diff --git a/Cargo.lock b/Cargo.lock index f82e195..f8f0fe6 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -244,6 +244,7 @@ version = "0.1.0" dependencies = [ "anyhow", "criterion", + "regex", ] [[package]] diff --git a/Cargo.toml b/Cargo.toml index 71ab6a2..420cd65 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -8,11 +8,12 @@ name = "othello" path = "src/lib.rs" [[bin]] -name = "othello-gui" +name = "othello-cli" path = "src/main.rs" [dependencies] anyhow = "1.0.100" +regex = "1.12.2" [dev-dependencies] criterion = "0.7.0" diff --git a/src/ai.rs b/src/ai.rs new file mode 100644 index 0000000..18b35d4 --- /dev/null +++ b/src/ai.rs @@ -0,0 +1,81 @@ +use crate::{ + board::{Board, explode_board}, + game::{Game, Team}, +}; + +/// Using alpha-beta pruning and the minimax algorithm, determine the best move +/// for a game with a recursion depth of `depth`. +pub fn alphabeta(game: Game, depth: u8, mut alpha: i8, mut beta: i8) -> (Board, i8) { + if depth == 0 { + return (0, game.score().diff()); + } + let moves = game.available(); + if moves == 0 { + return (0, game.score().diff()); + } + + let mut best_move: Board = 0; + // I just establish a convention of maximizing for black and minimizing for white. + // I'm not sure if that's conventional or not, but it's what I chose. + match game.current_team { + Team::Black => { + for mv in explode_board(moves) { + let mut g = game.clone(); + g.play(mv); + // maximize for the evaluation of subsequent moves + let evaluation = alphabeta(g, depth - 1, alpha, beta).1; + if evaluation > alpha { + alpha = evaluation; + best_move = mv; + }; + if beta <= alpha { + break; + } + } + (best_move, alpha) + } + Team::White => { + for mv in explode_board(moves) { + let mut g = game.clone(); + g.play(mv); + // maximize for the evaluation of subsequent moves + let evaluation = alphabeta(g, depth - 1, alpha, beta).1; + if evaluation < beta { + beta = evaluation; + best_move = mv; + }; + if beta <= alpha { + break; + } + } + (best_move, beta) + } + } +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::board::view::View; + use crate::board::{BitBoard, squares::*}; + use crate::game::Game; + + #[test] + // just a sanity check to ensure that my AI performs up to snuff with another popular engine + fn opening() { + let mut game = Game::default(); + + println!("{}", game.board().render(View::RankAsc, vec![])); + game.play(D3); + let (best_move, _) = alphabeta(game.clone(), 12, i8::MIN + 1, i8::MAX - 1); + println!( + "dis:\n{}", + BitBoard { + boards: [0, best_move] + } + ); + game.play(best_move); + println!("{}", game.board().render(View::RankAsc, vec![])); + assert_eq!(best_move, C3); + } +} diff --git a/src/board/mod.rs b/src/board/mod.rs index ba2d439..eaf3202 100644 --- a/src/board/mod.rs +++ b/src/board/mod.rs @@ -12,6 +12,64 @@ pub mod view; pub type Board = u64; +/// Represents the score at a given moment in the game. It is computed as +/// the number of black discs vs white discs. Structured as (black, white) +#[derive(Debug, PartialEq)] +pub struct Score(pub u8, pub u8); +impl Score { + /// Get black's current score + pub fn black(&self) -> u8 { + self.0 + } + /// Get white's current score + pub fn white(&self) -> u8 { + self.1 + } + + /// Compute diff of evaluation. Useful for easily comparing a bunch of scores. + pub fn diff(&self) -> i8 { + self.0 as i8 - self.1 as i8 + } +} + +/// Explode a single board into an iterator over all of its excited one-hot +/// boards. +/// +/// For example: +/// `0b1010` will explode into an iterator over `[0b0010, 0b1000]`. +/// +/// The boards will be sorted by rank-ascending. +#[inline] +pub fn explode_board(mut b: Board) -> impl Iterator { + // a naive solution would be to simply start at the rightmost bit and + // shift until we reach an excited bit, AND it for result, and