QL Node4 geql2:          QL factor, level 2 Node1 QL Node1->Node4 Node3 geqlf:          QL factor Node1->Node3 Node7 {un,or}g2l:     step in ungql Node1->Node7 Node5 {un,or}gql:     generate explicit Q from geqlf Node1->Node5 Node8 {un,or}m2l:     step in unmql Node1->Node8 Node6 {un,or}mql:     multiply by Q from geqlf Node1->Node6 Node2 Orthogonal/unitary factors (QR, CS, etc.) Node2->Node1 .