tail_remainder_ZZ()

void gbA::tail_remainder_ZZ ( POLY & f, int degf )

private

Definition at line 1921 of file gb-default.cpp.

{
  gbvector head;
  gbvector *frem = &head;
  int count = 0;
  POLY h = f;
 
  exponents_t EXP = ALLOCATE_EXPONENTS(exp_size);
 
  frem->next = h.f;
  frem = frem->next;
  h.f = h.f->next;
  frem->next = nullptr;
 
  while (!R->gbvector_is_zero(h.f))
    {
      int gap;
      R->gbvector_get_lead_exponents(_F, h.f, EXP);
      int x = h.f->comp;
      int w = find_good_monomial_divisor_ZZ(
          h.f->coeff.get_mpz(), EXP, x, degf, gap);
      // replaced gap, g.
      if (w < 0 || gap > 0)
        {
          frem->next = h.f;
          frem = frem->next;
          h.f = h.f->next;
          frem->next = nullptr;
        }
      else
        {
          POLY g = gb[w]->g;
          if (!R->gbvector_reduce_lead_term_ZZ(
                  _F, _Fsyz, h.f, h.fsyz, g.f, g.fsyz))
            {
              // This term is still there, so we must move it to result.
              frem->next = h.f;
              frem = frem->next;
              h.f = h.f->next;
              frem->next = nullptr;
            }
          count++;
          //      stats_ntail++;
          if (M2_gbTrace == 15)
            {
              buffer o;
              o << "    tail red by g" << w;
              o << ", yielding ";
              R->gbvector_text_out(o, _F, h.f, 3);
              emit_line(o.str());
            }
        }
    }
  h.f = head.next;
  // Negate these if needed
  if (h.f != nullptr && mpz_sgn(h.f->coeff.get_mpz()) < 0)
    {
      R->gbvector_mult_by_coeff_to(h.f, globalZZ->minus_one());
      R->gbvector_mult_by_coeff_to(h.fsyz, globalZZ->minus_one());
    }
  f.f = h.f;
  f.fsyz = h.fsyz;
  if ((M2_gbTrace & PRINT_SPAIR_TRACKING) != 0)
    {
      buffer o;
      o << "number of reduction steps was " << count;
      emit_line(o.str());
    }
  else if (M2_gbTrace >= 4 && M2_gbTrace != 15)
    {
      buffer o;
      o << "," << count;
      emit_wrapped(o.str());
    }
}

References _F, _Fsyz, ALLOCATE_EXPONENTS, gbvector::coeff, gbvector::comp, emit_line(), emit_wrapped(), exp_size, POLY::f, find_good_monomial_divisor_ZZ(), POLY::fsyz, gb(), ring_elem::get_mpz(), globalZZ, M2_gbTrace, gbvector::next, POLY, PRINT_SPAIR_TRACKING, R, buffer::str(), and x.

Referenced by replace_gb_element_ZZ().