perf: use iterator in bitboard serialization

3 files changed, 19 insertions, 13 deletions

diff --git a/src/bitboard.rs b/src/bitboard.rs
index 056822b..48a60d8 100644
--- a/src/bitboard.rs
+++ b/src/bitboard.rs
@@ -28,7 +28,7 @@ pub trait BitboardFns {
     fn bitscan_and_reset(&mut self) -> Square;
 
     /// Convert bitboard into the list of squares
-    fn serialize(self) -> Vec<Square>;
+    fn serialize(self) -> SquareIterator;
 
     /// Return bitboard shifted nort, no wrap occurs
     fn nort_one(self) -> Self;
@@ -109,12 +109,8 @@ impl BitboardFns for Bitboard {
         square
     }
 
-    fn serialize(mut self) -> Vec<Square> {
-        let mut serialized = Vec::with_capacity(64);
-        while self > 0 {
-            serialized.push(self.bitscan_and_reset());
-        }
-        serialized
+    fn serialize(self) -> SquareIterator {
+        SquareIterator(self)
     }
 
     fn nort_one(self) -> Self {
@@ -150,6 +146,18 @@ impl BitboardFns for Bitboard {
     }
 }
 
+pub struct SquareIterator (Bitboard);
+impl Iterator for SquareIterator {
+    type Item = Square;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.0 > 0 {
+            return Some(self.0.bitscan_and_reset());
+        }
+        None
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -184,7 +192,7 @@ mod tests {
     #[test]
     fn test_serialize_bitboard() {
         let bb = 1 << 4 | 1 << 15 | 1 << 60;
-        let serialized = bb.serialize();
+        let serialized = bb.serialize().collect::<Vec<_>>();
         assert_eq!(serialized[0], Square::from(4));
         assert_eq!(serialized[1], Square::from(15));
         assert_eq!(serialized[2], Square::from(60));
diff --git a/src/board/move_generation.rs b/src/board/move_generation.rs
index 98df056..0735309 100644
--- a/src/board/move_generation.rs
+++ b/src/board/move_generation.rs
@@ -99,7 +99,6 @@ impl Board {
             if player_pieces[Piece::King as usize].bitscan() == king_home_position {
                 for rook_square in player_pieces[Piece::Rook as usize]
                     .serialize()
-                    .iter()
                     .filter(|rook_square| rook_square.rank() == king_home_position.rank())
                 {
                     match rook_square.file() {
diff --git a/src/grossmeister/evaluation.rs b/src/grossmeister/evaluation.rs
index 6669545..b78c49a 100644
--- a/src/grossmeister/evaluation.rs
+++ b/src/grossmeister/evaluation.rs
@@ -190,7 +190,7 @@ impl Grossmeister {
                 }
                 _ => panic!("Unreachable")
             };
-            total + bitboard.serialize().iter().fold(0., |acc, &square| {
+            total + bitboard.serialize().fold(0., |acc, square| {
                 let pst_index = match color {
                     Color::White => square.mirror(),
                     Color::Black => square,
@@ -280,8 +280,8 @@ impl Grossmeister {
             Color::White => self.board.piece_sets[Piece::PawnBlack as usize],
         };
 
-        let pawn_attacked_squares = opponent_pawns.serialize().iter().fold(0u64, |acc, square| {
-            acc | self.board.attacks.pawn[color.flip() as usize][*square as usize]
+        let pawn_attacked_squares = opponent_pawns.serialize().fold(0u64, |acc, square| {
+            acc | self.board.attacks.pawn[color.flip() as usize][square as usize]
         });
 
         // Exclude squares controlled by enemy pawns from mobility
@@ -325,7 +325,6 @@ impl Grossmeister {
                         if *piece == king_home_position.to_bitboard() {
                             for rook_square in player_pieces[Piece::Rook as usize]
                                 .serialize()
-                                .iter()
                                 .filter(|rook_square| rook_square.rank() == king_home_position.rank())
                                 {
                                     match rook_square.file() {