[mpich-discuss] mpi_comm_spawn - process not destroyed

[Min Si]

Hi Stanislav,

This seems interesting. Could you please also attach the MPICH 
config.log ? You can find under the directory where you build MPICH. I 
will look into this problem then and keep you updated.

Min

On 8/11/17 1:31 PM, Stanislav Simko wrote:
> Dear all,
>
> I'm just trying some very basic stuff with MPI_COMM_SPAWN in python 
> (i.e. I use mpi4py package), but I see behaviour that I do not 
> understand - the child process gets spawned, does its stuff and then 
> "should" finish. I see though, that the process created for the child 
> stays alive. I see this only with the MPICH, OPENMPI does what I would 
> (naively) expect. In this way I can end up with N "ghost" process, 
> after calling SPAWN N-times. My minimal working example is following:
>
>
> ______________________________________________
> parent.py
>
> from __future__ import print_function
> from mpi4py import MPI
> comm = MPI.COMM_WORLD
> spawned = MPI.COMM_SELF.Spawn(sys.executable,args=['child.py'],maxprocs=1)
> print("parent process is waiting for child")
> spawned.Barrier()
>
>
> ______________________________________________
> child.py
>
> from __future__ import print_function
> from mpi4py import MPI
> parent = MPI.Comm.Get_parent()
> # just do some stupid stuff that takes a bit of time
> for i in range(5000000):
>     a = i*i+1-(i*10) + math.sin(math.pow(i,i%8))
> parent.Barrier()
>
> ______________________________________________
>
> I run with e.g.:
> mpirun -n 1 python mpi.py
>
> Do I miss something with SPAWN method?
> (I tested on two independent systems, our local cluster with mpich 
> v3.0.4, and my laptop - fedora 26, mpich v3.2.8 from repositories)
>
> thank you very much for suggestions.
>
> Regards,
> stanislav.
>
>
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