How to make this faster

Helmut Jarausch jarausch at igpm.rwth-aachen.de
Fri Jul 5 12:53:35 CEST 2013


On Fri, 05 Jul 2013 11:13:33 +0100, Oscar Benjamin wrote:

> My one comment is that you're not really making the most out of numpy
> arrays. Numpy's ndarrays are efficient when each line of Python code
> is triggering a large number of numerical computations performed over
> the array. Because of their N-dimensional nature and the fact that
> they are in some sense second class citizens in CPython they are often
> not as good as lists for this kind of looping and indexing.
> 
> I would actually expect this program to run faster with ordinary
> Python lists and lists of lists. It means that you need to change e.g.
> Grid[r, c] to Grid[r][c] but really I think that the indexing syntax
> is all you're getting out of numpy here.
> 

Thanks Oscar, that was a big improvement, indeed.
Using lists of lists instead of numpy arrays made the code more than
twice as fast (13 seconds down to 6 seconds)

Since I don't do any numerical stuff with the arrays, Numpy doesn't seem to be
a good choice. I think this is an argument to add real arrays to Python.

I even tried to use dictionaries instead of Numpy arrays. This version is a bit
slower then the lists of lists version (7.2 seconds instead of 6 second) but still
much faster than the Numpy array solution.

Helmut




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