100% CPU

[bill salkin]

The simple VB.NET loop:

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
TIA,

Bill

[Chris Morse]

On Sun, 28 Dec 2003 19:44:38 -0800, "bill salkin"
<an*******@disc ussions.microso ft.com> wrote:

The simple VB.NET loop:

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
TIA,

Bill

Add this:

System.Threadin g.Thread.Sleep( 0)

Specifying 0 for the sleep will cause the thread to suspend so that
other waiting threads can execute.

// CHRIS

[Tom Dacon]

Throw an Application.DoE vents() call into the body of the loop.

"bill salkin" <an*******@disc ussions.microso ft.com> wrote in message
news:04******** *************** *****@phx.gbl.. .

The simple VB.NET loop:

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
TIA,

Bill

[Chris Morse]

On Sun, 28 Dec 2003 19:44:38 -0800, "bill salkin"
<an*******@disc ussions.microso ft.com> wrote:

The simple VB.NET loop:

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
TIA,

Bill

Thought I should add that if you're doing a loop that many times,
30 million, you should also limit the number of times you call Sleep.
The overhead involved will definitely add up.

Maybe something like this:

for i = 1 to 30000000
if i mod 5000 = 0 Then System.Threadin g.Thread.Sleep( 0)
next i
// CHRIS

[Chris Morse]

On Sun, 28 Dec 2003 20:49:06 -0800, "Tom Dacon" <To**@t-dacons.com>
wrote:

Throw an Application.DoE vents() call into the body of the loop.

Beware of using a DoEvents(). Calling this method can cause code to
be re-entered if a message raises an event.

// CHRIS

[Cor]

Hi Bill,

I never tried it, but did you tried the
threading.threa d.priority = threadpriority. lowest

Will you give us a sign if it did help than we know it also?

Cor

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?

[Pieter Philippaerts]

"bill salkin" <an*******@disc ussions.microso ft.com> wrote in message

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?

That's the entire point of multi-threading -- the operating system will do
this for you. Simply keep the code you're currently using. Whenever another
application also needs CPU time, the operating system will split the
available time over the two processes.
If your application is running at 100% CPU time, it means that there's no
other application that requires processor time.

If you wish to run your code in a low-priority background thread, take a
look at the Thread.CurrentT hread.Priority property.

Regards,
Pieter Philippaerts
Managed SSL/TLS: http://www.mentalis.org/go.php?sl

[Ken Tucker [MVP]]

Hi,

If you place it in a thread the cpu usage will stay at 100%.
However the program will not lock up. You still can start other procedures
and handle events. The thread will only run when it has time. Here is an
example. I assume you have a form level variable mbStop and a cancel button
btnCancel.

Public Sub MyLongProcess()

For i As Long = 1 To 30000000

Me.Text = i.ToString

If mbStop Then Exit For

Next

MessageBox.Show ("Done")

End Sub

Private Sub btnCancel_Click (ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles btnCancel.Click

mbStop = True

End Sub

To start thread

Dim trdMyLongProces s As New Threading.Threa d(AddressOf Me.MyLongProces s)

mbStop = False

trdMyLongProces s.Start()

Ken
-----------------
"bill salkin" <an*******@disc ussions.microso ft.com> wrote in message
news:04******** *************** *****@phx.gbl.. .

The simple VB.NET loop:

for i = 1 to 30000000
' do something
next

drives the CPU on my computer to 100% utilization for the
duration of the loop. (Several minutes)

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
TIA,

Bill

[Herfried K. Wagner [MVP]]

* Chris Morse <ch***@sorry.no .spam.com> scripsit:

Throw an Application.DoE vents() call into the body of the loop.

Beware of using a DoEvents(). Calling this method can cause code to
be re-entered if a message raises an event.

ACK. And it won't reduce CPU usage...

:-)

--
Herfried K. Wagner [MVP]
<http://www.mvps.org/dotnet>

[Chris Morse]

On Mon, 29 Dec 2003 10:12:43 +0100, "Pieter Philippaerts"
<Pi****@nospam. mentalis.org> wrote:

"bill salkin" <an*******@disc ussions.microso ft.com> wrote in message

How can I modify this loop to let other (unrelated)
applications running on the same box get some CPU time?
That's the entire point of multi-threading -- the operating system will do
this for you. Simply keep the code you're currently using. Whenever another
application also needs CPU time, the operating system will split the
available time over the two processes.

Yes, in theory, but in practice this is sometimes not the case. I
have had "runaway processes" (like, once in a while, the File Transfer
window in pcAnywhere) that hog the CPU almost completely and make it
almost impossible to do anything else.
If your application is running at 100% CPU time, it means that there's no
other application that requires processor time.
Absolutely not. Dozens of processes are then competing for what
little CPU time that's left over. You should avoid 100% cpu
utilization if possible. Adding a sleep() call now and then can
drastically improve overall system performance. Likewise, as Cor
pointed out, you can run the thread at a lower priority. This will
help keep a CPU hog from (what appears to be) locking the system up;
though you'll still have 100% CPU utilization; just that other
processes will get more time to do their thing.
If you wish to run your code in a low-priority background thread, take a
look at the Thread.CurrentT hread.Priority property.
That's a good idea.
Regards,
Pieter Philippaerts
Managed SSL/TLS: http://www.mentalis.org/go.php?sl

// CHRIS