本文整理汇总了VB.NET中System.Threading.Tasks.Parallel.For方法的典型用法代码示例。如果您正苦于以下问题：VB.NET Parallel.For方法的具体用法？VB.NET Parallel.For怎么用？VB.NET Parallel.For使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类System.Threading.Tasks.Parallel的用法示例。
在下文中一共展示了Parallel.For方法的6个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于我们的系统推荐出更棒的VB.NET代码示例。
示例1: Example
' 导入命名空间
Imports System.Threading
Imports System.Threading.Tasks
Module Example
Public Sub Main()
Dim rnd As New Random()
Dim breakIndex As Integer = rnd.Next(1, 11)
Dim lowest As New Nullable(Of Long)()
Console.WriteLine("Will call Break at iteration {0}", breakIndex)
Console.WriteLine()
Dim result = Parallel.For(1, 101, Sub(i, state)
Console.WriteLine("Beginning iteration {0}", i)
Dim delay As Integer
Monitor.Enter(rnd)
delay = rnd.Next(1, 1001)
Monitor.Exit(rnd)
Thread.Sleep(delay)
If state.ShouldExitCurrentIteration Then
If state.LowestBreakIteration < i Then
Return
End If
End If
If i = breakIndex Then
Console.WriteLine("Break in iteration {0}", i)
state.Break()
If state.LowestBreakIteration.HasValue Then
If lowest < state.LowestBreakIteration Then
lowest = state.LowestBreakIteration
Else
lowest = state.LowestBreakIteration
End If
End If
End If
Console.WriteLine("Completed iteration {0}", i)
End Sub )
Console.WriteLine()
If lowest.HasValue Then
Console.WriteLine("Lowest Break Iteration: {0}", lowest)
Else
Console.WriteLine("No lowest break iteration.")
End If
End Sub
End Module
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:49，代码来源:Parallel.For 输出：
Will call Break at iteration 8
Beginning iteration 1
Beginning iteration 13
Beginning iteration 97
Beginning iteration 25
Beginning iteration 49
Beginning iteration 37
Beginning iteration 85
Beginning iteration 73
Beginning iteration 61
Completed iteration 85
Beginning iteration 86
Completed iteration 61
Beginning iteration 62
Completed iteration 86
Beginning iteration 87
Completed iteration 37
Beginning iteration 38
Completed iteration 38
Beginning iteration 39
Completed iteration 25
Beginning iteration 26
Completed iteration 26
Beginning iteration 27
Completed iteration 73
Beginning iteration 74
Completed iteration 62
Beginning iteration 63
Completed iteration 39
Beginning iteration 40
Completed iteration 40
Beginning iteration 41
Completed iteration 13
Beginning iteration 14
Completed iteration 1
Beginning iteration 2
Completed iteration 97
Beginning iteration 98
Completed iteration 49
Beginning iteration 50
Completed iteration 87
Completed iteration 27
Beginning iteration 28
Completed iteration 50
Beginning iteration 51
Beginning iteration 88
Completed iteration 14
Beginning iteration 15
Completed iteration 15
Completed iteration 2
Beginning iteration 3
Beginning iteration 16
Completed iteration 63
Beginning iteration 64
Completed iteration 74
Beginning iteration 75
Completed iteration 41
Beginning iteration 42
Completed iteration 28
Beginning iteration 29
Completed iteration 29
Beginning iteration 30
Completed iteration 98
Beginning iteration 99
Completed iteration 64
Beginning iteration 65
Completed iteration 42
Beginning iteration 43
Completed iteration 88
Beginning iteration 89
Completed iteration 51
Beginning iteration 52
Completed iteration 16
Beginning iteration 17
Completed iteration 43
Beginning iteration 44
Completed iteration 44
Beginning iteration 45
Completed iteration 99
Beginning iteration 4
Completed iteration 3
Beginning iteration 8
Completed iteration 4
Beginning iteration 5
Completed iteration 52
Beginning iteration 53
Completed iteration 75
Beginning iteration 76
Completed iteration 76
Beginning iteration 77
Completed iteration 65
Beginning iteration 66
Completed iteration 5
Beginning iteration 6
Completed iteration 89
Beginning iteration 90
Completed iteration 30
Beginning iteration 31
Break in iteration 8
Completed iteration 8
Completed iteration 6
Beginning iteration 7
Completed iteration 7
Lowest Break Iteration: 8
示例2: Example
' 导入命名空间
Imports System.Threading.Tasks
Module Example
Public Sub Main()
Dim result As ParallelLoopResult = Parallel.For(0, 100, Sub(ctr)
Dim rnd As New Random(ctr * 100000)
Dim bytes(99) As Byte
rnd.NextBytes(bytes)
Dim sum As Integer
For Each byt In bytes
sum += byt
Next
Console.WriteLine("Iteration {0,2}: {1:N0}", ctr, sum)
End Sub)
Console.WriteLine("Result: {0}", If(result.IsCompleted, "Completed Normally",
String.Format("Completed to {0}", result.LowestBreakIteration)))
End Sub
End Module
' The following is a portion of the output displayed by the example:
' Iteration 0: 12,509
' Iteration 50: 12,823
' Iteration 51: 11,275
' Iteration 52: 12,531
' Iteration 1: 13,007
' Iteration 53: 13,799
' Iteration 4: 12,945
' Iteration 2: 13,246
' Iteration 54: 13,008
' Iteration 55: 12,727
' Iteration 56: 13,223
' Iteration 57: 13,717
' Iteration 5: 12,679
' Iteration 3: 12,455
' Iteration 58: 12,669
' Iteration 59: 11,882
' Iteration 6: 13,167
' ...
