squeeze out some performance

[Robin Becker]

On 06/12/2013 22:07, Joel Goldstick wrote:
..........
>>
>
> Not that this will speed up your code but you have this:
>
>      if not clockwise:
>          s = start
>          start = end
>          end = s
>
> Python people would write:
>      end, start = start, end

this works for some small number of variables, but on my machine with python 2.7 
I start losing with 4 variables eg

> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "a,b,c,d=b,c,d,a"
> 1000000 loops, best of 3: 0.206 usec per loop
>
> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4" "t=a;a=b;b=c;c=d;d=t"
> 10000000 loops, best of 3: 0.118 usec per loop


It doesn't seem to make much difference that the variables are related as I see 
a similar behaviour for simple assignments

> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a,b,c,d=e,f,g,h"
> 1000000 loops, best of 3: 0.204 usec per loop
>
> C:\code\optichrome\74663>python -mtimeit -s"a=1;b=2;c=3;d=4;e=5;f=6;g=7;h=8" "a=e;b=f;c=g;d=h"
> 10000000 loops, best of 3: 0.103 usec per loop

for less than 4 variables the tuple method is faster.
-- 
Robin Becker