Example of thread synchronization
Refers of the idea of using multiples thread in a process
When you stats using thread, you will notice that the speed of each thread is not very important. You will notice that synchronization is more important because sometimes, you want a thread to be completed before starting and other one. You could try to use or check for the Thread status using the IsAlive and IsBackground properties, but you will find it mostly hard to get reliable things.
That is why synchronization between asynchronous tasks is the key for success. If you master the basic of timing between functions, nothing will stop you from doing more complex application or games.
MMORPG (stands for Massive Multi Online Role Player Game) is the perfect example of challenge for a programmer or a team where each player has different computer speed and network performance.
HereVB a code sample I made in less than 15 minutes. Yes, it is very simple. The concept is also simple. I made a WinForm using 4 ProgressBar. The last ProgressBar will only start if the 3 previous have completed. In other words, the last ProgressBar must wait for the 3 others.
This sample could be use in any situation in the modern world.
By pressing the button START, 4 independent threads will start. Each Thread has their speed.
The last Thread is blocked by 3 ManualResetEvent. If the 3 ManualResetEvent are set, then the last task could start.
''' <summary> ''' Author : Check-Kay Wong ''' Description: ''' This is a sample of synchronasation between multiples task ''' using a Simple WaitOne and a Set from a ManualResetEvent ''' ''' Comment : this is an exemple ''' </summary> ''' <remarks></remarks> Public Class Form1 Private tTask1 As System.Threading.Thread Private tTask2 As System.Threading.Thread Private tTask3 As System.Threading.Thread Private tTask4 As System.Threading.Thread Private mreTask1 As System.Threading.ManualResetEvent Private mreTask2 As System.Threading.ManualResetEvent Private mreTask3 As System.Threading.ManualResetEvent Private mreTask4 As System.Threading.ManualResetEvent Private Delegate Sub dTask1() Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click StartAllTasks() End Sub ''' <summary> ''' all working stuff inside the thread are simulated by progressbar ''' </summary> ''' <remarks></remarks> #Region "Working Thread 1, 2 and 3" Private Sub Task1() Do Me.BeginInvoke(New dTask1(AddressOf sTask1)) System.Threading.Thread.Sleep(100) Loop Until ProgressBar1.Value >= ProgressBar1.Maximum mreTask1.Set() End Sub Private Sub sTask1() Me.ProgressBar1.PerformStep() End Sub Private Sub Task2() Do Me.BeginInvoke(New dTask1(AddressOf sTask2)) System.Threading.Thread.Sleep(100) Loop Until ProgressBar2.Value >= ProgressBar2.Maximum mreTask2.Set() End Sub Private Sub sTask2() Me.ProgressBar2.PerformStep() End Sub Private Sub Task3() Do Me.BeginInvoke(New dTask1(AddressOf sTask3)) System.Threading.Thread.Sleep(100) Loop Until ProgressBar3.Value >= ProgressBar3.Maximum mreTask3.Set() End Sub Private Sub sTask3() Me.ProgressBar3.PerformStep() End Sub #End Region #Region "Finale Task Thread" Private Sub Task4() mreTask1.WaitOne() mreTask2.WaitOne() mreTask3.WaitOne() Do Me.BeginInvoke(New dTask1(AddressOf sTask4)) System.Threading.Thread.Sleep(100) Loop Until ProgressBar4.Value >= ProgressBar4.Maximum mreTask4.Set() My.Computer.Audio.PlaySystemSound(Media.SystemSounds.Beep) 'a little bell End Sub Private Sub sTask4() Me.ProgressBar4.PerformStep() End Sub #End Region ''' <summary> ''' Init stuff ''' </summary> ''' <param name="sender"></param> ''' <param name="e"></param> ''' <remarks></remarks> Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load Me.Text = My.Application.Info.ProductName & " from " & My.Application.Info.CompanyName ProgressBar1.Maximum = 200 ProgressBar2.Maximum = 100 ProgressBar3.Maximum = 140 ProgressBar4.Maximum = 240 'create the ManualResetEvent mreTask1 = New System.Threading.ManualResetEvent(False) mreTask2 = New System.Threading.ManualResetEvent(False) mreTask3 = New System.Threading.ManualResetEvent(False) mreTask4 = New System.Threading.ManualResetEvent(False) End Sub ''' <summary> ''' Start All Task at the same time ''' </summary> ''' <remarks></remarks> Private Sub StartAllTasks() If tTask1 IsNot Nothing Then tTask1 = Nothing tTask1 = New System.Threading.Thread(AddressOf Task1) tTask1.IsBackground = True tTask1.Start() If tTask2 IsNot Nothing Then tTask2 = Nothing tTask2 = New System.Threading.Thread(AddressOf Task2) tTask2.IsBackground = True tTask2.Start() If tTask3 IsNot Nothing Then tTask3 = Nothing tTask3 = New System.Threading.Thread(AddressOf Task3) tTask3.IsBackground = True tTask3.Start() If tTask4 IsNot Nothing Then tTask4 = Nothing tTask4 = New System.Threading.Thread(AddressOf Task4) tTask4.IsBackground = True tTask4.Start() End Sub End Class |
I use Microsoft Visual Studio 2010 to do all my projects. I suggest you to buy and get the best IDE in the world and the newest one: Microsoft Visual Studio 2012 on Amazon
or
Download the sample code here: ManualResetEventExample.zip
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