[Pw_forum] Wall time vs. CPU time

[Paolo Giannozzi]

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

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