Multi-Threaded App

29 Jul 2006 4:49 PM

askhuy

Hi All

    Would someone please explain to me why my threads are not running at the
sametime? Here is what I don't understand. When I invoke the TestThread()
procedure, I always get the output of main thread first and then the
secondary thread's output. Shouldn't the ouput show the mixed messages

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
        TestThread()
    End Sub

    Private Sub TestThread()
        'Create new thread and define its starting point
        Dim t As New Thread(New ThreadStart(AddressOf DoSomeTask))
        'run the new thread
        t.Start()

        ' print some messages to screen
        Dim i As Integer
        For i = 1 To 1000
            TextBox1.Text &= "from main thread # = " & i.ToString & vbCrLf
        Next
    End Sub

    Sub DoSomeTask()
        Dim i As Integer

        For i = 1 To 1000
            TextBox1.Text &= "from secondary thread # = " & i.ToString &
vbCrLf
        Next
    End Sub

Here are my outputs

from main thread # = 1
from main thread # = 2
from main thread # = 3
from main thread # = 4
from main thread # = 5
from main thread # = 6
from main thread # = 7
from main thread # = 8
from main thread # = 9
from main thread # = 10
from secondary thread # = 1
from secondary thread # = 2
from secondary thread # = 3
from secondary thread # = 4
from secondary thread # = 5
from secondary thread # = 6
from secondary thread # = 7
from secondary thread # = 8
from secondary thread # = 9
from secondary thread # = 10

29 Jul 2006 7:23 PM

Michel Posseth [MCP]

No not in this case ,, wich is also bad coding practice for multithreading

1. ever heard of thread switching and thread prio`s ?
2. do you know that GUI controls run on the main thread ?
and dealing from sperate threads should invoke a synchronization
mechanism ?

You probably wrote this in .Net 2003 ?? as in .Net 2005 it should not be
possible to run this code

about point 1 ,,, you also probably run this on a SP system and not on a MP
system ,, however you could force a thread switch by coding some thread
sleeps in the 2 procedures . but as i said the shown code is a practicce to
show how MT should not be implemented

regards

Michel Posseth [MCP]

Show quoteHide quote

"askhuy" <ask***@yahoo.com> schreef in bericht
news:%23oxAq7ysGHA.1876@TK2MSFTNGP06.phx.gbl...
> Hi All
>
>    Would someone please explain to me why my threads are not running at
> the sametime? Here is what I don't understand. When I invoke the
> TestThread() procedure, I always get the output of main thread first and
> then the secondary thread's output. Shouldn't the ouput show the mixed
> messages
>
>
>
>    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
>        TestThread()
>    End Sub
>
>
>
>    Private Sub TestThread()
>        'Create new thread and define its starting point
>        Dim t As New Thread(New ThreadStart(AddressOf DoSomeTask))
>        'run the new thread
>        t.Start()
>
>        ' print some messages to screen
>        Dim i As Integer
>        For i = 1 To 1000
>            TextBox1.Text &= "from main thread # = " & i.ToString & vbCrLf
>        Next
>    End Sub
>
>    Sub DoSomeTask()
>        Dim i As Integer
>
>        For i = 1 To 1000
>            TextBox1.Text &= "from secondary thread # = " & i.ToString &
> vbCrLf
>        Next
>    End Sub
>
>
> Here are my outputs
>
> from main thread # = 1
> from main thread # = 2
> from main thread # = 3
> from main thread # = 4
> from main thread # = 5
> from main thread # = 6
> from main thread # = 7
> from main thread # = 8
> from main thread # = 9
> from main thread # = 10
> from secondary thread # = 1
> from secondary thread # = 2
> from secondary thread # = 3
> from secondary thread # = 4
> from secondary thread # = 5
> from secondary thread # = 6
> from secondary thread # = 7
> from secondary thread # = 8
> from secondary thread # = 9
> from secondary thread # = 10
>
>
>
>

29 Jul 2006 9:21 PM

askhuy

Hi guys,

Thanks for your helps. I tried with the console windows and both threads
execute at the same time.

Regards

Sam

Show quoteHide quote

"Michel Posseth [MCP]" <M***@posseth.com> wrote in message
news:uV1%23hR0sGHA.4420@TK2MSFTNGP04.phx.gbl...
> No not in this case ,, wich is also bad coding practice for multithreading
>
> 1. ever heard of thread switching and thread prio`s ?
> 2. do you know that GUI controls run on the main thread ?
>    and dealing from sperate threads should invoke a synchronization
> mechanism ?
>
> You probably wrote this in .Net 2003 ?? as in .Net 2005 it should not be
> possible to run this code
>
> about point 1 ,,, you also probably run this on a SP system and not on a
> MP system ,, however you could force a thread switch by coding some thread
> sleeps in the 2 procedures . but as i said the shown code is a practicce
> to show how MT should not be implemented
>
>
> regards
>
> Michel Posseth [MCP]
>
>
>
>
>
>
>
>
> "askhuy" <ask***@yahoo.com> schreef in bericht
> news:%23oxAq7ysGHA.1876@TK2MSFTNGP06.phx.gbl...
>> Hi All
>>
>>    Would someone please explain to me why my threads are not running at
>> the sametime? Here is what I don't understand. When I invoke the
>> TestThread() procedure, I always get the output of main thread first and
>> then the secondary thread's output. Shouldn't the ouput show the mixed
>> messages
>>
>>
>>
>>    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
>> System.EventArgs) Handles Button1.Click
>>        TestThread()
>>    End Sub
>>
>>
>>
>>    Private Sub TestThread()
>>        'Create new thread and define its starting point
>>        Dim t As New Thread(New ThreadStart(AddressOf DoSomeTask))
>>        'run the new thread
>>        t.Start()
>>
>>        ' print some messages to screen
>>        Dim i As Integer
>>        For i = 1 To 1000
>>            TextBox1.Text &= "from main thread # = " & i.ToString & vbCrLf
>>        Next
>>    End Sub
>>
>>    Sub DoSomeTask()
>>        Dim i As Integer
>>
>>        For i = 1 To 1000
>>            TextBox1.Text &= "from secondary thread # = " & i.ToString &
>> vbCrLf
>>        Next
>>    End Sub
>>
>>
>> Here are my outputs
>>
>> from main thread # = 1
>> from main thread # = 2
>> from main thread # = 3
>> from main thread # = 4
>> from main thread # = 5
>> from main thread # = 6
>> from main thread # = 7
>> from main thread # = 8
>> from main thread # = 9
>> from main thread # = 10
>> from secondary thread # = 1
>> from secondary thread # = 2
>> from secondary thread # = 3
>> from secondary thread # = 4
>> from secondary thread # = 5
>> from secondary thread # = 6
>> from secondary thread # = 7
>> from secondary thread # = 8
>> from secondary thread # = 9
>> from secondary thread # = 10
>>
>>
>>
>>
>
>

