Hi,
Simply check the original Numpy aka Numerical Python docs where it’s
comprehensively explained that the library is implemented in C with a thin
Python wrapper. The docs were written circa ‘98 by the original library author.
The library was optimised over a long period before being released. I’ve seen
similar results when replacing an optimised Fortran library with C/C++ the key
is the effort given to optimisation, and care with avoiding unnecessary memory
allocation.
I’ll dig out the reference when I’ve tracked it down.
Best of Luck
Ed Hartley
> On 25 Feb 2022, at 09:42, Giorgio Zoppi <giorgio.zo...@gmail.com> 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.belahc...@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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