35 lines
747 B
C++
35 lines
747 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::qrdcmp(Mat_IO_DP &a, Vec_O_DP &c, Vec_O_DP &d, bool &sing)
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{
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int i,j,k;
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DP scale,sigma,sum,tau;
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int n=a.nrows();
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sing=false;
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for (k=0;k<n-1;k++) {
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scale=0.0;
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for (i=k;i<n;i++) scale=MAX(scale,fabs(a[i][k]));
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if (scale == 0.0) {
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sing=true;
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c[k]=d[k]=0.0;
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} else {
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for (i=k;i<n;i++) a[i][k] /= scale;
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for (sum=0.0,i=k;i<n;i++) sum += SQR(a[i][k]);
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sigma=SIGN(sqrt(sum),a[k][k]);
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a[k][k] += sigma;
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c[k]=sigma*a[k][k];
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d[k] = -scale*sigma;
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for (j=k+1;j<n;j++) {
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for (sum=0.0,i=k;i<n;i++) sum += a[i][k]*a[i][j];
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tau=sum/c[k];
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for (i=k;i<n;i++) a[i][j] -= tau*a[i][k];
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}
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}
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}
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d[n-1]=a[n-1][n-1];
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if (d[n-1] == 0.0) sing=true;
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}
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