Why is this loop heavy code so slow in Python? Possible Project Euler spoilers
rzed
rzantow at gmail.com
Sun Sep 2 15:36:45 CEST 2007
jwrweatherley at gmail.com wrote in
news:1188733902.513512.87510 at r34g2000hsd.googlegroups.com:
> The puzzle is: p is the perimeter of a right angle triangle with
> integral length sides, {a,b,c}. which value of p < 1000, is the
> number of solutions {a,b,c} maximised?
>
> Here's my python code:
>
> #!/usr/local/bin/python
>
> solutions = [0] * 1001
> p = 0
>
> for a in xrange(1, 1000):
> for b in xrange(1, 1000 - a):
> for c in xrange(1, 1000 - a - b):
> p = a + b + c
> if p < 1000:
> if a ** 2 + b ** 2 == c ** 2:
> solutions[p] += 1
>
Once p >= 1000, it ain't goin' back. If you break out of the
innermost loop here after that happens, you'll save a bunch of
time.
> max = 0
> maxIndex = 0
> index = 0
> for solution in solutions:
> if solution > max:
> max = solution
> maxIndex = index
> index += 1
>
> print maxIndex
>
>
> It takes 2 minutes and twelve seconds on a 2.4GHz Core2Duo
> MacBook Pro.
>
[...]
> The resulting executable takes 0.24 seconds to run. I'm not
> expecting a scripting language to run faster than native code,
> but I was surprised at how much slower it was in this case. Any
> ideas as to what is causing python so much trouble in the above
> code?
>
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