keigen.c

#include <math.h>
#include <stdlib.h>
#include "keigen.h"

void ke_core_strq(int n, double *q, double *b, double *c)
{
	int	i, j, k, u, v;
	double h, f, g, h2;
	for (i = n - 1; i >= 1; i--) {
		h = 0.0;
		if (i > 1)
			for (k = 0; k < i; k++) {
				u = i * n + k;
				h = h + q[u] * q[u];
			}
		if (h + 1.0 == 1.0) {
			c[i] = 0.0;
			if (i == 1)
				c[i] = q[i * n + i - 1];
			b[i] = 0.0;
		} else {
			c[i] = sqrt(h);
			u = i * n + i - 1;
			if (q[u] > 0.0)
				c[i] = -c[i];
			h = h - q[u] * c[i];
			q[u] = q[u] - c[i];
			f = 0.0;
			for (j = 0; j < i; j++) {
				q[j * n + i] = q[i * n + j] / h;
				g = 0.0;
				for (k = 0; k <= j; k++)
					g = g + q[j * n + k] * q[i * n + k];
				if (j + 1 < i)
					for (k = j + 1; k <= i - 1; k++)
						g = g + q[k * n + j] * q[i * n + k];
				c[j] = g / h;
				f = f + g * q[j * n + i];
			}
			h2 = f / (h + h);
			for (j = 0; j < i; j++) {
				f = q[i * n + j];
				g = c[j] - h2 * f;
				c[j] = g;
				for (k = 0; k <= j; k++) {
					u = j * n + k;
					q[u] = q[u] - f * c[k] - g * q[i * n + k];
				}
			}
			b[i] = h;
		}
	}
	for (i = 0; i < n - 1; i++)
		c[i] = c[i + 1];
	c[n - 1] = 0.0;
	b[0] = 0.0;
	for (i = 0; i < n; i++) {
		if (b[i] != 0.0 && i - 1 >= 0)
			for (j = 0; j < i; j++) {
				g = 0.0;
				for (k = 0; k < i; k++)
					g = g + q[i * n + k] * q[k * n + j];
				for (k = 0; k < i; k++) {
					u = k * n + j;
					q[u] = q[u] - g * q[k * n + i];
				}
			}
		u = i * n + i;
		b[i] = q[u];
		q[u] = 1.0;
		if (i - 1 >= 0)
			for (j = 0; j < i; j++) {
				q[i * n + j] = 0.0;
				q[j * n + i] = 0.0;
			}
	}
}

int ke_core_sstq(int n, double *b, double *c, double *q, int cal_ev, double eps, int l)
{
	int i, j, k, m, it, u, v;
	double d, f, h, g, p, r, e, s;
	c[n - 1] = 0.0;
	d = 0.0;
	f = 0.0;
	for (j = 0; j < n; j++) {
		it = 0;
		h = eps * (fabs(b[j]) + fabs(c[j]));
		if (h > d)
			d = h;
		m = j;
		while (m < n && fabs(c[m]) > d)
			m = m + 1;
		if (m != j) {
			do {
				if (it == l) return KE_EXCESS_ITER;
				it = it + 1;
				g = b[j];
				p = (b[j + 1] - g) / (2.0 * c[j]);
				r = sqrt(p * p + 1.0);
				if (p >= 0.0)
					b[j] = c[j] / (p + r);
				else
					b[j] = c[j] / (p - r);
				h = g - b[j];
				for (i = j + 1; i < n; i++)
					b[i] = b[i] - h;
				f = f + h;
				p = b[m];
				e = 1.0;
				s = 0.0;
				for (i = m - 1; i >= j; i--) {
					g = e * c[i];
					h = e * p;
					if (fabs(p) >= fabs(c[i])) {
						e = c[i] / p;
						r = sqrt(e * e + 1.0);
						c[i + 1] = s * p * r;
						s = e / r;
						e = 1.0 / r;
					} else {
						e = p / c[i];
						r = sqrt(e * e + 1.0);
						c[i + 1] = s * c[i] * r;
						s = 1.0 / r;
						e = e / r;
					}
					p = e * b[i] - s * g;
					b[i + 1] = h + s * (e * g + s * b[i]);
					if (cal_ev) {
						for (k = 0; k < n; k++) {
							u = k * n + i + 1;
							v = u - 1;
							h = q[u];
							q[u] = s * q[v] + e * h;
							q[v] = e * q[v] - s * h;
						}
					}
				}
				c[j] = s * p;
				b[j] = e * p;
			}
			while (fabs(c[j]) > d);
		}
		b[j] = b[j] + f;
	}
	for (i = 0; i < n; i++) {
		k = i;
		p = b[i];
		if (i + 1 < n) {
			j = i + 1;
			while (j < n && b[j] <= p) {
				k = j;
				p = b[j];
				j = j + 1;
			}
		}
		if (k != i) {
			b[k] = b[i];
			b[i] = p;
			for (j = 0; j < n; j++) {
				u = j * n + i;
				v = j * n + k;
				p = q[u];
				q[u] = q[v];
				q[v] = p;
			}
		}
	}
	return 0;
}

#define MALLOC(type, size) ((type*)malloc(size * sizeof(type)))

int ke_eigen_sd(int n, double *a, double *v, int cal_ev, double eps, int max_iter)
{
	double *c;
	int r;
	if (1.0 + eps <= 1.0) eps = 1e-7;
	if (max_iter <= 0) max_iter = 50;
	c = MALLOC(double, n);
	ke_core_strq(n, a, v, c);
	r = ke_core_sstq(n, v, c, a, cal_ev, eps, max_iter);
	free(c);
	return r;
}