Parallel Python 並行開發多核心並行程式（例3）

#-*- coding: UTF-8 -*-#-------------------------------------------------------------------------------# Name:        # Purpose:     ## Author:      ankier## Created:     05-02-2013# Copyright:   (c) ankier 2013# Licence:     <your licence>#-------------------------------------------------------------------------------import math, sys, md5, timeimport ppdef part_sum(start, end):    """Calculates partial sum"""    sum = 0    for x in xrange(start, end):        if x % 2 == 0:           sum -= 1.0 / x         else:           sum += 1.0 / x     return sumstart = 1end = 20000000# Divide the task into 64 subtasksparts = 64step = (end - start) / parts + 1# Create jobserverjob_server = pp.Server()# Execute the same task with different amount of active workers and measure the timefor ncpus in (1, 2, 4, 8, 16, 1):    job_server.set_ncpus(ncpus)    jobs = []    start_time = time.time()    print "Starting ", job_server.get_ncpus(), " workers"    for index in xrange(parts):        starti = start+index*step        endi = min(start+(index+1)*step, end)        jobs.append(job_server.submit(part_sum, (starti, endi)))       # Retrieve all the results and calculate their sum    part_sum1 = sum([job() for job in jobs])    # Print the partial sum    print "Partial sum is", part_sum1, "| diff =", math.log(2) - part_sum1    print "Time elapsed: ", time.time() - start_time, "s"    printjob_server.print_stats()

運行結果：

Starting  1  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  3.40600013733 sStarting  2  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  2.04699993134 sStarting  4  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  1.6740000248 sStarting  8  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  1.66700005531 sStarting  16  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  1.67000007629 sStarting  1  workersPartial sum is 0.69314720556 | diff = -2.50000427027e-08Time elapsed:  3.36299991608 sJob execution statistics: job count | % of all jobs | job time sum | time per job | job server       384 |        100.00 |      29.3340 |     0.076391 | localTime elapsed since server creation 15.20600008960 active tasks, 1 cores