🐛 FIX: Minor fixes and tweaks

src/chess/movegen.rs

@@ -341,7 +341,11 @@ fn pawn_pushes(color: Color, from: Square, occ: Bitboard) -> Bitboard {
     pushes &= !occ;
 
     if pushes.any() && color.fold(from.rank() == Rank::_2, from.rank() == Rank::_7) {
-        let double = color.fold(from + 16, from - 16);
+        // fold is not appropriate here because it may overflow with the square maths
+        let double = match color {
+            Color::WHITE => from + 16,
+            Color::BLACK => from - 16,
+        };
         pushes.toggle(double);
         pushes &= !occ;
     }

src/state.rs

@@ -12,11 +12,7 @@ pub const NUMBER_FEATURES: usize = 768 * 3;
 #[derive(Clone)]
 pub struct State {
     board: Board,
-
-    // 101 should be enough to track 50-move rule, but some games in the dataset
-    // can go above this. Hence we add a little space
-    prev_state_hashes: ArrayVec<u64, 128>,
-
+    prev_state_hashes: ArrayVec<u64, 100>,
     prev_moves: [Option<Move>; 2],
 }
 
@@ -105,18 +101,19 @@ impl State {
 
         if is_pawn_move || capture.is_some() {
             self.prev_state_hashes.clear();
+        } else {
+            self.prev_state_hashes.push(self.hash());
         }
-        self.prev_state_hashes.push(self.hash());
 
         self.board.make_move(mov);
     }
 
     pub fn halfmove_counter(&self) -> usize {
-        self.prev_state_hashes.len() - 1
+        self.prev_state_hashes.len()
     }
 
     pub fn drawn_by_fifty_move_rule(&self) -> bool {
-        self.prev_state_hashes.len() > 100
+        self.prev_state_hashes.len() >= 100
     }
 
     pub fn is_repetition(&self) -> bool {