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use crate::{bitboard::pop_count, board::*};
#[derive(Debug, Default, PartialEq)]
pub struct PerftResult {
leaf_nodes: u64,
captures: u64,
en_passants: u64,
castles: u64,
checks: u64,
}
impl Board {
pub fn perft(&mut self, depth: u8, print: bool) -> PerftResult {
let mut result = PerftResult::default();
if depth == 0 {
result.leaf_nodes = 1;
return result;
}
let color = self.color();
let moves = self.generate_pseudolegal_moves(color);
if print {
println!("Running perft for depth {}. Color to move is {:?}\n{} moves available", depth, color, moves.len());
println!("{} moves available", moves.len());
}
for mov in moves {
let ep_target_before = self.ep_target.clone();
let castling_rights_before = self.castling_rights.clone();
let captured_piece = self.make_move(mov);
// King can not be in check after our own move
if !self.is_king_in_check(color) {
if depth == 1 {
match mov.kind {
MoveKind::Capture => {
result.captures += 1;
}
MoveKind::EnPassant => {
result.en_passants += 1;
result.captures += 1;
}
MoveKind::Castle => {
result.castles += 1;
}
_ => {}
}
if self.is_king_in_check(color.flip()) {
result.checks += 1;
}
}
if print {
println!("{:?}", mov);
self.print();
}
let subtree_result = self.perft(depth - 1, print);
result.leaf_nodes += subtree_result.leaf_nodes;
result.captures += subtree_result.captures;
result.checks += subtree_result.checks;
result.castles += subtree_result.castles;
result.en_passants += subtree_result.en_passants;
}
self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
}
if print {
println!("Found {} leaf nodes in this subtree (depth {})", result.leaf_nodes, depth);
}
result
}
/// Compute material advantage relative to the current player
pub fn material_advantage(&self) -> f32 {
let mut eval = 0f32;
for (piece_index, bitboard) in self.pieces.iter().enumerate() {
let piece_type = PieceType::from(piece_index);
let sign = if Color::from_piece(piece_type) == self.color() {
1.
} else {
-1.
};
let multiplier = match piece_type.without_color() {
PieceType::Pawn => 1.,
PieceType::Bishop => 3.,
PieceType::Knight => 3.,
PieceType::Rook => 4.5,
PieceType::Queen => 9.,
PieceType::King => 0.,
_ => panic!("Piece should be without color"),
};
eval += sign * multiplier * pop_count(*bitboard) as f32;
}
eval
}
pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8) -> f32 {
let color = Color::from(self.ply as u8 % 2);
if depth_left == 0 {
return self.material_advantage();
}
let moves = self.generate_pseudolegal_moves(color);
for mov in moves {
let ep_target_before = self.ep_target.clone();
let castling_rights_before = self.castling_rights.clone();
let captured_piece = self.make_move(mov);
if !self.is_king_in_check(color) {
let evaluation = -self.negamax_search(-beta, -alpha, depth_left - 1);
self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
if evaluation >= beta {
return beta; // Fail-hard beta-cutoff
}
if evaluation > alpha {
alpha = evaluation
}
} else {
self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
}
}
alpha
}
}
#[cfg(test)]
mod tests {
use std::f32::INFINITY;
use crate::board::{Board, engine::PerftResult};
#[test]
fn perft() {
let mut board = Board::new();
assert_eq!(board.perft(0, false), PerftResult { leaf_nodes: 1, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
assert_eq!(board.perft(1, false), PerftResult { leaf_nodes: 20, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
assert_eq!(board.perft(2, false), PerftResult { leaf_nodes: 400, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
assert_eq!(board.perft(3, false), PerftResult { leaf_nodes: 8902, captures: 34, en_passants: 0, castles: 0 , checks: 12 });
assert_eq!(board.perft(4, false), PerftResult { leaf_nodes: 197281, captures: 1576, en_passants: 0, castles: 0 , checks: 469 });
// assert_eq!(board.perft(5, false), (4865609, 82719, 27351, 0, 258));
// assert_eq!(board.perft(6, false), (119060324, 2812008, 809099, 0, 5248));
}
#[test]
fn position_perft() {
let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
let mut board = Board::from_FEN(fen);
assert_eq!(board.perft(0, false), PerftResult { leaf_nodes: 1, captures: 0, en_passants: 0, castles: 0 , checks: 0 });
assert_eq!(board.perft(1, false), PerftResult { leaf_nodes: 48, captures: 8, en_passants: 0, castles: 2 , checks: 0 });
assert_eq!(board.perft(2, false), PerftResult { leaf_nodes: 2039, captures: 351, en_passants: 1, castles: 91 , checks: 3 });
assert_eq!(board.perft(3, false), PerftResult { leaf_nodes: 97862, captures: 17102, en_passants: 45, castles: 3162, checks: 993 });
}
#[test]
fn negamax_search() {
let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - ");
let mut board = Board::from_FEN(fen);
let eval = board.negamax_search(-INFINITY, INFINITY, 4);
println!("{}", eval);
}
#[test]
fn material_advantage() {
let board = Board::new();
assert_eq!(board.material_advantage(), 0.0, "Material advantage should be 0 at starting position");
}
}
|
