Method setNextKeys

kernel/linear_algebra/MinorProcessor.cc:169–203

}

bool MinorProcessor::setNextKeys(const int k)
{
  /* This method moves _minor to the next valid (k x k)-minor within
     _container. It returns true iff this is successful, i.e. iff
     _minor did not already encode the terminal (k x k)-minor. */
  if (_minor.compare(MinorKey(0, 0, 0, 0)) == 0)
  {
    /* This means that we haven't started yet. Thus, we are about
       to compute the first (k x k)-minor. */
    _minor.selectFirstRows(k, _container);
    _minor.selectFirstColumns(k, _container);
    return true;
  }
  else if (_minor.selectNextColumns(k, _container))
  {
    /* Here we were able to pick a next subset of columns
       within the same subset of rows. */
    return true;
  }
  else if (_minor.selectNextRows(k, _container))
  {
    /* Here we were not able to pick a next subset of columns
       within the same subset of rows. But we could pick a next
       subset of rows. We must hence reset the subset of columns: */
    _minor.selectFirstColumns(k, _container);
    return true;
  }
  else
  {
    /* We were neither able to pick a next subset
       of columns nor of rows. I.e., we have iterated through
       all sensible choices of subsets of rows and columns. */
    return false;
  }
}

bool MinorProcessor::isEntryZero (const int /*absoluteRowIndex*/,
                                  const int /*absoluteColumnIndex*/) const