<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body><div>Dear all,</div><div><br></div><div>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:</div><div><br></div><div><br></div><div>______________________________________________</div><div>parent.py</div><div><br></div><div>from __future__ import print_function</div><div></div><div>from mpi4py import MPI</div><div>comm = MPI.COMM_WORLD</div><div>spawned = MPI.COMM_SELF.Spawn(sys.executable,args=['child.py'],maxprocs=1)</div><div>print("parent process is waiting for child")</div><div></div><div>spawned.Barrier()</div><div><br></div><div><br></div><div>______________________________________________</div><div>child.py</div><div><br></div><div>from __future__ import print_function</div><div>from mpi4py import MPI</div><div>parent = MPI.Comm.Get_parent()</div><div># just do some stupid stuff that takes a bit of time</div><div>for i in range(5000000):</div><div> a = i*i+1-(i*10) + math.sin(math.pow(i,i%8))</div><div>parent.Barrier()</div><div><br></div><div>______________________________________________</div><div><br></div><div>I run with e.g.:</div><div>mpirun -n 1 python mpi.py</div><div><br></div><div>Do I miss something with SPAWN method?</div><div>(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)</div><div><br></div><div>thank you very much for suggestions.</div><div><br></div><div>Regards,</div><div>stanislav.</div><div></div><div></div><div></div><div></div><div></div><div></div><div></div><div><span></span></div><div><span></span></div></body></html>