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- /* specfunc/bessel_Ynu.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 3 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.
- */
- /* Author: G. Jungman */
- #include "gsl__config.h"
- #include "gsl_math.h"
- #include "gsl_errno.h"
- #include "gsl_sf_bessel.h"
- #include "gsl_specfunc__error.h"
- #include "gsl_specfunc__bessel.h"
- #include "gsl_specfunc__bessel_olver.h"
- #include "gsl_specfunc__bessel_temme.h"
- /* Perform forward recurrence for Y_nu(x) and Y'_nu(x)
- *
- * Y_{nu+1} = nu/x Y_nu - Y'_nu
- * Y'_{nu+1} = -(nu+1)/x Y_{nu+1} + Y_nu
- */
- #if 0
- static
- int
- bessel_Y_recur(const double nu_min, const double x, const int kmax,
- const double Y_start, const double Yp_start,
- double * Y_end, double * Yp_end)
- {
- double x_inv = 1.0/x;
- double nu = nu_min;
- double Y_nu = Y_start;
- double Yp_nu = Yp_start;
- int k;
- for(k=1; k<=kmax; k++) {
- double nuox = nu*x_inv;
- double Y_nu_save = Y_nu;
- Y_nu = -Yp_nu + nuox * Y_nu;
- Yp_nu = Y_nu_save - (nuox+x_inv) * Y_nu;
- nu += 1.0;
- }
- *Y_end = Y_nu;
- *Yp_end = Yp_nu;
- return GSL_SUCCESS;
- }
- #endif
- /*-*-*-*-*-*-*-*-*-*-*-* Functions with Error Codes *-*-*-*-*-*-*-*-*-*-*-*/
- int
- gsl_sf_bessel_Ynu_e(double nu, double x, gsl_sf_result * result)
- {
- /* CHECK_POINTER(result) */
- if(x <= 0.0 || nu < 0.0) {
- DOMAIN_ERROR(result);
- }
- else if(nu > 50.0) {
- return gsl_sf_bessel_Ynu_asymp_Olver_e(nu, x, result);
- }
- else {
- /* -1/2 <= mu <= 1/2 */
- int N = (int)(nu + 0.5);
- double mu = nu - N;
- gsl_sf_result Y_mu, Y_mup1;
- int stat_mu;
- double Ynm1;
- double Yn;
- double Ynp1;
- int n;
- if(x < 2.0) {
- /* Determine Ymu, Ymup1 directly. This is really
- * an optimization since this case could as well
- * be handled by a call to gsl_sf_bessel_JY_mu_restricted(),
- * as below.
- */
- stat_mu = gsl_sf_bessel_Y_temme(mu, x, &Y_mu, &Y_mup1);
- }
- else {
- /* Determine Ymu, Ymup1 and Jmu, Jmup1.
- */
- gsl_sf_result J_mu, J_mup1;
- stat_mu = gsl_sf_bessel_JY_mu_restricted(mu, x, &J_mu, &J_mup1, &Y_mu, &Y_mup1);
- }
- /* Forward recursion to get Ynu, Ynup1.
- */
- Ynm1 = Y_mu.val;
- Yn = Y_mup1.val;
- for(n=1; n<=N; n++) {
- Ynp1 = 2.0*(mu+n)/x * Yn - Ynm1;
- Ynm1 = Yn;
- Yn = Ynp1;
- }
- result->val = Ynm1; /* Y_nu */
- result->err = (N + 1.0) * fabs(Ynm1) * (fabs(Y_mu.err/Y_mu.val) + fabs(Y_mup1.err/Y_mup1.val));
- result->err += 2.0 * GSL_DBL_EPSILON * fabs(Ynm1);
- return stat_mu;
- }
- }
- /*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/
- #include "gsl_specfunc__eval.h"
- double gsl_sf_bessel_Ynu(const double nu, const double x)
- {
- EVAL_RESULT(gsl_sf_bessel_Ynu_e(nu, x, &result));
- }
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