use std::f32::INFINITY;
use crate::{board::{piece::Piece, color::Color, CastlingSide}, bitboard::{Bitboard, BitboardFns}, square::Square};
use super::Grossmeister;
/// Score in pawns (not centipawns)
pub type Score = f32;
const PAWN_BONUS: [Score; 64] = [
// A B C D E F G H
0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00,
0.50, 0.50, 0.50, 0.50, 0.50, 0.50, 0.50, 0.50,
0.10, 0.10, 0.20, 0.30, 0.30, 0.20, 0.10, 0.10,
0.05, 0.05, 0.10, 0.25, 0.25, 0.10, 0.05, 0.05,
0.00, 0.00, 0.00, 0.20, 0.20, 0.00, 0.00, 0.00,
0.05, -0.05, -0.10, 0.00, 0.00, -0.10, -0.05, 0.05,
0.05, 0.10, 0.10, -0.20, -0.20, 0.10, 0.10, 0.05,
0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00
];
const PAWN_BONUS_PASSER_ENDGAME: [Score; 64] = [
// A B C D E F G H
0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00,
2.00, 2.00, 2.00, 2.00, 2.00, 2.00, 2.00, 2.00,
1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00,
0.70, 0.70, 0.70, 0.70, 0.70, 0.70, 0.70, 0.70,
0.50, 0.50, 0.50, 0.50, 0.50, 0.50, 0.50, 0.50,
0.30, 0.30, 0.30, 0.30, 0.30, 0.30, 0.30, 0.30,
0.10, 0.10, 0.10, 0.10, 0.10, 0.10, 0.10, 0.10,
0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00,
];
const KNIGHT_BONUS: [Score; 64] = [
// A B C D E F G H
-0.50, -0.40, -0.30, -0.30, -0.30, -0.30, -0.40, -0.50,
-0.40, -0.20, 0.00, 0.00, 0.00, 0.00, -0.20, -0.40,
-0.30, 0.00, 0.10, 0.15, 0.15, 0.10, 0.00, -0.30,
-0.30, 0.05, 0.15, 0.20, 0.20, 0.15, 0.05, -0.30,
-0.30, 0.00, 0.15, 0.20, 0.20, 0.15, 0.00, -0.30,
-0.30, 0.05, 0.10, 0.15, 0.15, 0.10, 0.05, -0.30,
-0.40, -0.20, 0.00, 0.05, 0.05, 0.00, -0.20, -0.40,
-0.50, -0.40, -0.30, -0.30, -0.30, -0.30, -0.40, -0.50,
];
const BISHOP_BONUS: [Score; 64] = [
// A B C D E F G H
-0.20, -0.10, -0.10, -0.10, -0.10, -0.10, -0.10, -0.20,
-0.10, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.10,
-0.10, 0.00, 0.05, 0.10, 0.10, 0.05, 0.00, -0.10,
-0.10, 0.05, 0.05, 0.10, 0.10, 0.05, 0.05, -0.10,
-0.10, 0.00, 0.10, 0.10, 0.10, 0.10, 0.00, -0.10,
-0.10, 0.10, 0.10, 0.10, 0.10, 0.10, 0.10, -0.10,
-0.10, 0.25, 0.00, 0.00, 0.00, 0.00, 0.25, -0.10,
-0.20, -0.10, -0.10, -0.10, -0.10, -0.10, -0.10, -0.20,
];
const ROOK_BONUS: [Score; 64] = [
// A B C D E F G H
0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00,
0.05, 0.30, 0.30, 0.30, 0.30, 0.30, 0.30, 0.05,
-0.05, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.05,
-0.05, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.05,
-0.05, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.05,
-0.05, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.05,
-0.05, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.05,
0.00, 0.00, 0.00, 0.05, 0.05, 0.00, 0.00, 0.00
];
const QUEEN_BONUS: [Score; 64] = [
// A B C D E F G H
-0.20, -0.10, -0.10, -0.05, -0.05, -0.10, -0.10, -0.20,
-0.10, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, -0.10,
-0.10, 0.00, 0.05, 0.05, 0.05, 0.05, 0.00, -0.10,
-0.05, 0.00, 0.05, 0.05, 0.05, 0.05, 0.00, -0.05,
0.00, 0.00, 0.05, 0.05, 0.05, 0.05, 0.00, -0.05,
-0.10, 0.05, 0.05, 0.05, 0.05, 0.05, 0.00, -0.10,
-0.10, 0.00, 0.05, 0.00, 0.00, 0.00, 0.00, -0.10,
-0.20, -0.10, -0.10, -0.05, -0.05, -0.10, -0.10, -0.20
];
const KING_BONUS: [Score; 64] = [
// A B C D E F G H
-0.30, -0.40, -0.40, -0.50, -0.50, -0.40, -0.40, -0.30,
