[petsc-users] Issue with KSPSolve when the number of CPUs are larger than four

[Matthew Knepley]

On Wed, Jan 10, 2018 at 4:41 PM, Mohammad R. Gohardoust <
gohardoust at email.arizona.edu> wrote:

> Hi,
>
> I hope you are doing well. I am Mohammad, a PhD student of environmental
> sciences at the University of Arizona.
>
> I do appreciate any help that can shed some light on the issue I have:
> recently I have added a feature to an existing parallel code called
> 'parswms' which solves water and solute transport in soils. The code uses
> MPI and parmetis for the parallelization purposes and petsc package
> (KSPSolve) for solving linear systems. I have it installed on the UofA
> HPC : the issue is that it works well if the number of CPUs are up to 4!
> but when I add to this number the numerical linear solver (here it is
> 'KSPCGS') stops with the error of 'KSP_DIVERGED_NANORINF'.
>
> Would you mind please giving me some hints, suggestions or resources in
> this regard?
>

It sounds like you might have a problem in matrix assembly. However, first
use -pc_type gmres instead since
it has nicer numerical behavior (I believe).

  Thanks,

     Matt


> Best Regards,
> Mohammad
>
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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