board: compute move ray bitboards

README.md

@@ -67,6 +67,8 @@ cp external/lichess-bot/config.yml.example /tmp/vatu-config/config.yml
 docker build -f res/docker/Dockerfile -t vatu .
 # Run with the config folder mounted at /config.
 docker run -v /tmp/vatu-config:/config -ti vatu
+# In the container, use the following command:
+python lichess-bot.py --config /config/config.yml
 ```
 
 
@@ -74,10 +76,11 @@ docker run -v /tmp/vatu-config:/config -ti vatu
 TODO
 ----
 
-- Support time constraints
-- Proper unmake mechanism instead of allocating boards like there is no tomorrow
-- Precompute some pieces moves, maybe
-- Transposition table that does not actually slows search down
-- Check Zobrist hashes for previous point
-- Actual bitboard
-- Multithreading (never)
+- [X] Support time constraints
+- [ ] Unmake mechanism instead of allocating nodes like there is no tomorrow
+- [X] Precompute some pieces moves, maybe (done for knights)
+- [ ] Transposition table that does not actually slows search down
+- [ ] Check Zobrist hashes for previous point
+- [X] Actual bitboard
+- [ ] Some kind of move ordering could be great
+- [ ] Multithreading (never)

res/scripts/gen_knight_rays.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+"""Pre-compute knight ray bitboards for each square."""
+
+TEMPLATE = """\
+const KNIGHT_RAYS: [Bitboard; 64] = [
+{}
+];
+"""
+
+DIRS = [(1, 2), (2, 1), (2, -1), (1, -2), (-1, -2), (-2, -1), (-2, 1), (-1, 2)]
+
+def bit_pos(square):
+    return 1 << square
+
+def get_rays():
+    rays = []
+    for f in range(8):
+        for r in range(8):
+            bitboard = 0
+            for dir_f, dir_r in DIRS:
+                ray_f = f + dir_f
+                ray_r = r + dir_r
+                if ray_f < 0 or ray_f > 7 or ray_r < 0 or ray_r > 7:
+                    continue
+                bitboard |= bit_pos(ray_f * 8 + ray_r)
+            rays.append("    0b{:064b},".format(bitboard))
+    return rays
+
+print(TEMPLATE.format("\n".join(get_rays())))

src/analysis.rs

@@ -103,7 +103,7 @@ impl Analyzer {
 
         if self.debug {
             self.log(format!("Analyzing node:\n{}", &self.node));
-            let moves = self.node.get_player_moves(true);
+            let moves = self.node.get_player_legal_moves();
             self.log(format!("Legal moves: {}", Move::list_to_uci_string(&moves)));
             self.log(format!("Move time: {}", self.time_limit));
         }
@@ -119,7 +119,7 @@ impl Analyzer {
         } else {
             // If no best move could be found, checkmate is unavoidable; send the first legal move.
             self.log("Checkmate is unavoidable.".to_string());
-            let moves = rules::get_player_moves(&self.node.board, &self.node.game_state, true);
+            let moves = rules::get_player_moves(&self.node.board, &self.node.game_state, false);
             let m = if moves.len() > 0 { Some(moves[0].clone()) } else { None };
             self.report_best_move(m);
         }
@@ -185,7 +185,7 @@ impl Analyzer {
         }
 
         // Get negamax for playable moves.
-        let moves = node.get_player_moves(true);
+        let moves = node.get_player_legal_moves();
         let mut alpha = alpha;
         let mut best_score = MIN_F32;
         let mut best_move = None;

src/board.rs

@@ -137,6 +137,26 @@ pub fn sq_to_string(square: Square) -> String {
 /// Bitboard for color or piece bits.
 pub type Bitboard = u64;
 
+pub const FILE_A: i8 = 0;
+pub const FILE_B: i8 = 1;
+pub const FILE_C: i8 = 2;
+pub const FILE_D: i8 = 3;
+pub const FILE_E: i8 = 4;
+pub const FILE_F: i8 = 5;
+pub const FILE_G: i8 = 6;
+pub const FILE_H: i8 = 7;
+pub const NUM_FILES: usize = 8;
+
+pub const RANK_1: i8 = 0;
+pub const RANK_2: i8 = 1;
+pub const RANK_3: i8 = 2;
+pub const RANK_4: i8 = 3;
+pub const RANK_5: i8 = 4;
+pub const RANK_6: i8 = 5;
+pub const RANK_7: i8 = 6;
+pub const RANK_8: i8 = 7;
+pub const NUM_RANKS: usize = 8;
+
 pub const FILES: [Bitboard; 8] = [
     0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_11111111,
     0b00000000_00000000_00000000_00000000_00000000_00000000_11111111_00000000,
@@ -172,18 +192,99 @@ pub const fn after_on_file(file: i8, rank: i8) -> Bitboard {
     FILES[file as usize] & bits_after(file, rank)
 }
 
-/// Get the bitboard of squares on lower ranks of the `square` file.
-#[inline]
-pub const fn before_on_square_file(square: Square) -> Bitboard {
-    before_on_file(sq_file(square), sq_rank(square))
+/// Debug only: count positive bits of the bitboard.
+#[allow(dead_code)]
+pub(crate) fn count_bits(bitboard: Bitboard) -> u8 {
+    let mut bitboard = bitboard;
+    let mut count = 0;
+    while bitboard > 0 {
+        count += bitboard & 1;
+        bitboard >>= 1;
+    }
+    count as u8
 }
 
-/// Get the bitboard of squares on upper ranks of the `square` file.
