[Wien] segmentation fault in lapwso

[Pavel Ondračka]

I'm CCing the list back as the crash was now diagnosed to a likely MKL
problem, see below for more details.
> 
> 
> > So just to be clear, explicitly setting OMP_STACKSIZE=1g does not
> > help
> > to solve the issue?
> > 
> 
> 
> Right! OMP_STACKSIZE=1g with OMP_NUM_THREADS=4 does not solve the
> problem!
>  
> > 
> > The problem is that the OpenMP code in lapwso is very simple, so I'm
> > having problems seeing how it could be causing the problems.
> > 
> > Could you also try to see what happens if run with:
> > OMP_NUM_THREADS=1
> > MKL_NUM_THREADS=4
> > 
> 
> 
> It does not work with these values, but I checked and it works
> reverting them:
> OMP_NUM_THREADS=4
> MKL_NUM_THREADS=1

This was very helpfull and IMO points to a problem with MKL instead of
Wien2k.

Unfortunatelly setting MKL_NUM_THREADS=1 globally will reduce the
OpenMP performance, mostly in lapw1 but also at other places. So if you
want to keep the OpenMP BLAS/lapack level parallelism you have to
either find some MKL version that works (if you do please report it
here), link with OpenBLAS (using it for lapwso is enough) or create a
simple wrapper that sets the MKL_NUM_THREADS=1 just for lapwso, i.e.,
rename lapwso binary in WIENROOT to lapwso_bin and create new lapwso
file there with:

#!/bin/bash
MKL_NUM_THREADS=1 lapwso_bin $1

and set it to executable with chmod +x lapwso.

Or maybe MKL has a non-OpenMP version which you could link with just
lapwso and use standard one in other parts, but dunno, I mostly use
OpenBLAS. If you need some further help, let me know.

Reporting the issue to intel could be also nice, however I never had
any real luck there and it is also a bit problematic as you can't
provide testcase due to Wien2k being proprietary code...

Best regards
Pavel

>  
> > 
> > This should disable the Wien2k-specific OpenMP parallelism but still
> > keep the rest of paralellism at the BLAS/lapack level.
> > 
> 
> 
> So, perhaps, the problem is related to MKL!
>  
> > 
> > Another option is that something is going wrong before lapwso and the
> > lapwso crash is just the symptom. What happens if you run everything
> > up
> > to lapwso without OpenMP (OMP_NUM_THREADS=1) and than enable it just
> > for lapwso?
> > 
> 
> 
> If I run lapw0 and lapw1 with OMP_NUM_THREADS=4 and then change it to 1
> just before lapwso, it works. 
> If I do the opposite, starting with OMP_NUM_THREADS=1 and then change
> it to 4 just before lapwso, it does not work.
> So I believe that the problem is really at lapwso.
>  
>    If you need more information, please, let me know!
>    All the best,
>             Luis