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Subject: Re: [OMPI users] Two Instances of Same Process Rather Than Two SeparateProcesses
From: Jeff Squyres (jsquyres) (jsquyres_at_[hidden])
Date: 2011-03-10 06:39:48

LAM/MPI is dead; all the developers (including me) moved to Open MPI years ago (literally).

Most of LAM's good ideas have been absorbed into Open MPI.

Switching from LAM to Open MPI is theoretically pretty easy - both use the same-named wrapper compilers (mpicc, mpif77, etc). You should be able to simply change your path to point to the Open MPI wrappers instead of the LAM wrappers and then build as you normally would.

Sent from my phone. No type good.

On Mar 9, 2011, at 11:52 PM, "Clark Britan" <c.britan.j2_at_[hidden]> wrote:

> Jeff,
> Thanks for the reply and you are correct about the error. Here is a
> summary of what happened, with an additional question at the end.
> I originally installed lam-mpi to run FDS, as suggested in the FDS
> manual. Everything works smoothly with lam-mpi, but on the lam-mpi
> website it suggests trying the newer open mpi, so I downloaded it. Then
> when I tried to run FDS in parallel using open mpi, I got the error that
> I mentioned in the previous email. I then deleted lam-mpi and tried
> running again using open mpi and I got an error saying that FDS was
> looking for the lam-mpi help file and that it couldn't find it. So, that
> leads me to believe that the pre-compiled version of FDS was compiled
> against lam-mpi (not sure if "compiled against lam-mpi" is the right
> wording) and therefore will not work with open mpi. I spent some time
> trying to compile the FDS source code with the open mpi compilers, but I
> realised this is quite difficult.
> Is open mpi significantly better than lam-mpi? I.e. should I continue my
> efforts in trying to run FDS with open mpi? And if so, would compiling
> the FDS source code using the open mpi compilers solve the problem?
> Thanks for the help.
> Regards,
> Clark
> On Tue, 2011-03-08 at 10:53 -0500, Gus Correa wrote:
>> Jeff Squyres (jsquyres) wrote:
>>> This usually indicates a mismatch of MPI installations - eg, you compiled against one MPI installation but then accidentally used the mpirun from a different MPI installation.
>>> Sent from my phone. No type good.
>>> On Mar 8, 2011, at 4:36 AM, "Clark Britan" <c.britan.j2_at_[hidden]> wrote:
>>>> I just installed OpenMPI on my Linux Ubuntu 10.04 LTS 64 bit computer. I
>>>> downloaded the most recent version of OpenMPI and ran the configure and make
>>>> commands.
>>>> I then tried to run a CFD software called FDS using 2 of the 12 available
>>>> processors (single node) as a test. I split my computational domain into two
>>>> meshes, as explained in the FDS manual and would like to run each mesh on a
>>>> separate core.
>>>> When I run the command mpirun -np 2 fds5_mpi_linux_64 room_fire.fds I get
>>>> the following error:
>>>> Process 0 of 0 is running on comp1
>>>> Process 0 of 0 is running on comp1
>>>> Mesh 1 is assigned to Process 0
>>>> Error: MPI_PROCESS greater than total number of processes
>>>> Why are two instances of the same process run instead of two separate
>>>> processes? What I expect to see after running the above command is:
>>>> Process 0 of 1 is running on comp1
>>>> Process 1 of 1 is running on comp1
>>>> Mesh 1 is assigned to Process 0
>>>> Mesh 2 is assigned to Process 1
>>>> ...
>>>> Any idea what is going on? Thanks for the help.
>>>> Kind Regards,
>>>> Clark
>> Hi Clark
>> Any chances that MPI_PROCESS was not properly set in your FDS parameter
>> file?
>> I am not familiar to the FDS software, but it looks like MPI_PROCESS is
>> part of the FDS setup, and the error message seems to complain
>> of a mismatch w.r.t. the number of processes (-np 2).
>> Maybe it takes a default value.
>> Also, if you just want to check your OpenMPI functionality, download
>> the OpenMPI source code, compile (with mpicc) and run (with mpirun)
>> the hello_c.c, connectivity_c.c, and ring_c.c programs in the 'examples'
>> directory. This will at least tell you if the problem is in OpenMPI or
>> in FDS.
>> My two cents,
>> Gus Correa
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