mpi4py usage

test-mpi.py

import random
from mpi4py import MPI

comm = MPI.COMM_WORLD

# each thread will have different rank, we treat 0 as master, others as slave
rank = comm.Get_rank()
# total number of threads
size = comm.Get_size()

if rank == 0:
# for master node

    # list to store data from slaves
    alist = [0 for i in range(0, size-1)]
    asum = 0

    print(rank, ": master is waiting for data from all slaves...")
    for i in range(1, size):
        req = comm.irecv(source=i, tag=0)
        datai = req.wait()
        alist[i-1] = datai

    print(rank, ": master has received all data, summation all the data...")
    print(rank, ": data, ", alist)
    asum = sum(alist)

    print(rank, ": master will send the sum results to all slaves...")
    for i in range(1, size):
        req = comm.isend(asum, dest=i, tag=1)
        req.wait()
    print(rank, ": master has sent all data to slaves!")

else:
# for all slave nodes

    print(rank, ": slave will generate a random value and send it to master node...")
    mydata = random.randint(0, 100)
    req = comm.isend(mydata, dest=0, tag=0)
    req.wait()

    print(rank, ": slave has sent the private data, waiting for final results...")
    req = comm.irecv(source=0, tag=1)
    resdata = req.wait()
    print(rank, ": slave has received the sum results,", resdata)