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Re: How can I make this piece of code even faster?

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On Sun, Jul 21, 2013 at 8:31 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> On Sun, 21 Jul 2013 03:19:24 -0700, pablobarhamalzas wrote:
>
>> Thank's for all the replies! I've tried some of the imporovements you
>> suggested (using math.exp() and sum() or math.fsum()). None of that made
>> the code faster, because they are functions you are calling lots of
>> times, and function calling is quite time expensive (same as x**(1/2) is
>> faster than math.sqrt(x)).
>
> You are *badly* mistaken. Not only is sqrt more accurate, but it is also
> much faster.
>
>
> [steve@ando ~]$ python3.3 -m timeit -s "x = 2.357e7" "x**0.5"
> 1000000 loops, best of 3: 0.319 usec per loop
> [steve@ando ~]$ python3.3 -m timeit -s "x = 2.357e7" -s "from math import
> sqrt" "sqrt(x)"
> 10000000 loops, best of 3: 0.172 usec per loop

Don't forget the cost of attribute lookup, which adds 50% to the
sqrt() figure. Still faster than exponentiation. (Figures from Python
3.4 alpha, but unlikely to be materially different.)

rosuav@sikorsky:~$ python3 -m timeit -s "x = 2.357e7" "x**0.5"
1000000 loops, best of 3: 0.239 usec per loop
rosuav@sikorsky:~$ python3 -m timeit -s "x = 2.357e7" -s "from math
import sqrt" "sqrt(x)"
10000000 loops, best of 3: 0.102 usec per loop
rosuav@sikorsky:~$ python3 -m timeit -s "x = 2.357e7" -s "import math"
"math.sqrt(x)"
10000000 loops, best of 3: 0.155 usec per loop

ChrisA

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Thread

How can I make this piece of code even faster? pablobarhamalzas@gmail.com - 2013-07-20 13:22 -0700
  Re: How can I make this piece of code even faster? Fabio Zadrozny <fabiofz@gmail.com> - 2013-07-20 18:05 -0300
  Re: How can I make this piece of code even faster? Roy Smith <roy@panix.com> - 2013-07-20 17:25 -0400
  Re: How can I make this piece of code even faster? pablobarhamalzas@gmail.com - 2013-07-20 15:45 -0700
  Re: How can I make this piece of code even faster? Chris Angelico <rosuav@gmail.com> - 2013-07-21 08:55 +1000
  Re: How can I make this piece of code even faster? pablobarhamalzas@gmail.com - 2013-07-20 16:24 -0700
    Re: How can I make this piece of code even faster? Chris Angelico <rosuav@gmail.com> - 2013-07-21 09:29 +1000
  Re: How can I make this piece of code even faster? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-21 05:11 +0000
    Re: How can I make this piece of code even faster? Paul Rudin <paul.nospam@rudin.co.uk> - 2013-07-21 08:11 +0100
      Re: How can I make this piece of code even faster? Chris Angelico <rosuav@gmail.com> - 2013-07-21 19:21 +1000
  Re: How can I make this piece of code even faster? Peter Otten <__peter__@web.de> - 2013-07-21 09:10 +0200
  Re: How can I make this piece of code even faster? Serhiy Storchaka <storchaka@gmail.com> - 2013-07-21 10:11 +0300
  Re: How can I make this piece of code even faster? Christian Gollwitzer <auriocus@gmx.de> - 2013-07-21 09:24 +0200
  Re: How can I make this piece of code even faster? pablobarhamalzas@gmail.com - 2013-07-21 03:19 -0700
    Re: How can I make this piece of code even faster? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-07-21 10:31 +0000
      Re: How can I make this piece of code even faster? pablobarhamalzas@gmail.com - 2013-07-21 03:48 -0700
        Re: How can I make this piece of code even faster? Stefan Behnel <stefan_ml@behnel.de> - 2013-07-21 14:49 +0200
      Re: How can I make this piece of code even faster? Chris Angelico <rosuav@gmail.com> - 2013-07-21 20:48 +1000
    Re: How can I make this piece of code even faster? Michael Torrie <torriem@gmail.com> - 2013-07-21 09:27 -0600
  Re: How can I make this piece of code even faster? Joshua Landau <joshua@landau.ws> - 2013-07-21 12:39 +0100

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