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#include <grass/gis.h>
#include <math.h>
#define MAX_ITERS 30
#define SIGN(a,b) ((b)<0 ? -fabs(a) : fabs(a))
int G_tqli(double d[], double e[], int n, double **z)
{
int m, l, iter, i, k;
double s, r, p, g, f, dd, c, b;
for (i = 1; i < n; i++)
e[i - 1] = e[i];
e[n - 1] = 0.0;
for (l = 0; l < n; l++) {
iter = 0;
do {
for (m = l; m < n - 1; m++) {
dd = fabs(d[m]) + fabs(d[m + 1]);
if (fabs(e[m]) + dd == dd)
break;
}
if (m != l) {
if (iter++ == MAX_ITERS)
return 0; /* Too many iterations in TQLI */
g = (d[l + 1] - d[l]) / (2.0 * e[l]);
r = sqrt((g * g) + 1.0);
g = d[m] - d[l] + e[l] / (g + SIGN(r, g));
s = c = 1.0;
p = 0.0;
for (i = m - 1; i >= l; i--) {
f = s * e[i];
b = c * e[i];
if (fabs(f) >= fabs(g)) {
c = g / f;
r = sqrt((c * c) + 1.0);
e[i + 1] = f * r;
c *= (s = 1.0 / r);
}
else {
s = f / g;
r = sqrt((s * s) + 1.0);
e[i + 1] = g * r;
s *= (c = 1.0 / r);
}
g = d[i + 1] - p;
r = (d[i] - g) * s + 2.0 * c * b;
p = s * r;
d[i + 1] = g + p;
g = c * r - b;
/* Next loop can be omitted if eigenvectors not wanted */
for (k = 0; k < n; k++) {
f = z[k][i + 1];
z[k][i + 1] = s * z[k][i] + c * f;
z[k][i] = c * z[k][i] - s * f;
}
}
d[l] = d[l] - p;
e[l] = g;
e[m] = 0.0;
}
} while (m != l);
}
return 1;
}
void G_tred2(double **a, int n, double d[], double e[])
{
int l, k, j, i;
double scale, hh, h, g, f;
for (i = n - 1; i >= 1; i--) {
l = i - 1;
h = scale = 0.0;
if (l > 0) {
for (k = 0; k <= l; k++)
scale += fabs(a[i][k]);
if (scale == 0.0)
e[i] = a[i][l];
else {
for (k = 0; k <= l; k++) {
a[i][k] /= scale;
h += a[i][k] * a[i][k];
}
f = a[i][l];
g = f > 0 ? -sqrt(h) : sqrt(h);
e[i] = scale * g;
h -= f * g;
a[i][l] = f - g;
f = 0.0;
for (j = 0; j <= l; j++) {
/* Next statement can be omitted if eigenvectors not wanted */
a[j][i] = a[i][j] / h;
g = 0.0;
for (k = 0; k <= j; k++)
g += a[j][k] * a[i][k];
for (k = j + 1; k <= l; k++)
g += a[k][j] * a[i][k];
e[j] = g / h;
f += e[j] * a[i][j];
}
hh = f / (h + h);
for (j = 0; j <= l; j++) {
f = a[i][j];
e[j] = g = e[j] - hh * f;
for (k = 0; k <= j; k++)
a[j][k] -= (f * e[k] + g * a[i][k]);
}
}
}
else
e[i] = a[i][l];
d[i] = h;
}
/* Next statement can be omitted if eigenvectors not wanted */
d[0] = 0.0;
e[0] = 0.0;
/* Contents of this loop can be omitted if eigenvectors not
wanted except for statement d[i]=a[i][i]; */
for (i = 0; i < n; i++) {
l = i - 1;
if (d[i]) {
for (j = 0; j <= l; j++) {
g = 0.0;
for (k = 0; k <= l; k++)
g += a[i][k] * a[k][j];
for (k = 0; k <= l; k++)
a[k][j] -= g * a[k][i];
}
}
d[i] = a[i][i];
a[i][i] = 1.0;
for (j = 0; j <= l; j++)
a[j][i] = a[i][j] = 0.0;
}
}
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