29 Jul 2006 7:26 PM

Chris

If you are using VB 2005 have a look at
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnvs05/html/threadinginvb2005.asp
for an awesome article that goes over the BackgroundWorker. There is even
sample code.

Chris

Show quoteHide quote

"askhuy" <ask***@yahoo.com> wrote in message
news:%23oxAq7ysGHA.1876@TK2MSFTNGP06.phx.gbl...
> Hi All
>
>    Would someone please explain to me why my threads are not running at
> the sametime? Here is what I don't understand. When I invoke the
> TestThread() procedure, I always get the output of main thread first and
> then the secondary thread's output. Shouldn't the ouput show the mixed
> messages
>
>
>
>    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
>        TestThread()
>    End Sub
>
>
>
>    Private Sub TestThread()
>        'Create new thread and define its starting point
>        Dim t As New Thread(New ThreadStart(AddressOf DoSomeTask))
>        'run the new thread
>        t.Start()
>
>        ' print some messages to screen
>        Dim i As Integer
>        For i = 1 To 1000
>            TextBox1.Text &= "from main thread # = " & i.ToString & vbCrLf
>        Next
>    End Sub
>
>    Sub DoSomeTask()
>        Dim i As Integer
>
>        For i = 1 To 1000
>            TextBox1.Text &= "from secondary thread # = " & i.ToString &
> vbCrLf
>        Next
>    End Sub
>
>
> Here are my outputs
>
> from main thread # = 1
> from main thread # = 2
> from main thread # = 3
> from main thread # = 4
> from main thread # = 5
> from main thread # = 6
> from main thread # = 7
> from main thread # = 8
> from main thread # = 9
> from main thread # = 10
> from secondary thread # = 1
> from secondary thread # = 2
> from secondary thread # = 3
> from secondary thread # = 4
> from secondary thread # = 5
> from secondary thread # = 6
> from secondary thread # = 7
> from secondary thread # = 8
> from secondary thread # = 9
> from secondary thread # = 10
>
>
>
>

29 Jul 2006 8:46 PM

Galen Somerville

Show quote Hide quote

"askhuy" <ask***@yahoo.com> wrote in message
news:%23oxAq7ysGHA.1876@TK2MSFTNGP06.phx.gbl...
> Hi All
>
>    Would someone please explain to me why my threads are not running at
> the sametime? Here is what I don't understand. When I invoke the
> TestThread() procedure, I always get the output of main thread first and
> then the secondary thread's output. Shouldn't the ouput show the mixed
> messages
>
>
>
>    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
> System.EventArgs) Handles Button1.Click
>        TestThread()
>    End Sub
>
>
>
>    Private Sub TestThread()
>        'Create new thread and define its starting point
>        Dim t As New Thread(New ThreadStart(AddressOf DoSomeTask))
>        'run the new thread
>        t.Start()
>
>        ' print some messages to screen
>        Dim i As Integer
>        For i = 1 To 1000
>            TextBox1.Text &= "from main thread # = " & i.ToString & vbCrLf
>        Next
>    End Sub
>
>    Sub DoSomeTask()
>        Dim i As Integer
>
>        For i = 1 To 1000
>            TextBox1.Text &= "from secondary thread # = " & i.ToString &
> vbCrLf
>        Next
>    End Sub
>
>
> Here are my outputs
>
> from main thread # = 1
> from main thread # = 2
> from main thread # = 3
> from main thread # = 4
> from main thread # = 5
> from main thread # = 6
> from main thread # = 7
> from main thread # = 8
> from main thread # = 9
> from main thread # = 10
> from secondary thread # = 1
> from secondary thread # = 2
> from secondary thread # = 3
> from secondary thread # = 4
> from secondary thread # = 5
> from secondary thread # = 6
> from secondary thread # = 7
> from secondary thread # = 8
> from secondary thread # = 9
> from secondary thread # = 10
>
>

In your TestThread you have "from main thread # = "
Then under DoSomeTask you have "from secondary thread # = "

Isn't that a reversal of meaning?

Galen

2 Aug 2006 12:29 PM

Phill W.

askhuy wrote:

> Would someone please explain to me why my threads are not running at the
> sametime? Here is what I don't understand. When I invoke the TestThread()
> procedure, I always get the output of main thread first and then the
> secondary thread's output. Shouldn't the ouput show the mixed messages

They /will/ run at the same time, provided each allows the other a look
in from time to time.
Add a call to ...

System.Threading.Thread.Sleep( 0 )

.... into each loop - this tells the thread to yield to other processes
(i.e. Threads). Without this, each Thread will "hog" the CPU, doing its
own thing until it's finished.

HTH,
Phill W.