3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
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 /* determines whether to optimize for linear ranges */
23 static int find (const size_t n, const double range[],
24 const double x, size_t * i);
27 find (const size_t n, const double range[], const double x, size_t * i)
29 size_t i_linear, lower, upper, mid;
41 /* optimize for linear case */
45 double u = (x - range[0]) / (range[n] - range[0]);
46 i_linear = (size_t) (u * n);
49 if (x >= range[i_linear] && x < range[i_linear + 1])
56 /* perform binary search */
61 while (upper - lower > 1)
63 mid = (upper + lower) / 2 ;
77 /* sanity check the result */
79 if (x < range[lower] || x >= range[lower + 1])
81 GSL_ERROR ("x not found in range", GSL_ESANITY);