xtred2.c

< C语言数值算法程序大全>>配套程序

/* Driver for routine tred2 */

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

#define NP 10

main()
{
	int i,j,k,l,m;
	float *d,*e,**a,**f;
	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);
	a=matrix(1,NP,1,NP);
	f=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);
	printf("diagonal elements\n");
	for (i=1;i<=NP;i++) {
		printf("%12.6f",d[i]);
		if ((i % 5) == 0) printf("\n");
	}
	printf("off-diagonal elements\n");
	for (i=2;i<=NP;i++) {
		printf("%12.6f",e[i]);
		if ((i % 5) == 0) printf("\n");
	}
	/* Check transformation matrix */
	for (j=1;j<=NP;j++) {
		for (k=1;k<=NP;k++) {
			f[j][k]=0.0;
			for (l=1;l<=NP;l++) {
				for (m=1;m<=NP;m++)
					f[j][k] += a[l][j]*c[l-1][m-1]*a[m][k];
			}
		}
	}
	/* How does it look? */
	printf("tridiagonal matrix\n");
	for (i=1;i<=NP;i++) {
		for (j=1;j<=NP;j++) printf("%7.2f",f[i][j]);
		printf("\n");
	}
	free_matrix(f,1,NP,1,NP);
	free_matrix(a,1,NP,1,NP);
	free_vector(e,1,NP);
	free_vector(d,1,NP);
	return 0;
}