-#[inline]
-pub const fn after_on_square_file(square: Square) -> Bitboard {
-    after_on_file(sq_file(square), sq_rank(square))
+/// Debug only: pretty print a bitboard
+#[allow(dead_code)]
+pub(crate) fn draw_bits(bitboard: Bitboard, f: &mut dyn std::io::Write) {
+    for rank in (0..8).rev() {
+        let mut rank_str = String::with_capacity(8);
+        for file in 0..8 {
+            rank_str.push(if bitboard & bit_pos(sq(file, rank)) == 0 { '.' } else { '1' });
+        }
+        writeln!(f, "{}", rank_str).unwrap();
+    }
 }
 
+// Generated by gen_knight_rays.py.
+/// Pre-computed knight rays.
+const KNIGHT_RAYS: [Bitboard; 64] = [
+    0b00000000_00000000_00000000_00000000_00000000_00000010_00000100_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_00000101_00001000_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_00001010_00010001_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_00010100_00100010_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_00101000_01000100_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_01010000_10001000_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_10100000_00010000_00000000,
+    0b00000000_00000000_00000000_00000000_00000000_01000000_00100000_00000000,
+    0b00000000_00000000_00000000_00000000_00000010_00000100_00000000_00000100,
+    0b00000000_00000000_00000000_00000000_00000101_00001000_00000000_00001000,
+    0b00000000_00000000_00000000_00000000_00001010_00010001_00000000_00010001,
+    0b00000000_00000000_00000000_00000000_00010100_00100010_00000000_00100010,
+    0b00000000_00000000_00000000_00000000_00101000_01000100_00000000_01000100,
+    0b00000000_00000000_00000000_00000000_01010000_10001000_00000000_10001000,
+    0b00000000_00000000_00000000_00000000_10100000_00010000_00000000_00010000,
+    0b00000000_00000000_00000000_00000000_01000000_00100000_00000000_00100000,
+    0b00000000_00000000_00000000_00000010_00000100_00000000_00000100_00000010,
+    0b00000000_00000000_00000000_00000101_00001000_00000000_00001000_00000101,
+    0b00000000_00000000_00000000_00001010_00010001_00000000_00010001_00001010,
+    0b00000000_00000000_00000000_00010100_00100010_00000000_00100010_00010100,
+    0b00000000_00000000_00000000_00101000_01000100_00000000_01000100_00101000,
+    0b00000000_00000000_00000000_01010000_10001000_00000000_10001000_01010000,
+    0b00000000_00000000_00000000_10100000_00010000_00000000_00010000_10100000,
+    0b00000000_00000000_00000000_01000000_00100000_00000000_00100000_01000000,
+    0b00000000_00000000_00000010_00000100_00000000_00000100_00000010_00000000,
+    0b00000000_00000000_00000101_00001000_00000000_00001000_00000101_00000000,
+    0b00000000_00000000_00001010_00010001_00000000_00010001_00001010_00000000,
+    0b00000000_00000000_00010100_00100010_00000000_00100010_00010100_00000000,
+    0b00000000_00000000_00101000_01000100_00000000_01000100_00101000_00000000,
+    0b00000000_00000000_01010000_10001000_00000000_10001000_01010000_00000000,
+    0b00000000_00000000_10100000_00010000_00000000_00010000_10100000_00000000,
+    0b00000000_00000000_01000000_00100000_00000000_00100000_01000000_00000000,
+    0b00000000_00000010_00000100_00000000_00000100_00000010_00000000_00000000,
+    0b00000000_00000101_00001000_00000000_00001000_00000101_00000000_00000000,
+    0b00000000_00001010_00010001_00000000_00010001_00001010_00000000_00000000,
+    0b00000000_00010100_00100010_00000000_00100010_00010100_00000000_00000000,
+    0b00000000_00101000_01000100_00000000_01000100_00101000_00000000_00000000,
+    0b00000000_01010000_10001000_00000000_10001000_01010000_00000000_00000000,
+    0b00000000_10100000_00010000_00000000_00010000_10100000_00000000_00000000,
+    0b00000000_01000000_00100000_00000000_00100000_01000000_00000000_00000000,
+    0b00000010_00000100_00000000_00000100_00000010_00000000_00000000_00000000,
+    0b00000101_00001000_00000000_00001000_00000101_00000000_00000000_00000000,
+    0b00001010_00010001_00000000_00010001_00001010_00000000_00000000_00000000,
+    0b00010100_00100010_00000000_00100010_00010100_00000000_00000000_00000000,
+    0b00101000_01000100_00000000_01000100_00101000_00000000_00000000_00000000,
+    0b01010000_10001000_00000000_10001000_01010000_00000000_00000000_00000000,
+    0b10100000_00010000_00000000_00010000_10100000_00000000_00000000_00000000,
+    0b01000000_00100000_00000000_00100000_01000000_00000000_00000000_00000000,
+    0b00000100_00000000_00000100_00000010_00000000_00000000_00000000_00000000,
+    0b00001000_00000000_00001000_00000101_00000000_00000000_00000000_00000000,
+    0b00010001_00000000_00010001_00001010_00000000_00000000_00000000_00000000,
+    0b00100010_00000000_00100010_00010100_00000000_00000000_00000000_00000000,
+    0b01000100_00000000_01000100_00101000_00000000_00000000_00000000_00000000,
+    0b10001000_00000000_10001000_01010000_00000000_00000000_00000000_00000000,
+    0b00010000_00000000_00010000_10100000_00000000_00000000_00000000_00000000,
+    0b00100000_00000000_00100000_01000000_00000000_00000000_00000000_00000000,
+    0b00000000_00000100_00000010_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_00001000_00000101_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_00010001_00001010_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_00100010_00010100_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_01000100_00101000_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_10001000_01010000_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_00010000_10100000_00000000_00000000_00000000_00000000_00000000,
+    0b00000000_00100000_01000000_00000000_00000000_00000000_00000000_00000000,
+];
+
 /// Board representation with color/piece bitboards.
