Benchmark repeated calls to a tail call optimisation decorator.

gistfile1.txt

[aliles@macbookpro ~]$ time python2.7 timeit_tco.py 100 60000
Maximum time on CPU: 0.00030600
Minimum time on CPU: 0.00014800
Average time on CPU: 0.00015401

real	0m9.586s
user	0m9.473s
sys	0m0.110s

[aliles@macbookpro ~]$ time pypy timeit_tco.py 100 60000
Maximum time on CPU: 0.00829600
Minimum time on CPU: 0.00003300
Average time on CPU: 0.00006019

real	0m4.557s
user	0m4.427s
sys	0m0.128s

[aliles@macbookpro ~]$ time python2.7 timeit_tco.py 1000 6000
Maximum time on CPU: 0.00230600
Minimum time on CPU: 0.00196600
Average time on CPU: 0.00200732

real	0m13.698s
user	0m13.654s
sys	0m0.033s

[aliles@macbookpro ~]$ time pypy timeit_tco.py 1000 6000
Maximum time on CPU: 0.01351100
Minimum time on CPU: 0.00179300
Average time on CPU: 0.00186320

real	0m19.049s
user	0m18.949s
sys	0m0.090s

timeit_tco.py

from collections import namedtuple
import sys
import time

Stats = namedtuple('Stats', 'maximum minimum average digits')

class tail_recursive(object):
    """Tail recursion decorator by George Sakkis

    http://code.activestate.com/recipes/496691-new-tail-recursion-decorator/#c3
    """

    def __init__(self, func):
        self.func = func
        self.firstcall = True
        self.CONTINUE = object()

    def __call__(self, *args, **kwd):
        if self.firstcall:
            func = self.func
            CONTINUE = self.CONTINUE
            self.firstcall = False
            try:
                while True:
                    result = func(*args, **kwd)
                    if result is CONTINUE: # update arguments
                        args, kwd = self.argskwd
                    else: # last call
                        return result
            finally:
                self.firstcall = True
        else: # return the arguments of the tail call
            self.argskwd = args, kwd
            return self.CONTINUE

@tail_recursive
def factorial(n, acc=1):
    "calculate a factorial"
    if n == 0:
       return acc
    res = factorial(n-1, n*acc)
    return res

def factorial_loop(depth, loops=1, step=0):
    maximum = None
    minimum = Ellipsis
    total = 0.0
    digits = 0
    for loop in xrange(loops):
        start = time.clock()
        value = factorial(depth)
        stop = time.clock()
        cost = stop - start
        maximum = max(maximum, cost)
        minimum = min(minimum, cost)
        total += cost
        digits += len(str(value))
        depth += step
    average = total / loops
    return Stats(maximum, minimum, average, digits)

if __name__ == '__main__':
    depth = int(sys.argv[1])
    loops = int(sys.argv[2])
    stats = factorial_loop(depth, loops, 0)._asdict()
    print "Maximum time on CPU: %(maximum).8f" % stats
    print "Minimum time on CPU: %(minimum).8f" % stats
    print "Average time on CPU: %(average).8f" % stats