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#
# Module providing the `Pool` class for managing a process pool
#
# multiprocessing/pool.py
#
# Copyright (c) 2007-2008, R Oudkerk --- see COPYING.txt
#
__all__ = ['Pool']
#
# Imports
#
import threading
import Queue
import itertools
import collections
import time
from multiprocessing import Process, cpu_count, TimeoutError
from multiprocessing.util import Finalize, debug
#
# Constants representing the state of a pool
#
RUN = 0
CLOSE = 1
TERMINATE = 2
#
# Miscellaneous
#
job_counter = itertools.count()
def mapstar(args):
return map(*args)
#
# Code run by worker processes
#
def worker(inqueue, outqueue, initializer=None, initargs=()):
put = outqueue.put
get = inqueue.get
if hasattr(inqueue, '_writer'):
inqueue._writer.close()
outqueue._reader.close()
if initializer is not None:
initializer(*initargs)
while 1:
try:
task = get()
except (EOFError, IOError):
debug('worker got EOFError or IOError -- exiting')
break
if task is None:
debug('worker got sentinel -- exiting')
break
job, i, func, args, kwds = task
try:
result = (True, func(*args, **kwds))
except Exception, e:
result = (False, e)
put((job, i, result))
#
# Class representing a process pool
#
class Pool(object):
'''
Class which supports an async version of the `apply()` builtin
'''
Process = Process
def __init__(self, processes=None, initializer=None, initargs=()):
self._setup_queues()
self._taskqueue = Queue.Queue()
self._cache = {}
self._state = RUN
if processes is None:
try:
processes = cpu_count()
except NotImplementedError:
processes = 1
self._pool = []
for i in range(processes):
w = self.Process(
target=worker,
args=(self._inqueue, self._outqueue, initializer, initargs)
)
self._pool.append(w)
w.name = w.name.replace('Process', 'PoolWorker')
w.daemon = True
w.start()
self._task_handler = threading.Thread(
target=Pool._handle_tasks,
args=(self._taskqueue, self._quick_put, self._outqueue, self._pool)
)
self._task_handler.daemon = True
self._task_handler._state = RUN
self._task_handler.start()
self._result_handler = threading.Thread(
target=Pool._handle_results,
args=(self._outqueue, self._quick_get, self._cache)
)
self._result_handler.daemon = True
self._result_handler._state = RUN
self._result_handler.start()
self._terminate = Finalize(
self, self._terminate_pool,
args=(self._taskqueue, self._inqueue, self._outqueue, self._pool,
self._task_handler, self._result_handler, self._cache),
exitpriority=15
)
def _setup_queues(self):
from .queues import SimpleQueue
self._inqueue = SimpleQueue()
self._outqueue = SimpleQueue()
self._quick_put = self._inqueue._writer.send
self._quick_get = self._outqueue._reader.recv
def apply(self, func, args=(), kwds={}):
'''
Equivalent of `apply()` builtin
'''
assert self._state == RUN
return self.apply_async(func, args, kwds).get()
def map(self, func, iterable, chunksize=None):
'''
Equivalent of `map()` builtin
'''
assert self._state == RUN
return self.map_async(func, iterable, chunksize).get()
def imap(self, func, iterable, chunksize=1):
'''
Equivalent of `itertools.imap()` -- can be MUCH slower than `Pool.map()`
'''
assert self._state == RUN
if chunksize == 1:
result = IMapIterator(self._cache)
self._taskqueue.put((((result._job, i, func, (x,), {})
for i, x in enumerate(iterable)), result._set_length))
return result
else:
assert chunksize > 1
task_batches = Pool._get_tasks(func, iterable, chunksize)
result = IMapIterator(self._cache)
self._taskqueue.put((((result._job, i, mapstar, (x,), {})
for i, x in enumerate(task_batches)), result._set_length))
return (item for chunk in result for item in chunk)
def imap_unordered(self, func, iterable, chunksize=1):
'''
Like `imap()` method but ordering of results is arbitrary
'''
assert self._state == RUN
if chunksize == 1:
result = IMapUnorderedIterator(self._cache)
self._taskqueue.put((((result._job, i, func, (x,), {})
for i, x in enumerate(iterable)), result._set_length))
return result
else:
assert chunksize > 1
task_batches = Pool._get_tasks(func, iterable, chunksize)
result = IMapUnorderedIterator(self._cache)
self._taskqueue.put((((result._job, i, mapstar, (x,), {})
for i, x in enumerate(task_batches)), result._set_length))
return (item for chunk in result for item in chunk)
def apply_async(self, func, args=(), kwds={}, callback=None):
'''
