#

# 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 `itertool.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