GNU Scientific Library - Bugs: bug #58065, gsl_sf_gegenpoly_n returning...
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bug #58065: gsl_sf_gegenpoly_n returning unexpected values
Submitter: | Jackson Vanover <jacksonvanover> | ||
Submitted: | Sat 28 Mar 2020 05:25:33 PM UTC | ||
Category: | None | Severity: | 3 - Normal |
Operating System: | Ubuntu 18.04 | Status: | None |
Assigned to: | None | Open/Closed: | Open |
Release: | 2.6 |
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Depends on the following items: None found
Items that depend on this one: None found
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Corresponding source code
Using version 2.6 of GSL from ftp://ftp.gnu.org/gnu/gsl/gsl-2.6.tar.gz
OS is Ubuntu 18.04.2 LTS
Hardware is a Dell workstation with a 3.60 GHz Intel i7-4790 and 32 GB
of RAM
Compiler is gcc 7.4.0 with the -w option
When the second argument is 0, mpmath and scipy's implementations of
the gegenbauer polynomial agree that the output should be uniformly 0,
but gsl_sf_gegenpoly_n consistently returns nonzero values. This
happens regardless of the value of the first argument, though in
particular when the first argument is 1 and the second is 0, the
function returns twice the third argument...
#include <gsl/gsl_sf.h>
#include <stdio.h>
#include <gsl/gsl_math.h>
#include <float.h>
int main (void){
double out;
out = gsl_sf_gegenpoly_n(1, 0, 5);
printf("%.*f\n", DBL_DIG-1, out);
printf("%.21e\n", out);
return 0;
}