1 /* integration/err.c
2  *
3  * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough
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 #include "gsl__config.h"
21 #include <math.h>
22 #include <float.h>
23 #include "gsl_math.h"
24 #include "gsl_integration.h"
25 
26 static double rescale_error (double err, const double result_abs, const double result_asc) ;
27 
28 static double
29 rescale_error (double err, const double result_abs, const double result_asc)
30 {
31   err = fabs(err) ;
32 
33   if (result_asc != 0 && err != 0)
34       {
35         double scale = pow((200 * err / result_asc), 1.5) ;
36 
37         if (scale < 1)
38           {
39             err = result_asc * scale ;
40           }
41         else
42           {
43             err = result_asc ;
44           }
45       }
46   if (result_abs > GSL_DBL_MIN / (50 * GSL_DBL_EPSILON))
47     {
48       double min_err = 50 * GSL_DBL_EPSILON * result_abs ;
49 
50       if (min_err > err)
51         {
52           err = min_err ;
53         }
54     }
55 
56   return err ;
57 }
58 
59