3 * Copyright (C) 1996,1997,1998,1999,2000,2001,2002,2003 Gerard Jungman
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 /* Author: G. Jungman */
23 #include <gsl/gsl_math.h>
24 #include <gsl/gsl_errno.h>
25 #include <gsl/gsl_sf_pow_int.h>
26 #include <gsl/gsl_sf_trig.h>
27 #include <gsl/gsl_sf_bessel.h>
32 #include "bessel_olver.h"
34 /*-*-*-*-*-*-*-*-*-*-*-* Functions with Error Codes *-*-*-*-*-*-*-*-*-*-*-*/
36 int gsl_sf_bessel_j0_e(const double x, gsl_sf_result * result)
40 /* CHECK_POINTER(result) */
44 const double c1 = -1.0/6.0;
45 const double c2 = 1.0/120.0;
46 const double c3 = -1.0/5040.0;
47 const double c4 = 1.0/362880.0;
48 const double c5 = -1.0/39916800.0;
49 const double c6 = 1.0/6227020800.0;
50 result->val = 1.0 + y*(c1 + y*(c2 + y*(c3 + y*(c4 + y*(c5 + y*c6)))));
51 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val);
55 gsl_sf_result sin_result;
56 const int stat = gsl_sf_sin_e(x, &sin_result);
57 result->val = sin_result.val/x;
58 result->err = fabs(sin_result.err/x);
59 result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
65 int gsl_sf_bessel_j1_e(const double x, gsl_sf_result * result)
69 /* CHECK_POINTER(result) */
76 else if(ax < 3.1*GSL_DBL_MIN) {
77 UNDERFLOW_ERROR(result);
81 const double c1 = -1.0/10.0;
82 const double c2 = 1.0/280.0;
83 const double c3 = -1.0/15120.0;
84 const double c4 = 1.0/1330560.0;
85 const double c5 = -1.0/172972800.0;
86 const double sum = 1.0 + y*(c1 + y*(c2 + y*(c3 + y*(c4 + y*c5))));
87 result->val = x/3.0 * sum;
88 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val);
92 gsl_sf_result cos_result;
93 gsl_sf_result sin_result;
94 const int stat_cos = gsl_sf_cos_e(x, &cos_result);
95 const int stat_sin = gsl_sf_sin_e(x, &sin_result);
96 const double cos_x = cos_result.val;
97 const double sin_x = sin_result.val;
98 result->val = (sin_x/x - cos_x)/x;
99 result->err = (fabs(sin_result.err/x) + fabs(cos_result.err))/fabs(x);
100 result->err += 2.0 * GSL_DBL_EPSILON * (fabs(sin_x/(x*x)) + fabs(cos_x/x));
101 result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
102 return GSL_ERROR_SELECT_2(stat_cos, stat_sin);
107 int gsl_sf_bessel_j2_e(const double x, gsl_sf_result * result)
111 /* CHECK_POINTER(result) */
118 else if(ax < 4.0*GSL_SQRT_DBL_MIN) {
119 UNDERFLOW_ERROR(result);
122 const double y = x*x;
123 const double c1 = -1.0/14.0;
124 const double c2 = 1.0/504.0;
125 const double c3 = -1.0/33264.0;
126 const double c4 = 1.0/3459456.0;
127 const double c5 = -1.0/518918400;
128 const double c6 = 1.0/105859353600.0;
129 const double c7 = -1.0/28158588057600.0;
130 const double c8 = 1.0/9461285587353600.0;
131 const double c9 = -1.0/3916972233164390400.0;
132 const double sum = 1.0+y*(c1+y*(c2+y*(c3+y*(c4+y*(c5+y*(c6+y*(c7+y*(c8+y*c9))))))));
133 result->val = y/15.0 * sum;
134 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val);
138 gsl_sf_result cos_result;
139 gsl_sf_result sin_result;
140 const int stat_cos = gsl_sf_cos_e(x, &cos_result);
141 const int stat_sin = gsl_sf_sin_e(x, &sin_result);
142 const double cos_x = cos_result.val;
143 const double sin_x = sin_result.val;
144 const double f = (3.0/(x*x) - 1.0);
145 result->val = (f * sin_x - 3.0*cos_x/x)/x;
146 result->err = fabs(f * sin_result.err/x) + fabs((3.0*cos_result.err/x)/x);
147 result->err += 2.0 * GSL_DBL_EPSILON * (fabs(f*sin_x/x) + 3.0*fabs(cos_x/(x*x)));
148 result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
149 return GSL_ERROR_SELECT_2(stat_cos, stat_sin);
155 gsl_sf_bessel_jl_e(const int l, const double x, gsl_sf_result * result)
157 if(l < 0 || x < 0.0) {
158 DOMAIN_ERROR(result);
161 result->val = ( l > 0 ? 0.0 : 1.0 );
166 return gsl_sf_bessel_j0_e(x, result);
169 return gsl_sf_bessel_j1_e(x, result);
172 return gsl_sf_bessel_j2_e(x, result);
174 else if(x*x < 10.0*(l+0.5)/M_E) {
176 int status = gsl_sf_bessel_IJ_taylor_e(l+0.5, x, -1, 50, GSL_DBL_EPSILON, &b);
177 double pre = sqrt((0.5*M_PI)/x);
178 result->val = pre * b.val;
179 result->err = pre * b.err;
180 result->err += 2.0 * GSL_DBL_EPSILON * fabs(result->val);
183 else if(GSL_ROOT4_DBL_EPSILON * x > (l*l + l + 1.0)) {
