ABACUS/src/MATRIX/ludcmp_CX.cc

#include "ABACUS.h"
using namespace std;

void ABACUS::ludcmp_CX (SQMat_CX& a, Vect_INT& indx, DP& d)
{
  const complex<DP> TINY = 1.0e-200;
  int i, j, k;
  int imax = 0;
  complex<DP> big, dum, sum, temp;

  int n = a.size();
  if (n == 0) ABACUSerror("Zero-sized array in ludcmp_CX");
  Vect_CX vv(n);
  d = 1.0;
  for (i = 0; i < n; i++) {
    big = 0.0;
    for (j = 0; j < n; j++)
      if ((abs(temp = a[i][j])) > abs(big)) big = temp;
    if (big == 0.0) throw Divide_by_zero();
    vv[i] = 1.0/big;
  }
  for (j = 0; j < n; j++) {
    for (i = 0; i < j; i++) {
      sum = a[i][j];
      for (k = 0; k < i; k++) sum -= a[i][k] * a[k][j];
      a[i][j] = sum;
    }
    big = 0.0;
    for (i = j; i < n; i++) {
      sum = a[i][j];
      for (k = 0; k < j; k++) sum -= a[i][k] * a[k][j];
      a[i][j] = sum;
      if ((abs(dum = vv[i]*sum)) >= abs(big)) {
	big = dum;
	imax = i;
      }
    }
    if (j != imax) {
      for (k = 0; k < n; k++) {
	dum = a[imax][k];
	a[imax][k] = a[j][k];
	a[j][k] = dum;
      }
      d = -d;
      vv[imax] = vv[j];
    }
    indx[j] = imax;
    if (a[j][j] == 0.0) a[j][j] = TINY;
    if (j !=n-1) {
      dum = 1.0/(a[j][j]);
      for (i = j + 1; i < n; i++) a[i][j] *= dum;
    }
  }
}