prune_unit()

void MutableComplex::prune_unit	(	const iterator &	i,
		const size_t	flags )

Definition at line 118 of file mutablecomplex.cpp.

{
  const size_t n = i.index();
  const std::pair<size_t, size_t> u = *i;
  const bool trace = flags & FLAG_TRACE_MORPHISMS;
  /* There is some redundancy here, can set some stuff to zero.
     TODO: Maybe check to see which is more efficient?
           Compare with using rawReduceByPivot
  */
  // Move to last row
  mDifferential[n]->interchange_rows(u.first, mBetti[n] - 1);
  if (0 < n) mDifferential[n - 1]->interchange_columns(u.first, mBetti[n] - 1);
  if (trace) mMorphisms[n]->interchange_columns(u.first, mBetti[n] - 1);
  // Move to last column
  mDifferential[n]->interchange_columns(u.second, mBetti[n + 1] - 1);
  if (n < mDifferential.size() - 1)
    mDifferential[n + 1]->interchange_rows(u.second, mBetti[n + 1] - 1);
  if (trace)
    mMorphisms[n + 1]->interchange_columns(u.second, mBetti[n + 1] - 1);
  // Get the pivot
  ring_elem p, q, f;
  mDifferential[n]->get_entry(mBetti[n] - 1, mBetti[n + 1] - 1, p);
  p = mRing->invert(p);
  q = mRing->negate(p);
  // Clear the column
  for (size_t r = 0; r < mBetti[n] - 1; ++r)
    {
      mDifferential[n]->get_entry(r, mBetti[n + 1] - 1, f);
      mDifferential[n]->row_op(r, mRing->mult(f, q), mBetti[n] - 1);
      if (0 < n)
        mDifferential[n - 1]->column_op(mBetti[n] - 1, mRing->mult(f, p), r);
      if (trace) mMorphisms[n]->column_op(mBetti[n] - 1, mRing->mult(f, p), r);
    }
  // Clear the row
  for (size_t c = 0; c < mBetti[n + 1] - 1; ++c)
    {
      mDifferential[n]->get_entry(mBetti[n] - 1, c, f);
      mDifferential[n]->column_op(c, mRing->mult(f, q), mBetti[n + 1] - 1);
      if (n < mDifferential.size() - 1)
        mDifferential[n + 1]->row_op(mBetti[n + 1] - 1, mRing->mult(f, p), c);
      if (trace)
        mMorphisms[n + 1]->column_op(c, mRing->mult(f, q), mBetti[n + 1] - 1);
    }
  --mBetti[n];
  --mBetti[n + 1];
}

References FLAG_TRACE_MORPHISMS, flags, MutableComplex::iterator::index(), mBetti, mRing, and p.

Referenced by prune_matrix().