How to use mpi4py in IPython notebook?

Question

I have an ipcluster running with 8 engines for Ipython notebook. So the following:

from IPython import parallel
clients = parallel.Client()
clients.block = True  # use synchronous computations
print clients.ids

gives [0, 1, 2, 3, 4, 5, 6, 7]. But, I cannot get mpi4py to see these engines:

from mpi4py import MPI
print MPI.COMM_WORLD.size

gives 1. I guess, I am missing something basic, so I'd appreciate any help.

Armut · Accepted Answer · 2015-07-16 15:31:40Z

4

It turns out that it requires some magic. The first line of the cell should be:

%%px
from mpi4py import MPI
print MPI.COMM_WORLD.size

answered Jul 16, 2015 at 15:31

Armut

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3 Comments

What does px mean/stand for?

@jtlz2 not sure but maybe parallel execute. More info on %%px is here: ipython.org/ipython-doc/3/parallel/magics.html#px

@Armut s link is dead. ipyparallel is a separate package. See <ipyparallel.readthedocs.io/en/latest/reference/mpi.html> for using MPI.