[petsc-users] MPI_AllReduce vs VecScatterCreateToAll

[Matthew Knepley]

On Tue, Nov 8, 2011 at 4:42 AM, Robert Ellis <Robert.Ellis at geosoft.com>wrote:

>  Hello Petsc Developers,****
>
> ** **
>
> I have a predominantly Petsc application but for simplicity it uses a very
> few MPI_AllReduce calls. I am finding that the MPI_AllReduce operations are
> sometimes causing problems (appears to be semaphore time outs) if the
> interprocess communication is slow. I never have any problem with the Petsc
> operations. Is it reasonable that Petsc would be more robust that
> MPI_AllReduce?
>

No. There are a lot of Allreduce() calls in the source:

  find src -name "*.c" | xargs grep MPI_Allreduce

     Matt


> **
>
> Also, is the VecScatterCreateToAll set of operations the best way to
> replace the MPI_AllReduce?****
>
> ** **
>
> Thanks for any advice,****
>
> Rob****
>
> ** **
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111108/2eef8ff4/attachment.htm>