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Subject: Re: [OMPI devel] How is a MPI process launched ?
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-04-26 19:44:49


Ummmm....I sincerely hope you are kidding :-)

Is there some reason why you don't just use MPI_Comm_spawn? This is precisely what it was created to do. You can still execute it from a singleton, if you don't want to start your first process via mpirun (and is there some reason why you don't use mpirun???).

Yes, you -could- hack the MPI code to do this. Starting from scratch, with little knowledge of the code base - figure on taking awhile. I could probably come up with a way to do it, but this would have to be a very low priority for me.

On Apr 26, 2010, at 12:12 PM, Leo P. wrote:

> Hi Ralph,
>
> Thank you for your response. Really appreciate it as usual. :)
>
> It depends - if you have an environment like slurm, sge, or torque, then we use that to launch our daemons on each node. Otherwise, we default to using ssh.
>
> Once the daemons are launched, we then tell the daemons what processes each is to run. So it is a two-stage launch procedure.
>
> Ralph after starting the orte_deamon
> what is the role of ssh then ?
> Also i am assuming HNP is created before using ssh. Am i right ?
> Also Ralph i would to know how i can tell the daemon to run a process ?
> Ralph i am tying to create run a simple experiment where i can create a simple process between two computer using SSH module without using mpirun. I would to hack the mpi library so that i can send a simple "Hello World " from process A running in computer A to process B running in computer B. I would be create both the process myself. HOPE I AM BEING CLEAR.
>
> Basically what i am saying is i would to create the MPI_COMM_WORLD comprising of two process Process A and Process B. For that i would to create a functions called Create_Process_A and Create_Process_B and Send_Message by utilizing Open MPI source code.
>
> Also, I know i should be looking into PLM subsystem, RMAPS subsystem, ODLS subsystem, and ORTED subsystem. But Ralph if you guide me a bit i can finish the experiment with less sleepless night, headache, and stress.
>
> Leo P
>
>
> On Apr 26, 2010, at 2:22 AM, Leo P. wrote:
>
>> Hi everyone,
>>
>> I wanted to know how OpenMPI launches a MPI process in a cluster environment. I am assuming if the process lifecycle management it will be using rsh.
>>
>>
>> Anyhelp would be greatly appreciated.
>>
>>
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