Asynchronous equivalent of `apply()` builtin
'''
assert self._state == RUN
result = ApplyResult(self._cache, callback)
self._taskqueue.put(([(result._job, None, func, args, kwds)], None))
return result
def map_async(self, func, iterable, chunksize=None, callback=None):
'''
Asynchronous equivalent of `map()` builtin
'''
assert self._state == RUN
if not hasattr(iterable, '__len__'):
iterable = list(iterable)
if chunksize is None:
chunksize, extra = divmod(len(iterable), len(self._pool) * 4)
if extra:
chunksize += 1
task_batches = Pool._get_tasks(func, iterable, chunksize)
result = MapResult(self._cache, chunksize, len(iterable), callback)
self._taskqueue.put((((result._job, i, mapstar, (x,), {})
for i, x in enumerate(task_batches)), None))
return result
@staticmethod
def _handle_tasks(taskqueue, put, outqueue, pool):
thread = threading.current_thread()
for taskseq, set_length in iter(taskqueue.get, None):
i = -1
for i, task in enumerate(taskseq):
if thread._state:
debug('task handler found thread._state != RUN')
break
try:
put(task)
except IOError:
debug('could not put task on queue')
break
else:
if set_length:
debug('doing set_length()')
set_length(i+1)
continue
break
else:
debug('task handler got sentinel')
try:
# tell result handler to finish when cache is empty
debug('task handler sending sentinel to result handler')
outqueue.put(None)
# tell workers there is no more work
debug('task handler sending sentinel to workers')
for p in pool:
put(None)
except IOError:
debug('task handler got IOError when sending sentinels')
debug('task handler exiting')
@staticmethod
def _handle_results(outqueue, get, cache):
thread = threading.current_thread()
while 1:
try:
task = get()
except (IOError, EOFError):
debug('result handler got EOFError/IOError -- exiting')
return
if thread._state:
assert thread._state == TERMINATE
debug('result handler found thread._state=TERMINATE')
break
if task is None:
debug('result handler got sentinel')
break
job, i, obj = task
try:
cache[job]._set(i, obj)
except KeyError:
pass
while cache and thread._state != TERMINATE:
try:
task = get()
except (IOError, EOFError):
debug('result handler got EOFError/IOError -- exiting')
return
if task is None:
debug('result handler ignoring extra sentinel')
continue
job, i, obj = task
try:
cache[job]._set(i, obj)
except KeyError:
pass
if hasattr(outqueue, '_reader'):
debug('ensuring that outqueue is not full')
# If we don't make room available in outqueue then
# attempts to add the sentinel (None) to outqueue may
# block. There is guaranteed to be no more than 2 sentinels.
try:
for i in range(10):
if not outqueue._reader.poll():
break
get()
except (IOError, EOFError):
pass
debug('result handler exiting: len(cache)=%s, thread._state=%s',
len(cache), thread._state)
@staticmethod
def _get_tasks(func, it, size):
it = iter(it)
while 1:
x = tuple(itertools.islice(it, size))
if not x:
return
yield (func, x)
def __reduce__(self):
raise NotImplementedError(
'pool objects cannot be passed between processes or pickled'
)
def close(self):
debug('closing pool')
if self._state == RUN:
self._state = CLOSE
self._taskqueue.put(None)
def terminate(self):
debug('terminating pool')
self._state = TERMINATE
self._terminate()
def join(self):
debug('joining pool')
assert self._state in (CLOSE, TERMINATE)
self._task_handler.join()
self._result_handler.join()
for p in self._pool:
p.join()
@staticmethod
def _help_stuff_finish(inqueue, task_handler, size):
# task_handler may be blocked trying to put items on inqueue
debug('removing tasks from inqueue until task handler finished')
inqueue._rlock.acquire()
while task_handler.is_alive() and inqueue._reader.poll():
inqueue._reader.recv()
time.sleep(0)
@classmethod
def _terminate_pool(cls, taskqueue, inqueue, outqueue, pool,
task_handler, result_handler, cache):
# this is guaranteed to only be called once
debug('finalizing pool')
task_handler._state = TERMINATE
taskqueue.put(None) # sentinel
debug('helping task handler/workers to finish')
cls._help_stuff_finish(inqueue, task_handler, len(pool))
assert result_handler.is_alive() or len(cache) == 0
result_handler._state = TERMINATE
outqueue.put(None) # sentinel
if pool and hasattr(pool[0], 'terminate'):
debug('terminating workers')
for p in pool:
p.terminate()
debug('joining task handler')
task_handler.join(1e100)
debug('joining result handler')
