<T>)this).GetEnumerator();
}
public void Dispose()
{
if (!m_disposed)
{
// Only dispose the source enumerator if you are doing dynamic partitioning
if (!m_downcountEnumerators)
{
m_reader.Dispose();
}
m_disposed = true;
}
}
// Called from Dispose() method of spawned InternalEnumerator. During
// static partitioning, the source enumerator will be automatically
// disposed once all requested InternalEnumerators have been disposed.
public void DisposeEnumerator()
{
if (m_downcountEnumerators)
{
if (Interlocked.Decrement(ref m_activeEnumerators) == 0)
{
m_reader.Dispose();
}
}
}
}
// Internal class that serves as a shared enumerator for
// the underlying collection.
private class InternalEnumerator : IEnumerator<T>
{
T m_current;
IEnumerator<T> m_source;
InternalEnumerable m_controllingEnumerable;
bool m_disposed = false;
public InternalEnumerator(IEnumerator<T> source, InternalEnumerable controllingEnumerable)
{
m_source = source;
m_current = default(T);
m_controllingEnumerable = controllingEnumerable;
}
object IEnumerator.Current
{
get { return m_current; }
}
T IEnumerator<T>.Current
{
get { return m_current; }
}
void IEnumerator.Reset()
{
throw new NotSupportedException("Reset() not supported");
}
// This method is the crux of this class. Under lock, it calls
// MoveNext() on the underlying enumerator and grabs Current.
bool IEnumerator.MoveNext()
{
bool rval = false;
lock (m_source)
{
rval = m_source.MoveNext();
m_current = rval ? m_source.Current : default(T);
}
return rval;
}
void IDisposable.Dispose()
{
if (!m_disposed)
{
// Delegate to parent enumerable's DisposeEnumerator() method
m_controllingEnumerable.DisposeEnumerator();
m_disposed = true;
}
}
}
// Constructor just grabs the collection to wrap
public SingleElementPartitioner(IEnumerable<T> enumerable)
{
// Verify that the source IEnumerable is not null
if (enumerable == null)
throw new ArgumentNullException("enumerable");
m_referenceEnumerable = enumerable;
}
// Produces a list of "numPartitions" IEnumerators that can each be
// used to traverse the underlying collection in a thread-safe manner.
// This will return a static number of enumerators, as opposed to
// GetDynamicPartitions(), the result of which can be used to produce
// any number of enumerators.
public override IList<IEnumerator<T>> GetPartitions(int numPartitions)
{
if (numPartitions < 1)
throw new ArgumentOutOfRangeException("NumPartitions");
List<IEnumerator<T>> list = new List<IEnumerator<T>>(numPartitions);
// Since we are doing static partitioning, create an InternalEnumerable with reference
// counting of spawned InternalEnumerators turned on. Once all of the spawned enumerators
// are disposed, dynamicPartitions will be disposed.
var dynamicPartitions = new InternalEnumerable(m_referenceEnumerable.GetEnumerator(), true);
for (int i = 0; i < numPartitions; i++)
list.Add(dynamicPartitions.GetEnumerator());
return list;
}
// Returns an instance of our internal Enumerable class. GetEnumerator()
// can then be called on that (multiple times) to produce shared enumerators.
public override IEnumerable<T> GetDynamicPartitions()
{
// Since we are doing dynamic partitioning, create an InternalEnumerable with reference
// counting of spawned InternalEnumerators turned off. This returned InternalEnumerable
// will need to be explicitly disposed.
return new InternalEnumerable(m_referenceEnumerable.GetEnumerator(), false);
}
// Must be set to true if GetDynamicPartitions() is supported.
public override bool SupportsDynamicPartitions
{
get { return true; }
}
}
class Program
{
// Test our SingleElementPartitioner(T) class
static void Main()
{
// Our sample collection
string[] collection = new string[] {"red", "orange", "yellow", "green", "blue", "indigo",
"violet", "black", "white", "grey"};
// Instantiate a partitioner for our collection
SingleElementPartitioner<string> myPart = new SingleElementPartitioner<string>(collection);
//
// Simple test with ForEach
//
Console.WriteLine("Testing with Parallel.ForEach");
Parallel.ForEach(myPart, item =>
{
Console.WriteLine(" item = {0}, thread id = {1}", item, Thread.CurrentThread.ManagedThreadId);
});
//
//
// Demonstrate the use of static partitioning, which really means
// "using a static number of partitioners". The partitioners themselves
// may still be "dynamic" in the sense that their outputs may not be
// deterministic.
