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[board] Implement a PositionBuilder; refactor piece bitboards into a PieceBitBoards struct

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This makes Position immutable, even if declared mut. I think this will also make
it easier to build positions going forward.

Moving to a PieceBitBoards struct also required a lot of places that return owned
BitBoards to return refs. This is basically fine except for adding a few more &
here and there.

This was a huge refactoring project. All the move generators and a bunch of
BitBoard stuff needed to be updated.
This commit is contained in:
Eryn Wells 2024-01-19 18:08:41 -08:00
parent 939fac80d7
commit 24cce95a88
17 changed files with 472 additions and 381 deletions
Download patch file Download diff file Expand all files Collapse all files

83
board/src/position/builders.rs Normal file
View file

@ -0,0 +1,83 @@
// Eryn Wells <eryn@erynwells.me>
use super::{flags::Flags, piece_sets::PieceBitBoards};
use crate::{
piece::{PlacedPiece, Shape},
square::Rank,
BitBoard, Color, MakeMoveError, Move, Piece, Position, Square,
};
use std::collections::BTreeMap;
#[derive(Clone)]
pub struct Builder {
player_to_move: Color,
flags: Flags,
pieces: BTreeMap<Square, Piece>,
kings: [Square; 2],
}
impl Builder {
pub fn new() -> Self {
Self::default()
}
pub fn place_piece(&mut self, piece: PlacedPiece) -> &mut Self {
let square = piece.square();
if piece.shape() == Shape::King {
let color_index: usize = piece.color() as usize;
self.pieces.remove(&self.kings[color_index]);
self.kings[color_index] = square;
}
self.pieces.insert(square, piece.piece());
self
}
pub fn build(&self) -> Position {
let pieces = PieceBitBoards::from_iter(
self.pieces
.iter()
.map(PlacedPiece::from)
.filter(Self::is_piece_placement_valid),
);
Position::new(self.player_to_move, self.flags, pieces, None)
}
}
impl Builder {
fn is_piece_placement_valid(piece: &PlacedPiece) -> bool {
if piece.shape() == Shape::Pawn {
// Pawns cannot be placed on the first (back) rank of their side,
// and cannot be placed on the final rank without a promotion.
let rank = piece.square().rank();
return rank != Rank::One && rank != Rank::Eight;
}
true
}
}
impl Default for Builder {
fn default() -> Self {
let pieces = BTreeMap::from_iter([
(
Square::KING_STARTING_SQUARES[Color::White as usize],
piece!(White King),
),
(
Square::KING_STARTING_SQUARES[Color::Black as usize],
piece!(Black King),
),
]);
Self {
player_to_move: Color::White,
flags: Flags::default(),
pieces: pieces,
kings: Square::KING_STARTING_SQUARES,
}
}
}

12
board/src/position/diagram_formatter.rs
View file

@ -42,7 +42,7 @@ impl<'a> fmt::Display for DiagramFormatter<'a> {
mod tests {
use super::*;
use crate::piece::{Color, Piece};
use crate::Position;
use crate::{Position, PositionBuilder};
#[test]
fn empty() {
@ -53,13 +53,9 @@ mod tests {
#[test]
fn one_king() {
let mut pos = Position::empty();
pos.place_piece(
Piece::king(Color::Black),
Square::from_algebraic_str("h3").expect("h3"),
)
.expect("Unable to place piece");
let pos = PositionBuilder::new()
.place_piece(piece!(Black King on H3))
.build();
let diagram = DiagramFormatter(&pos);
println!("{}", diagram);
}

3
board/src/position/mod.rs
View file

@ -1,10 +1,13 @@
// Eryn Wells <eryn@erynwells.me>
mod builders;
mod diagram_formatter;
mod flags;
mod piece_sets;
mod pieces;
mod position;
pub use builders::Builder as PositionBuilder;
pub use diagram_formatter::DiagramFormatter;
pub use pieces::Pieces;
pub use position::Position;

