# Parallel processing

import warnings

class Pool:

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

        if args == None: args = ()

        if kwds == None: kwds = {}

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

        callback(func(*args, **kw_args))

def mk_pool(cpus=None):

    '''@return tuple(pool, cpus)'''

    try:

        if cpus == 0: raise ImportError('Parallel processing turned off')

        import multiprocessing

        import multiprocessing.pool

    except ImportError, e:

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

        pool = Pool()

    else:

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

        pool = multiprocessing.pool.Pool(processes=cpus)

    return (pool, cpus)