bitfield boards are workin great

2023-02-12 18:55:40 -05:00 · 2023-02-12 18:55:40 -05:00 · 8a61a3aedc
parent b2ea4fd2f3
commit 8a61a3aedc
4 changed files with 248 additions and 2 deletions
--- a/src/board.rs
+++ b/src/board.rs
@ -0,0 +1,164 @@
+// Bitpacked board:
+// One piece can be represented with 4 bits. Therefore, we can fit two pieces in one byte:
+// 0b0110_1110 -
+//   |          \
+//  Black king   \- White king
+// As there are 64 spaces on the board, we can pack the board into a 256-bit integer, and we use that as the index for transposition tables and such.
+// Boards are stored as two 128-bit bitfields, to make accessing them as efficient as possible.
+
+/*
+
+    a  b  c  d  e  f  g  h
+
+8   56 57 58 59 60 61 62 63   8 -+
+7   48 49 50 51 52 53 54 55   7  |- bf2
+6   40 41 42 43 44 45 46 47   6  |
+5   32 33 34 35 36 37 38 39   5 -+
+4   24 25 26 27 28 29 30 31   4 -+
+3   16 17 18 19 20 21 22 23   3  |
+2   8  9  10 11 12 13 14 15   2  |- bf1
+1   0  1  2  3  4  5  6  7    1 -+
+
+    a  b  c  d  e  f  g  h
+ */
+
+use crate::piece::{PieceColor, PieceType};
+
+type Boardfield = [u8; 32];
+pub trait BoardfieldOps {
+    fn new() -> Self where Self: Sized;
+    fn startpos() -> Self where Self: Sized;
+    fn get_pos(&self, boardloc: usize) -> u8;
+    fn set_pos(&mut self, boardloc: usize, piece: u8);
+}
+impl BoardfieldOps for Boardfield {
+    fn new() -> Self where Self: Sized {
+        [0u8; 32]
+    }
+
+    fn startpos() -> Self where Self: Sized {
+        let mut field = Self::new();
+
+        // a1-h1 (RNBQKBNR)
+        field.set_pos(0, PieceColor::White as u8 | PieceType::Rook as u8);
+        field.set_pos(1, PieceColor::White as u8 | PieceType::Knight as u8);
+        field.set_pos(2, PieceColor::White as u8 | PieceType::Bishop as u8);
+        field.set_pos(3, PieceColor::White as u8 | PieceType::Queen as u8);
+        field.set_pos(4, PieceColor::White as u8 | PieceType::King as u8);
+        field.set_pos(5, PieceColor::White as u8 | PieceType::Bishop as u8);
+        field.set_pos(6, PieceColor::White as u8 | PieceType::Knight as u8);
+        field.set_pos(7, PieceColor::White as u8 | PieceType::Rook as u8);
+
+        // a2-h2 (PPPPPPPP)
+        field.set_pos(8, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(9, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(10, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(11, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(12, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(13, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(14, PieceColor::White as u8 | PieceType::Pawn as u8);
+        field.set_pos(15, PieceColor::White as u8 | PieceType::Pawn as u8);
+
+        // a7-h7 (pppppppp)
+        field.set_pos(48, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(49, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(50, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(51, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(52, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(53, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(54, PieceColor::Black as u8 | PieceType::Pawn as u8);
+        field.set_pos(55, PieceColor::Black as u8 | PieceType::Pawn as u8);
+
+        // a8-h8 (RNBQKBNR)
+        field.set_pos(56, PieceColor::Black as u8 | PieceType::Rook as u8);
+        field.set_pos(57, PieceColor::Black as u8 | PieceType::Knight as u8);
+        field.set_pos(58, PieceColor::Black as u8 | PieceType::Bishop as u8);
+        field.set_pos(59, PieceColor::Black as u8 | PieceType::Queen as u8);
+        field.set_pos(60, PieceColor::Black as u8 | PieceType::King as u8);
+        field.set_pos(61, PieceColor::Black as u8 | PieceType::Bishop as u8);
+        field.set_pos(62, PieceColor::Black as u8 | PieceType::Knight as u8);
+        field.set_pos(63, PieceColor::Black as u8 | PieceType::Rook as u8);
+
+
+        field
+    }
+
+    fn get_pos(&self, boardloc: usize) -> u8 {
+        // bf1: 0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
+        // bf2: 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
+
+        if boardloc > 63 {
+            panic!("boardloc out of range");
+        }
+
+        let field = self[boardloc / 2];
+        let shift = 4 * (boardloc % 2);
+
+        (field & (0b1111 << shift)) >> shift
+    }
+
+    fn set_pos(&mut self, boardloc: usize, piece: u8) {
+        if boardloc > 63 {
+            panic!("boardloc out of range");
+        }
+
+        let field = self[boardloc / 2];
+        let shift = 4 * (boardloc % 2);
+
+        // clear out the field
+        let bf_cleared = field & !(0b1111 << shift);
+        // then shift over the actual piece data
+        let piece_shifted = piece << shift;
+        // then OR them together
+        let bf_new = bf_cleared | piece_shifted;
+
+        self[boardloc / 2] = bf_new;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::board::{Boardfield, BoardfieldOps};
+    use crate::piece::{PieceColor, PieceType};
+
+    #[test]
+    fn bitfield_board() {
+        let field = Boardfield::startpos();
+
+        assert_eq!(field.get_pos(0), PieceType::Rook as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(1), PieceType::Knight as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(2), PieceType::Bishop as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(3), PieceType::Queen as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(4), PieceType::King as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(5), PieceType::Bishop as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(6), PieceType::Knight as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(7), PieceType::Rook as u8 | PieceColor::White as u8);
+
+        assert_eq!(field.get_pos(8), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(9), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(10), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(11), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(12), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(13), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(14), PieceType::Pawn as u8 | PieceColor::White as u8);
+        assert_eq!(field.get_pos(15), PieceType::Pawn as u8 | PieceColor::White as u8);
+
+        assert_eq!(field.get_pos(48), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(49), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(50), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(51), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(52), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(53), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(54), PieceType::Pawn as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(55), PieceType::Pawn as u8 | PieceColor::Black as u8);
+
+        assert_eq!(field.get_pos(56), PieceType::Rook as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(57), PieceType::Knight as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(58), PieceType::Bishop as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(59), PieceType::Queen as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(60), PieceType::King as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(61), PieceType::Bishop as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(62), PieceType::Knight as u8 | PieceColor::Black as u8);
+        assert_eq!(field.get_pos(63), PieceType::Rook as u8 | PieceColor::Black as u8);
+    }
+}
--- a/src/main.rs
+++ b/src/main.rs
@ -5,6 +5,8 @@ use crate::uci::{uci_handle_command, UCIState};
 use spin::Mutex;

