[mpich-discuss] Strange, inconsistent behaviour with MPI_Comm_spawn
raffenet at mcs.anl.gov
Thu Jun 15 15:51:45 CDT 2017
On 06/15/2017 10:54 AM, Alexander Rast wrote:
> See my subsequent message - I'd already tried that and it didn't work,
> or possibly I'm using the wrong method here. The documentation is
> unclear where the hosts file should be and how it should be specified in
> the case of an MPI_Comm_spawn command in the code run by mpiexec. Is the
> intention that the hosts file should be specified with the mpiexec
> command (in which case how does it get passed to MPI_Comm_spawn?
The hostfile should be available on the host running mpiexec, and
mpiexec -f <hostfile> <...>
mpiexec handles the launching of spawned processes in MPICH, so it will
have access to the file when needed.
> Is this
> brought in via argv?), or is the intention that the MPI_Comm_spawn
> command should specify this via an info variable (in which case where
> should the file reside?
Info is another option that will work. If using info, you can specify a
KV pair like:
value=<list of hostnames>
to control the placement. This would need to be specified on all ranks
in the comm where MPI_Comm_spawn is called.
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