Profiling weirdness: Timer.timeit(), fibonacci and memoization

Rob Williscroft rtw at freenet.co.uk
Sat Aug 2 23:14:11 CEST 2008


Stefaan Himpe wrote in news:2m3lk.118118$9I1.20910 at newsfe16.ams2 in 
comp.lang.python:

> Nothing weird about this ...
> The difference will become larger as your input value becomes larger.
> 
> You can easily understand why if you try to calculate fib(10) by hand,
> i.e. work through the algorithm with pencil and paper,
> then compare the work you have to do to the memoized version which just 
> takes fib(9) and fib(8) from memory and adds them together.
> 

I think you missed the point.

The problem is that the un-decorated, loop only version takes 
35 seconds when called by timeit.Timer.  However if you apply
the decorator it takes less that a second.  In *both* cases
the function (fib) only gets called once.

Note, I timed the call fib(100) with time.clock() and got a
value of less than 1 ms, the memozed version takes about 10 
times longer.

So the question is: whats going on with timeit.Timer ?

Rob.
-- 
http://www.victim-prime.dsl.pipex.com/



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