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OpenMPI hangs on large message

To reproduce the problem, run below script with

mpirun -n 2 python test_largemsg.py

cat test_largemsg.py

from mpi4py import MPI

comm = MPI.COMM_WORLD

rank = comm.Get_rank()

size = comm.Get_size()


import numpy as np


n = 20000

if rank == 0:

    data = np.arange(n, dtype='i')

else:

    data = np.empty(n, dtype='i')

comm.Bcast(data, root=0)


print(f'rank={rank} data[-1]={data[-1]}')

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