149
board/src/position/piece_sets.rs Normal file
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@ -0,0 +1,149 @@
// Eryn Wells <eryn@erynwells.me>
use crate::{
piece::{Piece, PlacedPiece},
BitBoard, Color, Square,
};
#[derive(Debug, Eq, PartialEq)]
pub enum PlacePieceStrategy {
Replace,
PreserveExisting,
}
#[derive(Debug, Eq, PartialEq)]
pub enum PlacePieceError {
ExisitingPiece,
}
impl Default for PlacePieceStrategy {
fn default() -> Self {
Self::Replace
}
}
#[derive(Clone, Debug, Default, Eq, Hash, PartialEq)]
pub(super) struct PieceBitBoards {
by_color: ByColor,
by_color_and_shape: ByColorAndShape,
}
#[derive(Clone, Debug, Default, Eq, Hash, PartialEq)]
struct ByColor(BitBoard, [BitBoard; 2]);
#[derive(Clone, Debug, Default, Eq, Hash, PartialEq)]
struct ByColorAndShape([[BitBoard; 6]; 2]);
impl PieceBitBoards {
pub(super) fn new(pieces: [[BitBoard; 6]; 2]) -> Self {
let white_pieces = pieces[Color::White as usize]
.iter()
.fold(BitBoard::empty(), std::ops::BitOr::bitor);
let black_pieces = pieces[Color::White as usize]
.iter()
.fold(BitBoard::empty(), std::ops::BitOr::bitor);
let all_pieces = white_pieces | black_pieces;
Self {
by_color: ByColor(all_pieces, [white_pieces, black_pieces]),
by_color_and_shape: ByColorAndShape(pieces),
}
}
pub(super) fn all_pieces(&self) -> &BitBoard {
self.by_color.all()
}
pub(super) fn all_pieces_of_color(&self, color: Color) -> &BitBoard {
self.by_color.bitboard(color)
}
pub(super) fn bitboard_for_color(&self, color: Color) -> &BitBoard {
self.by_color.bitboard(color)
}
pub(super) fn bitboard_for_color_mut(&mut self, color: Color) -> &mut BitBoard {
self.by_color.bitboard_mut(color)
}
pub(super) fn bitboard_for_piece(&self, piece: Piece) -> &BitBoard {
self.by_color_and_shape.bitboard_for_piece(piece)
}
pub(super) fn bitboard_for_piece_mut(&mut self, piece: Piece) -> &mut BitBoard {
self.by_color_and_shape.bitboard_for_piece_mut(piece)
}
pub(super) fn place_piece(&mut self, piece: PlacedPiece) -> Result<(), PlacePieceError> {
self.place_piece_with_strategy(piece, Default::default())
}
pub(super) fn place_piece_with_strategy(
&mut self,
piece: PlacedPiece,
strategy: PlacePieceStrategy,
) -> Result<(), PlacePieceError> {
let color = piece.color();
let square = piece.square();
if self.by_color.bitboard(color).is_set(piece.square()) {
match strategy {
PlacePieceStrategy::Replace => todo!(),
PlacePieceStrategy::PreserveExisting => {
return Err(PlacePieceError::ExisitingPiece)
}
}
}
self.by_color.set_square(square, color);
self.bitboard_for_piece_mut(piece.piece())
.set_square(square);
Ok(())
}
}
impl FromIterator<PlacedPiece> for PieceBitBoards {
fn from_iter<T: IntoIterator<Item = PlacedPiece>>(iter: T) -> Self {
let mut pieces = Self::default();
for piece in iter {
let _ = pieces.place_piece(piece);
}
pieces
}
}
impl ByColor {
fn all(&self) -> &BitBoard {
&self.0
}
pub(super) fn bitboard(&self, color: Color) -> &BitBoard {
&self.1[color as usize]
}
pub(super) fn bitboard_mut(&mut self, color: Color) -> &mut BitBoard {
&mut self.1[color as usize]
}
fn set_square(&mut self, square: Square, color: Color) {
self.0.set_square(square);
self.1[color as usize].set_square(square)
}
}
impl ByColorAndShape {
fn bitboard_for_piece(&self, piece: Piece) -> &BitBoard {
&self.0[piece.color() as usize][piece.shape() as usize]
}
fn bitboard_for_piece_mut(&mut self, piece: Piece) -> &mut BitBoard {
&mut self.0[piece.color() as usize][piece.shape() as usize]
}
fn set_square(&mut self, square: Square, piece: Piece) {
self.bitboard_for_piece_mut(piece).set_square(square);
}
}

