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3 commits

Author SHA1 Message Date
Bruno BELANYI 602847e573 Refactor en-passant updates in 'ChessBoard'
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2024-04-13 23:03:11 +01:00
Bruno BELANYI 06b5751702 Add Zobrist hashing to 'ChessBoard' 2024-04-13 23:03:11 +01:00
Bruno BELANYI c850529257 Add zobrist hash tables 2024-04-13 23:03:11 +01:00
4 changed files with 1051 additions and 13 deletions

View file

@ -106,7 +106,7 @@ impl TryFrom<ChessBoardBuilder> for ChessBoard {
let total_plies = (turn_count - 1) * 2 + if side == Color::White { 0 } else { 1 };
let board = ChessBoard {
let mut board = ChessBoard {
piece_occupancy,
color_occupancy,
combined_occupancy,
@ -115,7 +115,9 @@ impl TryFrom<ChessBoardBuilder> for ChessBoard {
half_move_clock,
total_plies,
side,
hash: 0,
};
board.hash = board.compute_hash();
board.validate()?;
Ok(board)

View file

@ -1,6 +1,6 @@
use crate::movegen;
use super::{Bitboard, CastleRights, Color, File, Move, Piece, Rank, Square};
use super::{zobrist, Bitboard, CastleRights, Color, File, Move, Piece, Rank, Square};
mod builder;
pub use builder::*;
@ -29,6 +29,8 @@ pub struct ChessBoard {
total_plies: u32, // Should be plenty.
/// The current player turn.
side: Color,
/// Zobrist hash for the board.
hash: u64,
}
/// The state which can't be reversed when doing/un-doing a [Move].
@ -123,12 +125,42 @@ impl ChessBoard {
self.compute_checkers(self.current_player())
}
/// Return the Zobrist hash for the board.
#[inline(always)]
pub fn hash(&self) -> u64 {
self.hash
}
/// Compute the Zobrist hash for the board.
fn compute_hash(&self) -> u64 {
let mut res = 0;
// The side-to-move is only toggled on Black, and otherwise 0.
if self.current_player() == Color::Black {
res ^= zobrist::side_to_move();
}
if let Some(square) = self.en_passant() {
res ^= zobrist::en_passant(square.file());
}
res ^= zobrist::castling_rights(self.castle_rights);
for piece in Piece::iter() {
for color in Color::iter() {
for square in self.occupancy(piece, color) {
res ^= zobrist::moved_piece(color, piece, square);
}
}
}
res
}
/// Quickly add/remove a piece on the [Bitboard]s that are part of the [ChessBoard] state.
#[inline(always)]
fn xor(&mut self, color: Color, piece: Piece, square: Square) {
*self.piece_occupancy_mut(piece) ^= square;
*self.color_occupancy_mut(color) ^= square;
self.combined_occupancy ^= square;
self.hash ^= zobrist::moved_piece(color, piece, square);
}
/// Compute the change of [CastleRights] from moving/taking a piece.
@ -140,9 +172,22 @@ impl ChessBoard {
(Piece::King, _) => CastleRights::NoSide,
_ => return,
};
if new_rights != original {
*self.castle_rights_mut(color) = new_rights;
}
self.hash ^= zobrist::castling_rights(self.castle_rights);
*self.castle_rights_mut(color) = new_rights;
self.hash ^= zobrist::castling_rights(self.castle_rights);
}
fn update_en_passant(&mut self, en_passant: Option<Square>) {
self.hash ^= self
.en_passant()
.map(Square::file)
.map(zobrist::en_passant)
.unwrap_or(0);
self.hash ^= en_passant
.map(Square::file)
.map(zobrist::en_passant)
.unwrap_or(0);
self.en_passant = en_passant;
}
/// Play the given [Move], return a copy of the board with the resulting state.
@ -182,15 +227,16 @@ impl ChessBoard {
} else {
self.half_move_clock += 1;
}
if is_double_step {
let en_passant = if is_double_step {
let target_square = Square::new(
chess_move.destination().file(),
self.current_player().third_rank(),
);
self.en_passant = Some(target_square);
Some(target_square)
} else {
self.en_passant = None;
}
None
};
self.update_en_passant(en_passant);
self.update_castling(self.current_player(), move_piece, chess_move.start().file());
if let Some(piece) = captured_piece {
self.xor(opponent, piece, chess_move.destination());
@ -203,6 +249,7 @@ impl ChessBoard {
self.xor(self.current_player(), move_piece, chess_move.destination());
self.total_plies += 1;
self.side = !self.side;
self.hash ^= zobrist::side_to_move();
state
}
@ -212,8 +259,12 @@ impl ChessBoard {
#[inline(always)]
pub fn unplay_move(&mut self, chess_move: Move, previous: NonReversibleState) {
// Restore non-revertible state
self.castle_rights = previous.castle_rights;
self.en_passant = previous.en_passant;
if self.castle_rights != previous.castle_rights {
self.hash ^= zobrist::castling_rights(self.castle_rights);
self.hash ^= zobrist::castling_rights(previous.castle_rights);
self.castle_rights = previous.castle_rights;
}
self.update_en_passant(previous.en_passant);
self.half_move_clock = previous.half_move_clock;
let move_piece = Piece::iter()
@ -231,6 +282,7 @@ impl ChessBoard {
self.xor(!self.current_player(), move_piece, chess_move.start());
self.total_plies -= 1;
self.side = !self.side;
self.hash ^= zobrist::side_to_move();
}
/// Return true if the current state of the board looks valid, false if something is definitely
@ -421,7 +473,7 @@ impl ChessBoard {
/// "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1" FEN string
impl Default for ChessBoard {
fn default() -> Self {
Self {
let mut res = Self {
piece_occupancy: [
// King
Square::E1 | Square::E8,
@ -449,7 +501,10 @@ impl Default for ChessBoard {
half_move_clock: 0,
total_plies: 0,
side: Color::White,
}
hash: 0,
};
res.hash = res.compute_hash();
res
}
}

