generators : random shootout

[Mark McEahern]

Tim Peters:
> Heh.  If you don't post gen.py and gen2.py, you realize nobody
> else has any idea what you're measuring -- right?  Or how you're
> measuring it.  From the output, looks like you're using
> time.clock() on a Linux box, but this kind of forced telepathy
> wears thin fast <wink>.

Silly me.

Here's gen.py:

    #! /usr/bin/env python
    # gen.py
    # based on: http://www.bagley.org/~doug/shootout/

    import sys

    IM = 139968
    IA = 3877
    IC = 29573

    LAST = 42
    def gen_random(max):
        global LAST
        LAST = (LAST * IA + IC) % IM
        return( (max * LAST) / IM )

    def main():
        try:
            N = int(sys.argv[1])
        except IndexError:
            N = 1000
        if N < 1:
            N = 1
        gr = gen_random
        for i in xrange(1,N):
            gr(100.0)
        print "%.9f" % gr(100.0)

    import time
    timeIn = time.time()
    main()
    timeOut = time.time()

    print "%f seconds." % (timeOut - timeIn)

Here's gen2.py:

    #! /usr/bin/env python
    # gen2.py
    # based on: http://www.bagley.org/~doug/shootout/

    from __future__ import generators

    import sys

    IM = 139968     # modulo
    IA = 3877       # multiplier
    IC = 29573      # increment

    def gen_random(max):
        last = 42                           # initialize
        while 1:                            # this generator can be called
indefinitely
            last = (last * IA + IC) % IM    # update prior value
            rand = max * last / IM          # generate the random number
            yield rand                      # yield it

    def main():
        try:
            N = int(sys.argv[1])
        except IndexError:
            N = 1000
        if N < 1:
            N = 1
        gr = gen_random(100.0)
        for i in xrange(1, N):
            gr.next()
        print "%.9f" % gr.next()

    import time
    timeIn = time.time()
    main()
    timeOut = time.time()

    print "%f seconds." % (timeOut - timeIn)

Cheers,

// mark