VB.NET并行与分布式编程(6)-线程与内核同步[1]

我们接着前面的例子讲述，这个例子的功能是3个线程共同完成对一个数的连续减法运算，在前面的例子,我们在每个线程做完减法运算后都加入了thread.sleep，以使线程能将执行机会给其它线程，同时也使得在这个例子一般不会发生线程同步问题，我们去掉sleep，可以发现由于没有解决同步问题，有线程读到了脏数据。

代码为：

 

Imports System
Imports System.Threading
Imports System.Diagnostics
Imports System.Diagnostics.ThreadState











Module Module1

    Sub Main()

        Dim mythread1 As Thread
        Dim mythread2 As Thread
        Dim mythread3 As Thread





        '创建线程对象
        mythread1 = New Thread(AddressOf mythreadrun)
        mythread2 = New Thread(AddressOf mythreadrun)
        mythread3 = New Thread(AddressOf mythreadrun)
        mythread1.Name = "thread_1"
        mythread2.Name = "thread_2"
        mythread3.Name = "thread_3"
        '设置线程是否允许动态优先级








        Console.WriteLine(Now.ToLongTimeString & "线程对象创建完毕,开始执行线程")
        Dim myprocess As Process = Process.GetCurrentProcess()
        Console.WriteLine("进程名称:" & myprocess.ProcessName)
        '执行线程
        mythread1.Start(myprocess)
        mythread2.Start(myprocess)
        mythread3.Start(myprocess)





        '等待线程完成
        mythread1.Join()
        mythread2.Join()
        mythread3.Join()


        '线程执行完毕
        Console.WriteLine(Now.ToLongTimeString & "线程执行完毕!")

    End Sub
    Public Sub mythreadrun(ByVal myprocess As Object)
        Dim mynum As Double


        Static Dim jg As Double = 100
        Try
            For mynum = 1 To 2 Step 0.1
                jg -= mynum
                Console.WriteLine(Thread.CurrentThread.Name & "==>" & Now.ToLongTimeString & "=>" & (jg + mynum) & "-" & mynum & "，计算结果为：" & jg)
                ' Thread.Sleep(50)
            Next
        Catch
            Console.WriteLine(Thread.CurrentThread.Name & "  " & Now.ToLongTimeString & "线程异常终止!")
            '终止线程
            Thread.CurrentThread.Abort()
        Finally
            Console.WriteLine(Thread.CurrentThread.Name & "优先级:  " & Thread.CurrentThread.Priority.ToString)
            Console.WriteLine(Thread.CurrentThread.Name & "  " & Now.ToLongTimeString & "线程运行完毕!")
        End Try
    End Sub
End Module

 

 我们将上述代码的thread.sleep(50)的注释去掉，可以发现程序正常执行了

sleep掩盖了同步问题的发生