//
//
// Perform static partitioning of collection
var staticPartitions = myPart.GetPartitions(2);
int index = 0;
Console.WriteLine("Static Partitioning, 2 partitions, 2 tasks:");
// Action will consume from static partitions
Action staticAction = () =>
{
int myIndex = Interlocked.Increment(ref index) - 1; // compute your index
var myItems = staticPartitions[myIndex]; // grab your static partition
int id = Thread.CurrentThread.ManagedThreadId; // cache your thread id
// Enumerate through your static partition
while (myItems.MoveNext())
{
Thread.Sleep(50); // guarantees that multiple threads have a chance to run
Console.WriteLine(" item = {0}, thread id = {1}", myItems.Current, Thread.CurrentThread.ManagedThreadId);
}
myItems.Dispose();
};
// Spawn off 2 actions to consume 2 static partitions
Parallel.Invoke(staticAction, staticAction);
//
//
// Demonstrate the use of dynamic partitioning
//
//
// Grab an IEnumerable which can then be used to generate multiple
// shared IEnumerables.
var dynamicPartitions = myPart.GetDynamicPartitions();
Console.WriteLine("Dynamic Partitioning, 3 tasks:");
// Action will consume from dynamic partitions
Action dynamicAction = () =>
{
// Grab an enumerator from the dynamic partitions
var enumerator = dynamicPartitions.GetEnumerator();
int id = Thread.CurrentThread.ManagedThreadId; // cache our thread id
// Enumerate through your dynamic enumerator
while (enumerator.MoveNext())
{
Thread.Sleep(50); // guarantees that multiple threads will have a chance to run
Console.WriteLine(" item = {0}, thread id = {1}", enumerator.Current, id);
}
enumerator.Dispose();
};
// Spawn 3 concurrent actions to consume the dynamic partitions
Parallel.Invoke(dynamicAction, dynamicAction, dynamicAction);
// Clean up
if (dynamicPartitions is IDisposable)
((IDisposable)dynamicPartitions).Dispose();
}
}
}
Imports System.Collections.Concurrent
Imports System.Threading
Imports System.Threading.Tasks
Module PartitionerDemo
' Simple partitioner that will extract one item at a time, in a thread-safe fashion,
' from the underlying collection.
Class SingleElementPartitioner(Of T)
Inherits Partitioner(Of T)
' The collection being wrapped by this Partitioner
Private m_referenceEnumerable As IEnumerable(Of T)
' Internal class that serves as a shared enumerable for the
' underlying collection.
Private Class InternalEnumerable
Implements IEnumerable(Of T)
Implements IDisposable
Private m_reader As IEnumerator(Of T)
Private m_disposed As Boolean = False
' These two are used to implement Dispose() when static partitioning is being performed
Private m_activeEnumerators As Integer
Private m_downcountEnumerators As Boolean
' "downcountEnumerators" will be true for static partitioning, false for
' dynamic partitioning.
Public Sub New(ByVal reader As IEnumerator(Of T), ByVal downcountEnumerators As Boolean)
m_reader = reader
m_activeEnumerators = 0
m_downcountEnumerators = downcountEnumerators
End Sub
Public Function GetEnumerator() As IEnumerator(Of T) Implements IEnumerable(Of T).GetEnumerator
If m_disposed Then
Throw New ObjectDisposedException("InternalEnumerable: Can't call GetEnumerator() after disposing")
End If
' For static partitioning, keep track of the number of active enumerators.
If m_downcountEnumerators Then
Interlocked.Increment(m_activeEnumerators)
End If
Return New InternalEnumerator(m_reader, Me)
End Function
Private Function GetEnumerator2() As IEnumerator Implements IEnumerable.GetEnumerator
Return DirectCast(Me, IEnumerable(Of T)).GetEnumerator()
End Function
Public Sub Dispose() Implements IDisposable.Dispose
If Not m_disposed Then
' Only dispose the source enumerator if you are doing dynamic partitioning
If Not m_downcountEnumerators Then
m_reader.Dispose()
End If
m_disposed = True
End If
End Sub
' Called from Dispose() method of spawned InternalEnumerator. During
' static partitioning, the source enumerator will be automatically
' disposed once all requested InternalEnumerators have been disposed.
