efficient memoize decorator?

[thattommyhallll@gmail.com]

sorry
memoize is
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496879
memoize2 is
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/466320

> im plugging away at the problems at
> http://www.mathschallenge.net/index.php?section=project
> im trying to use them as a motivator to get into advanced topics in
> python.
> one thing that Structure And Interpretation Of Computer Programs
> teaches is that memoisation is good.
> all of the memoize decorators at the python cookbook seem to make my
> code slower.
> is using a decorator a lazy and inefficient way of doing memoization?
> can anyone point me to where would explain how to do it quickly. or is
> my function at fault?
>
> the code in question is as follows
> """
> from memoize import memoize,memoize2
>
> @memoize
> def col(n, count):
>     if n == 1:
>         return count
>     elif n % 2 == 0:
>         return col(n/2, count+1)
>     else:
>         return col((3*n+1)/2, count+2)
>
> import psyco
> psyco.full()
>
> start = time()
> maxlength = 0
> best = 0
> for i in range(1, 1000001):
>     length = col(i,1)
>     if length > maxlength:
>         maxlength = length
>         best = i
>         print maxlength, best
> end = time()
> print 'took', end-start