[mpich-discuss] specifying machinefile for MPI_Comm_spawn

[Jitendra Kumar]

Hi,
I would appreciate your help with a doubt using MPI_Comm_spawn.

  In order to specify the target hosts for spawning new child processes 
through MPI_Comm_spawn call, what is correct "key" value that needs to 
be set in MPI_Info.

Normally I always specify the hosts to start the MPI processes, by 
passing the argument '-machinefile'
mpiexec -machinefile mf -n np ./program

However, passing machinefile key through MPI_Info in MPI_Comm_spawn 
seems to have no effect.
MPI_Info_set(hostinfo, "machinefile", "mf")

The spawned processes are getting started on arbitrary nodes on the 
cluster.

I tried to set the key "host" through MPI_Info_set(hostinfo, "host", 
"node2") and it works. But this way I can specify only single host, and 
is a problem if I am starting MPI_Comm_spawn with large number of 
processors and wants to have control on where they are started.

I believe I am missing the correct key to set for MPI_Info for passing 
the machinefile. Would be a great help if you can provide some pointers.

Thanks,
Jitu

-- 
Jitendra Kumar
Doctoral Student
Department of Civil, Construction and Environmental Engineering
North Carolina State University
Raleigh, NC 27695
jkumar at ncsu.edu
http://www4.ncsu.edu/~jkumar