[aspect-devel] aspect: error related to changing number of processors

Markus Bürg buerg at kit.edu
Fri Aug 31 06:06:24 PDT 2012

Hello Magali,
> - When I change this back to 1e-12, the model runs fine on 4 
> processors. Its interesting that
> using this smaller accuracy is only a problem on 4 processors, does 
> that make any sense to you?
This is one of the challenging tasks in using multiple processors. The 
results are becoming a little bit different depending on the number of 
processors on uses, because - briefly speaking - first the computations 
start on every processor independently and then the results are put 
together to form the global solution you obtain. Usually the 
differences, which happen by these different distributions of data among 
the processors, is neglectable small. But, since you have set the 
tolerance to a really small value of 1e-15, these differences became 
visible for you.

Best Regards,

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