-0.30, -0.40, -0.40, -0.50, -0.50, -0.40, -0.40, -0.30,
-0.30, -0.40, -0.40, -0.50, -0.50, -0.40, -0.40, -0.30,
-0.30, -0.40, -0.40, -0.50, -0.50, -0.40, -0.40, -0.30,
-0.20, -0.30, -0.30, -0.40, -0.40, -0.30, -0.30, -0.20,
-0.10, -0.20, -0.20, -0.20, -0.20, -0.20, -0.20, -0.10,
0.20, 0.20, 0.00, -0.10, -0.10, 0.00, 0.20, 0.20,
0.20, 0.10, 0.30, -0.20, 0.00, 0.10, 0.30, 0.20
];
const KING_BONUS_ENGAME: [Score; 64] = [
// A B C D E F G H
-0.50, -0.40, -0.30, -0.20, -0.20, -0.30, -0.40, -0.50,
-0.30, -0.20, -0.10, 0.00, 0.00, -0.10, -0.20, -0.30,
-0.30, -0.10, 0.20, 0.30, 0.30, 0.20, -0.10, -0.30,
-0.30, -0.10, 0.30, 0.40, 0.40, 0.30, -0.10, -0.30,
-0.30, -0.10, 0.30, 0.40, 0.40, 0.30, -0.10, -0.30,
-0.30, -0.10, 0.20, 0.30, 0.30, 0.20, -0.10, -0.30,
-0.30, -0.30, 0.00, 0.00, 0.00, 0.00, -0.30, -0.30,
-0.50, -0.30, -0.30, -0.30, -0.30, -0.30, -0.30, -0.50
];
impl Grossmeister {
pub fn passer_mask(&self, color: Color) -> Bitboard {
let black_pawns = self.board.piece_sets[Piece::PawnBlack as usize];
let white_pawns = self.board.piece_sets[Piece::Pawn as usize];
match color {
Color::Black => {
let mut front_fill = white_pawns.nort_fill().nort_one();
front_fill |= front_fill.east_one() | front_fill.west_one();
black_pawns & !front_fill
}
Color::White => {
let mut front_fill = black_pawns.sout_fill().sout_one();
front_fill |= front_fill.east_one() | front_fill.west_one();
white_pawns & !front_fill
}
}
}
/// Return number of pawns above the king (+left/right)
pub fn pawn_shield(&self, color: Color) -> f32 {
let behind_pawns = match color {
Color::White => self.board.piece_sets[Piece::Pawn as usize].sout_one(),
Color::Black => self.board.piece_sets[Piece::PawnBlack as usize].nort_one(),
};
let king = match color {
Color::White => self.board.piece_sets[Piece::King as usize],
Color::Black => self.board.piece_sets[Piece::KingBlack as usize],
};
(behind_pawns & (king | king.west_one() | king.east_one())).pop_count() as f32
}
/// Count the number of pawn islands of given color
pub fn pawn_islands(&self, color: Color) -> f32 {
let pawns = self.board.pieces_by_color(color)[Piece::Pawn as usize];
let fileset = pawns.nort_fill().sout_fill();
// Does not matter west/east, each island has both sides
let islands_west_files = fileset & !fileset.east_one();
(islands_west_files.pop_count() / 8) as f32
}
/// Compute total bonus for well-positioned pieces
/// according to Piece-Square Tables
pub fn pst_bonus(&self, color: Color, is_endgame: bool) -> f32 {
self.board.pieces_by_color(color).iter().enumerate().fold(0., |total, (piece_index, bitboard)| {
let pst = match Piece::from(piece_index).without_color() {
Piece::Pawn => if is_endgame && (bitboard & self.passer_mask(color) > 0) {
PAWN_BONUS_PASSER_ENDGAME
} else {
PAWN_BONUS
}
Piece::Knight => KNIGHT_BONUS,
Piece::Bishop => BISHOP_BONUS,
Piece::Rook => ROOK_BONUS,
Piece::Queen => QUEEN_BONUS,
Piece::King => if is_endgame {
KING_BONUS_ENGAME
} else {
KING_BONUS
}
_ => panic!("Unreachable")
};
total + bitboard.serialize().fold(0., |acc, square| {
let pst_index = match color {
Color::White => square.mirror(),
Color::Black => square,
} as usize;
acc + pst[pst_index]
})
})
}
/// Count raw material of the given color
