MPI4py spawn

testmanager.py

from mpi4py import MPI
import sys
import argparse

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('worker_count', type=int)
    args = parser.parse_args()

    mpi_info = MPI.Info.Create()
    mpi_info.Set("add-hostfile", "worker_hosts")

    comm = MPI.COMM_SELF.Spawn(sys.executable,
                               args=['testworker.py'],
                               maxprocs=args.worker_count,
                               info=mpi_info).Merge()
    process_rank = comm.Get_rank()
    process_count = comm.Get_size()
    process_host = MPI.Get_processor_name()

    print ', '.join(map(str, ('manager',
                              process_rank,
                              process_count,
                              process_host)))

main()

testworker.py

from mpi4py import MPI

def main():
    comm = MPI.Comm.Get_parent().Merge()

    process_rank = comm.Get_rank()
    process_count = comm.Get_size()
    process_host = MPI.Get_processor_name()
    
    print ', '.join(map(str, ('worker',
                              process_rank,
                              process_count,
                              process_host)))

main()

worker_hosts

myhead1 slots=2
mycompute1 slots=2
mycompute2 slots=2
mycompute3 slots=2
mycompute4 slots=3

Trying to get the manager to spawn workers on multiple hosts, but it's not working.

Switched option name to add-hostfile, as described by newer documentation. Now it works.