Python Threads + MPI

Barry Rountree rountree at cs.uga.edu
Tue Oct 19 01:47:07 CEST 2004


Hello,

I'd like to use a Python MPI wrapper (pypar, pyMPI, or ScientificPython) but
I can't get threading to work.  I'd like individual threads responsible for
MPI_Send and MPI_Recv.  Things tend to either work perfectly or hang,
depending on ordering and sleep times.  

My best guess is that the signal waking up the C-level MPI_Recv gets snagged
by another thread, which promptly ignores it.  (This theory is based
entirely on a single sentence culled from the thread module documentation: 
"Threads interact strangely with interrupts".

I've also tried surrounding the C call to MPI_Recv with
Py_BEGIN_ALLOW_THREADS and Py_END_ALLOW_THREADS, to no avail.

I guess this boils down to:  can I put C blocking socket calls in their own
Python threads and expect them to work?  If so, how?

Thanks much,

Barry Rountree

Sample code:

#!/opt/install/bin/mpipython

import Scientific.MPI as MPI
import time
import threading as T

class Sender(T.Thread):
        def run(self):
                count = 0
                while True:
                        time.sleep(0.2)
                        print "Starting send of", count
                        MPI.world.send( "x"+str(count)+"x", 0, count )
                        print "Finished send of", count
                        count+=1
                        break;
class Recver(T.Thread):
        def run(self):
                count = 0
                while True:
                        time.sleep(1.0)
                        print "Starting recv"
                        x = MPI.world.receiveString()
                        print "Received", x
                        count += 1

r = Recver()
s = Sender()


r.start()
s.start()




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