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Subject: Re: [OMPI users] How to specify hosts for MPI_Comm_spawn
From: Mark Borgerding (markb_at_[hidden])
Date: 2008-07-30 08:49:33

I keep checking my email in hopes that someone will come up with
something that Matt or I might've missed.

I'm just having a hard time accepting that something so fundamental
would be so broken.
The MPI_Comm_spawn command is essentially useless without the ability to
spawn processes on other nodes.

If this is true, then my personal scorecard reads:
    # Days spent using openmpi: 4 (off and on)
    # identified bugs in openmpi :2
    # useful programs built: 0

Please prove me wrong. I'm eager to be shown my ignorance -- to find
out where I've been stupid and what documentation I should've read.

Matt Hughes wrote:
> I've found that I always have to use mpirun to start my spawner
> process, due to the exact problem you are having: the need to give
> OMPI a hosts file! It seems the singleton functionality is lacking
> somehow... it won't allow you to spawn on arbitrary hosts. I have not
> tested if this is fixed in the 1.3 series.
> Try
> mpiexec -np 1 -H op2-1,op2-2 spawner op2-2
> mpiexec should start the first process on op2-1, and the spawn call
> should start the second on op2-2. If you don't use the Info object to
> set the hostname specifically, then on 1.2.x it will automatically
> start on op2-2. With 1.3, the spawn call will start processes
> starting with the first item in the host list.
> mch