Re: [Bug-gsl] bug in gsl_sf_choose ?

[Patrick Alken]

Its happening when you case gsl_sf_choose() to (int). Try this instead:

int nchoosetwo_gsl = (int) round(gsl_sf_choose(n,2))

On 08/02/2016 06:34 AM, Eldon, Bjarki wrote:
> Dear GSL,
>
> I'm using GSL  version 1.16-5.1.3 on  openSUSE-13.2-Oss  on x86_64 arch.
>
>
> the C code  below  returns a lot of 1s; is there a bug in gsl_sf_choose or am I 
> doing something wrong?
>
> best regards
> bjarki
>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <math.h>
> #include <gsl/gsl_errno.h>
> #include <gsl/gsl_sf_elementary.h>
> #include <gsl/gsl_sf_gamma.h>
> #include <gsl/gsl_sf_exp.h>
>
>
>
> int main()
> {
>    unsigned int n ;
>    int nchoosetwo ;
>
>    for( n = 2 ; n <= 102 ; n++){
>      nchoosetwo = (int) ( ( (double)( n*(n-1)) )/2. ) ;
>
>      printf( "%d:  %d\n", n, (nchoosetwo != (int)gsl_sf_choose( n,2)) ? 1 : 0 
> ); }
>
>    return GSL_SUCCESS;
>
> }