58
board/src/position/pieces.rs
View file

@ -38,7 +38,7 @@ impl<'a> Iterator for Pieces<'a> {
}
let mut current_shape: Option<Shape> = None;
let mut next_nonempty_bitboard: Option<BitBoard> = None;
let mut next_nonempty_bitboard: Option<&BitBoard> = None;
while let Some(shape) = self.shape_iterator.next() {
let piece = Piece::new(self.color, *shape);
@ -76,15 +76,10 @@ impl<'a> Iterator for Pieces<'a> {
mod tests {
use super::*;
use crate::piece::{Color, Piece, Shape};
use crate::Position;
use crate::Square;
use crate::{Position, PositionBuilder};
use std::collections::HashSet;
fn place_piece_in_position(pos: &mut Position, piece: Piece, sq: Square) {
pos.place_piece(piece, sq)
.expect("Unable to place {piece:?} queen on {sq}");
}
#[test]
fn empty() {
let pos = Position::empty();
@ -94,40 +89,45 @@ mod tests {
#[test]
fn one() {
let sq = Square::E4;
let mut pos = Position::empty();
place_piece_in_position(&mut pos, Piece::new(Color::White, Shape::Queen), Square::E4);
println!("{:?}", &pos);
let pos = PositionBuilder::new()
.place_piece(piece!(White Queen on E4))
.build();
println!("{:#?}", &pos);
let mut pieces = pos.pieces(Color::White);
assert_eq!(
pieces.next(),
Some(PlacedPiece::new(Piece::new(Color::White, Shape::Queen), sq))
);
assert_eq!(pieces.next(), Some(piece!(White Queen on E4)));
assert_eq!(pieces.next(), Some(piece!(White King on E1)));
assert_eq!(pieces.next(), None);
}
#[test]
fn multiple_pieces() {
let mut pos = Position::empty();
place_piece_in_position(&mut pos, Piece::new(Color::White, Shape::Queen), Square::E4);
place_piece_in_position(&mut pos, Piece::new(Color::White, Shape::King), Square::E1);
place_piece_in_position(&mut pos, Piece::new(Color::White, Shape::Pawn), Square::B2);
place_piece_in_position(&mut pos, Piece::new(Color::White, Shape::Pawn), Square::C2);
println!("{:?}", &pos);
let pos = PositionBuilder::new()
.place_piece(piece!(White Queen on E4))
.place_piece(piece!(White King on A1))
.place_piece(piece!(White Pawn on B2))
.place_piece(piece!(White Pawn on C2))
.build();
println!("{}", crate::position::DiagramFormatter::new(&pos));
let expected_placed_pieces = HashSet::from([
PlacedPiece::new(Piece::new(Color::White, Shape::Queen), Square::E4),
PlacedPiece::new(Piece::new(Color::White, Shape::King), Square::E1),
PlacedPiece::new(Piece::new(Color::White, Shape::Pawn), Square::B2),
PlacedPiece::new(Piece::new(Color::White, Shape::Pawn), Square::C2),
piece!(White Queen on E4),
piece!(White King on A1),
piece!(White Pawn on B2),
piece!(White Pawn on C2),
]);
let placed_pieces = HashSet::from_iter(pos.pieces(Color::White));
assert_eq!(placed_pieces, expected_placed_pieces);
assert_eq!(
placed_pieces,
expected_placed_pieces,
"{:#?}",
placed_pieces
.symmetric_difference(&expected_placed_pieces)
.into_iter()
.map(|pp| format!("{}", pp))
.collect::<Vec<String>>()
);
}
}

