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