 #[derive(Clone, PartialEq)]
 pub struct Board {
@@ -245,9 +346,7 @@ impl Board {
         }
         board
     }
-}
 
-impl Board {
     /// Get combined white/black pieces bitboard.
     #[inline]
     pub fn combined(&self) -> Bitboard {
@@ -330,16 +429,52 @@ impl Board {
         None
     }
 
-    /// Debug only: count number of pieces on board.
-    #[allow(dead_code)]  // Currently used in tests only.
-    pub(crate) fn num_pieces(&self) -> u8 {
-        let mut cbb = self.combined();
-        let mut count = 0;
-        while cbb > 0 {
-            count += cbb & 1;
-            cbb >>= 1;
+    pub fn get_bishop_rays(&self, square: Square, color: Color) -> Bitboard {
+        self.get_blockable_rays(square, color, &[(1, 1), (1, -1), (-1, -1), (-1, 1)])
     }
-        count as u8
+
+    pub fn get_rook_rays(&self, square: Square, color: Color) -> Bitboard {
+        self.get_blockable_rays(square, color, &[(1, 0), (0, 1), (-1, 0), (0, -1)])
+    }
+
+    pub fn get_queen_rays(&self, square: Square, color: Color) -> Bitboard {
+        self.get_blockable_rays(
+            square, color, &[(1, 0), (1, 1), (0, 1), (-1, 1), (-1, 0), (-1, -1), (0, -1), (1, -1)]
+        )
+    }
+
+    fn get_blockable_rays(&self,
+        square: Square,
+        color: Color,
+        directions: &[(i8, i8)]
+    ) -> Bitboard {
+        let mut rays_bb: Bitboard = 0;
+        let color_bb = self.by_color(color);
+        let enemy_bb = self.by_color(opposite(color));
+        for dir in directions {
+            let mut ray_f = sq_file(square);
+            let mut ray_r = sq_rank(square);
+            loop {
+                ray_f += dir.0;
+                ray_r += dir.1;
+                if ray_f < 0 || ray_f > 7 || ray_r < 0 || ray_r > 7 {
+                    break
+                }
+                let bp = bit_pos(sq(ray_f, ray_r));
+                if color_bb & bp != 0 {
+                    break
+                }
+                rays_bb |= bp;
+                if enemy_bb & bp != 0 {
+                    break
+                }
+            }
+        }
+        rays_bb
+    }
+
+    pub fn get_knight_rays(&self, square: Square, color: Color) -> Bitboard {
+        KNIGHT_RAYS[square as usize] & !self.by_color(color)
     }
 
     /// Debug only: write a text view of the board.
@@ -372,7 +507,7 @@ impl Board {
             }
             writeln!(f, "{} {}", rank + 1, rank_str).unwrap();
         }
-        write!(f, "  abcdefgh").unwrap();
+        writeln!(f, "  abcdefgh").unwrap();
     }
 }
 
@@ -410,35 +545,41 @@ mod tests {
     // Bitboard
 
     #[test]
-    fn test_before_on_square_file() {
-        // Only should the 4 lowest files for readability.
-        assert_eq!(before_on_square_file(A1), 0b00000000_00000000_00000000_00000000);
-        assert_eq!(before_on_square_file(A2), 0b00000000_00000000_00000000_00000001);
-        assert_eq!(before_on_square_file(A4), 0b00000000_00000000_00000000_00000111);
-        assert_eq!(before_on_square_file(A8), 0b00000000_00000000_00000000_01111111);
-        assert_eq!(before_on_square_file(B1), 0b00000000_00000000_00000000_00000000);
-        assert_eq!(before_on_square_file(C1), 0b00000000_00000000_00000000_00000000);
-        assert_eq!(before_on_square_file(C4), 0b00000000_00000111_00000000_00000000);
-        // 4 highest files.
