graph/coloring: simplify dSaturExact
@@ -174,11 +174,13 @@ func (c dSaturColoring) uncolor(id int64) {
// returned as nil.
func dSaturExact(term Terminator, selector *saturationDegree, cand dSaturColoring, k, ub int, best map[int64]int) (newK int, colors map[int64]int, err error) {
if len(cand.uncolored) == 0 {
- if k < ub {
+ // In the published algorithm, this is guarded by k < ub,
+ // but dSaturExact is never called with k >= ub; in the
+ // initial call we have excluded cases where k == ub and
+ // it cannot be greater, and in the recursive call, we
+ // have already checked that k < ub.
return k, clone(cand.colors), nil
}
- return ub, best, nil
- }
if term != nil {
select {
