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Subject: Re: [OMPI users] launching the mpi runtime
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2010-11-22 18:23:23


On Nov 22, 2010, at 11:52 AM, Hicham Mouline wrote:

> i have now a application with a gui. The gui launches the calculations
> in-process serially.
> No MPI involved. Fine. The objective is to parallelize.

Gotcha.

> I want to keep the GUI(windows) as the control to start calcs and display
> results.
>
> The GUI could be the master process of the mpi processes.
> That's bad because the executable image has deps on the GUI library and
> there's no need for all the mpi processes (the same executable) to have
> anything to do with the display.

Sounds reasonable. You likely want to have (at least) 2 executables, then: the GUI and the compute worker.

> besides, i have a win box and a couple of linux boxes, and openmpi cannot
> mix both in the same group of mpi processes.

Sadly true. There has been (very) little demand for this, so we haven't spent much (any) time on making it work.

> therefore, I guess I need to separate the GUI binary from the mpi-processes
> binary and have the GUI process talk to the "master" mpi process (on linux)
> for calc requests.
>
> I was hoping I wouldn't have to write a custom code to do that.

MPI doesn't necessarily mean SPMD -- you can certainly have the GUI call MPI_INIT and then call MPI_COMM_SPAWN to launch a different executable to do the compute working stuff.

-- 
Jeff Squyres
jsquyres_at_[hidden]
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