matrix_lift()

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

virtual

Implements GBComputation.

Definition at line 1099 of file gb-homog2.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;
    }
  start_computation();
  MatrixConstructor mat_remainder(m->rows(), m->cols(), m->degree_shift());
  MatrixConstructor mat_quotient(_Fsyz, 0);
  bool all_zeroes = true;
  for (int i = 0; i < m->n_cols(); i++)
    {
      ring_elem denom;
      gbvector *f = originalR->translate_gbvector_from_vec(_F, (*m)[i], denom);
      gbvector *fsyz = _GR->gbvector_zero();
 
      gb_reduce(f, fsyz);
      if (f != nullptr) all_zeroes = false;
 
      vec fv = originalR->translate_gbvector_to_vec_denom(_F, f, denom);
      _K->negate_to(denom);
      vec fsyzv =
          originalR->translate_gbvector_to_vec_denom(_Fsyz, fsyz, denom);
      mat_remainder.set_column(i, fv);
      mat_quotient.append(fsyzv);
    }
  *result_remainder = mat_remainder.to_matrix();
  *result_quotient = mat_quotient.to_matrix();
  return all_zeroes;
}

References _F, _Fsyz, _GR, _K, MatrixConstructor::append(), Matrix::cols(), Matrix::degree_shift(), ERROR, gb_reduce(), Matrix::get_ring(), Matrix, Matrix::n_cols(), Matrix::n_rows(), originalR, Matrix::rows(), MatrixConstructor::set_column(), start_computation(), and MatrixConstructor::to_matrix().