46 lines
799 B
C++
46 lines
799 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::bandec(Mat_IO_DP &a, const int m1, const int m2, Mat_O_DP &al,
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Vec_O_INT &indx, DP &d)
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{
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const DP TINY=1.0e-20;
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int i,j,k,l,mm;
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DP dum;
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int n=a.nrows();
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mm=m1+m2+1;
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l=m1;
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for (i=0;i<m1;i++) {
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for (j=m1-i;j<mm;j++) a[i][j-l]=a[i][j];
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l--;
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for (j=mm-l-1;j<mm;j++) a[i][j]=0.0;
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}
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d=1.0;
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l=m1;
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for (k=0;k<n;k++) {
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dum=a[k][0];
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i=k;
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if (l<n) l++;
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for (j=k+1;j<l;j++) {
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if (fabs(a[j][0]) > fabs(dum)) {
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dum=a[j][0];
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i=j;
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}
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}
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indx[k]=i+1;
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if (dum == 0.0) a[k][0]=TINY;
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if (i != k) {
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d = -d;
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for (j=0;j<mm;j++) SWAP(a[k][j],a[i][j]);
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}
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for (i=k+1;i<l;i++) {
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dum=a[i][0]/a[k][0];
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al[k][i-k-1]=dum;
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for (j=1;j<mm;j++) a[i][j-1]=a[i][j]-dum*a[k][j];
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a[i][mm-1]=0.0;
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}
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}
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}
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