[petsc-users] Configuring petsc with MPI on ubuntu quad-core

[Vijay S. Mahadevan]

Matt,

The -with-debugging=1 option is certainly not meant for performance
studies but I didn't expect it to yield the same cpu time as a single
processor for snes/ex20 i.e., my runs with 1 and 2 processors take
approximately the same amount of time for computation of solution. But
I am currently configuring without debugging symbols and shall let you
know what that yields.

On a similar note, is there something extra that needs to be done to
make use of multi-core machines while using MPI ? I am not sure if
this is even related to PETSc but could be an MPI configuration option
that maybe either I or the configure process is missing. All ideas are
much appreciated.

Vijay

On Wed, Feb 2, 2011 at 4:53 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Wed, Feb 2, 2011 at 4:46 PM, Vijay S. Mahadevan <vijay.m at gmail.com>
> wrote:
>>
>> Hi,
>>
>> I am trying to configure my petsc install with an MPI installation to
>> make use of a dual quad-core desktop system running Ubuntu. But
>> eventhough the configure/make process went through without problems,
>> the scalability of the programs don't seem to reflect what I expected.
>> My configure options are
>>
>> --download-f-blas-lapack=1 --with-mpi-dir=/usr/lib/ --download-mpich=1
>> --with-mpi-shared=0 --with-shared=0 --COPTFLAGS=-g
>> --download-parmetis=1 --download-superlu_dist=1 --download-hypre=1
>> --download-blacs=1 --download-scalapack=1 --with-clanguage=C++
>> --download-plapack=1 --download-mumps=1 --download-umfpack=yes
>> --with-debugging=1 --with-errorchecking=yes
>
> 1) For performance studies, make a build using --with-debugging=0
> 2) Look at -log_summary for a breakdown of performance
>    Matt
>
>>
>> Is there something else that needs to be done as part of the configure
>> process to enable a decent scaling ? I am only comparing programs with
>> mpiexec (-n 1) and (-n 2) but they seem to be taking approximately the
>> same time as noted from -log_summary. If it helps, I've been testing
>> with snes/examples/tutorials/ex20.c for all purposes with a custom
>> -grid parameter from command-line to control the number of unknowns.
>>
>> If there is something you've witnessed before in this configuration or
>> if you need anything else to analyze the problem, do let me know.
>>
>> Thanks,
>> Vijay
>
>
>
> --
> 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
>