1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
/* solv.c CCMATH mathematics library source code.
*
* Copyright (C) 2000 Daniel A. Atkinson All rights reserved.
* This code may be redistributed under the terms of the GNU general
* public license. ( See the gpl.license file for details.)
* ------------------------------------------------------------------------
*/
#include <stdlib.h>
#include "ccmath.h"
int solv(double *a, double *b, int n)
{
int i, j, k, lc;
double *ps, *p, *q, *pa, *pd;
double *q0, s, t, tq = 0., zr = 1.e-15;
q0 = (double *)calloc(n, sizeof(double));
for (j = 0, pa = a, pd = a; j < n; ++j, ++pa, pd += n + 1) {
if (j) {
for (i = 0, q = q0, p = pa; i < n; ++i, p += n)
*q++ = *p;
for (i = 1; i < n; ++i) {
lc = i < j ? i : j;
for (k = 0, p = pa + i * n - j, q = q0, t = 0.; k < lc; ++k)
t += *p++ * *q++;
q0[i] -= t;
}
for (i = 0, q = q0, p = pa; i < n; ++i, p += n)
*p = *q++;
}
s = fabs(*pd);
lc = j;
for (k = j + 1, ps = pd; k < n; ++k) {
if ((t = fabs(*(ps += n))) > s) {
s = t;
lc = k;
}
}
tq = tq > s ? tq : s;
if (s < zr * tq) {
free(q0);
return -1;
}
if (lc != j) {
t = b[j];
b[j] = b[lc];
b[lc] = t;
for (k = 0, p = a + n * j, q = a + n * lc; k < n; ++k) {
t = *p;
*p++ = *q;
*q++ = t;
}
}
for (k = j + 1, ps = pd, t = 1. / *pd; k < n; ++k)
*(ps += n) *= t;
}
for (j = 1, ps = b + 1; j < n; ++j) {
for (k = 0, p = a + n * j, q = b, t = 0.; k < j; ++k)
t += *p++ * *q++;
*ps++ -= t;
}
for (j = n - 1, --ps, pd = a + n * n - 1; j >= 0; --j, pd -= n + 1) {
for (k = j + 1, p = pd, q = b + j, t = 0.; k < n; ++k)
t += *++p * *++q;
*ps -= t;
*ps-- /= *pd;
}
free(q0);
return 0;
}
|
