diff options
| -rw-r--r-- | Cargo.toml | 4 | ||||
| -rw-r--r-- | benches/negamax.rs | 20 | ||||
| -rw-r--r-- | src/board/engine.rs | 25 | ||||
| -rw-r--r-- | src/board/mod.rs | 2 |
4 files changed, 40 insertions, 11 deletions
@@ -11,3 +11,7 @@ num_enum = "0.5.7" [[bench]] name = "perft" harness = false + +[[bench]] +name = "negamax" +harness = false diff --git a/benches/negamax.rs b/benches/negamax.rs new file mode 100644 index 0000000..b9e38df --- /dev/null +++ b/benches/negamax.rs @@ -0,0 +1,20 @@ +use std::{time::Instant, f32::INFINITY}; +use chessnost::board::Board; + +fn main() { + let fen = String::from("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1"); + let mut board = Board::from_FEN(fen); + board.ply = 0; + + let depth = 4; + let start = Instant::now(); + let (eval, pv) = board.negamax_search(-INFINITY, INFINITY, depth); + println!("Negamax search (depth = {}) finished in {:?}: {:?}", depth, start.elapsed(), eval); + board.print(); + for mov in pv { + println!("{:?}", mov); + board.make_move(mov); + board.print(); + println!("Eval for {:?}: {}", board.color(), board.material_advantage()); + } +} diff --git a/src/board/engine.rs b/src/board/engine.rs index 9b0e36c..ff071ea 100644 --- a/src/board/engine.rs +++ b/src/board/engine.rs @@ -99,11 +99,11 @@ impl Board { 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); - + pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8) -> (f32, Vec<Move>) { + let mut principal_variation = Vec::new(); + let color = self.color(); if depth_left == 0 { - return self.material_advantage(); + return (self.material_advantage(), principal_variation); } let moves = self.generate_pseudolegal_moves(color); @@ -113,20 +113,24 @@ impl Board { let captured_piece = self.make_move(mov); if !self.is_king_in_check(color) { - let evaluation = -self.negamax_search(-beta, -alpha, depth_left - 1); + let (mut evaluation, mut subtree_pv) = self.negamax_search(-beta, -alpha, depth_left - 1); + evaluation *= -1.; self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before); if evaluation >= beta { - return beta; // Fail-hard beta-cutoff + return (beta, principal_variation); // Fail-hard beta-cutoff } if evaluation > alpha { - alpha = evaluation + alpha = evaluation; + principal_variation = Vec::with_capacity(depth_left as usize); + principal_variation.push(mov); + principal_variation.append(&mut subtree_pv); } } else { self.unmake_move(mov, captured_piece, ep_target_before, castling_rights_before); } } - alpha + (alpha, principal_variation) } } @@ -166,8 +170,9 @@ mod tests { 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); + let (eval, pv) = board.negamax_search(-INFINITY, INFINITY, 4); + assert_eq!(eval, 0.0); + assert_eq!(pv.len(), 4); } #[test] diff --git a/src/board/mod.rs b/src/board/mod.rs index 5e2f4e3..d339f1d 100644 --- a/src/board/mod.rs +++ b/src/board/mod.rs @@ -123,7 +123,7 @@ impl Board { } /// Color to move at this ply - fn color(&self) -> Color { + pub fn color(&self) -> Color { Color::from(self.ply as u8 % 2) } |