1 #!/usr/bin/env python 2 3 """ 4 A simple example of parallel computation. 5 """ 6 7 import pprocess 8 import time 9 10 # Array size and a limit on the number of processes. 11 12 N = 100 13 limit = 10 14 15 def make_array(n): 16 17 "Make an 'n' * 'n' array initialised with zeros." 18 19 return [list(x) for x in [(0,) * n] * n] 20 21 def calculate(ch, i, j): 22 23 """ 24 A time-consuming calculation, using 'ch' to communicate with the parent 25 process, with 'i' and 'j' as operands. 26 """ 27 28 time.sleep(1) 29 ch.send((i, j, i * N + j)) 30 31 class MyExchange(pprocess.Exchange): 32 33 "Parallel convenience class containing the array assignment operation." 34 35 def store_data(self, ch): 36 i, j, result = ch.receive() 37 self.D[i][j] = result 38 39 # Main program. 40 41 if __name__ == "__main__": 42 43 # Initialise the communications exchange with a limit on the number of 44 # channels/processes. 45 46 exchange = MyExchange(limit=limit) 47 48 # Initialise an array - it is stored in the exchange to permit automatic 49 # assignment of values as the data arrives. 50 51 exchange.D = make_array(N) 52 53 # The parallel computation. 54 55 print "Calculating..." 56 for i in range(0, N): 57 for j in range(0, N): 58 ch = pprocess.start(calculate, i, j) 59 exchange.add_wait(ch) 60 61 print "Finishing..." 62 exchange.finish() 63 64 # Show the result. 65 66 print 67 for row in exchange.D: 68 print row 69 70 # vim: tabstop=4 expandtab shiftwidth=4
