Thread.Sleep slowing down the whole application

  • Thread starter Thread starter davidst95
  • Start date Start date
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davidst95

Hello,

I have a program that runs a long process. I tried to add a thread
to check if the use hit a cancel button to abort the process.

Dim t As Threading.Thread
t = New Threading.Thread(AddressOf StartProcess)
t.IsBackground = True
t.Priority = ThreadPriority.Highest
t.Start()

Do

Thread.CurrentThread.Sleep(500)
Application.DoEvents()
if bCancel=true then
t.Abort()
exit do
end if

Loop


When I add 'StartProcess' into a thread, it's about twice as slow if it
just ran it without a thread. Could anyone tell me what I'm not doing
right? Thanks. I played around with this all day and I'm lost.
Thanks.

David
 
(e-mail address removed) wrote in @m7g2000cwm.googlegroups.com:
Hello,

I have a program that runs a long process. I tried to add a thread
to check if the use hit a cancel button to abort the process.

Dim t As Threading.Thread
t = New Threading.Thread(AddressOf StartProcess)
t.IsBackground = True
t.Priority = ThreadPriority.Highest
t.Start()

When I add 'StartProcess' into a thread, it's about twice as slow if it
just ran it without a thread. Could anyone tell me what I'm not doing
right? Thanks. I played around with this all day and I'm lost.
Thanks.
Click to expand...


I noticed that you set the thread priority to highest - I think when it's
set to highest, it will not yield CPU time to other processes.

You should leave the thread priority to normal and try again.

Also, take a look at callback functions - depending on the situation,
they're abit better than firing a thread to run a long running function.
 
Also, take a look at callback functions - depending on the situation,
they're abit better than firing a thread to run a long running function.
Click to expand...

Could you give a small example?
 
Thank you very much for the information. I been playing around with
it all day. I have to wait until tomorrow to try this out but I think
this might work.

David
 
Dim t As Threading.Thread
t = New Threading.Thread(AddressOf StartProcess)
t.IsBackground = True
t.Priority = ThreadPriority.Highest
t.Start()
Click to expand...

Good, you've created a new thread :)
Do

Thread.CurrentThread.Sleep(500)
Application.DoEvents()
if bCancel=true then
t.Abort()
exit do
end if

Loop
Click to expand...

Ahh, you are sleeping the CurrentThread, which is your main thread, not the
thread you created. So, instead of sleeping there, you should sleep in
StartProcess. Secondly, it's rather bad to call "t.Abort". You will get no
end of problems especially if your thread is handling COM objects. The
accepted pattern for dealing with threads is to flag a "bCancel" inside the
thread that it checks periodically so it can terminate cleanly.
 
Thanks for the reply. Wouldn't "t.Sleep(1000)' just slow down the
whole thread? I tried it out and have similar results. What I want
to try to do is run a thread and have another thread refresh the form
and check the cancel button without slowing down the 'StartProcess'
thread.

When I remove the thread itself and just run 'StartProcess', the time
decreases in half.

Thanks again.

David
 
Thanks for the reply. Wouldn't "t.Sleep(1000)' just slow down the
whole thread? I tried it out and have similar results. What I want
to try to do is run a thread and have another thread refresh the form
and check the cancel button without slowing down the 'StartProcess'
thread.

When I remove the thread itself and just run 'StartProcess', the time
decreases in half.

Thanks again.

David
Click to expand...

Oh okay, I misunderstood. I thought you were wanting to sleep the worker
thread so it didn't take too much time away from the main GUI thread (which
is the more normal scenario). I suggest you re-archietect what you are
doing slightly. Let your worker thread run free inside a loop checking for
"cancelled = true", at which point it exits. You then can "fire and forget"
the worker thread.

When your main thread is finished, it can "invoke" a delegate on your form
to say it's finished, or a delegate to say it was cancelled or a delegate to
say it was failed (or you can put all 3 into the same method).

Something like this:

User Action
Create Thread
Start Thread (
[Thread loops doing it's business]
[If bCancelled Then Exit Thread]
Exit:
Invoke Completed Method on Main Form )

Completed:
Update UI
 
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