-        assert_eq!(before_on_square_file(H4), 0b00000111_00000000_00000000_00000000 << 32);
-        assert_eq!(before_on_square_file(H7), 0b00111111_00000000_00000000_00000000 << 32);
-        assert_eq!(before_on_square_file(H8), 0b01111111_00000000_00000000_00000000 << 32);
+    fn test_count_bits() {
+        assert_eq!(count_bits(Board::new_empty().combined()), 0);
+        assert_eq!(count_bits(Board::new().combined()), 32);
     }
 
     #[test]
-    fn test_after_on_file() {
-        assert_eq!(after_on_square_file(A1), 0b00000000_00000000_00000000_11111110);
-        assert_eq!(after_on_square_file(A2), 0b00000000_00000000_00000000_11111100);
-        assert_eq!(after_on_square_file(A4), 0b00000000_00000000_00000000_11110000);
-        assert_eq!(after_on_square_file(A8), 0b00000000_00000000_00000000_00000000);
-        assert_eq!(after_on_square_file(B1), 0b00000000_00000000_11111110_00000000);
-        assert_eq!(after_on_square_file(C1), 0b00000000_11111110_00000000_00000000);
-        assert_eq!(after_on_square_file(C4), 0b00000000_11110000_00000000_00000000);
-        assert_eq!(after_on_square_file(C8), 0b00000000_00000000_00000000_00000000);
+    fn test_before_on_file() {
+        // Only should the 4 lowest files for readability.
+        assert_eq!(before_on_file(FILE_A, RANK_1), 0b00000000_00000000_00000000_00000000);
+        assert_eq!(before_on_file(FILE_A, RANK_2), 0b00000000_00000000_00000000_00000001);
+        assert_eq!(before_on_file(FILE_A, RANK_4), 0b00000000_00000000_00000000_00000111);
+        assert_eq!(before_on_file(FILE_A, RANK_8), 0b00000000_00000000_00000000_01111111);
+        assert_eq!(before_on_file(FILE_B, RANK_1), 0b00000000_00000000_00000000_00000000);
+        assert_eq!(before_on_file(FILE_C, RANK_1), 0b00000000_00000000_00000000_00000000);
+        assert_eq!(before_on_file(FILE_C, RANK_4), 0b00000000_00000111_00000000_00000000);
         // 4 highest files.
-        assert_eq!(after_on_square_file(H4), 0b11110000_00000000_00000000_00000000 << 32);
-        assert_eq!(after_on_square_file(H7), 0b10000000_00000000_00000000_00000000 << 32);
-        assert_eq!(after_on_square_file(H8), 0b00000000_00000000_00000000_00000000 << 32);
+        assert_eq!(before_on_file(FILE_H, RANK_4), 0b00000111_00000000_00000000_00000000 << 32);
+        assert_eq!(before_on_file(FILE_H, RANK_7), 0b00111111_00000000_00000000_00000000 << 32);
+        assert_eq!(before_on_file(FILE_H, RANK_8), 0b01111111_00000000_00000000_00000000 << 32);
+    }
+
+    #[test]
+    fn test_after_on_square_file() {
+        assert_eq!(after_on_file(FILE_A, RANK_1), 0b00000000_00000000_00000000_11111110);
+        assert_eq!(after_on_file(FILE_A, RANK_2), 0b00000000_00000000_00000000_11111100);
+        assert_eq!(after_on_file(FILE_A, RANK_4), 0b00000000_00000000_00000000_11110000);
+        assert_eq!(after_on_file(FILE_A, RANK_8), 0b00000000_00000000_00000000_00000000);
+        assert_eq!(after_on_file(FILE_B, RANK_1), 0b00000000_00000000_11111110_00000000);
+        assert_eq!(after_on_file(FILE_C, RANK_1), 0b00000000_11111110_00000000_00000000);
+        assert_eq!(after_on_file(FILE_C, RANK_4), 0b00000000_11110000_00000000_00000000);
+        assert_eq!(after_on_file(FILE_C, RANK_8), 0b00000000_00000000_00000000_00000000);
+        // 4 highest files.
+        assert_eq!(after_on_file(FILE_H, RANK_4), 0b11110000_00000000_00000000_00000000 << 32);
+        assert_eq!(after_on_file(FILE_H, RANK_7), 0b10000000_00000000_00000000_00000000 << 32);
+        assert_eq!(after_on_file(FILE_H, RANK_8), 0b00000000_00000000_00000000_00000000 << 32);
     }
 
     // Board
@@ -486,8 +627,95 @@ mod tests {
     }
 
     #[test]
-    fn test_num_pieces() {
-        assert_eq!(Board::new_empty().num_pieces(), 0);
-        assert_eq!(Board::new().num_pieces(), 32);
+    fn test_get_bishop_rays() {
+        let mut b = Board::new_empty();
+
+        // A bishop has maximum range when it's in a center square.
+        b.set_square(D4, WHITE, BISHOP);
+        let rays_bb = b.get_bishop_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 13);
+        // Going top-right.
+        assert!(rays_bb & bit_pos(E5) != 0);
+        assert!(rays_bb & bit_pos(F6) != 0);
+        assert!(rays_bb & bit_pos(G7) != 0);
+        assert!(rays_bb & bit_pos(H8) != 0);
+        // Going bottom-right.
+        assert!(rays_bb & bit_pos(E3) != 0);
+        assert!(rays_bb & bit_pos(F2) != 0);
+        assert!(rays_bb & bit_pos(G1) != 0);
+        // Going bottom-left.
+        assert!(rays_bb & bit_pos(C3) != 0);
+        assert!(rays_bb & bit_pos(B2) != 0);
+        assert!(rays_bb & bit_pos(A1) != 0);
+        // Going top-left.
+        assert!(rays_bb & bit_pos(C5) != 0);
+        assert!(rays_bb & bit_pos(B6) != 0);
+        assert!(rays_bb & bit_pos(A7) != 0);
+
+        // When blocking commit to one square with friendly piece, lose 2 moves.
