[petsc-users] Using multithreaded MKL in PETSc

[Vasileios Kalantzis]

Hi Barry,

thanks for your note, I am aware of that too. Having only the MKL solver
being able to see the second level of parallelism is fine with me.

Thanks for the clarification too! As a sidenote, I set all environmental
variables correctly but Pardiso prints that is running on 1 OpenMP
thread only. I can see in the compile line (when I make) that ${CLINKER}
links with flags -lmkl_intel_lp64 -lmkl_core -lmkl_sequential -lpthread
-lm.
Could the -lmkl_sequential flag be the reason that MKL sees only a
single thread?  Can I edit ${CLINKER} or somehow remove the sequential
flag?

Thanks again!

On Tue, Mar 8, 2016 at 2:22 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Mar 8, 2016, at 2:07 PM, Vasileios Kalantzis <kalan019 at umn.edu>
> wrote:
> >
> > Hi everyone,
> >
> > Assuming that I want to use MKL's Pardiso in the
> > context of PETSc (I need it as a local solver for
> > block Jacobi type preconditioning), how should I form
> > my ./configure so that I can take advantage of
> > multi-threading when calling MKL's Pardiso?
> >
> > For example, do I simply have to configure with
> > --with-openmp=1 --with-pthread=1 and/or similar?
> > I have tried different combinations and thought
> > of asking,
> >
> > Thank you!
> >
> > ps. right now I use flat MPI and works fine, I want
> > to use threading to add a second level of parallelism,
>
>   If you do this then the only part of the code that takes advantage of
> that "second level of parallelism" will be within the MKL solver. The rest
> of the code will not use those "extra" threads. You must make sure you run
> MPI on less cores so there are enough "free" cores to run the threads for
> the the MKL solver.
>
>   To utilize MKL's Pardiso you don't need to configure PETSc with any
> mention of openmp or pthreads you just need to set appropriate MKL
> environmental variables so that MKL's Pardiso will use multiple threads. Or
> you can use MatMkl_PardisoSetCntl() see the manual page for
> MATSOLVERMKL_PARDISO etc
>
>
>
>    Barry
>
>
>
> >
> >
>
>
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