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

[Shi Jin]

> There is a point which is not clear for me.
> 
> When you run in your shared-memory machine...
> 
> - Are you running your as a 'sequential' program
> with a global,shared
> memory space?
> 
> - Or are you running it through MPI, as a
> distributed memory
> application using MPI message passing (where shared
> mem is the
> underlying communication 'channel') ?

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?
Thank you.

Shi



 
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