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add zobrist hashing, WIP transposition table

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jackjohn7 2026-05-04 20:49:31 -05:00
parent aa562d4ab6
commit 88131d9ab0
9 changed files with 362 additions and 137 deletions
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279
Cargo.lock generated
View file

@ -35,6 +35,12 @@ version = "1.5.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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@ -53,6 +59,17 @@ version = "1.0.4"
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@ -105,6 +122,15 @@ version = "0.7.6"
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@ -176,15 +202,29 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
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"cfg-if",
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[[package]]
@ -198,6 +238,45 @@ dependencies = [
"zerocopy",
]
[[package]]
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]
[[package]]
name = "itertools"
version = "0.13.0"
@ -223,12 +302,24 @@ dependencies = [
"wasm-bindgen",
]
[[package]]
name = "leb128fmt"
version = "0.1.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
name = "libc"
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[[package]]
name = "memchr"
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@ -295,12 +386,13 @@ dependencies = [
]
[[package]]
name = "ppv-lite86"
version = "0.2.21"
name = "prettyplease"
version = "0.2.37"
source = "registry+https://github.com/rust-lang/crates.io-index"
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dependencies = [
"zerocopy",
"proc-macro2",
"syn",
]
[[package]]
@ -323,38 +415,26 @@ dependencies = [
[[package]]
name = "r-efi"
version = "5.3.0"
version = "6.0.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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[[package]]
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dependencies = [
"rand_chacha",
"rand_core",
]
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name = "rand_chacha"
version = "0.9.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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"chacha20",
"getrandom",
"rand_core",
]
[[package]]
name = "rand_core"
version = "0.9.3"
version = "0.10.1"
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[[package]]
name = "rayon"
@ -426,6 +506,12 @@ dependencies = [
"winapi-util",
]
[[package]]
name = "semver"
version = "1.0.28"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "8a7852d02fc848982e0c167ef163aaff9cd91dc640ba85e263cb1ce46fae51cd"
[[package]]
name = "serde"
version = "1.0.228"
@ -496,6 +582,12 @@ version = "1.0.22"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "9312f7c4f6ff9069b165498234ce8be658059c6728633667c526e27dc2cf1df5"
[[package]]
name = "unicode-xid"
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[[package]]
name = "walkdir"
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@ -512,7 +604,16 @@ version = "1.0.1+wasi-0.2.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0562428422c63773dad2c345a1882263bbf4d65cf3f42e90921f787ef5ad58e7"
dependencies = [
"wit-bindgen",
"wit-bindgen 0.46.0",
]
[[package]]
name = "wasip3"
version = "0.4.0+wasi-0.3.0-rc-2026-01-06"
source = "registry+https://github.com/rust-lang/crates.io-index"
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dependencies = [
"wit-bindgen 0.51.0",
]
[[package]]
@ -560,6 +661,40 @@ dependencies = [
"unicode-ident",
]
[[package]]
name = "wasm-encoder"
version = "0.244.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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dependencies = [
"leb128fmt",
"wasmparser",
]
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name = "wasm-metadata"
version = "0.244.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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"indexmap",
"wasm-encoder",
"wasmparser",
]
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source = "registry+https://github.com/rust-lang/crates.io-index"
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"hashbrown 0.15.5",
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]
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@ -600,6 +735,94 @@ version = "0.46.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
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]
[[package]]
name = "zerocopy"
version = "0.8.27"

2
Cargo.toml
View file

@ -13,11 +13,11 @@ path = "src/main.rs"
[dependencies]
anyhow = "1.0.100"
rand = "0.10.1"
regex = "1.12.2"
[dev-dependencies]
criterion = "0.7.0"
rand = "0.9.2"
[[bench]]
name = "generation"

100
src/ai.rs
View file

@ -142,106 +142,6 @@ 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::*;

18
src/board/mod.rs
View file

@ -6,6 +6,7 @@ use std::fmt::{Debug, Display};
use crate::{
board::view::{Overlay, View},
game::Team,
zobrist::{ZOBRIST_TABLE, ZOBRIST_TURN},
};
pub mod view;
@ -446,6 +447,23 @@ impl BitBoard {
self.boards[1].count_ones() as u8,
)
}
pub fn compute_hash(&self, playing: Team) -> u64 {
let mut hash = 0;
for (player, board) in self.boards.iter().enumerate() {
for offset in 0..64 as u64 {
if (1 << offset) & board > 0 {
hash ^= ZOBRIST_TABLE[player][offset as usize];
}
}
}
if matches!(playing, Team::White) {
hash ^= *ZOBRIST_TURN;
}
hash
}
}
pub mod squares {

