PETSc runs slower on a shared memory machine than on a cluster

Lisandro Dalcin dalcinl at
Fri Feb 2 17:16:57 CST 2007

On 2/2/07, Shi Jin <jinzishuai at> wrote:
> Thank you for replying.
> I run the code on a shared memory machine through MPI,
> just like what I do on a cluster. I simply did:
> petscmpirun -np 18 ./code
> I am not 100% sure whether MPICH-2 will automatically
> use shared memory as the underlying commnunication
> channel instead of the network but I know most MPI
> implementations are smart enough to do so (like
> LAM-MPI I used before). Could anyone confirm this?

Please read the following...

I think for shared-memory you should try to configure MPICH2 with the following:


If not, perhaps configure will default to --with-device=ch3:sock and
MPICH2 will use TCP sockets.

I hope this help you.


Lisandro Dalcín
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594

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