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add the multiprocessing package to fulfill PEP 371
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Benjamin Peterson
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311
Doc/includes/mp_pool.py
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311
Doc/includes/mp_pool.py
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#
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# A test of `multiprocessing.Pool` class
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#
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import multiprocessing
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import time
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import random
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import sys
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#
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# Functions used by test code
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#
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def calculate(func, args):
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result = func(*args)
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return '%s says that %s%s = %s' % (
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multiprocessing.current_process().get_name(),
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func.__name__, args, result
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)
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def calculatestar(args):
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return calculate(*args)
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def mul(a, b):
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time.sleep(0.5*random.random())
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return a * b
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def plus(a, b):
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time.sleep(0.5*random.random())
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return a + b
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def f(x):
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return 1.0 / (x-5.0)
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def pow3(x):
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return x**3
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def noop(x):
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pass
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#
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# Test code
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#
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def test():
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print 'cpu_count() = %d\n' % multiprocessing.cpu_count()
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#
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# Create pool
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#
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PROCESSES = 4
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print 'Creating pool with %d processes\n' % PROCESSES
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pool = multiprocessing.Pool(PROCESSES)
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print 'pool = %s' % pool
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print
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#
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# Tests
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#
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TASKS = [(mul, (i, 7)) for i in range(10)] + \
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[(plus, (i, 8)) for i in range(10)]
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results = [pool.apply_async(calculate, t) for t in TASKS]
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imap_it = pool.imap(calculatestar, TASKS)
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imap_unordered_it = pool.imap_unordered(calculatestar, TASKS)
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print 'Ordered results using pool.apply_async():'
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for r in results:
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print '\t', r.get()
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print
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print 'Ordered results using pool.imap():'
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for x in imap_it:
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print '\t', x
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print
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print 'Unordered results using pool.imap_unordered():'
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for x in imap_unordered_it:
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print '\t', x
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print
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print 'Ordered results using pool.map() --- will block till complete:'
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for x in pool.map(calculatestar, TASKS):
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print '\t', x
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print
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#
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# Simple benchmarks
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#
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N = 100000
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print 'def pow3(x): return x**3'
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t = time.time()
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A = map(pow3, xrange(N))
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print '\tmap(pow3, xrange(%d)):\n\t\t%s seconds' % \
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(N, time.time() - t)
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t = time.time()
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B = pool.map(pow3, xrange(N))
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print '\tpool.map(pow3, xrange(%d)):\n\t\t%s seconds' % \
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(N, time.time() - t)
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t = time.time()
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C = list(pool.imap(pow3, xrange(N), chunksize=N//8))
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print '\tlist(pool.imap(pow3, xrange(%d), chunksize=%d)):\n\t\t%s' \
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' seconds' % (N, N//8, time.time() - t)
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assert A == B == C, (len(A), len(B), len(C))
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print
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L = [None] * 1000000
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print 'def noop(x): pass'
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print 'L = [None] * 1000000'
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t = time.time()
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A = map(noop, L)
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print '\tmap(noop, L):\n\t\t%s seconds' % \
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(time.time() - t)
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t = time.time()
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B = pool.map(noop, L)
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print '\tpool.map(noop, L):\n\t\t%s seconds' % \
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(time.time() - t)
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t = time.time()
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C = list(pool.imap(noop, L, chunksize=len(L)//8))
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print '\tlist(pool.imap(noop, L, chunksize=%d)):\n\t\t%s seconds' % \
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(len(L)//8, time.time() - t)
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assert A == B == C, (len(A), len(B), len(C))
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print
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del A, B, C, L
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#
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# Test error handling
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#
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print 'Testing error handling:'
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try:
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print pool.apply(f, (5,))
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except ZeroDivisionError:
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print '\tGot ZeroDivisionError as expected from pool.apply()'
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else:
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raise AssertionError, 'expected ZeroDivisionError'
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try:
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print pool.map(f, range(10))
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except ZeroDivisionError:
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print '\tGot ZeroDivisionError as expected from pool.map()'
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else:
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raise AssertionError, 'expected ZeroDivisionError'
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try:
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print list(pool.imap(f, range(10)))
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except ZeroDivisionError:
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print '\tGot ZeroDivisionError as expected from list(pool.imap())'
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else:
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raise AssertionError, 'expected ZeroDivisionError'
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it = pool.imap(f, range(10))
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for i in range(10):
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try:
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x = it.next()
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except ZeroDivisionError:
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if i == 5:
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pass
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except StopIteration:
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break
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else:
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if i == 5:
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raise AssertionError, 'expected ZeroDivisionError'
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assert i == 9
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print '\tGot ZeroDivisionError as expected from IMapIterator.next()'
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print
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#
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# Testing timeouts
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#
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print 'Testing ApplyResult.get() with timeout:',
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res = pool.apply_async(calculate, TASKS[0])
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while 1:
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sys.stdout.flush()
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try:
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sys.stdout.write('\n\t%s' % res.get(0.02))
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break
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except multiprocessing.TimeoutError:
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sys.stdout.write('.')