180
board/src/position/position.rs
View file

@ -1,11 +1,11 @@
// Eryn Wells <eryn@erynwells.me>
use super::{flags::Flags, Pieces};
use super::{flags::Flags, piece_sets::PieceBitBoards, Pieces};
use crate::{
move_generator::Moves,
piece::{Color, Piece, PiecePlacementError, PlacedPiece, Shape},
piece::{Color, Piece, PlacedPiece, Shape},
sight::Sight,
BitBoard, Square,
BitBoard, Move, Square,
};
use std::cell::OnceCell;
@ -21,15 +21,8 @@ pub(crate) enum BoardSide {
pub struct Position {
color_to_move: Color,
flags: Flags,
/// Composite bitboards for all the pieces of a particular color.
pieces_per_color: [BitBoard; 2],
/// Bitboards representing positions of particular piece types per color.
pieces_per_type: [[BitBoard; 6]; 2],
pieces: PieceBitBoards,
en_passant_square: Option<Square>,
sight: [OnceCell<BitBoard>; 2],
}
@ -38,32 +31,14 @@ impl Position {
Position {
color_to_move: Color::White,
flags: Default::default(),
pieces_per_color: [BitBoard::empty(); 2],
pieces_per_type: [
[
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
],
[
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
BitBoard::empty(),
],
],
pieces: PieceBitBoards::default(),
en_passant_square: None,
sight: [OnceCell::new(), OnceCell::new()],
}
}
/// Return a starting position.
pub fn starting() -> Position {
pub fn starting() -> Self {
let white_pieces = [
BitBoard::new(0x00FF000000000000),
BitBoard::new(0x4200000000000000),
@ -82,19 +57,19 @@ impl Position {
BitBoard::new(0x0008),
];
Position {
Self {
color_to_move: Color::White,
flags: Default::default(),
pieces_per_color: [
white_pieces.iter().fold(BitBoard::empty(), |a, b| a | *b),
black_pieces.iter().fold(BitBoard::empty(), |a, b| a | *b),
],
pieces_per_type: [white_pieces, black_pieces],
flags: Flags::default(),
pieces: PieceBitBoards::new([white_pieces, black_pieces]),
en_passant_square: None,
sight: [OnceCell::new(), OnceCell::new()],
}
}
pub fn player_to_move(&self) -> Color {
self.color_to_move
}
/// Returns true if the player has the right to castle on the given side of
/// the board.
///
@ -112,39 +87,28 @@ impl Position {
self.flags.player_has_right_to_castle(color, side)
}
pub fn place_piece(&mut self, piece: Piece, square: Square) -> Result<(), PiecePlacementError> {
let type_bb = self.bitboard_for_piece_mut(piece);
if type_bb.is_set(square) {
return Err(PiecePlacementError::ExistsOnSquare);
}
type_bb.set_square(square);
self.bitboard_for_color_mut(piece.color())
.set_square(square);
Ok(())
}
pub fn moves(&self) -> Moves {
Moves::new(self, self.color_to_move)
}
/// Return a BitBoard representing the set of squares containing a piece.
#[inline]
pub(crate) fn occupied_squares(&self) -> BitBoard {
self.pieces_per_color[Color::White as usize] | self.pieces_per_color[Color::Black as usize]
pub(crate) fn occupied_squares(&self) -> &BitBoard {
&self.pieces.all_pieces()
}
#[inline]
pub(crate) fn friendly_pieces(&self) -> BitBoard {
self.bitboard_for_color(self.color_to_move)
pub(crate) fn friendly_pieces(&self) -> &BitBoard {
self.pieces.all_pieces_of_color(self.color_to_move)
}
#[inline]
pub(crate) fn opposing_pieces(&self) -> BitBoard {
