Multi-Threaded App

  • Thread starter Thread starter askhuy
  • Start date Start date
A

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
 
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 said:
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
Click to expand...
In your TestThread you have "from main thread # = "
Then under DoSomeTask you have "from secondary thread # = "

Isn't that a reversal of meaning?

Galen
 
Hi guys,

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

Regards

Sam



Michel Posseth said:
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 said:
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
Click to expand...
Click to expand...
 
askhuy said:
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
Click to expand...

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.
 
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