subduct() [2/2]

ring_elem sagbi::subduct ( int numslots, const PolyRing * R, ring_elem f, const RingMap * phi, GBComputation * J )

static

Definition at line 7 of file sagbi.cpp.

{
  Nterm *f = a;
  Nterm head;
  Nterm *result = &head;
  MatrixConstructor mat(R->make_FreeModule(1), 1);
 
  while (f != nullptr)
    {
      Nterm *g = f;
      f = f->next;
      g->next = nullptr;
 
      mat.set_entry(0, 0, g);
      Matrix *m = mat.to_matrix();
      const Matrix *n = J->matrix_remainder(m);
      ring_elem g1 = n->elem(0, 0);
      delete m;
      delete n;
 
      // Is g1 a monomial in the new variables?
      if (R->in_subring(numslots, g1))
        {
          g->next = f;
          f = g;
          ring_elem phi_g1 = R->eval(phi, g1, 0);
          ring_elem fr = f;
          R->internal_subtract_to(fr, phi_g1);
          f = fr;
        }
      else
        {
          result->next = g;
          result = g;
        }
    }
 
  result->next = nullptr;
  return head.next;
}

References Matrix::elem(), PolyRing::eval(), PolyRing::in_subring(), PolyRing::internal_subtract_to(), Ring::make_FreeModule(), Matrix, GBComputation::matrix_remainder(), Nterm::next, result(), MatrixConstructor::set_entry(), and MatrixConstructor::to_matrix().

Referenced by rawSubduction(), and subduct().