self.bitboard_for_color(self.color_to_move.other())
pub(crate) fn opposing_pieces(&self) -> &BitBoard {
self.pieces.all_pieces_of_color(self.color_to_move.other())
}
pub(crate) fn all_pieces(&self) -> (&BitBoard, &BitBoard) {
(self.friendly_pieces(), self.opposing_pieces())
}
/// Return a BitBoard representing the set of squares containing a piece.
@ -154,28 +118,11 @@ impl Position {
!self.occupied_squares()
}
pub(crate) fn bitboard_for_piece(&self, piece: Piece) -> BitBoard {
self.pieces_per_type[piece.color() as usize][piece.shape() as usize]
}
fn bitboard_for_piece_mut(&mut self, piece: Piece) -> &mut BitBoard {
&mut self.pieces_per_type[piece.color() as usize][piece.shape() as usize]
}
pub(crate) fn bitboard_for_color(&self, color: Color) -> BitBoard {
self.pieces_per_color[color as usize]
}
fn bitboard_for_color_mut(&mut self, color: Color) -> &mut BitBoard {
&mut self.pieces_per_color[color as usize]
}
pub fn piece_on_square(&self, sq: Square) -> Option<PlacedPiece> {
for color in Color::iter() {
for shape in Shape::iter() {
let piece = Piece::new(color, *shape);
let bb = self.bitboard_for_piece(piece);
if bb.is_set(sq) {
if self.pieces.bitboard_for_piece(piece).is_set(sq) {
return Some(PlacedPiece::new(piece, sq));
}
}
@ -206,11 +153,49 @@ impl Position {
}
fn king_square(&self) -> Square {
self.bitboard_for_piece(Piece::king(self.color_to_move))
self.pieces
.bitboard_for_piece(Piece::king(self.color_to_move))
.occupied_squares()
.next()
.unwrap()
}
pub(crate) fn move_is_legal(&self, mv: Move) -> bool {
true
}
}
// crate::position methods
impl Position {
pub(super) fn new(
player_to_move: Color,
flags: Flags,
pieces: PieceBitBoards,
en_passant_square: Option<Square>,
) -> Self {
Self {
color_to_move: player_to_move,
flags,
en_passant_square,
pieces,
sight: [OnceCell::new(), OnceCell::new()],
}
}
pub(super) fn flags(&self) -> Flags {
self.flags
}
}
// crate methods
impl Position {
pub(crate) fn bitboard_for_color(&self, color: Color) -> &BitBoard {
self.pieces.bitboard_for_color(color)
}
pub(crate) fn bitboard_for_piece(&self, piece: Piece) -> &BitBoard {
self.pieces.bitboard_for_piece(piece)
}
}
#[cfg(test)]
@ -226,46 +211,9 @@ impl Default for Position {
}
}
impl FromIterator<PlacedPiece> for Position {
fn from_iter<T: IntoIterator<Item = PlacedPiece>>(iter: T) -> Self {
let mut position = Position::empty();
for placed_piece in iter {
_ = position.place_piece(placed_piece.piece(), placed_piece.square());
}
position
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::piece::Shape;
#[test]
fn place_piece() {
let mut position = Position::empty();
let piece = Piece::new(Color::White, Shape::Queen);
let square = Square::E4;
position
.place_piece(piece, square)
.expect("Unable to place white queen on e4");
assert_eq!(
position.bitboard_for_color(piece.color()).clone(),
BitBoard::new(1 << 28)
);
assert_eq!(
position.bitboard_for_piece(piece).clone(),
BitBoard::new(1 << 28)
);
position
.place_piece(piece, square)
.expect_err("Placed white queen on e4 a second time?!");
}
use crate::position;
#[test]
fn king_is_in_check() {