[Pw_forum] Wall time vs. CPU time

Paolo Giannozzi giannozz at democritos.it
Sat Aug 28 20:54:33 CEST 2010

On Aug 28, 2010, at 20:14 , Vo, Trinh (388C) wrote:

> For all my jobs, the wall time is usually significantly larger than  
> the CPU time
> [...] I don’t know what are the possible reasons that causes this  
> delay.

1) time spent in I/O
2) time spent in communications (in parallel execution)

>  What factors I should look at to fix this problem.

1) reduce I/O, or use fast I/O channels
2) faster communication hardware, or usage of parallelization
levels requiring less communications.

More in the user guide

Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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