[python-uk] C is it faster than numpy

[SW]

I think it uses fortran (or used to?) but yes, still close to the metal.

Thanks,
S

On 25/02/2022 10:41, Giorgio Zoppi wrote:
> Well,
> numpy is written in C :) Maybe your C is not the numpy equivalent?
> Best Regards,
> Giorgio
>
> Il giorno ven 25 feb 2022 alle ore 09:03 BELAHCENE Abdelkader 
> <abdelkader.belahcene at enst.dz> ha scritto:
>
>     Hi,
>     a lot of people think that C (or C++) is faster than python, yes I
>     agree, but I think that's not the case with numpy, I believe numpy
>     is faster than C, at least in some cases.
>     *Is there another explanation ?
>     Or where can find  a doc speaking  about the subject?
>     *Thanks a lot
>     Regards
>     Numpy implements vectorization for arrays, or I'm wrong. Anyway
>     here is an example Let's look at the following case:
>     Here is the result on my laptop i3:
>
>     Labs$ *python3 tempsExe.py  50000*
>       sum with Python: 1250025000 and NumPy 1250025000
>           time used Python Sum: *37.28 sec *
>           time used  Numpy Sum: *1.85 sec*
>
>     Labs$ *./tt    50000 *
>     *  CPU  time :7.521730
>         The value : 1250025000
>     *--------------------------------------------
>
>     This is the Python3 program :
>
>     import timeit as it
>     import numpy as np
>     import sys
>     try :
>     n=eval(sys.argv[1])
>     except:
>     print ("needs integer as argument") ; exit()
>
>     a=range(1,n+1)
>     b=np.array(a)
>     def func1():     return sum(a)
>     def func2(): return np.sum(b)
>
>     print(f"sum with Python: {func1()} and NumPy {func2()} ")
>     tm1=it.timeit(stmt=func1, number=n)
>     print(f"time used Python Sum: {round(tm1,2)} sec")
>     tm2=it.timeit(stmt=func2, number=n)
>     print(f"time used  Numpy Sum: {round(tm2,2)} sec")
>
>     and Here the C program:
>     #include <time.h>
>     #include <stdio.h>
>     #include <stdlib.h>
>     long func1(int n){
>              long  r=0;
>             for (int  i=1; i<= n;i++) r+= i;
>              return r;
>     }
>     int main(int argc, char* argv[]){
>              clock_t c0, c1;
>             long v,count; int n;
>            if ( argc < 2) {
>                   printf("Please give an argument");
>                  return -1;
>           }
>         n=atoi(argv[1]);
>         c0 = clock();
>     *for (int j=0;j < n;j++) v=func1(n);*
>          c1 = clock();
>          printf ("\tCPU  time :%.2f sec", (float)(c1 -
>     c0)/CLOCKS_PER_SEC);
>          printf("\n\tThe value : %ld\n",  v);
>     }
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>
>
> -- 
> Life is a chess game - Anonymous.
>
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