+        b.set_square(B2, WHITE, PAWN);
+        let rays_bb = b.get_bishop_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 11);
+
+        // When blocking commit to one square with enemy piece, lose only 1 move.
+        b.set_square(B2, BLACK, PAWN);
+        let rays_bb = b.get_bishop_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 12);
+    }
+
+    #[test]
+    fn test_get_knight_moves() {
+        let mut b = Board::new_empty();
+
+        // A knight is never blocked; if it's in the center of the board,
+        // it can have up to 8 moves.
+        b.set_square(D4, WHITE, KNIGHT);
+        let rays_bb = b.get_knight_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 8);
+
+        // If on a side if has only 4 moves.
+        b.set_square(A4, WHITE, KNIGHT);
+        let rays_bb = b.get_knight_rays(A4, WHITE);
+        assert_eq!(count_bits(rays_bb), 4);
+
+        // And in a corner, only 2 moves.
+        b.set_square(A1, WHITE, KNIGHT);
+        let rays_bb = b.get_knight_rays(A1, WHITE);
+        assert_eq!(count_bits(rays_bb), 2);
+
+        // Add 2 friendly pieces and it is totally blocked.
+        b.set_square(B3, WHITE, PAWN);
+        b.set_square(C2, WHITE, PAWN);
+        let rays_bb = b.get_knight_rays(A1, WHITE);
+        assert_eq!(count_bits(rays_bb), 0);
+
+        // If one of those pieces is an enemy, it can be taken.
+        b.set_square(B3, BLACK, PAWN);
+        let rays_bb = b.get_knight_rays(A1, WHITE);
+        assert_eq!(count_bits(rays_bb), 1);
+    }
+
+    #[test]
+    fn test_get_rook_moves() {
+        let mut b = Board::new_empty();
+
+        b.set_square(D4, WHITE, ROOK);
+        let rays_bb = b.get_rook_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 14);
+        b.set_square(D6, BLACK, PAWN);
+        let rays_bb = b.get_rook_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 12);
+        b.set_square(D6, WHITE, PAWN);
+        let rays_bb = b.get_rook_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 11);
+    }
+
+    #[test]
+    fn test_get_queen_moves() {
+        let mut b = Board::new_empty();
+
+        b.set_square(D4, WHITE, QUEEN);
+        let rays_bb = b.get_queen_rays(D4, WHITE);
+        assert_eq!(count_bits(rays_bb), 14 + 13);
     }
 }

src/movement.rs

@@ -152,12 +152,12 @@ mod tests {
         assert!(b.is_empty(D4));
         assert_eq!(b.get_color_on(E6), WHITE);
         assert_eq!(b.get_piece_on(E6), KNIGHT);
-        assert_eq!(b.num_pieces(), 2);
+        assert_eq!(count_bits(b.combined()), 2);
         // Sack it with black knight
         Move::new(F4, E6).apply_to_board(&mut b);
         assert_eq!(b.get_color_on(E6), BLACK);
         assert_eq!(b.get_piece_on(E6), KNIGHT);
-        assert_eq!(b.num_pieces(), 1);
+        assert_eq!(count_bits(b.combined()), 1);
     }
 
     #[test]

src/node.rs

@@ -29,8 +29,8 @@ impl Node {
     }
 
     /// Return player moves from this node.
-    pub fn get_player_moves(&self, commit: bool) -> Vec<Move> {
-        rules::get_player_moves(&self.board, &self.game_state, commit)
+    pub fn get_player_legal_moves(&self) -> Vec<Move> {
+        rules::get_player_moves(&self.board, &self.game_state, false)
     }
 
     /// Compute stats for both players for this node.

src/rules.rs

@@ -53,17 +53,18 @@ impl std::fmt::Display for GameState {
 
 /// Get a list of moves for all pieces of the playing color.
 ///
-/// If `commit` is false, do not check for illegal moves. This is used
-/// to avoid endless recursion when checking if a P move is illegal,
-/// as it needs to check all possible following enemy moves, e.g. to
-/// see if P's king can be taken. Consider a call with true `commit` as
-/// a collection of attacked squares instead of legal move collection.
+/// If `pseudo_legal` is true, do not check for illegal moves. This is
+/// used to avoid endless recursion when checking if a P move is
+/// illegal, as it needs to check all possible following enemy moves,
+/// e.g. to see if P's king can be taken. Consider a call with true
+/// `pseudo_legal` as a collection of attacked squares instead of legal
+/// move collection.
 pub fn get_player_moves(
     board: &Board,
     game_state: &GameState,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
-    let mut moves = Vec::with_capacity(256);
+    let mut moves = Vec::with_capacity(32);
     for r in 0..8 {
         for f in 0..8 {
             let square = sq(f, r);
@@ -72,7 +73,7 @@ pub fn get_player_moves(
             }
             if board.get_color_on(square) == game_state.color {
                 moves.append(
-                    &mut get_piece_moves(board, game_state, square, game_state.color, commit)
+                    &mut get_piece_moves(board, game_state, square, game_state.color, pseudo_legal)
                 );
             }
         }
@@ -86,21 +87,21 @@ pub fn get_player_moves(
 /// of the piece on `square`; it could technically be found from the
 /// board but that would require an additional lookup and this function
 /// is always called in a context where the piece color is known.
