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#!/usr/bin/env python
"""
A simple example of parallel computation using message exchanges and the create
function.
NOTE: We could use the with statement in the innermost loop to package the
NOTE: try...finally functionality.
"""
import pprocess
import time
#import random
# Array size and a limit on the number of processes.
N = 10
limit = 10
delay = 1
# Monitoring class.
class MyExchange(pprocess.Exchange):
"Parallel convenience class containing the array assignment operation."
def store_data(self, ch):
i, j, result = ch.receive()
self.D[i*N+j] = result
# Main program.
if __name__ == "__main__":
t = time.time()
# Initialise the communications exchange with a limit on the number of
# channels/processes.
exchange = MyExchange(limit=limit)
# Initialise an array - it is stored in the exchange to permit automatic
# assignment of values as the data arrives.
results = exchange.D = [0] * N * N
# Perform the work.
print "Calculating..."
for i in range(0, N):
for j in range(0, N):
ch = exchange.create()
if ch:
try: # Calculation work.
#time.sleep(delay * random.random())
time.sleep(delay)
ch.send((i, j, i * N + j))
finally: # Important finalisation.
pprocess.exit(ch)
# Wait for the results.
print "Finishing..."
exchange.finish()
# Show the results.
for i in range(0, N):
for result in results[i*N:i*N+N]:
print result,
print
print "Time taken:", time.time() - t
# vim: tabstop=4 expandtab shiftwidth=4
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