// all the nodes (with indexes lower than rank) reachable through the column elimination tree (etree) rooted at node k.
// Note: if the diagonal entry does not exist, then its contribution must be explicitly added,
// thus the trick with found_diag that permits to do one more iteration on the diagonal element if this one has not been found.
for (typename MatrixType::InnerIterator itp(m_pmat, col); itp || !found_diag; ++itp)
for (typename QRMatrixType::InnerIterator itp(m_pmat, col); itp || !found_diag; ++itp)
{
Index curIdx = nonzeroCol ;
if(itp) curIdx = itp.row();
if(nonzeroCol<n)
// Permute the triangular factor to put the 'dead' columns to the end
MatrixType tempR(m_R);
QRMatrixType tempR(m_R);
m_R = tempR * m_pivotperm;
// Update the column permutation