pub fn material(&self, color: Color) -> f32 {
self.board.pieces_by_color(color).iter().enumerate().fold(0., |acc, (piece_index, bitboard)| {
acc + Piece::from(piece_index).static_eval() * bitboard.pop_count() as f32
})
}
// Returns a value in [0, 240] representing how
// much material is left in the game
// Note: not related to actual material counting
pub fn phase(&self) -> u8 {
let knight_phase = 10;
let bishop_phase = 10;
let rook_phase = 20;
let queen_phase = 40;
let total_phase = knight_phase*4 + bishop_phase*4 + rook_phase*4 + queen_phase*2;
// If you change it, make sure to update denominator in interpolation
debug_assert_eq!(total_phase, 240);
self.board.piece_sets.iter().enumerate().fold(0, |acc, (piece_index, &bitboard)| {
acc + match Piece::from(piece_index).without_color() {
Piece::King => 0,
Piece::Pawn => 0,
Piece::Knight => knight_phase,
Piece::Bishop => bishop_phase,
Piece::Rook => rook_phase,
Piece::Queen => queen_phase,
_ => panic!("Unreachable")
} * bitboard.pop_count()
})
}
/// Evaluate a position relative to the current player
pub fn evaluate(&self) -> Score {
let color = self.board.color();
let opponent_color = color.flip();
let winnable = self.board.is_theoretically_winnable(color);
let loseable = self.board.is_theoretically_winnable(opponent_color);
if !winnable && !loseable {
return 0.0
}
let material_advantage = self.material(color) - self.material(opponent_color);
let mobility_advantage = self.mobility(color) - self.mobility(opponent_color);
let pawn_shield_advantage = self.pawn_shield(color) - self.pawn_shield(opponent_color);
let pawn_islands_advantage = self.pawn_islands(opponent_color) - self.pawn_islands(color);
// Middlegame eval, assumming all pieces are on the Board
let middlegame_eval =
mobility_advantage * 0.05 +
pawn_shield_advantage * 0.20 +
pawn_islands_advantage * 0.10 +
(self.pst_bonus(color, false) - self.pst_bonus(opponent_color, false));
// Engame eval, assuming no pieces are left on the Board (only kings and pawns)
let endgame_eval =
mobility_advantage * 0.03 +
pawn_shield_advantage * 0.05 +
pawn_islands_advantage * 0.15 +
(self.pst_bonus(color, true) - self.pst_bonus(opponent_color, true));
// Interpolate evalutaion based on amount of pieces to remove discontinuity
let phase = self.phase();
let tapered_eval = (middlegame_eval * phase as f32 + endgame_eval * (240 - phase) as f32) / 240.;
let eval = (material_advantage + tapered_eval)
.min(if winnable { INFINITY } else { 0.0 }) // Can not score > 0 if not winnable
.max(if loseable { -INFINITY } else { 0.0 }); // Can not score < 0 if not loseable
(eval * 100.0).round() / 100.0
}
/// Count pseudo-legal moves without actually generating them
/// Also exclude all moves that put a piece under attack of a pawn - so called safe mobility
pub fn mobility(&self, color: Color) -> f32 {
let mut mobility = 0.;
let opponent_occupancy = self.board.color_occupancy(color.flip());
let player_pieces = self.board.pieces_by_color(color);
let opponent_pawns = match color {
Color::Black => self.board.piece_sets[Piece::Pawn as usize],
Color::White => self.board.piece_sets[Piece::PawnBlack as usize],
};
let pawn_attacked_squares = opponent_pawns.serialize().fold(0u64, |acc, square| {
acc | self.board.attacks.pawn[color.flip() as usize][square as usize]
