Trivial parallelism using multiprocessing in python

Question

I would like to use the most trivial example of parallelism in python and I am failing to understand how to do this from the multiprocessing documentation.

Here is some sample toy code that shows what I would like do.

import igraph

n = 10
g = igraph.Graph()
g.add_vertices(n)
h= igraph.Graph()
h.add_vertices(n)
[add some nodes and edges to g and h]
print "h omega is ", h.omega()
print "g alpha is", g.alpha()

I would like the last two lines to run in parallel as I have multiple cores and they take a long time to run. Each one simply outputs an integer and I don't care which order I get the results in.

Is there a simple way to do this python?

please have a look at this tutorial on multiprocessing

Pynchia
– Pynchia

2015-08-07 21:43:10 +00:00
Commented Aug 7, 2015 at 21:43 — Pynchia
– Pynchia, Commented Aug 7, 2015 at 21:43

khol · Accepted Answer · 2015-08-07 21:34:12Z

2

Assuming that omega() and alpha() are pure functions that don't change the state of your environment, you could kick off two separate processes for each call. These processes will run in parallel.

p1=multiprocessing.Process(target=lambda x: print x.omega(), args=(h,))
p2=multiprocessing.Process(target=lambda y: print y.alpha(), args=(g,))
p1.start()
p2.start()

edited Aug 7, 2015 at 21:34

answered Aug 7, 2015 at 21:27

khol

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2 Comments

Pynchia Over a year ago

it also works with a simplified lambda, without passing any arguments to it: p1=multiprocessing.Process(target=lambda: h.omega())

khol Over a year ago

Absolutely, good point. I made it obvious how to pass in arguments in case the example in the question was trivialized.

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