/* Driver for routine tqli */

#include <stdio.h>
#include <math.h>
#include "nr.h"
#include "nrutil.h"

#define NP 10
#define TINY 1.0e-6

main()
{
	int i,j,k;
	float *d,*e,*f,**a;
	static float c[NP][NP]={
		5.0, 4.3, 3.0, 2.0, 1.0, 0.0,-1.0,-2.0,-3.0,-4.0,
		4.3, 5.1, 4.0, 3.0, 2.0, 1.0, 0.0,-1.0,-2.0,-3.0,
		3.0, 4.0, 5.0, 4.0, 3.0, 2.0, 1.0, 0.0,-1.0,-2.0,
		2.0, 3.0, 4.0, 5.0, 4.0, 3.0, 2.0, 1.0, 0.0,-1.0,
		1.0, 2.0, 3.0, 4.0, 5.0, 4.0, 3.0, 2.0, 1.0, 0.0,
		0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 4.0, 3.0, 2.0, 1.0,
	   -1.0, 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 4.0, 3.0, 2.0,
	   -2.0,-1.0, 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 4.0, 3.0,
	   -3.0,-2.0,-1.0, 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 4.0,
	   -4.0,-3.0,-2.0,-1.0, 0.0, 1.0, 2.0, 3.0, 4.0, 5.0};

	d=vector(1,NP);
	e=vector(1,NP);
	f=vector(1,NP);
	a=matrix(1,NP,1,NP);
	for (i=1;i<=NP;i++)
		for (j=1;j<=NP;j++) a[i][j]=c[i-1][j-1];
	tred2(a,NP,d,e);
	tqli(d,e,NP,a);
	printf("\nEigenvectors for a real symmetric matrix\n");
	for (i=1;i<=NP;i++) {
		for (j=1;j<=NP;j++) {
			f[j]=0.0;
			for (k=1;k<=NP;k++)
				f[j] += (c[j-1][k-1]*a[k][i]);
		}
		printf("%s %3d %s %10.6f\n","eigenvalue",i," =",d[i]);
		printf("%11s %14s %9s\n","vector","mtrx*vect.","ratio");
		for (j=1;j<=NP;j++) {
			if (fabs(a[j][i]) < TINY)
				printf("%12.6f %12.6f %12s\n",
					a[j][i],f[j],"div. by 0");
			else
				printf("%12.6f %12.6f %12.6f\n",
					a[j][i],f[j],f[j]/a[j][i]);
		}
		printf("Press ENTER to continue...\n");
		(void) getchar();
	}
	free_matrix(a,1,NP,1,NP);
	free_vector(f,1,NP);
	free_vector(e,1,NP);
	free_vector(d,1,NP);
	return 0;
}