Do not redo steps that would not improve the solution

src/main.rs

@@ -36,18 +36,25 @@ fn main() {
                   MIN_WEIGHT_SCORE, MAX_WEIGHT_SCORE, DB_CHOICE_PROBABILITY);
         population::populate_using_db(&mut layout, &mut rng, &db, MIN_WEIGHT_SCORE, MAX_WEIGHT_SCORE, DB_CHOICE_PROBABILITY);
         eprintln!("Finished random init, price: {}, houses: {}", layout.price(), layout.houses().len());
+        let mut last_improved_step = -1;
         loop {
-            let mut improved = false;
+            if last_improved_step == 1 {
+                break;
+            }
             eprintln!("Starting moving individual houses...");
             if optimization::improve_move_individual_houses(&mut layout, &mut rng) {
                 dump_layout(&layout, &mut best_price, seed);
-                improved = true;
+                last_improved_step = 1;
             }
             eprintln!("Finished moving individual houses...");
+
+            if last_improved_step == 2 {
+                break;
+            }
             eprintln!("Starting pairwise house merge...");
             if optimization::improve_merge_pairwise(&mut layout) {
                 dump_layout(&layout, &mut best_price, seed);
-                improved = true;
+                last_improved_step = 2;
             }
             eprintln!("Finished pairwise house merge");
             //eprintln!("Starting pairwise house move...");
@@ -56,9 +63,6 @@ fn main() {
             //    improved = true;
             //}
             //eprintln!("Finished pairwise house move");
-            if !improved {
-                break;
-            }
         }
         db.add_layout(&layout.houses(), true).expect("Failed to insert into DB");
     }