Example that shows how to wait for an MPI message without pegging the CPU to 100%.

polling_mpi.py

#!/usr/bin/env python

from mpi4py import MPI
import logging
import time
import sys


def polling_receive(comm, source):
    # Set this to 0 for maximum responsiveness, but that will peg CPU to 100%
    sleep_seconds = 0.1
    if sleep_seconds > 0:
        while not comm.Iprobe(source=MPI.ANY_SOURCE):
            time.sleep(sleep_seconds)
    
    status = MPI.Status()
    result = comm.recv(source=MPI.ANY_SOURCE, status=status)
            
    return result

def main():
    logging.basicConfig(level=logging.INFO,
                        format='%(asctime)s[%(levelname)s]%(message)s')
    comm = MPI.COMM_WORLD
    process_count = comm.Get_size()
    if process_count < 2:
        if len(sys.argv) == 1:
            comm = MPI.COMM_SELF.Spawn(sys.executable,
                                       args=sys.argv + ['worker'],
                                       maxprocs=1).Merge()
        else:
            comm = MPI.Comm.Get_parent().Merge()
    process_rank = comm.Get_rank()

    if process_rank == 0:
        logging.info('Master start.')
        worker_rank = 1
        while True:
            duration = int(raw_input(
                'How long should the worker work? (0 to quit.)\n'))
            comm.send(duration, dest=worker_rank)
            if duration == 0:
                break
            result = polling_receive(comm, source=worker_rank)
            logging.info('Master received %d', result)
        logging.info('Master done.')
    else:
        logging.info('Worker start.')
        master_rank = 0
        while True:
            duration = polling_receive(comm, source=master_rank)
            if duration == 0:
                break
            logging.info('Worker working for %ds.', duration)
            time.sleep(duration)
            comm.send(duration * duration, dest=master_rank)
        logging.info('Worker done.')
        
main()