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#include <stdlib.h>
#include <math.h>
#include <grass/gis.h>
#include <grass/gmath.h>
/***************************************************************************/
/* this does not use the Jacobi method, but it should give the same result */
int jacobi(double a[MX][MX], long n, double d[MX], double v[MX][MX])
{
double *aa[MX], *vv[MX], *dd;
int i;
for (i = 0; i < n; i++) {
aa[i] = &a[i + 1][1];
vv[i] = &v[i + 1][1];
}
dd = &d[1];
eigen(aa, vv, dd, n);
return 0;
}
/***************************************************************************/
static int egcmp(const void *pa, const void *pb)
{
const double *a = *(const double *const *)pa;
const double *b = *(const double *const *)pb;
if (*a > *b)
return -1;
if (*a < *b)
return 1;
return 0;
}
int egvorder(double d[MX], double z[MX][MX], long bands)
{
double *buff;
double **tmp;
int i, j;
/* allocate temporary matrix */
buff = (double *)G_malloc(bands * (bands + 1) * sizeof(double));
tmp = (double **)G_malloc(bands * sizeof(double *));
for (i = 0; i < bands; i++)
tmp[i] = &buff[i * (bands + 1)];
/* concatenate (vertically) z and d into tmp */
for (i = 0; i < bands; i++) {
for (j = 0; j < bands; j++)
tmp[i][j + 1] = z[j + 1][i + 1];
tmp[i][0] = d[i + 1];
}
/* sort the combined matrix */
qsort(tmp, bands, sizeof(double *), egcmp);
/* split tmp into z and d */
for (i = 0; i < bands; i++) {
for (j = 0; j < bands; j++)
z[j + 1][i + 1] = tmp[i][j + 1];
d[i + 1] = tmp[i][0];
}
/* free temporary matrix */
G_free(tmp);
G_free(buff);
return 0;
}
/***************************************************************************/
int transpose(double eigmat[MX][MX], long bands)
{
int i, j;
for (i = 1; i <= bands; i++)
for (j = 1; j < i; j++) {
double tmp = eigmat[i][j];
eigmat[i][j] = eigmat[j][i];
eigmat[j][i] = tmp;
}
return 0;
}
/***************************************************************************/
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