58 lines
1.1 KiB
C
58 lines
1.1 KiB
C
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#include <math.h>
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#define NRANSI
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#include "nrutil.h"
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void tqli(float d[], float e[], int n, float **z)
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{
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float pythag(float a, float b);
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int m,l,iter,i,k;
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float s,r,p,g,f,dd,c,b;
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for (i=2;i<=n;i++) e[i-1]=e[i];
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e[n]=0.0;
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for (l=1;l<=n;l++) {
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iter=0;
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do {
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for (m=l;m<=n-1;m++) {
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dd=fabs(d[m])+fabs(d[m+1]);
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if ((float)(fabs(e[m])+dd) == dd) break;
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}
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if (m != l) {
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if (iter++ == 30) nrerror("Too many iterations in tqli");
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g=(d[l+1]-d[l])/(2.0*e[l]);
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r=pythag(g,1.0);
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g=d[m]-d[l]+e[l]/(g+SIGN(r,g));
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s=c=1.0;
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p=0.0;
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for (i=m-1;i>=l;i--) {
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f=s*e[i];
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b=c*e[i];
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e[i+1]=(r=pythag(f,g));
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if (r == 0.0) {
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d[i+1] -= p;
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e[m]=0.0;
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break;
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}
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s=f/r;
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c=g/r;
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g=d[i+1]-p;
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r=(d[i]-g)*s+2.0*c*b;
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d[i+1]=g+(p=s*r);
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g=c*r-b;
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for (k=1;k<=n;k++) {
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f=z[k][i+1];
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z[k][i+1]=s*z[k][i]+c*f;
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z[k][i]=c*z[k][i]-s*f;
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}
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}
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if (r == 0.0 && i >= l) continue;
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d[l] -= p;
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e[l]=g;
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e[m]=0.0;
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}
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} while (m != l);
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}
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}
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#undef NRANSI
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