The FOCUS procedure is greedy and will not yield globally optimal results. Global optimal reordering of the rows and columns of a grid can be recasted into a TSP (travelling salesman problem), in particular, as a Equality Generalized Traveling Salesman Problem (E-GTPS), i.e. a TSP including additional constraints, which is known to be NP-hard.
The FOCUS procedure is greedy and will not yield globally optimal results. Global optimal reordering of the rows and columns of a grid can be recasted into a TSP (travelling salesman problem), in particular, as a Equality Generalized Traveling Salesman Problem (E-GTPS), i.e. a TSP including additional constraints, which is known to be NP-hard.