cleaned up, added random AI for testing

Cargo.lock

@@ -175,6 +175,18 @@ version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi",
+ "wasip2",
+]
+
 [[package]]
 name = "half"
 version = "2.7.1"
@@ -211,6 +223,12 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "libc"
+version = "0.2.177"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2874a2af47a2325c2001a6e6fad9b16a53b802102b528163885171cf92b15976"
+
 [[package]]
 name = "memchr"
 version = "2.7.6"
@@ -244,6 +262,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "criterion",
+ "rand",
  "regex",
 ]
 
@@ -275,6 +294,15 @@ dependencies = [
  "plotters-backend",
 ]
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
+dependencies = [
+ "zerocopy",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.103"
@@ -293,6 +321,41 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core",
+]
+
+[[package]]
+name = "rand_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
+dependencies = [
+ "getrandom",
+]
+
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -443,6 +506,15 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "wasip2"
+version = "1.0.1+wasi-0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0562428422c63773dad2c345a1882263bbf4d65cf3f42e90921f787ef5ad58e7"
+dependencies = [
+ "wit-bindgen",
+]
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.105"
@@ -522,6 +594,12 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "wit-bindgen"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f17a85883d4e6d00e8a97c586de764dabcc06133f7f1d55dce5cdc070ad7fe59"
+
 [[package]]
 name = "zerocopy"
 version = "0.8.27"

Cargo.toml

@@ -17,6 +17,7 @@ regex = "1.12.2"
 
 [dev-dependencies]
 criterion = "0.7.0"
+rand = "0.9.2"
 
 [[bench]]
 name = "generation"

src/ai.rs

@@ -142,13 +142,123 @@ pub fn alphabeta(mut game: Game, depth: u8, mut alpha: i8, mut beta: i8) -> (Boa
     }
 }
 
+/// Using alpha-beta pruning with printing of intermediate data for debugging
+/// and monitoring purposes.
+pub fn alphabeta_with_printing(game: Game, depth: u8) -> (Board, i8) {
+    let (b, moves, eval) = alphabeta_with_printing_inner(game, depth, i8::MIN + 1, i8::MAX - 1);
+    println!("beep. boop. we assessed {} moves.", moves);
+    (b, eval)
+}
+
+/// Using alpha-beta pruning and the minimax algorithm, determine the best move
+/// for a game with a recursion depth of `depth`.
+///
+/// We use a very simple evaluation heuristic: (Black squares - White squares).
+fn alphabeta_with_printing_inner(
+    mut game: Game,
+    depth: u8,
+    mut alpha: i8,
+    mut beta: i8,
+) -> (Board, usize, i8) {
+    // if we reach our maximum recursion depth, return evaluation
+    if depth == 0 {
+        return (0, 0, game.score().diff());
+    }
+    let moves = game.available();
+    if moves == 0 {
+        // if no move, skip and continue recursion
+        // this seems to technically introduce a bias against move-chains
+        // that include skips. I haven't found it to be a big deal in play.
+        game.skip();
+        return (
+            0,
+            0,
+            alphabeta_with_printing_inner(game, depth - 1, alpha, beta).2,
+        );
+    }
+
+    // just initially assume that the best move is no move at all. This will
+    // inevitably be corrected.
+    let mut best_move: Board = 0;
+    // we initially rank moves based on a couple basic heuristics:
+    // - corner pieces are best
+    // - edge pieces are great
+    // - others considered last
+    // This just allows us to prune the tree a bit more aggressively
+    // since we're considering the "best" moves first.
+    // We do this by mapping moves to ranked moves and then sorting.
+    let mut moves = explode_board(moves).map(MoveRank::from).collect::<Vec<_>>();
+    moves.sort();
+    let moves = moves
+        .into_iter()
+        .map(MoveRank::into_inner)
+        .collect::<Vec<_>>();
+    let mut num_moves = moves.len();
+    // 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 moves {
+                let mut g = game.clone();
+                g.play(mv);
+                // maximize for the evaluation of subsequent moves
+                let (_, num_moves_prime, evaluation) =
+                    alphabeta_with_printing_inner(g, depth - 1, alpha, beta);
+                num_moves += num_moves_prime;
+                // if our evaluated move is superior to the alpha, update
+                // it.
+                if evaluation > alpha {
+                    alpha = evaluation;
+                    best_move = mv;
+                };
+                // if our beta is less than alpha, prune the node.
+                if beta <= alpha {
+                    break;
+                }
+            }
+            (best_move, num_moves, alpha)
+        }
+        Team::White => {
+            for mv in moves {
+                let mut g = game.clone();
+                g.play(mv);
+                // minimize for the evaluation of subsequent moves
+                let (_, num_moves_prime, evaluation) =
+                    alphabeta_with_printing_inner(g, depth - 1, alpha, beta);
+                num_moves += num_moves_prime;
+                // if our evaluated move produces lower eval than the beta,
+                // update beta.
+                if evaluation < beta {
+                    beta = evaluation;
+                    best_move = mv;
+                };
+                // if our beta is less than alpha, prune the node.
+                if beta <= alpha {
+                    break;
+                }
+            }
+            (best_move, num_moves, beta)
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::board::BitBoard;
     use crate::board::view::View;
+    use crate::board::{BitBoard, Board, Score};
     use crate::game::Game;
 
