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Question Small CPU time usage 

Keywords: performance CPU time
Forum: Run Management
Date: 21 Sep, 2005
From: MLucia <lucia.magliozzi@iss.infn.it>

Dear G4Users,

I noticed that my Geant4 simulation of a discrete gamma camera, 
uses a small amount of CPU usage (< 5%) 
when processing events with few particles (3-5) 
while the CPU time increases to more than 70% 
when the events contain several particles (>1000).

It seems that in the first case most of the time is spent in I/O calls.

In fact, in verbose mode, when Geant4 simulates events with few particles, 
I get a lot of the following messages on stack operations:

> ### pop requested out of 0 stacked tracks.
> ### 0 waiting tracks are re-classified to
>     0 urgent tracks and 0 waiting tracks.
> NULL returned from G4StackManager.

Is it possible that these calls to the stack is 
the cause of the small CPU usage, 
or there are other explanations?

Eventually, are there ways to increase the CPU usage ?

Thanks in advance

Maria Lucia Magliozzi

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