result_handler.join(1e100)
if pool and hasattr(pool[0], 'terminate'):
debug('joining pool workers')
for p in pool:
p.join()
#
# Class whose instances are returned by `Pool.apply_async()`
#
class ApplyResult(object):
def __init__(self, cache, callback):
self._cond = threading.Condition(threading.Lock())
self._job = job_counter.next()
self._cache = cache
self._ready = False
self._callback = callback
cache[self._job] = self
def ready(self):
return self._ready
def successful(self):
assert self._ready
return self._success
def wait(self, timeout=None):
self._cond.acquire()
try:
if not self._ready:
self._cond.wait(timeout)
finally:
self._cond.release()
def get(self, timeout=None):
self.wait(timeout)
if not self._ready:
raise TimeoutError
if self._success:
return self._value
else:
raise self._value
def _set(self, i, obj):
self._success, self._value = obj
if self._callback and self._success:
self._callback(self._value)
self._cond.acquire()
try:
self._ready = True
self._cond.notify()
finally:
self._cond.release()
del self._cache[self._job]
#
# Class whose instances are returned by `Pool.map_async()`
#
class MapResult(ApplyResult):
def __init__(self, cache, chunksize, length, callback):
ApplyResult.__init__(self, cache, callback)
self._success = True
self._value = [None] * length
self._chunksize = chunksize
if chunksize <= 0:
self._number_left = 0
self._ready = True
else:
self._number_left = length//chunksize + bool(length % chunksize)
def _set(self, i, success_result):
success, result = success_result
if success:
self._value[i*self._chunksize:(i+1)*self._chunksize] = result
self._number_left -= 1
if self._number_left == 0:
if self._callback:
self._callback(self._value)
del self._cache[self._job]
self._cond.acquire()
try:
self._ready = True
self._cond.notify()
finally:
self._cond.release()
else:
self._success = False
self._value = result
del self._cache[self._job]
self._cond.acquire()
try:
self._ready = True
self._cond.notify()
finally:
self._cond.release()
#
# Class whose instances are returned by `Pool.imap()`
#
class IMapIterator(object):
def __init__(self, cache):
self._cond = threading.Condition(threading.Lock())
self._job = job_counter.next()
self._cache = cache
self._items = collections.deque()
self._index = 0
self._length = None
self._unsorted = {}
cache[self._job] = self
def __iter__(self):
return self
def next(self, timeout=None):
self._cond.acquire()
try:
try:
item = self._items.popleft()
except IndexError:
if self._index == self._length:
raise StopIteration
self._cond.wait(timeout)
try:
item = self._items.popleft()
except IndexError:
if self._index == self._length:
raise StopIteration
raise TimeoutError
finally:
self._cond.release()
success, value = item
if success:
return value
raise value
__next__ = next # XXX
def _set(self, i, obj):
self._cond.acquire()
try:
if self._index == i:
self._items.append(obj)
self._index += 1
while self._index in self._unsorted:
obj = self._unsorted.pop(self._index)
self._items.append(obj)
self._index += 1
self._cond.notify()
else:
self._unsorted[i] = obj
if self._index == self._length:
del self._cache[self._job]
finally:
self._cond.release()
def _set_length(self, length):
self._cond.acquire()
try:
self._length = length
if self._index == self._length:
self._cond.notify()
del self._cache[self._job]
finally:
self._cond.release()
#
# Class whose instances are returned by `Pool.imap_unordered()`
#
class IMapUnorderedIterator(IMapIterator):
def _set(self, i, obj):
self._cond.acquire()
try:
self._items.append(obj)
self._index += 1
self._cond.notify()
if self._index == self._length:
del self._cache[self._job]
finally:
self._cond.release()
#
#
#
class ThreadPool(Pool):
from .dummy import Process
def __init__(self, processes=None, initializer=None, initargs=()):
Pool.__init__(self, processes, initializer, initargs)
def _setup_queues(self):
self._inqueue = Queue.Queue()
self._outqueue = Queue.Queue()
self._quick_put = self._inqueue.put
self._quick_get = self._outqueue.get
@staticmethod
def _help_stuff_finish(inqueue, task_handler, size):
# put sentinels at head of inqueue to make workers finish
inqueue.not_empty.acquire()
try:
inqueue.queue.clear()
inqueue.queue.extend([None] * size)
inqueue.not_empty.notify_all()
finally:
inqueue.not_empty.release()
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