});
// Exclude squares controlled by enemy pawns from mobility
let empty = self.board.empty() & !pawn_attacked_squares;
for (piece_type, piece) in player_pieces.iter().enumerate() {
match Piece::from(piece_type) {
Piece::Pawn => {
for source in piece.serialize() {
let ep_bitboard = match self.board.ep_target {
Some(square) => {
let rank = square.rank();
if (rank == 2 && color == Color::Black) || (rank == 5 && color == Color::White) {
square.to_bitboard()
} else {
0
}
}
None => 0,
};
mobility += (self.board.attacks.pawn[color as usize][source as usize] & (opponent_occupancy | ep_bitboard)).pop_count() as f32;
mobility += (self.board.attacks.pawn_pushes[color as usize][source as usize] & empty).pop_count() as f32;
}
let able_to_double_push_mask = match color {
Color::White => empty >> 8,
Color::Black => empty << 8,
};
for source in (*piece & able_to_double_push_mask).serialize() {
mobility += (self.board.attacks.pawn_double_pushes[color as usize][source as usize] & empty).pop_count() as f32;
}
}
Piece::King => {
for source in piece.serialize() {
mobility += (self.board.attacks.king[source as usize] & (empty | opponent_occupancy)).pop_count() as f32;
// Castling
let king_home_position = match color {
Color::White => Square::E1,
Color::Black => Square::E8,
};
if *piece == king_home_position.to_bitboard() {
for rook_square in player_pieces[Piece::Rook as usize]
.serialize()
.filter(|rook_square| rook_square.rank() == king_home_position.rank())
{
match rook_square.file() {
0 => {
let castle_line = [
king_home_position.west_one(),
king_home_position.west_one().west_one(),
];
let all_empty = castle_line.iter().all(|square| empty & square.to_bitboard() > 0);
let any_checks = castle_line.iter().any(|square| self.board.is_square_attacked(*square, color.flip()));
if all_empty && !any_checks && self.board.castling_rights[color as usize][CastlingSide::Queen as usize] {
mobility += 1.;
}
},
7 => {
let castle_line = [
king_home_position.east_one(),
king_home_position.east_one().east_one(),
];
let all_empty = castle_line.iter().all(|square| empty & square.to_bitboard() > 0);
let any_checks = castle_line.iter().any(|square| self.board.is_square_attacked(*square, color.flip()));
if all_empty && !any_checks && self.board.castling_rights[color as usize][CastlingSide::King as usize] {
mobility += 1.;
}
},
_ => {},
}
}
}
}
}
Piece::Knight => {
for source in piece.serialize() {
mobility += (self.board.attacks.knight[source as usize] & (empty | opponent_occupancy)).pop_count() as f32;
}
}
Piece::Bishop => {
for source in piece.serialize() {
mobility += (self.board.attacks.bishop(self.board.occupancy, source) & (empty | opponent_occupancy)).pop_count() as f32;
}
}
Piece::Rook => {
for source in piece.serialize() {
mobility += (self.board.attacks.rook(self.board.occupancy, source) & (empty | opponent_occupancy)).pop_count() as f32;
}
}
Piece::Queen => {
// Do not account queen in mobility
}
incorrect_type => panic!("Incorrect piece type: {:?}", incorrect_type),
}
}
mobility
}
}
#[cfg(test)]
mod tests {
use crate::{board::{Board, io::IO}, moves::{Move, MoveKind}};
use super::*;
#[test]
fn castle_bonus() {
assert_eq!(KING_BONUS[Square::E1.mirror() as usize], 0.0);
