| /* 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; |
| } |
| |
| |
| |
| |
| |