[petsc-dev] Slowness of PetscSortIntWithArrayPair in MatAssembly

Fande Kong fdkong.jd at gmail.com
Tue Jul 2 12:12:48 CDT 2019


PetscSortIntWithArrayPair is used in MatStashSortCompress_Private.

Any way to avoid to use PetscSortIntWithArrayPair in


On Tue, Jul 2, 2019 at 11:09 AM Fande Kong <fdkong.jd at gmail.com> wrote:

> Hi Developers,
> John just noticed that the matrix assembly was slow when having sufficient
> amount of off-diagonal entries. It was not a MPI issue since I was  able to
> reproduce the issue using two cores on my desktop, that is, "mpirun -n 2".
> I turned  on a profiling, and 99.99% of the time was spent
> on PetscSortIntWithArrayPair (recursively calling).   It took THREE MINUTES
>  to get the assembly done. And then changed to use the option
> "-matstash_legacy" to restore
> the code to the old assembly routine, and the same code took ONE SECOND to
> get the matrix assembly done.
> Should write any better sorting algorithms?
> Fande,
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20190702/3a921242/attachment.html>

More information about the petsc-dev mailing list