[petsc-dev] Possible bugs when using TS with ViennaCL

[Karl Rupp]

Hey,

 >> There is only a little bit of code in
>>    src/sys/threadcomm/impls/openmp/tcopenmp.c
>>    src/sys/threadcomm/impls/openmp/tcopenmpimpl.h
>> in addition to the registration of OpenMP functionality in
>>    src/sys/threadcomm/interface/threadcommregi.c
>> I really don't see how this could affect the execution of GPU code if
>> the threadcomm-default 'nothread' is used.
>
> There is a bunch of conditional compilation guarded by the
> (nonconforming style) PETSC_THREADCOMM_ACTIVE.  Seems to me it's more
> likely that something bad happens in one of those blocks than that
> -fopenmp causes the compiler to misbehave.

I should have been more precise: If we configure PETSc to use OpenMP 
through threadcomm, then we run into issues. OpenMP and OpenCL code  per 
se, i.e. without any PETSc-code involved, is not causing troubles (and 
is a common build with ViennaCL). If I configure
  --with-openmp
but without
  --with-threadcomm --with-pthreadclasses
then execution is fine. Conversely, configuring
  --with-threadcomm --with-pthreadclasses
but without
  --with-openmp
also works. If all three options are supplied, wrong results are 
obtained. Weird. I'll keep it on my list, but will focus on other items 
first.

Best regards,
Karli