why memoizing is faster

[Terry Reedy]

On 3/25/2011 5:16 AM, Stefan Behnel wrote:

> Terry's version is playing with the fact that default arguments are only
> instantiated once, i.e. (unless overridden by passing an explicit
> argument) the "_cache" is shared over all calls to the function. This is
> similar to what your memoization decorator does, but without the
> additional dict. And, it also "suffers" from the same timing problem
> that I mentioned before.

It depends on what one wants to measure. If one is memoizing because one 
expects to call the function 1000s of times in some program, then the 
fast lookup time of repeated calls represents the actual 
post-initialization burden on that program. If one want to measure the 
initialization time, then the cache can easily be restarted with each 
call (once one knows how): fib_iter(100,_cache=[0,1])

-- 
Terry Jan Reedy