many_move_tail fix

.gitignore

@@ -1,2 +1,8 @@
 build/
 ideas/
+*.json
+*.exe
+.vscode/
+*.log
+.DS_Store
+.github/

src/cell_tree_agent.hpp

@@ -73,7 +73,6 @@ Dir move_to_parent(Grid<Coord> const& cell_parents, Coord a) {
   throw "move_to_parent";
 }
 
-
 Unreachables cell_tree_unreachables(GameBase const& game, Grid<Step> const& dists) {
   auto cell_parents = cell_tree_parents(game.dimensions(), game.snake);
   auto can_move = [&](Coord from, Coord to, Dir dir) {
@@ -82,6 +81,38 @@ Unreachables cell_tree_unreachables(GameBase const& game, Grid<Step> const& dist
   return unreachables(can_move, game, dists);
 }
 
+bool should_use_cached_path_for_move_tail(const Unreachables& unreachable, Lookahead lookahead, const std::vector<Coord>& cached_path) {
+  if (lookahead == Lookahead::many_move_tail) {
+    if ((unreachable.any) && (unreachable.dist_to_farthest >= INT_MAX) && !cached_path.empty()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+Unreachables get_unreachables(
+    const GameBase& game, 
+    const std::vector<Coord>& path, 
+    Lookahead lookahead, 
+    const Grid<Step>& dists) {
+  if (lookahead == Lookahead::many_move_tail) {
+    auto after = after_moves(game, path, Lookahead::many_move_tail);
+    auto unreachable = cell_tree_unreachables(after, dists);
+
+    if (!unreachable.any) {
+      return unreachable;
+    } else {
+      auto after = after_moves(game, path, Lookahead::many_keep_tail);
+      auto unreachable = cell_tree_unreachables(after, dists);
+      return unreachable;
+    }
+  } else {
+    auto after = after_moves(game, path, lookahead);
+    auto unreachable = cell_tree_unreachables(after, dists);
+    return unreachable;
+  }
+}
+
 enum class DetourStrategy {
   none,
   any,
@@ -156,9 +187,14 @@ struct CellTreeAgent : Agent {
     }
 
     // Heuristic 3: prevent making parts of the grid unreachable
-    if (detour != DetourStrategy::none) {
-      auto after = after_moves(game, path, lookahead);
-      auto unreachable = cell_tree_unreachables(after, dists);
+    if (detour != DetourStrategy::none) {    
+      const Unreachables unreachable = get_unreachables(game, path, lookahead, dists);
+      if (should_use_cached_path_for_move_tail(unreachable, lookahead, cached_path)) {
+        pos2 = cached_path.back();
+        cached_path.pop_back();
+        return pos2 - pos;
+      }
+
       if (unreachable.any) {
         if (log) {
           Grid<bool> unreachable_grid(game.dimensions());

src/game_util.hpp

@@ -43,7 +43,9 @@ GameBase after_moves(GameBase const& game, std::vector<Coord> const& path, Looka
 struct Unreachables {
   bool any = false;
   Coord nearest = {-1,-1};
+  Coord farthest = {-1,-1};
   int dist_to_nearest = INT_MAX;
+  int dist_to_farthest = 0;
   Grid<bool> reachable;
 
   Unreachables(Grid<bool> const& reachable)
@@ -68,6 +70,10 @@ Unreachables unreachables(CanMove can_move, GameLike const& game, Grid<Step> con
         out.nearest = a;
         out.dist_to_nearest = dists[a].dist;
       }
+      if (dists[a].dist > out.dist_to_farthest) {  // track the farthest unreachable coordinate
+        out.farthest = a;
+        out.dist_to_farthest = dists[a].dist;
+      }
     }
   }
   return out;
@@ -171,7 +177,7 @@ Grid<Coord> random_spanning_tree(CoordRange dims, RNG& rng) {
     }
   }
   while (!queue.empty()) {
-    int i = rng.random(queue.size());
+    int i = rng.random(static_cast<int>(queue.size()));
     Coord parent = queue[i].first;
     Coord node   = queue[i].second;
     queue[i] = queue.back();

src/snake.cpp

@@ -449,7 +449,7 @@ Stats play_multiple_threaded(AgentGen make_agent, Config& config) {
     t.join();
   }
   // done
-  if (!config.quiet) std::cout << "\033[K\r";
+  if (!config.quiet) std::cout << std::endl;
   return stats;
 }
 
@@ -467,7 +467,7 @@ Stats play_multiple(AgentGen make_agent, Config& config) {
       std::cout << (i+1) << "/" << config.num_rounds << "  " << stats << "\033[K\r" << std::flush;
     }
   }
-  if (!config.quiet) std::cout << "\033[K\r";
+  if (!config.quiet) std::cout << std::endl;
   return stats;
 }