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Subject: Re: [OMPI users] mpirun runs in serial even I set np to several processors
From: Gus Correa (gus_at_[hidden])
Date: 2014-04-14 15:51:24


On 04/14/2014 01:15 PM, Djordje Romanic wrote:
> Hi,
>
> I am trying to run WRF-ARW in parallel. This is configuration of my system:
> -------------------------------------------------
> Architecture: x86_64
> CPU op-mode(s): 32-bit, 64-bit
> Byte Order: Little Endian
> CPU(s): 4
> On-line CPU(s) list: 0-3
> Thread(s) per core: 1
> Core(s) per socket: 4
> Socket(s): 1
> NUMA node(s): 1
> Vendor ID: AuthenticAMD
> CPU family: 16
> Model: 2
> Stepping: 3
> CPU MHz: 1150.000
> BogoMIPS: 4587.84
> Virtualization: AMD-V
> L1d cache: 64K
> L1i cache: 64K
> L2 cache: 512K
> L3 cache: 2048K
> NUMA node0 CPU(s): 0-3
> -------------------------------------------------
>
> When I start wrf with mpirun -np 4 ./wrf.exe, I get this:
> -------------------------------------------------
> starting wrf task 0 of 1
> starting wrf task 0 of 1
> starting wrf task 0 of 1
> starting wrf task 0 of 1
> -------------------------------------------------
> This indicates that it is not using 4 processors, but 1.
>
> Any idea what might be the problem?
>
> Thanks,
> Djordje
>

Did you compile WRF with MPI enabled (i.e. serial,
not OpenMP, or openMP only, which is a different beast than OpenMPI =
note the trailing "I") ?

If you compiled serial, or OpenMP and did not set OMP_NUM_THREADS,
the mpirun command above will launch 4
separate/independent/repetitive/non-communicating processes
doing the same exact thing (and probably overwriting each other's
output, etc).

Did you compile and link to the OpenMPI libraries, or perhaps to
another MPI implementation?

I hope this helps,
Gus Correa