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[Help-gsl] problem with gsl_sf_elljac_e
From: |
Robin Hankin |
Subject: |
[Help-gsl] problem with gsl_sf_elljac_e |
Date: |
Wed, 24 Nov 2004 08:50:17 +0000 |
Hi
If I have
/* to compile:
gcc -lgsl -lm -lgslcblas ellj.c
*/
#include <stdio.h>
#include <gsl/gsl_sf_elljac.h>
#include <gsl/gsl_sf_ellint.h>
#include <math.h>
#include <gsl/gsl_math.h>
int
main (void)
{
double m = 0.5;
double phi = M_PI_2;
double sn;
double cn;
double dn1,dn2;
double K;
int ignore;
K = gsl_sf_ellint_F(M_PI_2,sqrt(m), GSL_PREC_DOUBLE);
ignore = gsl_sf_elljac_e(3*K,m,&sn, &cn, &dn1);
ignore = gsl_sf_elljac_e(3*K + 0.0000000000001, m, &sn, &cn, &dn2);
printf("%.18e\n", dn1);
printf("%.18e\n", dn2);
return 0;
}
and compile and run it, I get
octopus:~/unix/rksh/R.packages% gcc -lgsl -lm -lgslcblas ellj.c
octopus:~/unix/rksh/R.packages% ./a.out
1.000000000000000000e+00
7.101757734594013050e-01
octopus:~/unix/rksh/R.packages%
The second figure is roughly what I get from tables; the first looks
a bit odd (I expected
the two numbers to differ by a small amount as dn(x) is continuous).
I get this with a redhat fedora PC and also a G5. What's going on here?
--
Robin Hankin
Uncertainty Analyst
Southampton Oceanography Centre
SO14 3ZH
tel +44(0)23-8059-7743
address@hidden (edit in obvious way; spam precaution)
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- Re: [Help-gsl] a new wrapper for the GSL, Robin Hankin, 2004/11/19
- Re: [Help-gsl] a new wrapper for the GSL, Andre Lehovich, 2004/11/19
- Re: [Help-gsl] a new wrapper for the GSL, Brian Gough, 2004/11/22
- [Help-gsl] problem with gsl_sf_elljac_e,
Robin Hankin <=
- Re: [Help-gsl] problem with gsl_sf_elljac_e, Brian Gough, 2004/11/29