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Imports Microsoft.VisualBasic.Parallel.Tasks
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''' <summary>
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''' Using parallel linq that may stuck the program when a linq task partion wait a long time task to complete.
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''' By using this parallel function that you can avoid this problem from parallel linq, and also you can
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''' controls the task thread number manually by using this parallel task function.
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''' (由于LINQ是分片段来执行的，当某个片段有一个线程被卡住之后整个进程都会被卡住，所以执行大型的计算任务的时候效率不太好，
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''' 使用这个并行化函数可以避免这个问题，同时也可以自己手动控制线程的并发数)
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''' </summary>
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''' <typeparam name="TOut"></typeparam>
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Public Class ThreadTask(Of TOut)
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Dim taskList As Queue(Of Func(Of TOut))
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Dim threads As AsyncHandle(Of TOut)()
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Dim size As Integer
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Sub New(task As IEnumerable(Of Func(Of TOut)))
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Me.taskList = New Queue(Of Func(Of TOut))(task)
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Me.size = Me.taskList.Count
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End Sub
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Public Shared Function CreateThreads(Of T)(items As IEnumerable(Of T), task As Func(Of T, Func(Of TOut))) As ThreadTask(Of TOut)
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Return New ThreadTask(Of TOut)(items.Select(task))
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End Function
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Public Shared Function CreateThreads(Of T)(items As IEnumerable(Of T), task As Func(Of T, TOut)) As ThreadTask(Of TOut)
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Return New ThreadTask(Of TOut)(items.Select(Function(i) New Func(Of TOut)(Function() task(i))))
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End Function
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''' <summary>
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''' You can controls the parallel tasks number from this parameter, smaller or equals to ZERO means auto
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''' config the thread number, If want single thread, not parallel, set this value to 1, and positive
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''' value greater than 1 will makes the tasks parallel.
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''' (可以在这里手动的控制任务的并发数，这个数值小于或者等于零则表示自动配置线程的数量, 1为单线程)
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''' </summary>
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''' <param name="n_threads"></param>
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''' <returns></returns>
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Public Function WithDegreeOfParallelism(n_threads As Integer) As ThreadTask(Of TOut)
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threads = New AsyncHandle(Of TOut)(n_threads) {}
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Return Me
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End Function
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Private Function GetEmptyThread() As Integer
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For i As Integer = 0 To threads.Length - 1
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If threads(i) Is Nothing Then
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Return i
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End If
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Next
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Return -1
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End Function
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Private Function GetCompleteThread() As Integer
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For i As Integer = 0 To threads.Length - 1
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If (Not threads(i) Is Nothing) AndAlso threads(i).IsCompleted Then
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Return i
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End If
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Next
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Return -1
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End Function
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Public Overrides Function ToString() As String
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Dim free$ = threads.Where(Function(t) t Is Nothing).Count
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Dim running$ = threads.Where(Function(t) t IsNot Nothing AndAlso Not t.IsCompleted).Count
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Dim finished$ = threads.Where(Function(t) t IsNot Nothing AndAlso t.IsCompleted).Count
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Dim delta As Integer = size - taskList.Count
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Return $"[free: {free}, running: {running}, finished: {finished}, progress: {delta} - {CInt(delta / size * 100)}%]"
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End Function
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''' <summary>
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'''
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''' </summary>
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''' <returns></returns>
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Public Iterator Function RunParallel() As IEnumerable(Of TOut)
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Do While taskList.Count > 0
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Dim i As Integer = GetEmptyThread()
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If i > -1 Then
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threads(i) = New AsyncHandle(Of TOut)(taskList.Dequeue).Run
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Call Console.WriteLine($"{ToString()} submit new task on thread [{i + 1}]!")
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End If
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Dim j As Integer = GetCompleteThread()
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If j > -1 Then
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Yield threads(j).GetValue
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threads(j) = Nothing
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Call Console.WriteLine($"{ToString()} [thread_{j + 1}] job done!")
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End If
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Loop
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Do While Not threads.All(Function(t) t Is Nothing)
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Dim j As Integer = GetCompleteThread()
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If j > -1 Then
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Yield threads(j).GetValue
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threads(j) = Nothing
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Call Console.WriteLine($"{ToString()} [thread_{j + 1}] job done!")
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End If
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Loop
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End Function
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End Class
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