[petsc-users] MPI v. Pthreads ?

[John Chludzinski]

I assume you mean: neither pthreads nor MPI "offers very little potential
performance improvement on a system like this"?

I work for a small company (in Huntsville) of mechanical engineers with a
limited budget where such machines are their staple.  I'm looking at PETSc
and SLEPc to help with some of their large scale problems (e.g., generalized
eigenvalue problems for matrices from 10K x 10K to matrices over 100K x
100K).

I'm also looking at ways to parallelize of own codes, hence pthreads vs.
MPI?

---John

On Sun, Jul 10, 2011 at 2:23 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Sun, Jul 10, 2011 at 13:15, John Chludzinski <jchludzinski at gmail.com>wrote:
>
>> "If you don't have a real MPI installed"?
>>
>> I installed (on Cygwin) using: ./configure CC=gcc FC=gfortran
>> --download-mpich=1 PETSC_ARCH=arch-cygwin-gnu
>>
>> I've compiled some example MPI code using mpicc. And I've run the
>> generated executable with: mpiexec -n <some int> <executable>.
>>
>> "ps" says it created n-number of processes.
>>
>> But it is on a 2-proc/4-core Windows box running Cygwin (of course, not
>> configured as a cluster).
>>
>> Do I have "real MPI" installed?
>>
>
> Yes.
>
> Note that threading offers very little potential performance improvement on
> a system like this. It becomes more important if you have many "fat" nodes,
> for example if each node has 4 sockets with 12 cores per socket and you want
> to "strong scale" such that the subdomains become very small (less than 10k
> unknowns if inexpensive preconditioners are working, also depending on the
> network and intra-node bandwidth).
>
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