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add numerical recipes library

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yenru0
2025-09-12 18:55:25 +09:00
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lib/nr/ansi/examples/xtred2.c Normal file
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/* Driver for routine tred2 */
#include <stdio.h>
#define NRANSI
#include "nr.h"
#include "nrutil.h"
#define NP 10
int main(void)
{
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;
}
#undef NRANSI