 pub mod uci;
+pub mod board;
+pub mod piece;

 pub const ENGINE_NAME: &str = "Bamboo";
 pub const ENGINE_VERSION: &str = "1.0";
--- a/src/piece.rs
+++ b/src/piece.rs
@ -0,0 +1,82 @@
+#[repr(u8)]
+pub enum PieceType {
+    Pawn = 1,
+    Knight = 2,
+    Bishop = 3,
+    Rook = 4,
+    Queen = 5,
+    King = 6
+}
+
+#[repr(u8)]
+pub enum PieceColor {
+    White = 8,
+    Black = 0
+}
+
+pub type Piece = u8;
+pub trait PieceOps {
+    fn is_white(value: u8) -> bool;
+
+    fn is_black(value: u8) -> bool;
+}
+impl PieceOps for Piece {
+    fn is_white(value: u8) -> bool {
+        if value < 8 {
+            false
+        } else {
+            value & PieceColor::White as u8 != 0
+        }
+    }
+
+    fn is_black(value: u8) -> bool {
+        !Self::is_white(value)
+    }
+}
+
+#[cfg(test)]
+mod piece_tests {
+    use crate::piece::{Piece, PieceColor, PieceOps, PieceType};
+
+    #[test]
+    fn piece_serialization() {
+        assert_eq!(PieceType::Pawn as u8 | PieceColor::White as u8, 0b1001);
+        assert_eq!(PieceType::Pawn as u8 | PieceColor::Black as u8, 0b0001);
+
+        assert_eq!(PieceType::Knight as u8 | PieceColor::White as u8, 0b1010);
+        assert_eq!(PieceType::Knight as u8 | PieceColor::Black as u8, 0b0010);
+
+        assert_eq!(PieceType::Bishop as u8 | PieceColor::White as u8, 0b1011);
+        assert_eq!(PieceType::Bishop as u8 | PieceColor::Black as u8, 0b0011);
+
+        assert_eq!(PieceType::Rook as u8 | PieceColor::White as u8, 0b1100);
+        assert_eq!(PieceType::Rook as u8 | PieceColor::Black as u8, 0b0100);
+
+        assert_eq!(PieceType::Queen as u8 | PieceColor::White as u8, 0b1101);
+        assert_eq!(PieceType::Queen as u8 | PieceColor::Black as u8, 0b0101);
+
+        assert_eq!(PieceType::King as u8 | PieceColor::White as u8, 0b1110);
+        assert_eq!(PieceType::King as u8 | PieceColor::Black as u8, 0b0110);
+    }
+
+    #[test]
+    fn piece_color_checks() {
+        assert!(!Piece::is_white(PieceType::Pawn as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::Pawn as u8 | PieceColor::White as u8));
+
+        assert!(!Piece::is_white(PieceType::Knight as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::Knight as u8 | PieceColor::White as u8));
+
+        assert!(!Piece::is_white(PieceType::Bishop as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::Bishop as u8 | PieceColor::White as u8));
+
+        assert!(!Piece::is_white(PieceType::Rook as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::Rook as u8 | PieceColor::White as u8));
+
+        assert!(!Piece::is_white(PieceType::Queen as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::Queen as u8 | PieceColor::White as u8));
+
+        assert!(!Piece::is_white(PieceType::King as u8 | PieceColor::Black as u8));
+        assert!(Piece::is_white(PieceType::King as u8 | PieceColor::White as u8));
+    }
+}
--- a/src/uci.rs
+++ b/src/uci.rs
@ -1,8 +1,6 @@
 use std::error::Error;
 use crate::{ENGINE_AUTHOR, ENGINE_NAME, ENGINE_VERSION};
 use std::fmt::Write;
-use std::fs;
-use std::path::Path;
 use std::sync::{Arc};
 use spin::Mutex;