-pub fn get_piece_moves(
+fn get_piece_moves(
     board: &Board,
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     match board.get_piece_on(square) {
-        PAWN => get_pawn_moves(board, game_state, square, color, commit),
-        BISHOP => get_bishop_moves(board, game_state, square, color, commit),
-        KNIGHT => get_knight_moves(board, game_state, square, color, commit),
-        ROOK => get_rook_moves(board, game_state, square, color, commit),
-        QUEEN => get_queen_moves(board, game_state, square, color, commit),
-        KING => get_king_moves(board, game_state, square, color, commit),
-        _ => vec!(),
+        PAWN => get_pawn_moves(board, game_state, square, color, pseudo_legal),
+        BISHOP => get_bishop_moves(board, game_state, square, color, pseudo_legal),
+        KNIGHT => get_knight_moves(board, game_state, square, color, pseudo_legal),
+        ROOK => get_rook_moves(board, game_state, square, color, pseudo_legal),
+        QUEEN => get_queen_moves(board, game_state, square, color, pseudo_legal),
+        KING => get_king_moves(board, game_state, square, color, pseudo_legal),
+        _ => { panic!("No piece on square.") },
     }
 }
 
@@ -109,7 +110,7 @@ fn get_pawn_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let (f, r) = (sq_file(square), sq_rank(square));
     let mut moves = vec!();
@@ -133,7 +134,7 @@ fn get_pawn_moves(
             if (dir > 0 && forward_r == POS_MAX) || (dir < 0 && forward_r == POS_MIN) {
                 m.promotion = Some(QUEEN)
             }
-            if can_register(commit, board, game_state, &m) {
+            if pseudo_legal || !is_illegal(board, game_state, &m) {
                 moves.push(m);
             }
         }
@@ -145,7 +146,7 @@ fn get_pawn_moves(
                 if !board.is_empty(diag) {
                     let diag_color = board.get_color_on(diag);
                     if let Some(m) = get_capture_move(color, square, diag_color, diag, true) {
-                        if can_register(commit, board, game_state, &m) {
+                        if pseudo_legal || !is_illegal(board, game_state, &m) {
                             moves.push(m);
                         }
                     }
@@ -158,7 +159,7 @@ fn get_pawn_moves(
                 if !board.is_empty(diag) {
                     let diag_color = board.get_color_on(diag);
                     if let Some(m) = get_capture_move(color, square, diag_color, diag, true) {
-                        if can_register(commit, board, game_state, &m) {
+                        if pseudo_legal || !is_illegal(board, game_state, &m) {
                             moves.push(m);
                         }
                     }
@@ -175,7 +176,7 @@ fn get_bishop_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let (f, r) = (sq_file(square), sq_rank(square));
     let mut views = [true; 4];  // Store diagonals where a piece blocks commit.
@@ -199,7 +200,7 @@ fn get_bishop_moves(
             }
             let ray_square = sq(ray_f, ray_r);
 
-            match get_move_type(board, game_state, square, ray_square, color, commit) {
+            match get_move_type(board, game_state, square, ray_square, color, pseudo_legal) {
                 MoveType::Simple(m) => { moves.push(m) }
                 MoveType::Capture(m) => { moves.push(m); views[dir] = false; }
                 MoveType::CantTakeFriend => { views[dir] = false; }
@@ -215,7 +216,7 @@ fn get_knight_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let (f, r) = (sq_file(square), sq_rank(square));
     let mut moves = Vec::with_capacity(8);
@@ -230,7 +231,7 @@ fn get_knight_moves(
         }
         let ray_square = sq(ray_f, ray_r);
 
-        match get_move_type(board, game_state, square, ray_square, color, commit) {
+        match get_move_type(board, game_state, square, ray_square, color, pseudo_legal) {
             MoveType::Simple(m) | MoveType::Capture(m) => moves.push(m),
             _ => {}
         }
@@ -243,7 +244,7 @@ fn get_rook_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let (f, r) = (sq_file(square), sq_rank(square));
     let mut moves = Vec::with_capacity(8);
@@ -266,7 +267,7 @@ fn get_rook_moves(
             }
             let ray_square = sq(ray_f, ray_r);
 
-            match get_move_type(board, game_state, square, ray_square, color, commit) {
+            match get_move_type(board, game_state, square, ray_square, color, pseudo_legal) {
                 MoveType::Simple(m) => { moves.push(m) }
                 MoveType::Capture(m) => { moves.push(m); views[dir] = false; }
                 MoveType::CantTakeFriend => { views[dir] = false; }
@@ -282,12 +283,12 @@ fn get_queen_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let mut moves = Vec::with_capacity(16);
     // Easy way to get queen moves, but may be a bit quicker if everything was rewritten here.
-    moves.append(&mut get_bishop_moves(board, game_state, square, color, commit));
-    moves.append(&mut get_rook_moves(board, game_state, square, color, commit));
+    moves.append(&mut get_bishop_moves(board, game_state, square, color, pseudo_legal));
+    moves.append(&mut get_rook_moves(board, game_state, square, color, pseudo_legal));
     moves
 }
 
@@ -296,7 +297,7 @@ fn get_king_moves(
     game_state: &GameState,
     square: Square,
     color: Color,
-    commit: bool,
+    pseudo_legal: bool,
 ) -> Vec<Move> {
     let (f, r) = (sq_file(square), sq_rank(square));
     let mut moves = Vec::with_capacity(8);
@@ -311,14 +312,14 @@ fn get_king_moves(
         }
         let ray_square = sq(ray_f, ray_r);
 
-        match get_move_type(board, game_state, square, ray_square, color, commit) {
+        match get_move_type(board, game_state, square, ray_square, color, pseudo_legal) {
             MoveType::Simple(m) | MoveType::Capture(m) => moves.push(m),
             _ => {}
         }
     }
 
-    // Stop here for uncommitted moves.
