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/* sys/gsl_compare.c
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*
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* Copyright (C) 2002 Gert Van den Eynde
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* Based on fcmp 1.2.2 Copyright (c) 1998-2000 Theodore C. Belding
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* University of Michigan Center for the Study of Complex Systems
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* Ted.Belding@umich.edu
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*
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*/
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#include <config.h>
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#include <gsl/gsl_sys.h>
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#include <math.h>
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int
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gsl_fcmp (const double x1, const double x2, const double epsilon)
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{
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int exponent;
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double delta, difference;
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/* Find exponent of largest absolute value */
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{
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double max = (fabs (x1) > fabs (x2)) ? x1 : x2;
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frexp (max, &exponent);
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}
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/* Form a neighborhood of size 2 * delta */
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delta = ldexp (epsilon, exponent);
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difference = x1 - x2;
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if (difference > delta) /* x1 > x2 */
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{
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return 1;
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}
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else if (difference < -delta) /* x1 < x2 */
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{
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return -1;
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}
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else /* -delta <= difference <= delta */
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{
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return 0; /* x1 ~=~ x2 */
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}
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}
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