6
src/cli/mod.rs
View file

@ -1,7 +1,7 @@
use std::io;
use othello::{
ai::{alphabeta, alphabeta_with_printing},
ai::alphabeta,
board::{
Board, Score,
view::{Overlay, View},
@ -106,10 +106,6 @@ pub fn run() -> anyhow::Result<()> {
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;
}

33
src/game.rs
View file

@ -1,4 +1,7 @@
use crate::board::{BitBoard, Board, Score};
use crate::{
board::{BitBoard, Board, Score},
zobrist::{ZOBRIST_TABLE, ZOBRIST_TURN},
};
#[repr(u8)]
#[derive(Copy, Clone, Debug, PartialEq, Default)]
@ -19,16 +22,31 @@ impl Team {
}
}
#[derive(Default, Clone)]
// TODO: Look into potentially better memory alignment for this
#[derive(Clone)]
pub struct Game {
pub current_team: Team,
hash: u64,
board: BitBoard,
}
impl Default for Game {
fn default() -> Self {
let board = BitBoard::default();
let team = Team::default();
Self {
current_team: team,
board: Default::default(),
hash: board.compute_hash(team),
}
}
}
impl Game {
/// Play a move. Automatically transitions state to next player.
pub fn play(&mut self, player_move: Board) {
self.hash ^=
ZOBRIST_TABLE[self.current_team as usize][player_move.trailing_zeros() as usize];
self.hash ^= *ZOBRIST_TURN;
self.board.play(self.current_team, player_move);
self.current_team = self.current_team.next();
}
@ -45,6 +63,7 @@ impl Game {
/// Skip the current player
pub fn skip(&mut self) {
self.hash ^= *ZOBRIST_TURN;
self.current_team = self.current_team.next();
}
@ -76,6 +95,7 @@ impl Game {
pub(crate) fn from_parts(current_team: Team, board: BitBoard) -> Self {
Self {
current_team,
hash: board.compute_hash(current_team),
board,
}
}
@ -85,6 +105,13 @@ impl Game {
mod tests {
use super::*;
use crate::board::squares::*;
#[test]
fn game_inits_with_hash() {
let game = Game::default();
assert_ne!(game.hash, 0);
}
#[test]
fn play_switches_team() {
let mut game = Game::default();

2
src/lib.rs
View file

@ -1,3 +1,5 @@
pub mod ai;
pub mod board;
pub mod game;
mod table;
mod zobrist;

32
src/table.rs Normal file
View file

@ -0,0 +1,32 @@
use std::collections::HashMap;
use crate::{board::BitBoard, game::Game, zobrist::ZOBRIST_TABLE};
pub enum Bound {
Exact,
Lower,
Upper,
}
pub struct TTEntry {
bound: Bound,
evaluation: i8,
depth: u8,
}
#[derive(Default)]
pub struct TTable {
// replace with `DashMap` if we utilize concurrency
inner: HashMap<u64, TTEntry>,
}
impl TTable {
pub fn new() -> Self {
Self::default()
}
pub fn upsert(&mut self, game: &Game) {
//self.inner.entry(key).or_insert(default)
todo!()
}
}

27
src/zobrist.rs Normal file
View file

@ -0,0 +1,27 @@
use std::sync::LazyLock;
use rand::{RngExt, SeedableRng, rngs::StdRng};
pub static ZOBRIST_TABLE: LazyLock<[[u64; 64]; 2]> = LazyLock::new(generate_zobrist);
pub static ZOBRIST_TURN: LazyLock<u64> = LazyLock::new(generate_zobrist_turn);
fn generate_zobrist() -> [[u64; 64]; 2] {
let seed: u64 = std::env::var("ZOBRIST_SEED")
.unwrap_or("42".into())
.parse()
.expect("Zobrist seed must be a valid unsigned integer");
let mut rng = StdRng::seed_from_u64(seed);
std::array::from_fn(|_| std::array::from_fn(|_| rng.random()))
}
fn generate_zobrist_turn() -> u64 {
let seed: u64 = std::env::var("ZOBRIST_TURN_SEED")
.unwrap_or("24".into())
.parse()
.expect("Zobrist turn seed must be a valid unsigned integer");
let mut rng = StdRng::seed_from_u64(seed);
rng.random()
}