create() [2/3]

SchreyerOrder * SchreyerOrder::create ( const Matrix * m )

static

Definition at line 29 of file schorder.cpp.

{
  int i;
  const Ring *R = m->get_ring();
  const SchreyerOrder *S = m->rows()->get_schreyer_order();
  const PolynomialRing *P = R->cast_to_PolynomialRing();
  if (P == nullptr)
    {
      throw exc::engine_error("expected polynomial ring");
    }
  const Monoid *M = P->getMonoid();
  SchreyerOrder *result = new SchreyerOrder(M);
  int rk = m->n_cols();
  if (rk == 0) return result;
  monomial base = M->make_one();
  int *tiebreaks = newarray_atomic(int, rk);
  int *ties = newarray_atomic(int, rk);
  for (i = 0; i < rk; i++)
    {
      vec v = (*m)[i];
      if (v == nullptr || S == nullptr)
        tiebreaks[i] = i;
      else
        tiebreaks[i] = i + rk * S->compare_num(v->comp);
    }
  // Now sort tiebreaks in increasing order.
  std::sort<int *>(tiebreaks, tiebreaks + rk);
  for (i = 0; i < rk; i++) ties[tiebreaks[i] % rk] = i;
  for (i = 0; i < rk; i++)
    {
      vec v = (*m)[i];
      if (v == nullptr)
        M->one(base);
      else if (S == nullptr)
        M->copy(P->lead_flat_monomial(v->coeff), base);
      else
        {
          int x = v->comp;
          M->mult(P->lead_flat_monomial(v->coeff), S->base_monom(x), base);
        }
 
      result->append(ties[i], base);
    }
 
  intern_SchreyerOrder(result);
  M->remove(base);
  freemem(tiebreaks);
  freemem(ties);
  return result;
}

References base, base_monom(), Ring::cast_to_PolynomialRing(), compare_num(), freemem(), Matrix::get_ring(), FreeModule::get_schreyer_order(), PolynomialRing::getMonoid(), intern_SchreyerOrder(), PolynomialRing::lead_flat_monomial(), M, Matrix, monomial, Matrix::n_cols(), newarray_atomic, result(), Matrix::rows(), SchreyerOrder(), and x.