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use crate::{bitboard::pop_count, board::*};
impl Board {
pub fn perft(&mut self, depth: u8, print: bool) -> (u64, u64, u64, u64, u64) {
if depth == 0 {
return (1, 0, 0, 0, 0) // This a leaf, exactly one node
}
let color = self.color_to_move();
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());
}
let mut total = 0;
let mut captures = 0;
let mut checks = 0;
let mut castles = 0;
let mut en_passants = 0;
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 => {
captures += 1;
}
MoveKind::EnPassant => {
en_passants += 1;
captures += 1;
}
MoveKind::Castle => {
castles += 1;
}
_ => {}
}
if self.is_king_in_check(color.flip()) {
checks += 1;
}
}
if print {
println!("{:?}", mov);
self.print();
}
let (children_total, children_tactical, children_checks, children_castles, children_ep) = self.perft(depth - 1, print);
total += children_total;
captures += children_tactical;
checks += children_checks;
castles += children_castles;
en_passants += children_ep;
}
self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before);
}
if print {
println!("Found {} nodes in this subtree (depth {})", total, depth);
}
(total, captures, checks, castles, en_passants)
}
pub fn evaluate(&self) -> f32 {
let mut eval = 0f32;
let pieces = self.pieces_by_color(self.color());
eval += pop_count(pieces[PieceType::Pawn as usize]) as f32;
eval += pop_count(pieces[PieceType::Bishop as usize]) as f32 * 3.;
eval += pop_count(pieces[PieceType::Knight as usize]) as f32 * 3.;
eval += pop_count(pieces[PieceType::Rook as usize]) as f32 * 4.5;
eval += pop_count(pieces[PieceType::Queen as usize]) as f32 * 9.;
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);
self.print();
if depth_left == 0 {
return self.evaluate();
}
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;
#[test]
fn perft() {
let mut board = Board::new();
assert_eq!(board.perft(0, false), (1, 0, 0, 0, 0));
assert_eq!(board.perft(1, false), (20, 0, 0, 0, 0));
assert_eq!(board.perft(2, false), (400, 0, 0, 0, 0));
assert_eq!(board.perft(3, false), (8902, 34, 12, 0, 0));
assert_eq!(board.perft(4, false), (197281, 1576, 469, 0, 0));
// 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), (1, 0, 0, 0, 0));
assert_eq!(board.perft(1, false), (48, 8, 0, 2, 0));
assert_eq!(board.perft(2, false), (2039, 351, 3, 91, 1));
assert_eq!(board.perft(3, false), (97862, 17102, 993, 3162, 45));
}
#[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);
}
}
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