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

Magali Billen mibillen at ucdavis.edu
Fri Aug 31 09:36:16 PDT 2012

Thank you for the explanation.

On Aug 31, 2012, at 6:06 AM, Markus Bürg wrote:

> 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,
> Markus
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