View file

@ -27,3 +27,6 @@ pub use rank::*;
pub mod square;
pub use square::*;
pub mod zobrist;
pub use zobrist::*;

978
src/board/zobrist.rs Normal file
View file

@ -0,0 +1,978 @@
// vim: foldmethod=marker
use super::{CastleRights, Color, File, Piece, Square};
type Hash = u64;
type EnPassantHashesType = [Hash; File::NUM_VARIANTS];
type CastlingHashesType = [[Hash; CastleRights::NUM_VARIANTS]; CastleRights::NUM_VARIANTS];
type PieceHashesType = [[[Hash; Square::NUM_VARIANTS]; Piece::NUM_VARIANTS]; Color::NUM_VARIANTS];
// region:sourcegen {{{
static BLACK_TO_MOVE: Hash = 64934999470316615;
static EN_PASSANT_HASHES: EnPassantHashesType = [
15459456780870779090,
13715484424881807779,
17718572936700675021,
14587996314750246637,
6677028061025754322,
13431580652429297681,
10925346160689749684,
14880644562654141744,
];
static CASTLING_HASHES: CastlingHashesType = [
[
1045274958981515586,
5392148996167941106,
14319713487061152634,
15981422700840256970,
],
[
11438431953559128973,
15165640837126078406,
9682374909294934964,
3746638112738371362,
],
[
13000030342210934332,
12451924122435870810,
1313989399406774579,
3743948554594595520,
],
[
1870378950492858291,
9613620781770901799,
1269273018318959782,
13819231333457059,
],
];
static PIECE_HASHES: PieceHashesType = [
[
[
15846310122511714997,
15565321750356536561,
3955109975630601799,
3742215252323203816,
11547754013648268969,
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10024580902115404844,
13461155397890310677,
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15012810188093697577,
14104378448227943386,
2251111072992350966,
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11590981376022443418,
9179472875549373335,
14751486135220696139,
14770349609267618816,
15794210789350854238,
8074262070310026138,
9807231349326167510,
17878059168006197756,
17020217056933277306,
8168773538726665343,
10540649568352071500,
16427391340497996472,
12836595115039890498,
13099644563326246186,
15638621634497942258,
2470341953153926693,
17228296995745787514,
12051949271418111299,
6735994487591330742,
9945519289001331203,
8761273995014635795,
1134254747965098098,
149908616240508937,
947996201587548444,
10050792753492913065,
6389723739863027484,
4054114923002827406,
12342721822805852545,
5603619551769484817,
1502519545082924996,
6629729157787095604,
6505804100374502042,
6551044912839567696,
17519353744604830596,
18262046566844392781,
8444802205465859643,
12318372284896528480,
16384512768777965260,
13872119029325166208,
551553250648480702,
12194494366773487659,
8903817316641024797,
2856044415979638552,
17626060259890197188,
6204959673627423824,
1196712911958154145,
2299761267346255152,
13890713223244418265,
13545009731095633715,
5588589786121212040,
],
[
13394976401688450359,
13458262092976265526,
6458425333551298230,
16068454197931831293,
18115196974811588644,
1945822552233231513,
18242988029158079236,
3508136533350863061,
9221855519679203686,
3417028073401167173,
13676868907893858811,
7891128041711130824,
4438008134626964309,
828375571561672767,
5211525107864059583,
9951912569669194338,
15797222372094286515,
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8459483884800911883,
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9494401018484929627,
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11903697614114951560,
],
[
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14501119344146015188,
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13599329138906238118,
