Hi Davide,
Thanks a lot.
> Hi Artur
>
> As it has already been pointed out in this list, if you have a plain SMP
> system you should not worry much about on which socket/core your
> parallel processes run within a single node, provided you have a recent
> enough kernel (multicore/hyperthread aware) it will probably do a good
> scheduling job.
kernel 2.6.18.8-0.5 with suse 10.2 is it recent enough ?
> Concerning the way to spread multiple processes on different nodes, it
> may surely depend on the application, I would add to Tim's answer that I
> saw some benchmarks where the same MPI application (whose performance
> bottlencks are memory access and communication) had the following
> behavior (supposing to have dual processor*dual core nodes):
>
> on Opteron systems maximum performance was obtained with 4 MPI processes
> per node, thus using all the cores =>communication bottleneck
>
> on Xeon systems the maxiumum performance was reached using double number
> of nodes but starting only 2 processes per node, even if some other
> process were running on the same nodes =>memory access bottleneck
>
> best regards, Davide
>
>
I also did some tests and this is what I observed on 8 dual cores
workstation (16 cores)
When I run 2 jobs (mpirun -np 8 ./job_1 and mpirun -np 8 ./job_2)
simultaneously then the execution time of each of them is about 20%
longer than when I run these jobs consecutively, i.e. first mpirun -np 8
./job_1 and then when it finished mpirun -np 8 ./job_2. Is it common
behavior?
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