Add iterated local search to solver for more stable results

main.go

@@ -1066,13 +1066,9 @@ func handleSolve(db *sql.DB) http.HandlerFunc {
 			return currentScore
 		}
 
-		for restart := 0; restart < 50; restart++ {
+		randomPlacement := func() bool {
-			if restart == 0 {
-				copy(assignment, initialAssignment)
-			} else {
 			perm := rand.Perm(len(groupList))
 			for i := range roomCap { roomCap[i] = roomSize }
-				ok := true
 			for _, pi := range perm {
 				grp := groupList[pi]
 				placed := false
@@ -1098,16 +1094,48 @@ func handleSolve(db *sql.DB) http.HandlerFunc {
 					placed = true
 					break
 				}
-					if !placed {
+				if !placed { return false }
-						ok = false
-						break
 			}
+			return true
+		}
+
+		perturb := func(src []int, count int) {
+			copy(assignment, src)
+			indices := rand.Perm(len(uniqueGroups))
+			if count > len(indices) { count = len(indices) }
+			for _, gi := range indices[:count] {
+				grp := groups[uniqueGroups[gi]]
+				oldRoom := assignment[grp[0]]
+				rooms := rand.Perm(numRooms)
+				for _, room := range rooms {
+					if room == oldRoom { continue }
+					if roomCount(assignment, room)+len(grp) > roomSize { continue }
+					for _, m := range grp { assignment[m] = room }
+					if feasible(assignment) { break }
+					for _, m := range grp { assignment[m] = oldRoom }
 				}
-				if !ok {
-					copy(assignment, initialAssignment)
 			}
 		}
 
+		copy(assignment, initialAssignment)
+		s := hillClimb(assignment)
+		if s > bestScore {
+			bestScore = s
+			copy(bestAssignment, assignment)
+		}
+
+		for restart := 0; restart < 30; restart++ {
+			if randomPlacement() {
+				s := hillClimb(assignment)
+				if s > bestScore {
+					bestScore = s
+					copy(bestAssignment, assignment)
+				}
+			}
+		}
+
+		for ils := 0; ils < 200; ils++ {
+			perturb(bestAssignment, 2+rand.Intn(3))
 			s := hillClimb(assignment)
 			if s > bestScore {
 				bestScore = s