LU() [3/4]

M2_arrayintOrNull Lapack::LU ( const DMatRR * A, DMatRR * L, DMatRR * U )

static

Definition at line 195 of file lapack.cpp.

{
  int rows = static_cast<int>(A->numRows());
  int cols = static_cast<int>(A->numColumns());
  int info;
  int min = (rows <= cols) ? rows : cols;
  M2_arrayint result = M2_makearrayint(rows);
 
  L->resize(rows, min);
  U->resize(min, cols);
 
  if (min == 0)
    {
      if (rows > 0)
        for (int i = 0; i < rows; i++) result->array[i] = i;
      return result;
    }
 
  int* perm = new int[min];
  std::vector<double> copyA = make_lapack_array(*A);
 
  dgetrf_(&rows, &cols, copyA.data(), &rows, perm, &info);
 
  fill_lower_and_upper(copyA, *L, *U);
 
  for (int i = 0; i < rows; i++) result->array[i] = i;
  for (int i = 0; i < min; i++)
    {
      int thisloc = perm[i] - 1;
      int tmp = result->array[thisloc];
      result->array[thisloc] = result->array[i];
      result->array[i] = tmp;
    }
 
  delete [] perm;
 
  if (info < 0)
    {
      ERROR("argument passed to dgetrf had an illegal value");
      return nullptr;
    }
 
  return result;
}

References dgetrf_(), ERROR, fill_lower_and_upper(), M2_makearrayint(), make_lapack_array(), DMat< ACoeffRing >::numColumns(), DMat< ACoeffRing >::numRows(), DMat< ACoeffRing >::resize(), and result().