assert!(KING_BONUS[Square::G1.mirror() as usize] > 0.0);
assert!(KING_BONUS[Square::C1.mirror() as usize] > 0.0);
assert!(KING_BONUS[Square::D1.mirror() as usize] < 0.0);
assert!(KING_BONUS[Square::E2.mirror() as usize] < 0.0);
assert_eq!(KING_BONUS[Square::E8 as usize], 0.0);
assert!(KING_BONUS[Square::G8 as usize] > 0.0);
assert!(KING_BONUS[Square::C8 as usize] > 0.0);
assert!(KING_BONUS[Square::D8 as usize] < 0.0);
assert!(KING_BONUS[Square::E2 as usize] < 0.0);
}
#[test]
fn mobility() {
let board = Board::new();
let gm = Grossmeister::new(board);
let white = gm.mobility(Color::White);
let black = gm.mobility(Color::Black);
assert_eq!(white, 20.);
assert_eq!(black, 20.);
}
#[test]
fn material() {
let board = Board::new();
let gm = Grossmeister::new(board);
assert_eq!(gm.material(Color::Black), gm.material(Color::White));
}
#[test]
fn initial_eval() {
let board = Board::new();
let gm = Grossmeister::new(board);
assert_eq!(gm.evaluate(), 0.0);
}
#[test]
fn king_tropism() {
let board = Board::new();
let mut gm = Grossmeister::new(board);
gm.board.make_move(Move { source: Square::D1, target: Square::F5, kind: MoveKind::Quiet });
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
assert!(score < 0.0);
assert!(score > -1.0);
}
#[test]
fn white_winning() {
let fen = String::from("8/5pk1/6p1/R4b1p/3P4/1P2N3/P1r2PPP/R5K1 w - - 1 27");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
assert!(score > 7.0);
}
#[test]
fn black_winning() {
let fen = String::from("8/p7/1k4K1/8/4P3/8/PP5r/8 w - - 1 38");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
assert!(score < -3.0);
}
#[test]
fn encourage_center_pawns() {
let score1 = {
let fen = String::from("rnbqkbnr/pppp1ppp/8/4p3/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
let score2 = {
let fen = String::from("rnbqkbnr/pppp1ppp/8/4p3/2P5/8/PP1PPPPP/RNBQKBNR w KQkq - 0 2");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
assert!(score1 > score2);
}
#[test]
fn discourage_edge_knights() {
let score1 = {
let fen = String::from("r1bqkbnr/pppp1ppp/2n5/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R w KQkq - 2 3");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
let score2 = {
let fen = String::from("r1bqkbnr/pppp1ppp/2n5/4p3/4P3/7N/PPPP1PPP/RNBQKB1R w KQkq - 2 3");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
assert!(score1 > score2);
}
#[test]
fn mirrored_evaluation() {
let score1 = {
let fen = String::from("r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 1");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
let score2 = {
let fen = String::from("r2q1rk1/pP1p2pp/Q4n2/bbp1p3/Np6/1B3NBn/pPPP1PPP/R3K2R b KQ - 0 1 ");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let score = gm.evaluate();
gm.board.print();
println!("Score {}", score);
score
};
assert_eq!(score1.abs(), score2.abs());
}
#[test]
fn passer() {
let fen = String::from("rnbqkbnr/ppp3pp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1");
let board = Board::from_FEN(fen);
let gm = Grossmeister::new(board);
let mask = gm.passer_mask(Color::White);
assert_eq!(mask, Square::E2.to_bitboard());
}
#[test]
fn no_passer() {
let board = Board::new();
let gm = Grossmeister::new(board);
let mask = gm.passer_mask(Color::White);
assert_eq!(mask, 0);
}
}