matrix_lift()

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

virtual

Implements GBComputation.

Definition at line 155 of file reducedgb.cpp.

{
  if (m->get_ring() != originalR)
    {
      ERROR("expected matrix over the same ring");
      *result_remainder = nullptr;
      *result_quotient = nullptr;
      return false;
    }
  if (m->n_rows() != F->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);
 
#ifdef DEVELOPMENT
#warning "K should be the denominator ring?"
#endif
  const Ring *K = R->get_flattened_coefficients();
  bool all_zeroes = true;
  for (int i = 0; i < m->n_cols(); i++)
    {
      ring_elem denom;
      POLY g;
      g.f = originalR->translate_gbvector_from_vec(F, (*m)[i], denom);
      g.fsyz = R->gbvector_zero();
 
      remainder(g, true, denom);
      if (g.f != nullptr) all_zeroes = false;
 
      vec fv = originalR->translate_gbvector_to_vec_denom(F, g.f, denom);
      K->negate_to(denom);
      vec fsyzv =
          originalR->translate_gbvector_to_vec_denom(Fsyz, g.fsyz, denom);
      mat_remainder.set_column(i, fv);
      mat_quotient.set_column(i, fsyzv);
 
      R->gbvector_remove(g.f);
      R->gbvector_remove(g.fsyz);
    }
  *result_remainder = mat_remainder.to_matrix();
  *result_quotient = mat_quotient.to_matrix();
  return all_zeroes;
}

References Matrix::cols(), Matrix::degree_shift(), ERROR, F, POLY::f, Fsyz, POLY::fsyz, Matrix::get_ring(), Matrix, Matrix::n_cols(), Matrix::n_rows(), Ring::negate_to(), originalR, POLY, R, remainder(), Matrix::rows(), MatrixConstructor::set_column(), and MatrixConstructor::to_matrix().