lift_up()

void LocalRing::lift_up ( const Ring * R, const Matrix * m, Matrix *& result ) const

virtual

Definition at line 227 of file localring.cpp.

{
  (void) R;
  const RingElement *a, *b, *d;
  MatrixConstructor mat(mRing->make_FreeModule(m->n_rows()), m->n_cols());
  Matrix::column_iterator i(m), end(m);
  for (int c = 0; c < m->n_cols(); c++)
    {
      // TODO: make this into a routine for vector LCM
      a = RingElement::make_raw(mRing, mRing->from_long(1));
      for (i = Matrix::column_iterator(m, c); i != end; ++i)
        {
          const local_elem * f = ((*i)->coeff).get_local_elem();
          b = RingElement::make_raw(mRing, f->denom);
          d = rawGCDRingElement(a, b, nullptr, false);
#if 0 // FIXME: GCD(8,2)=1 apparently ...
          // see https://github.com/Macaulay2/M2/issues/1958
          drelem(a);
          std::cout<<" ";
          drelem(b);
          std::cout<<" ";
          drelem(d);
          std::cout<<std::endl;
#endif
          d = *b / *d;
          a = *a * *d;
        }
      for (i = Matrix::column_iterator(m, c); i != end; ++i)
        {
          const local_elem * f = ((*i)->coeff).get_local_elem();
          mat.set_entry(
              (*i)->comp,
              c,
              mRing->mult(f->numer, mRing->divide(a->get_value(), f->denom)));
        }
    }
  mat.compute_column_degrees();
  result = mat.to_matrix();
}

References MatrixConstructor::compute_column_degrees(), local_elem::denom, drelem(), end(), RingElement::get_value(), RingElement::make_raw(), Matrix, mRing, Matrix::n_cols(), Matrix::n_rows(), local_elem::numer, rawGCDRingElement(), result(), Ring::Ring(), MatrixConstructor::set_entry(), and MatrixConstructor::to_matrix().

Referenced by rawLiftLocalMatrix().