store + // the current shift + 1 for the next iteration until `b` is zero. This + // is a bit wasteful, as we can abuse a handful of modular relationships + // with negation. + // + // we do this using the `u64::wrapping_neg` method. + // In two's-complement, negation can be used to isolate the least + // significant excited bit in a signed integer. For example, + // if `Board` were defined as `i64` instead, we could define LSB as + // `lsb = b & -b`. Since we're using `u64`, we can mimic this using + // `u64::wrapping_neg`. + std::iter::from_fn(move || { + // if we have no more excited bits, return None + if b == 0 { + None + } else { + // if we have more, continue isolating the LSB + let lsb = b & b.wrapping_neg(); + // If you're skeptical of the claim above about these being + // equivalent, comment out the line above this and uncomment + // the line below this. They both pass the test. + // let lsb = (b as i64 & -(b as i64)) as u64; + b &= b - 1; + Some(lsb) + } + }) +} + // Directions: // 7 8 9 // -1 0 1 @@ -380,11 +438,14 @@ impl BitBoard { } /// Compute the score (B, W) by counting the excited bits in each board. - pub fn score(&self) -> (u32, u32) { + pub fn score(&self) -> Score { // `u64::count_ones()` is implemented `unsafe` and makes use of primitives in the // low-level implementation of the language itself for maximum performance. Better // to use this than implement myself. - (self.boards[0].count_ones(), self.boards[1].count_ones()) + Score( + self.boards[0].count_ones() as u8, + self.boards[1].count_ones() as u8, + ) } } @@ -610,7 +671,6 @@ mod tests { fn test_available_no_moves_surrounded() { // Black piece at b7 completely surrounded by white let bb = BitBoard::from_jon("www/wbw/www////").expect("Valid board"); - println!("dis:\n{}", bb); // Black should have three moves in this position: d7, b5, and d5 assert_eq!(bb.available(Team::Black), D7 | B5 | D5); } @@ -619,7 +679,6 @@ mod tests { fn test_available_long_capture() { // Black at a4, white at b4-f4, empty g4, black at h4 let bb = BitBoard::from_jon("////bwwwww1b///").expect("Valid board"); - println!("dis:\n{}", bb); // Black can play at g4 to capture entire row of white pieces assert_eq!(bb.available(Team::Black), G4); } @@ -692,18 +751,27 @@ mod tests { #[test] fn play_works() { let mut bb = BitBoard::default(); - assert_eq!(bb.score(), (2, 2)); + assert_eq!(bb.score(), Score(2, 2)); bb.play(Team::Black, E6); assert_eq!(bb, BitBoard::new(D5 | E6 | E5 | E4, D4)); - assert_eq!(bb.score(), (4, 1)); + assert_eq!(bb.score(), Score(4, 1)); bb.play(Team::White, F4); assert_eq!(bb, BitBoard::new(D5 | E6 | E5, D4 | E4 | F4)); - assert_eq!(bb.score(), (3, 3)); + assert_eq!(bb.score(), Score(3, 3)); bb.play(Team::Black, G3); assert_eq!(bb, BitBoard::new(D5 | E6 | E5 | G3 | F4, D4 | E4)); - assert_eq!(bb.score(), (5, 2)); + assert_eq!(bb.score(), Score(5, 2)); bb.play(Team::White, E7); assert_eq!(bb, BitBoard::new(D5 | G3 | F4, D4 | E4 | E5 | E6 | E7)); - assert_eq!(bb.score(), (3, 5)); + assert_eq!(bb.score(), Score(3, 5)); + } + + #[test] + fn explode_works() { + let bb = BitBoard::default(); + assert_eq!( + explode_board(bb.available(Team::Black)).collect::>(), + vec![D3, C4, F5, E6] // they are sorted in rank-ascending + ); } } diff --git a/src/cli/mod.rs b/src/cli/mod.rs index e075ad4..7fe6563 100644 --- a/src/cli/mod.rs +++ b/src/cli/mod.rs @@ -1,18 +1,97 @@ -use othello::{board::view::Overlay, game::Game}; +use std::io; + +use othello::{ + ai::alphabeta, + board::{ + Board, Score, + view::{Overlay, View}, + }, + game::Game, +}; + +use anyhow::Context; +use regex::Regex; + +enum Action { + Play(Board), + Skip, + Ai, +} + +const PLAY_RE: &str = r"^(play - )?