185 int status = gsl_sf_bessel_Jnu_asympx_e(l + 0.5, x, &b);
186 double pre = sqrt((0.5*M_PI)/x);
187 result->val = pre * b.val;
188 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val) + pre * b.err;
191 else if(l > 1.0/GSL_ROOT6_DBL_EPSILON) {
193 int status = gsl_sf_bessel_Jnu_asymp_Olver_e(l + 0.5, x, &b);
194 double pre = sqrt((0.5*M_PI)/x);
195 result->val = pre * b.val;
196 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val) + pre * b.err;
199 else if(x > 1000.0 && x > l*l)
201 /* We need this path to avoid feeding large x to CF1 below; */
203 int status = gsl_sf_bessel_Jnu_asympx_e(l + 0.5, x, &b);
204 double pre = sqrt((0.5*M_PI)/x);
205 result->val = pre * b.val;
206 result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val) + pre * b.err;
212 /* The CF1 call will hit 10000 iterations for x > 10000 + l */
213 int stat_CF1 = gsl_sf_bessel_J_CF1(l+0.5, x, &ratio, &sgn);
214 double jellp1 = GSL_SQRT_DBL_EPSILON * ratio;
215 double jell = GSL_SQRT_DBL_EPSILON;
218 for(ell = l; ell > 0; ell--) {
219 jellm1 = -jellp1 + (2*ell + 1)/x * jell;
224 if(fabs(jell) > fabs(jellp1)) {
225 gsl_sf_result j0_result;
226 int stat_j0 = gsl_sf_bessel_j0_e(x, &j0_result);
227 double pre = GSL_SQRT_DBL_EPSILON / jell;
228 result->val = j0_result.val * pre;
229 result->err = j0_result.err * fabs(pre);
230 result->err += 4.0 * GSL_DBL_EPSILON * (0.5*l + 1.0) * fabs(result->val);
231 return GSL_ERROR_SELECT_2(stat_j0, stat_CF1);
234 gsl_sf_result j1_result;
235 int stat_j1 = gsl_sf_bessel_j1_e(x, &j1_result);
236 double pre = GSL_SQRT_DBL_EPSILON / jellp1;
237 result->val = j1_result.val * pre;
238 result->err = j1_result.err * fabs(pre);
239 result->err += 4.0 * GSL_DBL_EPSILON * (0.5*l + 1.0) * fabs(result->val);
240 return GSL_ERROR_SELECT_2(stat_j1, stat_CF1);
247 gsl_sf_bessel_jl_array(const int lmax, const double x, double * result_array)
249 /* CHECK_POINTER(result_array) */
251 if(lmax < 0 || x < 0.0) {
253 for(j=0; j<=lmax; j++) result_array[j] = 0.0;
254 GSL_ERROR ("error", GSL_EDOM);
258 for(j=1; j<=lmax; j++) result_array[j] = 0.0;
259 result_array[0] = 1.0;
263 gsl_sf_result r_jellp1;
264 gsl_sf_result r_jell;
265 int stat_0 = gsl_sf_bessel_jl_e(lmax+1, x, &r_jellp1);
266 int stat_1 = gsl_sf_bessel_jl_e(lmax, x, &r_jell);
267 double jellp1 = r_jellp1.val;
268 double jell = r_jell.val;
272 result_array[lmax] = jell;
273 for(ell = lmax; ell >= 1; ell--) {
274 jellm1 = -jellp1 + (2*ell + 1)/x * jell;
277 result_array[ell-1] = jellm1;
280 return GSL_ERROR_SELECT_2(stat_0, stat_1);
285 int gsl_sf_bessel_jl_steed_array(const int lmax, const double x, double * jl_x)
287 /* CHECK_POINTER(jl_x) */
289 if(lmax < 0 || x < 0.0) {
291 for(j=0; j<=lmax; j++) jl_x[j] = 0.0;
292 GSL_ERROR ("error", GSL_EDOM);
296 for(j=1; j<=lmax; j++) jl_x[j] = 0.0;
300 else if(x < 2.0*GSL_ROOT4_DBL_EPSILON) {
301 /* first two terms of Taylor series */
302 double inv_fact = 1.0; /* 1/(1 3 5 ... (2l+1)) */
303 double x_l = 1.0; /* x^l */
305 for(l=0; l<=lmax; l++) {
306 jl_x[l] = x_l * inv_fact;
307 jl_x[l] *= 1.0 - 0.5*x*x/(2.0*l+3.0);
308 inv_fact /= 2.0*l+3.0;
314 /* Steed/Barnett algorithm [Comp. Phys. Comm. 21, 297 (1981)] */
315 double x_inv = 1.0/x;
316 double W = 2.0*x_inv;
318 double FP = (lmax+1.0) * x_inv;
319 double B = 2.0*FP + x_inv;
320 double end = B + 20000.0*W;
326 /* continued fraction */
334 GSL_ERROR ("error", GSL_EMAXITER);
337 while(fabs(del) >= fabs(FP) * GSL_DBL_EPSILON);
342 /* downward recursion */
344 double PL = lmax * x_inv;
348 for(LP = 1; LP<=lmax; LP++) {
349 jl_x[L-1] = PL * jl_x[L] + XP2;
350 FP = PL*jl_x[L-1] - jl_x[L];
359 W = x_inv / hypot(FP, F);
363 for(L=1; L<=lmax; L++) {
373 /*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/
377 double gsl_sf_bessel_j0(const double x)
379 EVAL_RESULT(gsl_sf_bessel_j0_e(x, &result));
382 double gsl_sf_bessel_j1(const double x)
384 EVAL_RESULT(gsl_sf_bessel_j1_e(x, &result));
387 double gsl_sf_bessel_j2(const double x)
389 EVAL_RESULT(gsl_sf_bessel_j2_e(x, &result));
392 double gsl_sf_bessel_jl(const int l, const double x)
394 EVAL_RESULT(gsl_sf_bessel_jl_e(l, x, &result));