Limit CPU Usage

[Bill Martin]

I'm not sure if this is a VBA question, an Excel question, or an XP
question, but is there a way to limit how much CPU Excel burns?

I've written a macro that will endlessly run a Monte Carlo solution.
Normally I run it overnight and all is well. Sometimes however I run it
during the day, particularly if I'm tinkering with the code and want to run
it in the background to watch how it performs. When I do this it pegs CPU
usage at 100% and makes everything else on the machine painfully sluggish.

Is there some way to cut back on how much CPU Excel consumes? Ideally I'd
like my VBA routine to periodically sample CPU usage and adjust what Excel
consumes. Alternatively, is there someway I can manually adjust it?

Thanks.

Bill

 

[Jim Thomlinson]

I am not 100% sure if this will work for you or not but in the task manager
you can set the priority of the processes that are running. Open the Task
manager -> Select the Processes tab -> Right Click on Excel -> Select Set
Priority and lower the priority from normal to ??? This tells the OS what
priority to give each program when it requests CPU time. I think that might
work for you...

 

[Bill Martin]

That's a little scary. Before making the change it says:

"WARNING: Changing the priority class of this process may cause undesired
results including system instability." <Insert your favorite Microsoft
reliability joke here>

Anyhow, the good news is that it does make the rest of the machine become
responsive if I drop Excel's priority one notch. The bad news is that it
appears to bring Excel to a full dead stop rather than just throttling it
back a bit.

Bill
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[Vic Eldridge]

Hi Bill,

Try calling the DoEvents function throughout your code. If you have a loop
that's running millions of times, stick a DoEvents inside that loop.

Regards,
Vic Eldridge

 

[Charles Williams]

Sounds like a situation where a multi-core system would be ideal: Excel
versions prior to Excel2007 do single-threaded calculation so you would only
be using 1 cpu leaving the other free.
(In Excel 2007 you can control how many calculation threads to use).


BTW if you are using range.calculate in your montecarlo simulation it runs a
lot faster in excel versions 97 and 2000 than 2002 /2003.

regards
Charles
______________________
Decision Models
FastExcel 2.2 Beta now available
www.DecisionModels.com

 

[Bill Martin]

That has possibilities Vic. I have various levels of nested loops and I'll
find the one to put this into that balances responsiveness. Thanks.

Bill
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[Bill Martin]

You're probably right about multi-core. I don't know if XP gives you power
to manually assign processors in a multi-processor system? (i.e. Give one
CPU to Excel, and run everything else on the other.)

I've been considering resuscitating an old Win98 machine I have kicking
around and devoting it to running this problem (if the computer still runs).
That's sort of a poor man's multi processor approach. <g>

Bill
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