how fast is Python?

Alex Martelli aleax at aleax.it
Thu Aug 21 18:25:51 CEST 2003


Mark Carter wrote:
   ...
> The following algorithm was implemented in each of the target
> languages:
> 
> X = 0.5
> For I = 1 to 108
> X = 1 – X* X
> Next
> 
> Timings were made for the execution. The following results were
> obtained:
> 
> Language      Timing (seconds)
> VB – uncompiled       74
> VB – compiled 37
> VBA – Excel   75
> Python        401
> C++ - debug version   4
> C++ - release version 3
> Fortran       3

Interesting.  One wonders what and where you measured, e.g:

[alex at lancelot gmpy]$ cat a.cpp
int main()
{
    double X = 0.5;
    for(int i = 0; i < 108; i++)
            X = 1 + X * X;
    return 0;
}

[alex at lancelot gmpy]$ g++ -O3 a.cpp
[alex at lancelot gmpy]$ time ./a.out
0.01user 0.00system 0:00.00elapsed 333%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (186major+21minor)pagefaults 0swaps

i.e., it's just too fast to measure.  Not much better w/Python...:

[alex at lancelot gmpy]$ cat a.py

def main():
    X = 0.5
    for i in xrange(108):
        X = 1 + X*X

main()
[alex at lancelot gmpy]$ time python -O a.py
0.03user 0.01system 0:00.15elapsed 26%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (452major+260minor)pagefaults 0swaps

i.e., for all we can tell, the ratio COULD be 100:1 -- or just about
anything else!  Perhaps more details are warranted...


Alex





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