Public Sub DisposeEnumerator()
If m_downcountEnumerators Then
If Interlocked.Decrement(m_activeEnumerators) = 0 Then
m_reader.Dispose()
End If
End If
End Sub
End Class
' Internal class that serves as a shared enumerator for
' the underlying collection.
Private Class InternalEnumerator
Implements IEnumerator(Of T)
Private m_current As T
Private m_source As IEnumerator(Of T)
Private m_controllingEnumerable As InternalEnumerable
Private m_disposed As Boolean = False
Public Sub New(ByVal source As IEnumerator(Of T), ByVal controllingEnumerable As InternalEnumerable)
m_source = source
m_current = Nothing
m_controllingEnumerable = controllingEnumerable
End Sub
Private ReadOnly Property Current2() As Object Implements IEnumerator.Current
Get
Return m_current
End Get
End Property
Private ReadOnly Property Current() As T Implements IEnumerator(Of T).Current
Get
Return m_current
End Get
End Property
Private Sub Reset() Implements IEnumerator.Reset
Throw New NotSupportedException("Reset() not supported")
End Sub
' This method is the crux of this class. Under lock, it calls
' MoveNext() on the underlying enumerator and grabs Current.
Private Function MoveNext() As Boolean Implements IEnumerator.MoveNext
Dim rval As Boolean = False
SyncLock m_source
rval = m_source.MoveNext()
m_current = If(rval, m_source.Current, Nothing)
End SyncLock
Return rval
End Function
Private Sub Dispose() Implements IDisposable.Dispose
If Not m_disposed Then
' Delegate to parent enumerable's DisposeEnumerator() method
m_controllingEnumerable.DisposeEnumerator()
m_disposed = True
End If
End Sub
End Class
' Constructor just grabs the collection to wrap
Public Sub New(ByVal enumerable As IEnumerable(Of T))
' Verify that the source IEnumerable is not null
If enumerable Is Nothing Then
Throw New ArgumentNullException("enumerable")
End If
m_referenceEnumerable = enumerable
End Sub
' Produces a list of "numPartitions" IEnumerators that can each be
' used to traverse the underlying collection in a thread-safe manner.
' This will return a static number of enumerators, as opposed to
' GetDynamicPartitions(), the result of which can be used to produce
' any number of enumerators.
Public Overloads Overrides Function GetPartitions(ByVal numPartitions As Integer) As IList(Of IEnumerator(Of T))
If numPartitions < 1 Then
Throw New ArgumentOutOfRangeException("NumPartitions")
End If
Dim list As New List(Of IEnumerator(Of T))(numPartitions)
' Since we are doing static partitioning, create an InternalEnumerable with reference
' counting of spawned InternalEnumerators turned on. Once all of the spawned enumerators
' are disposed, dynamicPartitions will be disposed.
Dim dynamicPartitions = New InternalEnumerable(m_referenceEnumerable.GetEnumerator(), True)
For i As Integer = 0 To numPartitions - 1
list.Add(dynamicPartitions.GetEnumerator())
Next
Return list
End Function
' Returns an instance of our internal Enumerable class. GetEnumerator()
' can then be called on that (multiple times) to produce shared enumerators.
Public Overloads Overrides Function GetDynamicPartitions() As IEnumerable(Of T)
' Since we are doing dynamic partitioning, create an InternalEnumerable with reference
' counting of spawned InternalEnumerators turned off. This returned InternalEnumerable
' will need to be explicitly disposed.
Return New InternalEnumerable(m_referenceEnumerable.GetEnumerator(), False)
End Function
' Must be set to true if GetDynamicPartitions() is supported.
