[mesa-users] kap module and thread-safe conflict

[Bill Paxton]

1) mesa/star routinely calls kap from OpenMP loops without any problems, so i think you are wrong to suggest that kap fails when called from OpenMP loops.  please elaborate on your claim.
2) i believe your are wrong when you mention internal OMP constructs in the kap module -- I don't think there are any. 
3) it is of course possible that the problem is in kap rather than in your code; if so, please let us know so we can fix it.

bill



 

On Jul 13, 2015, at 4:33 AM, Ehsan Moravveji wrote:

> Dear MESA users,
> I am using and calling the kap module in an external code to get opacities for different temperatures and densities, using v.7678. Therefore, I have a nested do-loop that I can parallelise with OpenMP for (hopefully) faster fetching of opacities for a range of temperatures and densities. 
> With only one thread, the script runs OK, and the results are what I expect. The pseudo-code looks like
> 
>    !$OMP parallel do default(none) private(…) shared(…)
>    do logT in a range of temperatures
>         do logR in a range of densities
> 
>              kappa = get_kappa(logT, logR)
>              
>          enddo
>   enddo
>   !$OMP end parallel do
> 
> However, setting OMP_NUM_THREADS > 1, also invokes the internal OMP constructs in the kap module; the result of this is a significant speed up, but very spaghetti results. 
> 
> The problem is, by default MESA is installed with -fopenmp and I would like to keep it so, because of my other applications of MESA. However, my call to get_kappa() needs to be restricted to use only one thread. 
> Geert Jan Bex (in CC) and I also tried calling OMP_set_num_threads(1) before calling get_kappa(), but that did not work either.
> 
> So, my question is: Is it possible to use MESA modules in external programs that also include OpenMP directives, making sure that the whole computations are thread safe?
> I would be grateful if you enlighten me with your comments and ideas.
> 
> Best regards
> Ehsan.
> 
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