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From: Ralph H Castain (rhc_at_[hidden])
Date: 2006-06-30 09:08:45


Hi Amrita

I¹m not entirely sure I understand your questions, but will try to answer
them below. If you can share what you are doing, we¹d be happy to provide
advice.

Ralph

On 6/30/06 5:45 AM, "amrita mathuria" <amrita_mathuria18_at_[hidden]> wrote:

> hi...
>
> I am working with open mpi source code....
>
> I want to know what is the role of daemons in the whole process...

Generally, we use the host system's launch capability (rsh, ssh, SLURM,
etc.) to launch a daemon on every node that will be used for a job. The
daemons are then instructed to launch the application's processes on their
local node.

>
> After mpirun launches the daemons and daemons launches the process on
> different nodes.....
>

Daemons are used to forward I/O between mpirun and the application
processes, and also monitor the state of the processes they launched. In
this latter case, the daemons specifically alert mpirun to abnormal
terminations. Other than that, the daemons don't really do anything after
launch.

>
>
> And also do the mpirun interacts with the daemons after launching them....or
> it directly interact with the processes when there is a need....?????
>

Mpirun always interacts directly with the processes. The only exception is
when mpirun needs to order termination of the entire job (e.g., if the user
issues a ctrl-C) - in this case, the daemon can be ordered to "kill" the
local process.
  
>
>
>
>
> thanks
>
> Amrita
>
>
>
>
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