sub_matrix() [2/2]

Matrix * Matrix::sub_matrix	(	M2_arrayint	r,
		M2_arrayint	c ) const

Definition at line 470 of file matrix.cpp.

{
  const FreeModule *F = rows()->sub_space(r);
  const FreeModule *G = cols()->sub_space(c);
  if (F == nullptr || G == nullptr) return nullptr;
 
  int *minrow = newarray_atomic(int, n_rows());
  int *maxrow = newarray_atomic(int, n_rows());
  for (int i = 0; i < n_rows(); i++)
    {
      minrow[i] = n_rows();
      maxrow[i] = -1;
    }
 
  for (int i = 0; i < r->len; i++)
    if (r->array[i] >= 0 && r->array[i] < n_rows())
      {
        minrow[r->array[i]] = std::min(minrow[r->array[i]], i);
        maxrow[r->array[i]] = std::max(maxrow[r->array[i]], i);
      }
 
  MatrixConstructor mat(F, G, degree_shift());
  for (size_t j = 0; j < c->len; j++)
    {
      vec v = elem(c->array[j]);
      for (; v != nullptr; v = v->next)
        for (int i = minrow[v->comp]; i <= maxrow[v->comp]; i++)
          if (v->comp == r->array[i])
            mat.set_entry(i, j, v->coeff);
    }
  freemem(minrow);
  freemem(maxrow);
  return mat.to_matrix();
}

References cols(), degree_shift(), elem(), freemem(), FreeModule, G, Matrix(), MatrixConstructor, n_rows(), newarray_atomic, rows(), MatrixConstructor::set_entry(), sub_matrix(), and MatrixConstructor::to_matrix().

Referenced by IM2_Matrix_submatrix(), IM2_Matrix_submatrix1(), sub_matrix(), and sub_matrix().