74 lines
1.4 KiB
C++
74 lines
1.4 KiB
C++
#include <cmath>
|
|
#include "nr.h"
|
|
using namespace std;
|
|
|
|
void NR::tred2(Mat_IO_DP &a, Vec_O_DP &d, Vec_O_DP &e)
|
|
{
|
|
int l,k,j,i;
|
|
DP scale,hh,h,g,f;
|
|
|
|
int n=d.size();
|
|
for (i=n-1;i>0;i--) {
|
|
l=i-1;
|
|
h=scale=0.0;
|
|
if (l > 0) {
|
|
for (k=0;k<l+1;k++)
|
|
scale += fabs(a[i][k]);
|
|
if (scale == 0.0)
|
|
e[i]=a[i][l];
|
|
else {
|
|
for (k=0;k<l+1;k++) {
|
|
a[i][k] /= scale;
|
|
h += a[i][k]*a[i][k];
|
|
}
|
|
f=a[i][l];
|
|
g=(f >= 0.0 ? -sqrt(h) : sqrt(h));
|
|
e[i]=scale*g;
|
|
h -= f*g;
|
|
a[i][l]=f-g;
|
|
f=0.0;
|
|
for (j=0;j<l+1;j++) {
|
|
// Next statement can be omitted if eigenvectors not wanted
|
|
a[j][i]=a[i][j]/h;
|
|
g=0.0;
|
|
for (k=0;k<j+1;k++)
|
|
g += a[j][k]*a[i][k];
|
|
for (k=j+1;k<l+1;k++)
|
|
g += a[k][j]*a[i][k];
|
|
e[j]=g/h;
|
|
f += e[j]*a[i][j];
|
|
}
|
|
hh=f/(h+h);
|
|
for (j=0;j<l+1;j++) {
|
|
f=a[i][j];
|
|
e[j]=g=e[j]-hh*f;
|
|
for (k=0;k<j+1;k++)
|
|
a[j][k] -= (f*e[k]+g*a[i][k]);
|
|
}
|
|
}
|
|
} else
|
|
e[i]=a[i][l];
|
|
d[i]=h;
|
|
}
|
|
// Next statement can be omitted if eigenvectors not wanted
|
|
d[0]=0.0;
|
|
e[0]=0.0;
|
|
// Contents of this loop can be omitted if eigenvectors not
|
|
// wanted except for statement d[i]=a[i][i];
|
|
for (i=0;i<n;i++) {
|
|
l=i;
|
|
if (d[i] != 0.0) {
|
|
for (j=0;j<l;j++) {
|
|
g=0.0;
|
|
for (k=0;k<l;k++)
|
|
g += a[i][k]*a[k][j];
|
|
for (k=0;k<l;k++)
|
|
a[k][j] -= g*a[k][i];
|
|
}
|
|
}
|
|
d[i]=a[i][i];
|
|
a[i][i]=1.0;
|
|
for (j=0;j<l;j++) a[j][i]=a[i][j]=0.0;
|
|
}
|
|
}
|