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print
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print
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print 'Testing IMapIterator.next() with timeout:',
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it = pool.imap(calculatestar, TASKS)
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while 1:
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sys.stdout.flush()
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try:
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sys.stdout.write('\n\t%s' % it.next(0.02))
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except StopIteration:
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break
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except multiprocessing.TimeoutError:
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sys.stdout.write('.')
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print
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print
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#
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# Testing callback
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#
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print 'Testing callback:'
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A = []
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B = [56, 0, 1, 8, 27, 64, 125, 216, 343, 512, 729]
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r = pool.apply_async(mul, (7, 8), callback=A.append)
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r.wait()
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r = pool.map_async(pow3, range(10), callback=A.extend)
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r.wait()
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if A == B:
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print '\tcallbacks succeeded\n'
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else:
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print '\t*** callbacks failed\n\t\t%s != %s\n' % (A, B)
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#
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# Check there are no outstanding tasks
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#
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assert not pool._cache, 'cache = %r' % pool._cache
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#
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# Check close() methods
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#
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print 'Testing close():'
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for worker in pool._pool:
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assert worker.is_alive()
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result = pool.apply_async(time.sleep, [0.5])
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pool.close()
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pool.join()
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assert result.get() is None
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for worker in pool._pool:
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assert not worker.is_alive()
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print '\tclose() succeeded\n'
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#
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# Check terminate() method
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#
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print 'Testing terminate():'
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pool = multiprocessing.Pool(2)
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DELTA = 0.1
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ignore = pool.apply(pow3, [2])
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results = [pool.apply_async(time.sleep, [DELTA]) for i in range(100)]
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pool.terminate()
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pool.join()
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for worker in pool._pool:
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assert not worker.is_alive()
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print '\tterminate() succeeded\n'
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#
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# Check garbage collection
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#
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print 'Testing garbage collection:'
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pool = multiprocessing.Pool(2)
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DELTA = 0.1
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processes = pool._pool
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ignore = pool.apply(pow3, [2])
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results = [pool.apply_async(time.sleep, [DELTA]) for i in range(100)]
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results = pool = None
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time.sleep(DELTA * 2)
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for worker in processes:
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assert not worker.is_alive()
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print '\tgarbage collection succeeded\n'
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if __name__ == '__main__':
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multiprocessing.freeze_support()
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assert len(sys.argv) in (1, 2)
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if len(sys.argv) == 1 or sys.argv[1] == 'processes':
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print ' Using processes '.center(79, '-')
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elif sys.argv[1] == 'threads':
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print ' Using threads '.center(79, '-')
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import multiprocessing.dummy as multiprocessing
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else:
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print 'Usage:\n\t%s [processes | threads]' % sys.argv[0]
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raise SystemExit(2)
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test()
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