Enhance MPI scheduler to start/kill slaves only once and return function results

def start_slaves(mpi_service,logger_lvl="INFO", enable_console=False):
    if mpi_service.rank != 0:
        mpi_status = MPI.Status()
        while 1:
            # waiting sending works by master                                                                                                                                                                      
            msg = mpi_service.comm.recv(source=0, tag=MPI.ANY_TAG, status=mpi_status)
            if msg is None:
                print("Slave killed ({})".format(mpi_service.rank))
                return
            [task_job, task_param] = msg
            print("Received {}{}".format(task_job,task_param))
            slave_log = serviceLogger.Log_task(logger_lvl, enable_console)
            print("Starting job")
            slave_complete_log, start_date, end_date,resp = launchTask(task_job,
                                                                  task_param,
                                                                  slave_log,
                                                                  mpi_service)
            mpi_service.comm.send([mpi_service.rank, [start_date, end_date, slave_complete_log,resp]], dest=0, tag=0)

start_slaves(mpi_service,"DEBUG")

    if mpi_service.rank == 0:
        print("Starting work")
        tiles = parse_input_data()

        mpi_schedule_job_array(JobArray(create_tile_dir,tiles), mpi_service,"/home/mp/michelj//scratch/logs","DEBUG")
        tiles = mpi_schedule_job_array(JobArray(generate_common_masks,tiles), mpi_service,"/home/mp/michelj//scratch/logs","DEBUG")

        for tile in tiles:
            print("Mask: {}".format(tile.common_mask))

        kill_slaves(mpi_service)