Question

我的代码在DataTable上进行了大约20次计算。我没有逐个进行计算，而是希望通过为每个计算设置一个单独的线程来加快进程。下面的代码简化了我实际做的事情，但它应该足以帮助我。

我发现以下网站和帖子类似，但我仍然无法推断我的情况 - 我为我的白痴道歉。

Multi Threading with Return value : vb.net
MSDN: BackgroundWorker Class
Multithreading calculations with state and mutable objects in a class
Execute a statement after thread gets over
MSDN: ManualResetEvent Class

我知道以下代码是＆＃34;错误＆＃34;因为我在确定线程完成之前中止每个线程。这是BackgroundWorker类或ManualResetEvent类可能有用的地方。此外，在GenerateValues函数中实例化和运行线程会导致NULL对象引用错误;然而在CalculateSummary子例程中实例化和运行线程工作正常。理想情况下，代码实现将使用GenerateValues中的多个线程;但如果那是不可能的，那么我可以完全删除该函数并将其代码添加到子例程中。为了扩展我的目标受众，我用VB.NET（我实际使用的语言）和C＃编写了代码。

VB.NET ：

Imports System.Threading

Public Class GroupSummary

    Public Sub CalculateSummary(ByVal pGroupKey As Integer)

        Dim records As DataTable = Nothing ///actually calls code that reads a database.
        Dim result As Integer = GenerateValues(records)
        ///code that inserts result into a database.
    End Sub

    Private Function GenerateValues(ByVal pRecords As DataTable) As Integer

        Dim numberHeightTall As Integer = 0
        Dim numberWeightHeavy As Integer = 0
        Dim numberFemale As Integer = 0
        Dim numberBlueEyes As Integer = 0
        Dim numberBob As Integer = 0
        Dim thread1 As New Thread(Sub() numberHeightTall =
                           CInt(pRecords.Compute("Count(NameID)", "Height > 72")))
        Dim thread2 As New Thread(Sub() numberWeightHeavy =
                           CInt(pRecords.Compute("Count(NameID)", "Weight > 200")))
        Dim thread3 As New Thread(Sub() numberFemale =
                           CInt(pRecords.Compute("Count(NameID)", "Female = True")))
        Dim thread4 As New Thread(Sub() numberBlueEyes =
                           CInt(pRecords.Compute("Count(NameID)", "EyeColor = 'Blue'")))
        Dim thread5 As New Thread(Sub() numberBob =
                           CInt(pRecords.Compute("Count(NameID)", "Name = 'Bob'")))
        thread1.Start()
        thread2.Start()
        thread3.Start()
        thread4.Start()
        thread5.Start()
        thread1.Abort()
        thread2.Abort()
        thread3.Abort()
        thread4.Abort()
        thread5.Abort()

        Return numberHeightTall + numberWeightHeavy + numberFemale + numberBlueEyes +
               numberBob
    End Function
End Class

C＃：

using System.Threading;
using System.Data;
using System;

public class GroupSummary {

    public void CalculateSummary(int pGroupKey) {

        DataTable records = null; ///actually calls code that reads a database.

        int result = GenerateValues(records);

        ///code that inserts result into a database.
    }
    private int GenerateValues(DataTable pRecords) {

        int numberHeightTall = 0;
        int numberWeightHeavy = 0;
        int numberFemale = 0;
        int numberBlueEyes = 0;
        int numberBob = 0;
        Thread thread1 = new Thread(delegate () { numberHeightTall =
            Convert.ToInt32(pRecords.Compute("Count(NameID)", "Height > 72")); });
        Thread thread2 = new Thread(delegate () { numberWeightHeavy =
            Convert.ToInt32(pRecords.Compute("Count(NameID)", "Weight > 200")); });
        Thread thread3 = new Thread(delegate () { numberFemale =
            Convert.ToInt32(pRecords.Compute("Count(NameID)", "Female = True")); });
        Thread thread4 = new Thread(delegate () { numberBlueEyes =
            Convert.ToInt32(pRecords.Compute("Count(NameID)", "EyeColor = 'Blue'")); });
        Thread thread5 = new Thread(delegate () { numberBob =
            Convert.ToInt32(pRecords.Compute("Count(NameID)", "Name = 'Bob'")); });
        thread1.Start();
        thread2.Start();
        thread3.Start();
        thread4.Start();
        thread5.Start();
        thread1.Abort();
        thread2.Abort();
        thread3.Abort();
        thread4.Abort();
        thread5.Abort();

        return numberHeightTall + numberWeightHeavy + numberFemale + numberBlueEyes +
               numberBob;
    }
}

Answer 1

根据KDecker的建议，使用Task<TResult>类解决了我的问题。

以下是VB.NET实现：

Imports System.Data

Public Class GroupSummary

    Public Sub CalculateSummary(ByVal pGroupKey As Integer)

        Dim records As DataTable = Nothing ///actually calls code that reads a database
        Dim result As Integer = GenerateValues(records)
        ///code that inserts result into database.
    End Sub

    Private Function GenerateValues(ByVal pRecords As DataTable) As Integer

        Dim tasks(4) As Task(Of Integer)
        tasks(0) = Task.Run(Function() CInt(pRecords.Compute(
                                        "Count(NameID)", "Height > 72")))
        tasks(1) = Task.Run(Function() CInt(pRecords.Compute(
                                        "Count(NameID)", "Weight > 200")))
        tasks(2) = Task.Run(Function() CInt(pRecords.Compute(
                                        "Count(NameID)", "Female = True")))
        tasks(3) = Task.Run(Function() CInt(pRecords.Compute(
                                        "Count(NameID)", "EyeColor = 'Blue'")))
        tasks(4) = Task.Run(Function() CInt(pRecords.Compute(
                                        "Count(NameID)", "Name = 'Bob'")))
        Task.WaitAll(tasks)

        Return tasks(0).Result + tasks(1).Result + tasks(2).Result + tasks(3).Result +
               tasks(4).Result
    End Function
End Class

多线程DataTable计算只读VB或C＃

1 个答案: