54 lines
986 B
C++
54 lines
986 B
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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void NR::ludcmp(Mat_IO_DP &a, 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,imax,j,k;
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DP big,dum,sum,temp;
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int n=a.nrows();
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Vec_DP vv(n);
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d=1.0;
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for (i=0;i<n;i++) {
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big=0.0;
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for (j=0;j<n;j++)
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if ((temp=fabs(a[i][j])) > big) big=temp;
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if (big == 0.0) nrerror("Singular matrix in routine ludcmp");
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vv[i]=1.0/big;
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}
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for (j=0;j<n;j++) {
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for (i=0;i<j;i++) {
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sum=a[i][j];
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for (k=0;k<i;k++) sum -= a[i][k]*a[k][j];
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a[i][j]=sum;
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}
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big=0.0;
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for (i=j;i<n;i++) {
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sum=a[i][j];
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for (k=0;k<j;k++) sum -= a[i][k]*a[k][j];
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a[i][j]=sum;
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if ((dum=vv[i]*fabs(sum)) >= big) {
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big=dum;
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imax=i;
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}
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}
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if (j != imax) {
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for (k=0;k<n;k++) {
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dum=a[imax][k];
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a[imax][k]=a[j][k];
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a[j][k]=dum;
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}
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d = -d;
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vv[imax]=vv[j];
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}
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indx[j]=imax;
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if (a[j][j] == 0.0) a[j][j]=TINY;
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if (j != n-1) {
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dum=1.0/(a[j][j]);
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for (i=j+1;i<n;i++) a[i][j] *= dum;
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}
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}
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}
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