+    use rand::prelude::IndexedRandom;
+    use rand::rngs::StdRng;
+    use rand::{Rng, SeedableRng};
+
+    /// An AI player that only makes random moves
+    fn random_move(game: &Game, rng: &mut impl Rng) -> Board {
+        let moves = explode_board(game.available()).collect::<Vec<_>>();
+        *moves.choose(rng).unwrap()
+    }
+
     #[test]
     // just a sanity check to ensure that my AI performs up to snuff with another popular engine
     fn opening() {
@@ -171,21 +281,48 @@ mod tests {
     // I found that, despite the AI clobbering me, the AI could not
     // compete with itself very well. I'm honestly not quite sure why that is.
     #[test]
-    #[should_panic] // disabled until I fix whatever causes the AI not to tie
+    fn ai_beats_random() {
-    fn ai_ties_ai() {
+        // just contains pairings of starting_team and seed value
-        // just play through a game letting AI make all the moves.
+        let cases = vec![
-        let mut game = Game::default();
+            (Team::Black, 1231293),
-        while !game.is_complete() {
+            (Team::White, 491823),
-            if game.available() == 0 {
+            (Team::White, 12931),
-                game.skip();
+            (Team::Black, 982983713),
-            } else {
+            (Team::Black, 123),
-                let (mv, _) = alphabeta(game.clone(), 8, i8::MIN + 1, i8::MAX - 1);
+            (Team::White, 87132895),
+        ];
+
+        for (team, seed) in cases {
+            let mut rng = StdRng::seed_from_u64(seed);
+            let mut game = Game::default();
+            if team != Team::Black {
+                let mv = random_move(&game, &mut rng);
                 game.play(mv);
             }
-        }
 
-        // one would assume the AI would compete rather closely against itself.
+            while !game.is_complete() {
-        assert!(dbg!(game.score()).diff().abs() < 3);
+                if game.available() == 0 {
+                    game.skip();
+                    continue;
+                }
+                let mv = if game.current_team == team {
+                    alphabeta(game.clone(), 8, i8::MIN + 1, i8::MAX - 1).0
+                } else {
+                    random_move(&game, &mut rng)
+                };
+                game.play(mv);
+            }
+
+            assert!(
+                match (team, game.score()) {
+                    (Team::Black, Score(b, w)) => b - w,
+                    (Team::White, Score(b, w)) => w - b,
+                } > 4,
+                "game with seed {} and team {:?} failed to win by 4 points or more.",
+                seed,
+                team
+            );
+        }
     }
 
     #[test]

src/cli/mod.rs

@@ -1,7 +1,7 @@
 use std::io;
 
 use othello::{
-    ai::alphabeta,
+    ai::{alphabeta, alphabeta_with_printing},
     board::{
         Board, Score,
         view::{Overlay, View},
@@ -15,7 +15,9 @@ use regex::Regex;
 enum Action {
     Play(Board),
     Skip,
-    Ai,
+    /// Lets AI play. The boolean value indicates whether or not
+    /// to enable tracing.
+    Ai(bool),
 }
 
 /// Regex to match on valid play expressions. The file and rank are captured.
@@ -68,7 +70,8 @@ pub fn run() -> anyhow::Result<()> {
             // match raw strings for other options
             match raw_input.as_str().trim() {
                 "skip" => break Action::Skip,
-                "ai" => break Action::Ai,
+                "ai" => break Action::Ai(false),
+                "ai-trace" => break Action::Ai(true),
                 _ => println!("Invalid input"),
             }
         };
@@ -95,14 +98,18 @@ pub fn run() -> anyhow::Result<()> {
                     game.skip()
                 }
             }
-            Action::Ai => {
+            Action::Ai(tracing) => {
                 if legal_moves == 0 {
                     println!("beep. boop. no legal moves. skipping turn");
                     game.skip();
-                } else {
+                } else if !tracing {
                     let (mv, eval) = alphabeta(game.clone(), 14, i8::MIN + 1, i8::MAX - 1);
                     println!("beep. boop. eval = {eval}");
                     game.play(mv);
+                } else {
+                    let (mv, eval) = alphabeta_with_printing(game.clone(), 14);
+                    println!("beep. boop. eval = {eval}");
+                    game.play(mv);
                 }
                 board_changed = true;
             }
@@ -141,6 +148,7 @@ fn create_move(file: &str, rank: u8) -> Board {
 mod tests {
     use super::*;
     use othello::board::squares::*;
+
     #[test]
     fn create_move_works() {
         // validate that we can create moves from

src/main.rs

@@ -1,6 +1,6 @@
-///! Student: Jack Branch - 103-93-063
+// Student: Jack Branch - 103-93-063
-///! Prof:    Dr. Mike O'Neal
+// Prof:    Dr. Mike O'Neal
-///! Class:   Artificial Intelligence
+// Class:   Artificial Intelligence (CS 4753)
 mod cli;
 
 fn main() -> anyhow::Result<()> {