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/* svdval.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 library
* public license (LGPL). ( See the lgpl.license file for details.)
* ------------------------------------------------------------------------
*/
#include <stdlib.h>
#include "ccmath.h"
int svdval(double *d, double *a, int m, int n)
{
double *p, *p1, *q, *w, *v;
double s, h, u;
int i, j, k, mm, nm, ms;
if (m < n)
return -1;
w = (double *)calloc(m, sizeof(double));
for (i = 0, mm = m, nm = n - 1, p = a; i < n; ++i, --mm, --nm, p += n + 1) {
if (mm > 1) {
for (j = 0, q = p, s = 0.; j < mm; ++j, q += n) {
w[j] = *q;
s += *q * *q;
}
if (s > 0.) {
h = sqrt(s);
if (*p < 0.)
h = -h;
s += *p * h;
s = 1. / s;
w[0] += h;
for (k = 1, ms = n - i; k < ms; ++k) {
for (j = 0, q = p + k, u = 0.; j < mm; q += n)
u += w[j++] * *q;
u *= s;
for (j = 0, q = p + k; j < mm; q += n)
*q -= u * w[j++];
}
*p = -h;
}
}
p1 = p + 1;
if (nm > 1) {
for (j = 0, q = p1, s = 0.; j < nm; ++j, ++q)
s += *q * *q;
if (s > 0.) {
h = sqrt(s);
if (*p1 < 0.)
h = -h;
s += *p1 * h;
s = 1. / s;
*p1 += h;
for (k = n, ms = n * (m - i); k < ms; k += n) {
for (j = 0, q = p1, v = p1 + k, u = 0.; j < nm; ++j)
u += *q++ * *v++;
u *= s;
for (j = 0, q = p1, v = p1 + k; j < nm; ++j)
*v++ -= u * *q++;
}
*p1 = -h;
}
}
}
for (j = 0, p = a; j < n; ++j, p += n + 1) {
d[j] = *p;
if (j != n - 1)
w[j] = *(p + 1);
else
w[j] = 0.;
}
qrbdi(d, w, n);
for (i = 0; i < n; ++i)
if (d[i] < 0.)
d[i] = -d[i];
free(w);
return 0;
}
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