[mpich-discuss] How to spawn a non-MPI process with MPI_Comm_spawn

[Raffenetti, Kenneth J.]

I'm afraid I don't have a great answer for this. Hydra, the default 
MPICH process manager, uses fork/execvp to launch (or spawn) MPI 
processes. But this happens at the node-level daemon. As you noted, this 
may not be safe to do from the MPI-level, particularly if using an RDMA 
network. If MPICH is not configured for RDMA (i.e. TCP/IP), fork/exec 
should be OK for creating non-MPI processes.

Ken

On 1/7/20 10:07 AM, Mccall, Kurt E. (MSFC-EV41) wrote:
> Ken,
> 
> Issue created.  Can you suggest any other way to launch non-MPI processes?
> 
> Thanks,
> Kurt
> 
> -----Original Message-----
> From: Raffenetti, Kenneth J. <raffenet at mcs.anl.gov>
> Sent: Tuesday, January 7, 2020 9:32 AM
> To: discuss at mpich.org
> Cc: Mccall, Kurt E. (MSFC-EV41) <kurt.e.mccall at nasa.gov>
> Subject: [EXTERNAL] Re: [mpich-discuss] How to spawn a non-MPI process with MPI_Comm_spawn
> 
> We do not support such a key at this time, but it seems reasonable to add. Could you create an issue on our GitHub?
> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_pmodels_mpich&d=DwIF-g&c=ApwzowJNAKKw3xye91w7BE1XMRKi2LN9kiMk5Csz9Zk&r=6cP1IfXu3IZOHSDh_vBqciYiIh4uuVgs1MSi5K7l5fQ&m=H8FYbetRLxBRSaC9l0ktwX7ok3zyPRdhUlWXZZq9nsc&s=PFcC_rnOjUzKTea_1RX-vu-Nz1gCgfNP5fqj6BFly7I&e=
> 
> Thanks,
> Ken
> 
> On 1/6/20 9:50 AM, Mccall, Kurt E. (MSFC-EV41) via discuss wrote:
>> I'm attempting to use MPICH to manage a number of non-MPI processes.
>> The latter call system() and fork(), which as I understand it may
>> cause undefined behavior if they were spawned as MPI processes.   How
>> do I use
>> MPI_Comm_spawn() to launch these processes?
>>
>> For example, OpenMpi has a key for the "info" field named
>> "ompi_non_mpi", which causes a non-MPI process to be spawned.   Is
>> there something similar in MPICH?
>>
>> Thanks,
>>
>> Kurt
>>
>>
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