1 /* blas/source_nrm2_r.h
2  *
3  * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman
4  *
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.
9  *
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.
14  *
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.
18  */
19 
20 {
21   BASE scale = 0.0;
22   BASE ssq = 1.0;
23   INDEX i;
24   INDEX ix = 0;
25 
26   if (N <= 0 || incX <= 0) {
27     return 0;
28   } else if (N == 1) {
29     return fabs(X[0]);
30   }
31 
32   for (i = 0; i < N; i++) {
33     const BASE x = X[ix];
34 
35     if (x != 0.0) {
36       const BASE ax = fabs(x);
37 
38       if (scale < ax) {
39         ssq = 1.0 + ssq * (scale / ax) * (scale / ax);
40         scale = ax;
41       } else {
42         ssq += (ax / scale) * (ax / scale);
43       }
44     }
45 
46     ix += incX;
47   }
48 
49   return scale * sqrt(ssq);
50 }
51