' Iteration 92: 12,275
' Iteration 93: 13,282
' Iteration 94: 12,745
' Iteration 95: 11,957
' Iteration 96: 12,455
' Result: Completed Normally
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:44，代码来源:Parallel.For
示例3: LoopCancellation
' 导入命名空间
Imports System.Threading
Imports System.Threading.Tasks
Module LoopCancellation
' Demonstrated features:
' CancellationTokenSource
' Parallel.For()
' ParallelOptions
' ParallelLoopResult
' Expected results:
' An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
' The order of execution of the iterations is undefined.
' The iteration when i=2 cancels the loop.
' Some iterations may bail out or not start at all; because they are temporally executed in unpredictable order,
' it is impossible to say which will start/complete and which won't.
' At the end, an OperationCancelledException is surfaced.
' Documentation:
' http://msdn.microsoft.com/library/system.threading.cancellationtokensource(VS.100).aspx
Private Sub Main()
Dim cancellationSource As New CancellationTokenSource()
Dim options As New ParallelOptions()
options.CancellationToken = cancellationSource.Token
Try
Dim loopResult As ParallelLoopResult = _
Parallel.For(0, 10, options, Sub(i, loopState)
Console.WriteLine("Start Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)
' Simulate a cancellation of the loop when i=2
If i = 2 Then
cancellationSource.Cancel()
End If
' Simulates a long execution
For j As Integer = 0 To 9
Thread.Sleep(1 * 200)
' check to see whether or not to continue
If loopState.ShouldExitCurrentIteration Then
Exit Sub
End If
Next
Console.WriteLine("Finish Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)
End Sub)
If loopResult.IsCompleted Then
Console.WriteLine("All iterations completed successfully. THIS WAS NOT EXPECTED.")
End If
Catch e As AggregateException
' No exception is expected in this example, but if one is still thrown from a task,
' it will be wrapped in AggregateException and propagated to the main thread.
Console.WriteLine("An action has thrown an AggregateException. THIS WAS NOT EXPECTED." & vbLf & "{0}", e)
Catch e As OperationCanceledException
' Catching the cancellation exception
Console.WriteLine("An iteration has triggered a cancellation. THIS WAS EXPECTED." & vbLf & "{0}", e)
Finally
cancellationSource.Dispose()
End Try
End Sub
End Module
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:62，代码来源:Parallel.For
示例4: ParallelForDemo
' 导入命名空间
Imports System.Threading
Imports System.Threading.Tasks
Module ParallelForDemo
' Demonstrated features:
' Parallel.For()
' ParallelOptions
' Expected results:
' An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
' The order of execution of the iterations is undefined.
' Verify that no more than two threads have been used for the iterations.
' Documentation:
' http://msdn.microsoft.com/library/system.threading.tasks.parallel.for(VS.100).aspx
Sub Main()
Dim options As New ParallelOptions()
options.MaxDegreeOfParallelism = 2 ' -1 is for unlimited. 1 is for sequential.
Try
Parallel.For(0, 9, options, Sub(i)
Console.WriteLine("Thread={0}, i={1}", Thread.CurrentThread.ManagedThreadId, i)
End Sub)
Catch e As AggregateException
' No exception is expected in this example, but if one is still thrown from a task,
' it will be wrapped in AggregateException and propagated to the main thread.
Console.WriteLine("Parallel.For has thrown the following (unexpected) exception:" & vbLf & "{0}", e)
End Try
End Sub
End Module
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:32，代码来源:Parallel.For
示例5: SchedulerDemo
' 导入命名空间
Imports System.Collections.Concurrent
Imports System.Threading
Imports System.Threading.Tasks
Module SchedulerDemo
' Demonstrated features:
' TaskScheduler
' BlockingCollection
' Parallel.For()
' ParallelOptions
' Expected results:
' An iteration for each argument value (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) is executed.
' The TwoThreadTaskScheduler employs 2 threads on which iterations may be executed in a random order.
' A task is internally created for each thread of the task scheduler (plus an aditional internal task).
' Thus a scheduler thread may execute multiple iterations.
