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- /* 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 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_elementary.h"
- #include "gsl_specfunc__error.h"
- #include "gsl_specfunc__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 "gsl_specfunc__eval.h"
- double gsl_sf_multiply(const double x, const double y)
- {
- EVAL_RESULT(gsl_sf_multiply_e(x, y, &result));
- }
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