-    if !commit {
+    // Stop here for pseudo legal moves as castling is not considered along with them.
+    if pseudo_legal {
         return moves
     }
 
@@ -370,7 +371,7 @@ fn get_king_moves(
                 }
                 let castle = castling_side_mask & castling_color_mask;
                 let m = Move::get_castle_move(castle);
-                if can_register(commit, board, game_state, &m) {
+                if pseudo_legal || !is_illegal(board, game_state, &m) {
                     moves.push(m);
                 }
             }
@@ -390,7 +391,7 @@ fn get_move_type(
 ) -> MoveType {
     if board.is_empty(ray_square) {
         let m = Move::new(square, ray_square);
-        if can_register(commit, board, game_state, &m) {
+        if is_legal(commit, board, game_state, &m) {
             MoveType::Simple(m)
         } else {
             MoveType::CantRegister
@@ -398,7 +399,7 @@ fn get_move_type(
     } else {
         let ray_color = board.get_color_on(ray_square);
         if let Some(m) = get_capture_move(color, square, ray_color, ray_square, false) {
-            if can_register(commit, board, game_state, &m) {
+            if is_legal(commit, board, game_state, &m) {
                 MoveType::Capture(m)
             } else {
                 MoveType::CantRegister
@@ -420,15 +421,15 @@ enum MoveType {
     CantTakeFriend,
 }
 
-/// Return true if `commit` is false, or the move is not illegal,
+/// Return true if `pseudo_legal` is true, or the move is not illegal,
 ///
 /// Committing a move means that it can be safely played afterwards.
 /// Sometimes it is not what is needed to accept a move in a collection
 /// of moves, e.g. when simply checking if some moves would make a
 /// previous move illegal.
 #[inline]
-fn can_register(commit: bool, board: &Board, game_state: &GameState, m: &Move) -> bool {
-    !commit || !is_illegal(board, game_state, m)
+fn is_legal(pseudo_legal: bool, board: &Board, game_state: &GameState, m: &Move) -> bool {
+    pseudo_legal || !is_illegal(board, game_state, m)
 }
 
 /// Return a move from `square1` to `square2` if colors are opposite.
@@ -486,7 +487,7 @@ fn is_attacked(board: &Board, game_state: &GameState, square: Square) -> bool {
     let mut enemy_game_state = game_state.clone();
     enemy_game_state.color = opposite(game_state.color);
     // Do not attempt to commit moves, just check for attacked squares.
-    let enemy_moves = get_player_moves(board, &enemy_game_state, false);
+    let enemy_moves = get_player_moves(board, &enemy_game_state, true);
     for m in enemy_moves.iter() {
         if square == m.dest {
             return true
@@ -505,7 +506,7 @@ mod tests {
         let gs = GameState::new();
 
         // At first move, white has 16 pawn moves and 4 knight moves.
-        let moves = get_player_moves(&b, &gs, true);
+        let moves = get_player_moves(&b, &gs, false);
         assert_eq!(moves.len(), 20);
     }
 
@@ -516,12 +517,12 @@ mod tests {
 
         // Check that a pawn (here white queen's pawn) can move forward if the road is free.
         b.set_square(D3, WHITE, PAWN);
-        let moves = get_piece_moves(&b, &gs, D3, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, D3, WHITE, false);
         assert!(moves.len() == 1 && moves.contains(&Move::new(D3, D4)));
 
         // Check that a pawn (here white king's pawn) can move 2 square forward on first move.
         b.set_square(E2, WHITE, PAWN);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert_eq!(moves.len(), 2);
         assert!(moves.contains(&Move::new(E2, E3)));
         assert!(moves.contains(&Move::new(E2, E4)));
@@ -529,23 +530,23 @@ mod tests {
         // Check that a pawn cannot move forward if a piece is blocking its path.
         // 1. black pawn 2 square forward; only 1 square forward available from start pos.
         b.set_square(E4, BLACK, PAWN);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert!(moves.len() == 1 && moves.contains(&Move::new(E2, E3)));
         // 2. black pawn 1 square forward; no square available.
         b.set_square(E3, BLACK, PAWN);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert_eq!(moves.len(), 0);
         // 3. remove the e4 black pawn; the white pawn should not be able to jump above e3 pawn.
         b.clear_square(E4);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert_eq!(moves.len(), 0);
 
         // Check that a pawn can take a piece diagonally.
         b.set_square(F3, BLACK, PAWN);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert!(moves.len() == 1 && moves.contains(&Move::new(E2, F3)));
         b.set_square(D3, BLACK, PAWN);
-        let moves = get_piece_moves(&b, &gs, E2, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, E2, WHITE, false);
         assert_eq!(moves.len(), 2);
         assert!(moves.contains( &Move::new(E2, F3) ));
         assert!(moves.contains( &Move::new(E2, D3) ));
@@ -553,7 +554,7 @@ mod tests {
         // Check that a pawn moving to the last rank leads to queen promotion.