' Documentation:
' http://msdn.microsoft.com/library/system.threading.tasks.taskscheduler(VS.100).aspx
' http://msdn.microsoft.com/library/dd997413(VS.100).aspx
' More information:
' http://blogs.msdn.com/pfxteam/archive/2009/09/22/9898090.aspx
Sub Main()
Dim options As New ParallelOptions()
' Construct and associate a custom task scheduler
options.TaskScheduler = New TwoThreadTaskScheduler()
Try
Parallel.For(0, 10, options, Sub(i, localState)
Console.WriteLine("i={0}, Task={1}, Thread={2}", i, Task.CurrentId, Thread.CurrentThread.ManagedThreadId)
End Sub)
Catch e As AggregateException
' No exception is expected in this example, but if one is still thrown from a task,
' it will be wrapped in AggregateException and propagated to the main thread.
Console.WriteLine("An iteration has thrown an exception. THIS WAS NOT EXPECTED." & vbLf & "{0}", e)
End Try
End Sub
' This scheduler schedules all tasks on (at most) two threads
Private NotInheritable Class TwoThreadTaskScheduler
Inherits TaskScheduler
Implements IDisposable
' The runtime decides how many tasks to create for the given set of iterations, loop options, and scheduler's max concurrency level.
' Tasks will be queued in this collection
Private _tasks As New BlockingCollection(Of Task)()
' Maintain an array of threads. (Feel free to bump up _n.)
Private ReadOnly _n As Integer = 2
Private _threads As Thread()
Public Sub New()
_threads = New Thread(_n - 1) {}
' Create unstarted threads based on the same inline delegate
For i As Integer = 0 To _n - 1
_threads(i) = New Thread(Sub()
' The following loop blocks until items become available in the blocking collection.
' Then one thread is unblocked to consume that item.
For Each task In _tasks.GetConsumingEnumerable()
TryExecuteTask(task)
Next
End Sub)
' Start each thread
_threads(i).IsBackground = True
_threads(i).Start()
Next
End Sub
' This method is invoked by the runtime to schedule a task
Protected Overloads Overrides Sub QueueTask(ByVal task As Task)
_tasks.Add(task)
End Sub
' The runtime will probe if a task can be executed in the current thread.
' By returning false, we direct all tasks to be queued up.
Protected Overloads Overrides Function TryExecuteTaskInline(ByVal task As Task, ByVal taskWasPreviouslyQueued As Boolean) As Boolean
Return False
End Function
Public Overloads Overrides ReadOnly Property MaximumConcurrencyLevel() As Integer
Get
Return _n
End Get
End Property
Protected Overloads Overrides Function GetScheduledTasks() As IEnumerable(Of Task)
Return _tasks.ToArray()
End Function
' Dispose is not thread-safe with other members.
' It may only be used when no more tasks will be queued
' to the scheduler. This implementation will block
' until all previously queued tasks have completed.
Public Sub Dispose() Implements IDisposable.Dispose
If _threads IsNot Nothing Then
_tasks.CompleteAdding()
For i As Integer = 0 To _n - 1
_threads(i).Join()
_threads(i) = Nothing
Next
_threads = Nothing
_tasks.Dispose()
_tasks = Nothing
End If
End Sub
End Class
End Module
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:111，代码来源:Parallel.For
示例6: ThreadLocalForWithOptions
' 导入命名空间
Imports System.Threading
Imports System.Threading.Tasks
Module ThreadLocalForWithOptions
' The number of parallel iterations to perform.
Const N As Integer = 1000000
Sub Main()
' The result of all thread-local computations.
Dim result As Integer = 0
' This example limits the degree of parallelism to four.
' You might limit the degree of parallelism when your algorithm
' does not scale beyond a certain number of cores or when you
' enforce a particular quality of service in your application.
Parallel.For(0, N, New ParallelOptions With {.MaxDegreeOfParallelism = 4},
Function()
' Initialize the local states
Return 0
End Function,
Function(i, loopState, localState)
' Accumulate the thread-local computations in the loop body
Return localState + Compute(i)
End Function,
Sub(localState)
' Combine all local states
Interlocked.Add(result, localState)
End Sub
)
' Print the actual and expected results.
Console.WriteLine("Actual result: {0}. Expected 1000000.", result)
End Sub
' Simulates a lengthy operation.
Function Compute(ByVal n As Integer) As Integer
For i As Integer = 0 To 10000
Next
Return 1
End Function
End Module
开发者ID:VB.NET开发者，项目名称:System.Threading.Tasks，代码行数:44，代码来源:Parallel.For
注：本文中的System.Threading.Tasks.Parallel.For方法示例整理自Github/MSDocs等源码及文档管理平台，相关代码片段筛选自各路编程大神贡献的开源项目，源码版权归原作者所有，传播和使用请参考对应项目的License；未经允许，请勿转载。 |
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