matrix_lift()

M2_bool HermiteComputation::matrix_lift ( const Matrix * m, const Matrix ** result_remainder, const Matrix ** result_quotient )

virtual

Implements GBComputation.

Definition at line 485 of file hermite.cpp.

{
  if (m->get_ring() != globalZZ)
    {
      ERROR("expected matrix over ZZ");
      *result_remainder = nullptr;
      *result_quotient = nullptr;
      return false;
    }
  if (m->n_rows() != gens->rows()->rank())
    {
      ERROR("expected matrices to have same number of rows");
      *result_remainder = nullptr;
      *result_quotient = nullptr;
      return false;
    }
  MatrixConstructor mat_remainder(m->rows(), m->cols(), m->degree_shift());
  MatrixConstructor mat_quotient(Fsyz, m->cols(), nullptr);
  bool all_zeroes = true;
  for (int i = 0; i < m->n_cols(); i++)
    {
      vec f = globalZZ->copy_vec(m->elem(i));
      vec fsyz = nullptr;
 
      gb_reduce(f, fsyz);
      if (f != nullptr) all_zeroes = false;
 
      globalZZ->negate_vec_to(fsyz);
      mat_remainder.set_column(i, f);
      mat_quotient.set_column(i, fsyz);
    }
  *result_remainder = mat_remainder.to_matrix();
  *result_quotient = mat_quotient.to_matrix();
  return all_zeroes;
}

References Matrix::cols(), Matrix::degree_shift(), Matrix::elem(), ERROR, Fsyz, gb_reduce(), gens, Matrix::get_ring(), globalZZ, Matrix, Matrix::n_cols(), Matrix::n_rows(), Matrix::rows(), MatrixConstructor::set_column(), and MatrixConstructor::to_matrix().