17668204307700984669,
],
[
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],
[
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],
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],
],
];
// endregion:sourcegen }}}
/// Return the Zobrist hash for a [Piece] of a given [Color] on a given [Square].
pub fn moved_piece(color: Color, piece: Piece, square: Square) -> Hash {
PIECE_HASHES[color.index()][piece.index()][square.index()]
}
/// Return the Zobrist hash for the [CastleRights] for a [Color].
pub fn castling_rights(rights: [CastleRights; Color::NUM_VARIANTS]) -> Hash {
CASTLING_HASHES[rights[0].index()][rights[1].index()]
}
/// Return the Zobrist hash for the [File] of an en-passant capture.
pub fn en_passant(file: File) -> Hash {
EN_PASSANT_HASHES[file.index()]
}
/// Return the Zobrist hash for the given side-to-move being [Color::Black].
pub fn side_to_move() -> Hash {
BLACK_TO_MOVE
}
#[cfg(test)]
mod test {
use std::fmt::{Display, Write as _};
use super::*;
use crate::utils::SimpleRng;
fn split_twice<'a>(
text: &'a str,
start_marker: &str,
end_marker: &str,
) -> Option<(&'a str, &'a str, &'a str)> {
let (prefix, rest) = text.split_once(start_marker)?;
let (mid, suffix) = rest.split_once(end_marker)?;
Some((prefix, mid, suffix))
}
fn array_string<T: Display>(indent_level: usize, values: &[T]) -> String {
let inner = || -> Result<String, std::fmt::Error> {
let mut res = String::new();
writeln!(&mut res, "[")?;
for val in values {
let indent = (indent_level + 1) * 4;
writeln!(&mut res, "{:indent$}{},", "", val)?;
}
let indent = indent_level * 4;
write!(&mut res, "{:indent$}]", "")?;
Ok(res)
};
inner().unwrap()
}
#[test]
fn regen_zobrist_hashes() {
let mut rng = SimpleRng::new();
macro_rules! rng_iter {
($outer:expr, $( $inner:expr ),+) => {{
let mut res = vec![];
for _ in $outer {
res.push(rng_iter!($($inner),+));
}
res
}};
($iter:expr) => {{
let mut res = vec![];
for _ in $iter {
res.push(rng.gen());
}
res
}};
}
let black_to_move = rng.gen();
let en_passant = rng_iter!(File::iter());
let castle_rights = rng_iter!(CastleRights::iter(), CastleRights::iter());
let move_piece = rng_iter!(Color::iter(), Piece::iter(), Square::iter());
let original_text = std::fs::read_to_string(file!()).unwrap();
let new_text = {
let start_marker = "// region:sourcegen {{{\n";
let end_marker = "// endregion:sourcegen }}}\n";
let (prefix, _, suffix) =
split_twice(&original_text, start_marker, end_marker).unwrap();
let black_to_move = format!("static BLACK_TO_MOVE: Hash = {};\n", black_to_move);
let en_passant = format!(
"static EN_PASSANT_HASHES: EnPassantHashesType = {};\n",
array_string(0, &en_passant[..]),
);
let castle_rights = {
let strings: Vec<_> = castle_rights
.iter()
.map(|v| array_string(1, &v[..]))
.collect();
format!(
"static CASTLING_HASHES: CastlingHashesType = {};\n",
array_string(0, &strings[..])
)
};
let move_piece = {
let strings: Vec<_> = move_piece
.iter()
.map(|v| {
let strings: Vec<_> = v.iter().map(|v| array_string(2, &v[..])).collect();
array_string(1, &strings[..])
})
.collect();
format!(
"static PIECE_HASHES: PieceHashesType = {};\n",
array_string(0, &strings[..])
)
};
let hashes = format!("{black_to_move}\n{en_passant}\n{castle_rights}\n{move_piece}");
format!("{prefix}{start_marker}{hashes}{end_marker}{suffix}")
};
if new_text != original_text {
std::fs::write(file!(), new_text).unwrap();
panic!("source was not up-to-date")
}
}
}