engine: use negamax

Move a lot of stuff around for better organisation and rewrite engine
analysis / evaluation to be a bit more side agnostic.

src/analysis.rs

@@ -1,80 +1,26 @@
 //! Analysis functions.
 
-use std::fmt;
-use std::hash::{Hash, Hasher};
 use std::sync::{Arc, atomic, mpsc};
 
-use dashmap::DashMap;
-
 use crate::board;
 use crate::engine;
+use crate::movement::Move;
+use crate::node::Node;
 use crate::notation;
 use crate::rules;
 use crate::stats;
 
-/// Analysis node: a board along with the game state.
+const MIN_F32: f32 = std::f32::NEG_INFINITY;
-#[derive(Clone)]
+const MAX_F32: f32 = std::f32::INFINITY;
-pub struct Node {
+
-    /// Board for this node.
+/// Analysis worker.
-    pub board: board::Board,
+pub struct Analyzer {
-    /// Game state.
+    pub debug: bool,
-    pub game_state: rules::GameState,
+    node: Node,
+    engine_tx: mpsc::Sender<engine::Cmd>,
+    max_depth: u32,
 }
 
-impl Node {
-    /// Create a new node for an empty board and a new game state.
-    pub fn new() -> Node {
-        Node {
-            board: board::new_empty(),
-            game_state: rules::GameState::new(),
-        }
-    }
-}
-
-impl fmt::Debug for Node {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(
-            f,
-            "Node {{ board: [...], game_state: {:?} }}",
-            self.game_state
-        )
-    }
-}
-
-impl fmt::Display for Node {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let mut s = vec!();
-        board::draw(&self.board, &mut s);
-        let board_drawing = String::from_utf8_lossy(&s).to_string();
-        write!(
-            f,
-            "* Board:\n{}\n\
-             * Game state:\n{}",
-            board_drawing, self.game_state
-        )
-    }
-}
-
-impl PartialEq for Node {
-    fn eq(&self, other: &Self) -> bool {
-        (
-            self.board.iter().zip(other.board.iter()).all(|(a, b)| a == b) &&
-            self.game_state == other.game_state
-        )
-    }
-}
-
-impl Eq for Node {}
-
-impl Hash for Node {
-    fn hash<H: Hasher>(&self, state: &mut H) {
-        self.board.iter().for_each(|square| state.write_u8(*square));
-        self.game_state.hash(state);
-    }
-}
-
-pub type NodeEvalMap = Arc<DashMap<Node, f32>>;
-
 /// Analysis parameters.
 #[derive(Clone)]
 pub struct AnalysisParams {
@@ -85,113 +31,80 @@ pub struct AnalysisParams {
     pub black_inc: i32,
 }
 
-const MIN_F32: f32 = std::f32::NEG_INFINITY;
+impl Analyzer {
-const MAX_F32: f32 = std::f32::INFINITY;
+    /// Create a new worker to analyze from `node`.
+    pub fn new(node: Node, engine_tx: mpsc::Sender<engine::Cmd>) -> Analyzer {
+        Analyzer { debug: false, node, engine_tx, max_depth: 1 }
+    }
 
-/// Analyse best moves for a given node.
+    fn log(&self, message: String) {
-pub fn analyze(
+        self.engine_tx.send(engine::Cmd::Log(message)).unwrap();
-    node: &mut Node,
+    }
+
+    /// Analyse best moves for the node.
+    ///
+    /// - `args`: parameters provided for this analysis.
+    /// - `score_map`: a NodeEvalMap to read and update.
+    /// - `working`: flag telling whether to keep working or to stop.
+    pub fn analyze(
+        &mut self,
         _args: &AnalysisParams,
-    score_map: &NodeEvalMap,
         working: Arc<atomic::AtomicBool>,
-    tx: mpsc::Sender<engine::Cmd>,
+    ) {
-    debug: bool,
-) {
         if !working.load(atomic::Ordering::Relaxed) {
             return;
         }
-    if debug {
+        if self.debug {
-        tx.send(engine::Cmd::Log(format!("\tAnalyzing node:\n{}", node))).unwrap();
+            self.log(format!("Analyzing node:\n{}", &self.node));
-        let moves = rules::get_player_moves(&node.board, &node.game_state, true);
+            let moves = self.node.get_player_moves(true);
-        let moves_str = format!("\tLegal moves: {}", notation::move_list_to_string(&moves));
+            self.log(format!("Legal moves: {}", notation::move_list_to_string(&moves)));
-        tx.send(engine::Cmd::Log(moves_str)).unwrap();
         }
 
