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/* cheb/init.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <stdlib.h>
#include <gsl/gsl_math.h>
#include <gsl/gsl_errno.h>
#include <gsl/gsl_chebyshev.h>
/*-*-*-*-*-*-*-*-*-*-*-* Allocators *-*-*-*-*-*-*-*-*-*-*-*/
gsl_cheb_series *
gsl_cheb_alloc(const size_t order)
{
gsl_cheb_series * cs = (gsl_cheb_series *) malloc(sizeof(gsl_cheb_series));
if(cs == 0) {
GSL_ERROR_VAL("failed to allocate gsl_cheb_series struct", GSL_ENOMEM, 0);
}
cs->order = order;
cs->order_sp = order;
cs->c = (double *) malloc((order+1) * sizeof(double));
if(cs->c == 0) {
GSL_ERROR_VAL("failed to allocate cheb coefficients", GSL_ENOMEM, 0);
}
cs->f = (double *) malloc((order+1) * sizeof(double));
if(cs->f == 0) {
GSL_ERROR_VAL("failed to allocate cheb function space", GSL_ENOMEM, 0);
}
return cs;
}
void gsl_cheb_free(gsl_cheb_series * cs)
{
free(cs->f);
free(cs->c);
free(cs);
}
/*-*-*-*-*-*-*-*-*-*-*-* Initializer *-*-*-*-*-*-*-*-*-*-*-*/
int gsl_cheb_init(gsl_cheb_series * cs, const gsl_function *func,
const double a, const double b)
{
size_t k, j;
if(a >= b) {
GSL_ERROR_VAL("null function interval [a,b]", GSL_EDOM, 0);
}
cs->a = a;
cs->b = b;
/* cs->err = 0.0; */
{
double bma = 0.5 * (cs->b - cs->a);
double bpa = 0.5 * (cs->b + cs->a);
double fac = 2.0/(cs->order +1.0);
for(k = 0; k<=cs->order; k++) {
double y = cos(M_PI * (k+0.5)/(cs->order+1));
cs->f[k] = GSL_FN_EVAL(func, (y*bma + bpa));
}
for(j = 0; j<=cs->order; j++) {
double sum = 0.0;
for(k = 0; k<=cs->order; k++)
sum += cs->f[k]*cos(M_PI * j*(k+0.5)/(cs->order+1));
cs->c[j] = fac * sum;
}
}
return GSL_SUCCESS;
}
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