([abcdefghABCDEFGH])(\d)$"; pub fn run() -> anyhow::Result<()> { let mut game = Game::default(); + let mut board_changed = true; + + let play_re = Regex::new(PLAY_RE).unwrap(); + + while !game.is_complete() { + let legal_moves = game.available(); + if board_changed { + let Score(b, w) = game.score(); + println!("Score: (Black: {} , White: {}", b, w); + println!( + "{}", + game.board().render( + View::RankAsc, + vec![Overlay(legal_moves, "\x1b[95m*\x1b[37m")] + ) + ); + board_changed = false; + } + + let choice = loop { + println!("Please choose your action: [play - (move), skip, ai]"); + let mut raw_input = String::new(); + io::stdin() + .read_line(&mut raw_input) + .context("Failed to read input")?; + if let Some(captures) = play_re.captures(&raw_input.trim()) { + let file = captures.get(2).context("Failed to get file capture")?; + let rank = captures + .get(3) + .context("Failed to get rank capture")? + .as_str() + .parse::() + .context("Failed to parse rank")?; + break Action::Play(create_move(file.as_str(), rank)); + } + + match raw_input.as_str().trim() { + "skip" => break Action::Skip, + "ai" => break Action::Ai, + _ => println!("Invalid input"), + } + }; + + match choice { + Action::Play(mv) => { + if mv & legal_moves == 0 { + println!( + "Attempted illegal moves. Legal moves are indicated by asterisks (*)." + ); + } else { + game.play(mv); + board_changed = true; + } + } + Action::Skip => { + if legal_moves != 0 { + println!("Cannot skip with legal moves available. Must choose `play` or `ai`."); + } else { + game.skip() + } + } + Action::Ai => { + let (mv, eval) = alphabeta(game.clone(), 12, i8::MIN + 1, i8::MAX - 1); + println!("beep. boop. eval = {eval}"); + game.play(mv); + board_changed = true; + } + } + } - println!( - "{}", - game.board().render( - game.current_team, - vec![Overlay( - game.board().available(game.current_team), - "\x1b[95m*\x1b[37m" - )] - ) - ); game.play(othello::board::squares::E6); println!(); println!( @@ -28,3 +107,36 @@ pub fn run() -> anyhow::Result<()> { Ok(()) } + +/// Convert a file and rank into an actual board +fn create_move(file: &str, rank: u8) -> Board { + 1 << (match file { + "a" => 0, + "b" => 1, + "c" => 2, + "d" => 3, + "e" => 4, + "f" => 5, + "g" => 6, + "h" => 7, + _ => unreachable!("impossible file"), + } + (rank - 1) * 8) as Board +} + +#[cfg(test)] +mod tests { + use super::*; + use othello::board::squares::*; + #[test] + fn create_move_works() { + assert_eq!(create_move("a", 1), A1); + assert_eq!(create_move("d", 3), D3); + assert_eq!(create_move("h", 8), H8); + } + + #[test] + fn re_works() { + let play_re = Regex::new(PLAY_RE).unwrap(); + assert!(play_re.is_match("play - d3")); + } +} diff --git a/src/game.rs b/src/game.rs index dc9a676..c95a735 100644 --- a/src/game.rs +++ b/src/game.rs @@ -1,4 +1,4 @@ -use crate::board::{BitBoard, Board}; +use crate::board::{BitBoard, Board, Score}; #[repr(u8)] #[derive(Copy, Clone, Debug, PartialEq, Default)] @@ -19,7 +19,8 @@ impl Team { } } -#[derive(Default)] +#[derive(Default, Clone)] +// TODO: Look into potentially better memory alignment for this pub struct Game { pub current_team: Team, board: BitBoard, @@ -42,9 +43,31 @@ impl Game { Ok(()) } + /// Skip the current player + pub fn skip(&mut self) { + self.current_team = self.current_team.next(); + } + + /// Copy the board pub fn board(&self) -> BitBoard { self.board } + + /// Compute the available moves + pub fn available(&self) -> Board { + self.board.available(self.current_team) + } + + /// Compute the score of the game + pub fn score(&self) -> Score { + self.board.score() + } + + /// Determine whether or not the game has concluded + pub fn is_complete(&self) -> bool { + let score = self.board.score(); + score.0 + score.1 == 64 + } } #[cfg(test)] diff --git a/src/lib.rs b/src/lib.rs index 7d756d4..e68829a 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -1,2 +1,3 @@ +pub mod ai; pub mod board; pub mod game;