         // 1. by simply moving forward.
         b.set_square(A7, WHITE, PAWN);
-        let moves = get_piece_moves(&b, &gs, A7, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, A7, WHITE, false);
         assert!(moves.len() == 1 && moves.contains(&Move::new_promotion(A7, A8, QUEEN)));
     }
 
@@ -564,7 +565,7 @@ mod tests {
 
         // A bishop has maximum range when it's in a center square.
         b.set_square(D4, WHITE, BISHOP);
-        let moves = get_piece_moves(&b, &gs, D4, WHITE, true);
+        let moves = get_piece_moves(&b, &gs, D4, WHITE, false);
         assert_eq!(moves.len(), 13);
         // Going top-right.
         assert!(moves.contains(&Move::new(D4, E5)));
@@ -586,11 +587,11 @@ mod tests {
 
         // When blocking commit to one square with friendly piece, lose 2 moves.
         b.set_square(B2, WHITE, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 11);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 11);
 
         // When blocking commit to one square with enemy piece, lose only 1 move.
         b.set_square(B2, BLACK, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 12);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 12);
     }
 
     #[test]
@@ -601,20 +602,20 @@ mod tests {
         // A knight never has blocked commit; if it's in the center of the board, it can have up to
         // 8 moves.
         b.set_square(D4, WHITE, KNIGHT);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 8);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 8);
 
         // If on a side if has only 4 moves.
         b.set_square(A4, WHITE, KNIGHT);
-        assert_eq!(get_piece_moves(&b, &gs, A4, WHITE, true).len(), 4);
+        assert_eq!(get_piece_moves(&b, &gs, A4, WHITE, false).len(), 4);
 
         // And in a corner, only 2 moves.
         b.set_square(A1, WHITE, KNIGHT);
-        assert_eq!(get_piece_moves(&b, &gs, A1, WHITE, true).len(), 2);
+        assert_eq!(get_piece_moves(&b, &gs, A1, WHITE, false).len(), 2);
 
         // Add 2 friendly pieces and it is totally blocked.
         b.set_square(B3, WHITE, PAWN);
         b.set_square(C2, WHITE, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, A1, WHITE, true).len(), 0);
+        assert_eq!(get_piece_moves(&b, &gs, A1, WHITE, false).len(), 0);
     }
 
     #[test]
@@ -623,11 +624,11 @@ mod tests {
         let gs = GameState::new();
 
         b.set_square(D4, WHITE, ROOK);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 14);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 14);
         b.set_square(D6, BLACK, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 12);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 12);
         b.set_square(D6, WHITE, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 11);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 11);
     }
 
     #[test]
@@ -636,7 +637,7 @@ mod tests {
         let gs = GameState::new();
 
         b.set_square(D4, WHITE, QUEEN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 14 + 13);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 14 + 13);
     }
 
     #[test]
@@ -646,23 +647,23 @@ mod tests {
         // King can move 1 square in any direction.
         let mut b = Board::new_empty();
         b.set_square(D4, WHITE, KING);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 8);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 8);
         b.set_square(E5, WHITE, PAWN);
-        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, true).len(), 7);
+        assert_eq!(get_piece_moves(&b, &gs, D4, WHITE, false).len(), 7);
 
         // If castling is available, other moves are possible: 5 moves + 2 castles.
         let mut b = Board::new_empty();
         b.set_square(E1, WHITE, KING);
         b.set_square(A1, WHITE, ROOK);
         b.set_square(H1, WHITE, ROOK);
-        assert_eq!(get_piece_moves(&b, &gs, E1, WHITE, true).len(), 5 + 2);
+        assert_eq!(get_piece_moves(&b, &gs, E1, WHITE, false).len(), 5 + 2);
 
         // Castling works as well for black.
         gs.color = BLACK;
         b.set_square(E8, BLACK, KING);
         b.set_square(A8, BLACK, ROOK);
         b.set_square(H8, BLACK, ROOK);
-        assert_eq!(get_piece_moves(&b, &gs, E8, BLACK, true).len(), 5 + 2);
+        assert_eq!(get_piece_moves(&b, &gs, E8, BLACK, false).len(), 5 + 2);
     }
 
     #[test]
@@ -677,7 +678,7 @@ mod tests {
         // No castling available.
         gs.castling = 0;
         // 5 moves in absolute but only 2 are legal.
-        let all_wh_moves = get_piece_moves(&b, &gs, E1, WHITE, true);
+        let all_wh_moves = get_piece_moves(&b, &gs, E1, WHITE, false);
         assert_eq!(all_wh_moves.len(), 2);
     }
 

src/stats.rs

@@ -62,7 +62,7 @@ impl BoardStats {
         self.reset();
         let color = game_state.color;
         // Compute mobility for all pieces.
-        self.mobility = get_player_moves(board, game_state, true).len() as i32;
+        self.mobility = get_player_moves(board, game_state, false).len() as i32;
         // Compute amount of each piece.
         for file in 0..8 {
             for rank in 0..8 {
@@ -172,8 +172,6 @@ mod tests {
             mobility: 20,
         };
         let mut stats = BoardStats::new_from(&b, &gs);
-        eprintln!("{}", stats.0);
-        eprintln!("{}", stats.1);
         assert!(stats.0 == stats.1);
         assert!(stats.0 == initial_stats);