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

[Jed Brown]

Try telling your MPI to run each process on different sockets, or on the
same socket with different caches. This is easy with Open MPI and with
MPICH+Hydra. You can simply use taskset for serial jobs.

On Feb 3, 2011 5:46 PM, "Barry Smith" <bsmith at mcs.anl.gov> wrote:


  Based on these numbers (that is assuming these numbers are a correct
accounting of how much memory bandwidth you can get from the system*) you
essentially have a one processor machine that they sold to you as a 8
processor machine for sparse matrix computation. The one core run is using
almost all the memory bandwidth, adding more cores in the computation helps
very little because it is completely starved for memory bandwidth.

  Barry

* perhaps something in the OS is not configured correctly and thus not
allowing access to all the memory bandwidth, but this seems unlikely.


On Feb 3, 2011, at 4:29 PM, Vijay S. Mahadevan wrote:

> Barry,
>
> The outputs are attached. I do...
> <basicversion_np1.out><basicversion_np2.out>
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