threaded_map.py

import threading

class MapThread(threading.Thread):
    def initialize(self, function, sequence, *args):
        self._function = function
        self._sequence = sequence
        self._args = args

    def run(self):
        self._result = map(self._function, self._sequence, *self._args)

def threaded_map(nthreads, function, sequence, *args):
    threads = [MapThread() for i in xrange(nthreads)]
    n = len(sequence)
    seq_lengths = [i * n / nthreads for i in xrange(nthreads+1)]
    for i in xrange(nthreads):
        seq = sequence[seq_lengths[i]:seq_lengths[i+1]]
        nargs = ()
        for arg in args:
            nargs += (arg[seq_lengths[i]:seq_lengths[i+1]])
        threads[i].initialize(function, seq, *nargs)
        threads[i].start()

    result = []
    for thread in threads:
        thread.join()
        result += thread._result

    return result