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87 lines
1.8 KiB
C
87 lines
1.8 KiB
C
#include <math.h>
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#define NRANSI
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#include "nrutil.h"
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#define ROTATE(a,i,j,k,l) g=a[i][j];h=a[k][l];a[i][j]=g-s*(h+g*tau);\
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a[k][l]=h+s*(g-h*tau);
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void jacobi(double **a, int n, double d[], double **v, int *nrot)
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{
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int j,iq,ip,i;
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double tresh,theta,tau,t,sm,s,h,g,c,*b,*z;
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b=dvector(1,n);
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z=dvector(1,n);
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for (ip=1;ip<=n;ip++) {
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for (iq=1;iq<=n;iq++) v[ip][iq]=0.0;
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v[ip][ip]=1.0;
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}
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for (ip=1;ip<=n;ip++) {
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b[ip]=d[ip]=a[ip][ip];
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z[ip]=0.0;
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}
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*nrot=0;
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for (i=1;i<=50;i++) {
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sm=0.0;
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for (ip=1;ip<=n-1;ip++) {
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for (iq=ip+1;iq<=n;iq++)
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sm += fabs(a[ip][iq]);
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}
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if (sm == 0.0) {
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free_dvector(z,1,n);
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free_dvector(b,1,n);
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return;
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}
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if (i < 4)
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tresh=0.2*sm/(n*n);
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else
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tresh=0.0;
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for (ip=1;ip<=n-1;ip++) {
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for (iq=ip+1;iq<=n;iq++) {
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g=100.0*fabs(a[ip][iq]);
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if (i > 4 && (double)(fabs(d[ip])+g) == (double)fabs(d[ip])
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&& (double)(fabs(d[iq])+g) == (double)fabs(d[iq]))
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a[ip][iq]=0.0;
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else if (fabs(a[ip][iq]) > tresh) {
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h=d[iq]-d[ip];
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if ((double)(fabs(h)+g) == (double)fabs(h))
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t=(a[ip][iq])/h;
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else {
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theta=0.5*h/(a[ip][iq]);
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t=1.0/(fabs(theta)+sqrt(1.0+theta*theta));
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if (theta < 0.0) t = -t;
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}
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c=1.0/sqrt(1+t*t);
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s=t*c;
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tau=s/(1.0+c);
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h=t*a[ip][iq];
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z[ip] -= h;
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z[iq] += h;
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d[ip] -= h;
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d[iq] += h;
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a[ip][iq]=0.0;
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for (j=1;j<=ip-1;j++) {
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ROTATE(a,j,ip,j,iq)
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}
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for (j=ip+1;j<=iq-1;j++) {
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ROTATE(a,ip,j,j,iq)
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}
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for (j=iq+1;j<=n;j++) {
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ROTATE(a,ip,j,iq,j)
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}
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for (j=1;j<=n;j++) {
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ROTATE(v,j,ip,j,iq)
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}
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++(*nrot);
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}
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}
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}
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for (ip=1;ip<=n;ip++) {
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b[ip] += z[ip];
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d[ip]=b[ip];
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z[ip]=0.0;
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}
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}
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nrerror("Too many iterations in routine jacobi");
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}
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#undef ROTATE
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#undef NRANSI
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