# Parallel processing

import cPickle

import itertools

import Queue

import rand

import types

import warnings

import collection

import dicts

import exc

from Runnable import Runnable

def try_pickle(value):

    try: cPickle.dumps(value)

    except Exception, e:

        exc.add_msg(e, 'Tried to pickle: '+repr(value))

        raise

def prepickle(value, vars_id_dict_):

    def filter_(value, is_leaf):

        id_ = id(value)

        if id_ in vars_id_dict_: value = id_

        # Try pickling the value. If it fails, we'll get a full traceback here,

        # which is not provided with pickling errors in multiprocessing's Pool.

        elif is_leaf: try_pickle(value)

        return value

    return collection.rmap(filter_, value)

def post_unpickle(value, vars_id_dict_):

    def filter_(value, is_leaf):

        if type(value) == int: value = vars_id_dict_.get(value, value)

            # get() returns the value itself if it isn't a known id()

        return value

    return collection.rmap(filter_, value)

class SyncPool:

    '''A dummy synchronous Pool to use if multiprocessing is not available'''

    def __init__(self, processes=None): pass

    class Result:

        def __init__(self, value): self.value = value

        def get(timeout=None): return self.value

        def wait(timeout=None): pass

        def ready(): return True

        def successful(): return True # TODO: False if raised exception

    def apply_async(self, func, args=(), kw_args={}, callback=None):

        if callback == None: callback = lambda v: None

        value = func(*args, **kw_args)

        callback(value)

        return self.Result(value)

class MultiProducerPool:

    '''A multi-producer pool. You must call pool.main_loop() in the thread that

    created this to process new tasks.'''

    def __init__(self, processes=None, locals_={}, *shared):

        '''

        @param processes If 0, uses SyncPool

        @post The # processes actually used is made available in self.process_ct

        '''

        try:

            if processes == 0: raise ImportError('turned off')

            import multiprocessing

            import multiprocessing.pool

        except ImportError, e:

            warnings.warn(UserWarning('Not using parallel processing: '+str(e)))

            processes = 1

            Pool_ = SyncPool

            Queue_ = Queue.Queue

        else:

            if processes == None: processes = multiprocessing.cpu_count()

            Pool_ = multiprocessing.pool.Pool

            Queue_ = multiprocessing.Queue

        self.process_ct = processes

        self.pool = Pool_(processes)

        self.queue = Queue_()

        self.active_tasks = 0

        # Store a reference to the manager in self, because it will otherwise be

        # shutdown right away when it goes out of scope

        #self.manager = processing.Manager()

        #self.shared_rw = self.manager.Namespace()

        # Values that may be pickled by id()

        self.vars_id_dict = dicts.IdDict()

        self.share(self, *shared).share_vars(locals_).share_vars(globals())

    def share(self, *values):

        '''Call this on all values that should be shared writably between all

        processes (and be pickled by id())'''

        self.vars_id_dict.add(*values)

        return self

    def share_vars(self, vars_):

        '''Call this on all vars that should be pickled by id().

        Usage: self.share_vars(locals())

        @param vars_ {var_name: value}

        '''

        self.vars_id_dict.add_vars(vars_)

        return self

    def main_loop(self):

        '''Prime the task queue with at least one task before calling this''' 

        while True:

            try: call = self.queue.get(timeout=0.1) # sec

            except Queue.Empty:

                if self.active_tasks == 0: break # program done

                else: continue

            def handle_result(*args, **kw_args):

                self.active_tasks -= 1

                if call.callback != None: call.callback(*args, **kw_args)

            self.active_tasks += 1

            self.pool.apply_async(call.func, self.post_unpickle(call.args),

                self.post_unpickle(call.kw_args), handle_result)

    class Result:

        def get(timeout=None): raise NotImplementedError()

        def wait(timeout=None): raise NotImplementedError()

        def ready(): raise NotImplementedError()

        def successful(): raise NotImplementedError()

    def apply_async(self, func, args=(), kw_args={}, callback=None):

        assert callback == None, 'Callbacks not supported'

        call = Runnable(func, *self.prepickle(args), **self.prepickle(kw_args))

        call.callback = callback # store this inside the Runnable

        self.queue.put_nowait(call)

        return self.Result()

    def prepickle(self, value): return prepickle(value, self.vars_id_dict)

    def post_unpickle(self, value):

        return post_unpickle(value, self.vars_id_dict)