generators : random shootout

[Mark McEahern]

In trying to understand generators, I modified the Python code in the random
number generator shootout to use generators.

The shootout:

	http://www.bagley.org/~doug/shootout/bench/random/

The existing Python implementation:

	http://www.bagley.org/~doug/shootout/bench/random/random.python

Python random number generator (using generators) is at the bottom of this
post.

Doing some simple timing tests, it appears that the "old" method runs
slightly faster.  Is that expected?

Thanks,

// mark

#! /usr/bin/env python

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

main()