| /* specfunc/elementary.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. |
| */ |
| |
| /* Author: G. Jungman */ |
| |
| #include <config.h> |
| #include <gsl/gsl_math.h> |
| #include <gsl/gsl_errno.h> |
| #include <gsl/gsl_sf_elementary.h> |
| |
| #include "error.h" |
| #include "check.h" |
| |
| int |
| gsl_sf_multiply_e(const double x, const double y, gsl_sf_result * result) |
| { |
| const double ax = fabs(x); |
| const double ay = fabs(y); |
| |
| if(x == 0.0 || y == 0.0) { |
| /* It is necessary to eliminate this immediately. |
| */ |
| result->val = 0.0; |
| result->err = 0.0; |
| return GSL_SUCCESS; |
| } |
| else if((ax <= 1.0 && ay >= 1.0) || (ay <= 1.0 && ax >= 1.0)) { |
| /* Straddling 1.0 is always safe. |
| */ |
| result->val = x*y; |
| result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val); |
| return GSL_SUCCESS; |
| } |
| else { |
| const double f = 1.0 - 2.0 * GSL_DBL_EPSILON; |
| const double min = GSL_MIN_DBL(fabs(x), fabs(y)); |
| const double max = GSL_MAX_DBL(fabs(x), fabs(y)); |
| if(max < 0.9 * GSL_SQRT_DBL_MAX || min < (f * DBL_MAX)/max) { |
| result->val = GSL_COERCE_DBL(x*y); |
| result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val); |
| CHECK_UNDERFLOW(result); |
| return GSL_SUCCESS; |
| } |
| else { |
| OVERFLOW_ERROR(result); |
| } |
| } |
| } |
| |
| |
| int |
| gsl_sf_multiply_err_e(const double x, const double dx, |
| const double y, const double dy, |
| gsl_sf_result * result) |
| { |
| int status = gsl_sf_multiply_e(x, y, result); |
| result->err += fabs(dx*y) + fabs(dy*x); |
| return status; |
| } |
| |
| |
| /*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/ |
| |
| #include "eval.h" |
| |
| double gsl_sf_multiply(const double x, const double y) |
| { |
| EVAL_RESULT(gsl_sf_multiply_e(x, y, &result)); |
| } |
| |