Public Overloads Overrides ReadOnly Property SupportsDynamicPartitions() As Boolean
Get
Return True
End Get
End Property
End Class
Class Program
' Test our SingleElementPartitioner(T) class
Shared Sub Main()
' Our sample collection
Dim collection As String() = New String() {"red", "orange", "yellow", "green", "blue", "indigo", _
"violet", "black", "white", "grey"}
' Instantiate a partitioner for our collection
Dim myPart As New SingleElementPartitioner(Of String)(Collection)
'
' Simple test with ForEach
'
Console.WriteLine("Testing with Parallel.ForEach")
Parallel.ForEach(myPart,
Sub(item)
Console.WriteLine(" item = {0}, thread id = {1}", item, Thread.CurrentThread.ManagedThreadId)
End Sub)
'
'
' Demonstrate the use of static partitioning, which really means
' "using a static number of partitioners". The partitioners themselves
' may still be "dynamic" in the sense that their outputs may not be
' deterministic.
'
'
' Perform static partitioning of collection
Dim staticPartitions = myPart.GetPartitions(2)
Dim index As Integer = 0
Console.WriteLine("Static Partitioning, 2 partitions, 2 tasks:")
' Action will consume from static partitions
Dim staticAction As Action =
Sub()
Dim myIndex As Integer = Interlocked.Increment(index) - 1
' compute your index
Dim myItems = staticPartitions(myIndex)
' grab your static partition
Dim id As Integer = Thread.CurrentThread.ManagedThreadId
' cache your thread id
' Enumerate through your static partition
While myItems.MoveNext()
Thread.Sleep(50)
' guarantees that multiple threads have a chance to run
Console.WriteLine(" item = {0}, thread id = {1}", myItems.Current, Thread.CurrentThread.ManagedThreadId)
End While
myItems.Dispose()
End Sub
' Spawn off 2 actions to consume 2 static partitions
Parallel.Invoke(staticAction, staticAction)
'
'
' Demonstrate the use of dynamic partitioning
'
'
' Grab an IEnumerable which can then be used to generate multiple
' shared IEnumerables.
Dim dynamicPartitions = myPart.GetDynamicPartitions()
Console.WriteLine("Dynamic Partitioning, 3 tasks:")
' Action will consume from dynamic partitions
Dim dynamicAction As Action =
Sub()
' Grab an enumerator from the dynamic partitioner
Dim enumerator = dynamicPartitions.GetEnumerator()
Dim id As Integer = Thread.CurrentThread.ManagedThreadId
' cache our thread id
' Enumerate through your dynamic enumerator
While enumerator.MoveNext()
Thread.Sleep(50)
' guarantees that multiple threads will have a chance to run
Console.WriteLine(" item = {0}, thread id = {1}", enumerator.Current, id)
End While
enumerator.Dispose()
End Sub
' Spawn 3 concurrent actions to consume the dynamic partitions
Parallel.Invoke(dynamicAction, dynamicAction, dynamicAction)
' Clean up
If TypeOf dynamicPartitions Is IDisposable Then
DirectCast(dynamicPartitions, IDisposable).Dispose()
End If
End Sub
End Class
End Module
Remarks
For more information, see Custom Partitioners for PLINQ and TPL.
Constructors
| Partitioner<TSource>() |
Creates a new partitioner instance. |
Properties
| SupportsDynamicPartitions |
Gets whether additional partitions can be created dynamically. |
Methods
| Equals(Object) |
Determines whether the specified object is equal to the current object. (Inherited from Object) |
| GetDynamicPartitions() |
Creates an object that can partition the underlying collection into a variable number of partitions. |
| GetHashCode() |
Serves as the default hash function. (Inherited from Object) |
| GetPartitions(Int32) |
Partitions the underlying collection into the given number of partitions. |
| GetType() |
Gets the Type of the current instance. (Inherited from Object) |
| MemberwiseClone() |
Creates a shallow copy of the current Object. (Inherited from Object) |
| ToString() |
Returns a string that represents the current object. (Inherited from Object) |
Extension Methods
| AsParallel<TSource>(Partitioner<TSource>) |
Enables parallelization of a query, as sourced by a custom partitioner that is responsible for splitting the input sequence into partitions. |
Applies to
Thread Safety
The static methods on Partitioner<TSource> are all thread-safe and may be used concurrently from multiple threads. However, while a created partitioner is in use, the underlying data source should not be modified, whether from the same thread that is using a partitioner or from a separate thread.
See also
Sodelujte z nami v storitvi GitHub
Vir za to vsebino najdete v storitvi GitHub, kjer lahko tudi ustvarite in pregledate težave in zahtevke za uveljavitev sprememb. Če želite več informacij, glejte naš vodnik za sodelavce.
