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Subject: Re: [OMPI users] Duplicate independent processes
From: Ralph Castain (rhc_at_[hidden])
Date: 2011-01-06 18:43:20


Sounds to me like you are getting a heavy dose of version contamination. I can't see any way for a single instance of mpirun to launch two procs given an input line of

mpirun -np 1 my_prog

There isn't any way OMPI can (or would) uninstall a prior installation of MPICH2, or any other MPI for that matter. Many users maintain both on their systems without problem by simply installing them to different locations and letting $PATH and friends keep things separated.

On Jan 6, 2011, at 4:03 PM, Kristian Medri wrote:

> It appears to be due to not being able to fully remove MPICH2 on machines
> that have and aged install. Then Open MPI will not overwrite the remaining
> crumbs and is not automagically well configured. I tested this hypothesis on
> an additional pair of recent/aged MPICH2 install machines. Currently
> reinstalling CentOS 5 on the aged MPICH2 install machine.
>
> The problem is that the same command on the same hardware running the same
> code results in 2 communicating processes on the recent MPICH2 install
> machine that now has Open MPI on it and 2 individual processes on the aged
> MPICH2 install machine that now had Open MPI on it.
>
> -----Original Message-----
> From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On
> Behalf Of Ralph Castain
> Sent: January 5, 2011 8:09 PM
> To: Open MPI Users
> Subject: Re: [OMPI users] Duplicate independent processes
>
> I'm afraid I don't understand your example - are you saying you provide "-np
> 1" and get two processes instead of 1?
>
> If so, would you please provide info on the type of system where this
> happens? I've never seen it with mpich or ompi
>
>
> On Jan 5, 2011, at 4:57 PM, Kristian Medri wrote:
>
>> Any hints on what to look for to get the second machine to behave without
>> duplicate independent processes?
>>
>> "mpirun -np 2 ..."
>>
>> Provides as expected:
>>
>> "Using MPI version 2.1, 2 processes
>> .1.
>> .2."
>>
>> While on another similar machine:
>>
>> "Using MPI version 2.2, 1 processes
>> .1.
>> Using MPI version 2.2, 1 processes
>> .1.
>> .2.
>> .2."
>>
>> On both:
>>
>> /usr/lib64/openmpi/1.4-gcc/bin/mpirun --version
>>
>> Returns:
>>
>> mpirun (Open MPI) 1.4
>>
>> I looked in the FAQ and searched the list but did not find it yet. When I
>> worked with MPICH2 I also had this happen from time to time. I can provide
>> additional information should it not be as common here.
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
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