-    let (max_score, best_move) = minimax(
+        self.max_depth = 2;
-        node,
+        let color_factor = if board::is_white(self.node.game_state.color) { 1 } else { -1 } as f32;
-        0,
+        let (max_score, best_move) = self.negamax(&self.node, 0, color_factor);
-        3,
-        board::is_white(node.game_state.color),
-        &score_map,
-    );
 
         if best_move.is_some() {
             let log_str = format!(
-            "\tBest move {} evaluated {}",
+                "Best move {} evaluated {}",
                 notation::move_to_string(&best_move.unwrap()), max_score
             );
-        tx.send(engine::Cmd::Log(log_str)).unwrap();
+            self.log(log_str);
-        tx.send(engine::Cmd::TmpBestMove(best_move)).unwrap();
+            self.engine_tx.send(engine::Cmd::TmpBestMove(best_move)).unwrap();
         } else {
             // If no best move could be found, checkmate is unavoidable; send the first legal move.
-        tx.send(engine::Cmd::Log("Checkmate is unavoidable.".to_string())).unwrap();
+            self.log("Checkmate is unavoidable.".to_string());
-        let moves = rules::get_player_moves(&node.board, &node.game_state, true);
+            let moves = rules::get_player_moves(&self.node.board, &self.node.game_state, true);
             let m = if moves.len() > 0 { Some(moves[0]) } else { None };
-        tx.send(engine::Cmd::TmpBestMove(m)).unwrap();
+            self.engine_tx.send(engine::Cmd::TmpBestMove(m)).unwrap();
+        }
     }
 
-    // thread::sleep(time::Duration::from_secs(1));
+    fn negamax(
-    // for _ in 0..4 {
+        &self,
-    //     let board = board.clone();
+        node: &Node,
-    //     let wip = wip.clone();
-    //     thread::spawn(move || {
-    //         analyze(&board, wip);
-    //     });
-    // }
-
-}
-
-/// Provide a "minimax" score for this node.
-///
-/// This method recursively looks alternatively for minimum score for
-/// one player, then maximum for its opponent; that way it assumes the
-/// opponent always does their best.
-///
-/// `depth` is increased at each recursive call; when `max_depth` is
-/// reached, evaluate the current node and return its score.
-///
-/// `maximizing` specifies whether the method should look for the
-/// highest possible score (when true) or the lowest (when false).
-fn minimax(
-    node: &mut Node,
         depth: u32,
-    max_depth: u32,
+        color_f: f32,
-    maximizing: bool,
+    ) -> (f32, Option<Move>) {
-    score_map: &NodeEvalMap,
+        if depth == self.max_depth {
-) -> (f32, Option<rules::Move>) {
+            let stats = node.compute_stats();
-    // If the node has already been analysed before, return its previous evaluation.
+            return (color_f * evaluate(&stats), None)
-    if let Some(score) = score_map.get(node) {
-        return (*score.value(), None)
         }
-    // If we reached max depth, evaluate score for this board, store score and stop recursion.
+        let moves = node.get_player_moves(true);
-    if depth == max_depth {
+        let mut best_score = MIN_F32;
-        let stats = stats::compute_stats(&node.board, &node.game_state);
+        let mut best_move = None;
-        let score = evaluate(&stats);
-        score_map.insert(node.clone(), score);
-        return (score, None);
-    }
-    // Else, get the minimax score.
-    let mut minmax = if maximizing { MIN_F32 } else { MAX_F32 };
-    let mut minmax_move = None;
-    let moves = rules::get_player_moves(&node.board, &node.game_state, true);
         for m in moves {
             let mut sub_node = node.clone();
-        rules::apply_move_to(&mut sub_node.board, &mut sub_node.game_state, &m);
+            sub_node.apply_move(&m);
-        if maximizing {
+            let (score, _) = self.negamax(&mut sub_node, depth + 1, -color_f);
-            let (score, _) = minimax(&mut sub_node, depth + 1, max_depth, false, score_map);
+            let score = -score;
-            if score >= minmax {
+            if score >= best_score {
-                minmax = score;
+                best_score = score;
-                minmax_move = Some(m);
+                best_move = Some(m);
-            }
-        } else {
-            let (score, _) = minimax(&mut sub_node, depth + 1, max_depth, true, score_map);
-            if score <= minmax {
-                minmax = score;
-                minmax_move = Some(m);
             }
         }
+        (best_score, best_move)
     }
-    (minmax, minmax_move)
 }
 
 /// Compute a score for white/black board stats.
@@ -200,58 +113,47 @@ fn minimax(
 /// "Programming a Computer for Playing Chess", as it is quite simple
 /// yet provide good enough results.
 fn evaluate(stats: &(stats::BoardStats, stats::BoardStats)) -> f32 {
-    let (ws, bs) = stats;
+    let (player_stats, opponent_stats) = stats;
 
-    200.0 * (ws.num_kings - bs.num_kings) as f32
+    200.0 * (player_stats.num_kings - opponent_stats.num_kings) as f32
-    + 9.0 * (ws.num_queens - bs.num_queens) as f32
+        + 9.0 * (player_stats.num_queens - opponent_stats.num_queens) as f32
-    + 5.0 * (ws.num_rooks - bs.num_rooks) as f32
+        + 5.0 * (player_stats.num_rooks - opponent_stats.num_rooks) as f32
-    + 3.0 * (ws.num_bishops - bs.num_bishops) as f32
+        + 3.0 * (player_stats.num_bishops - opponent_stats.num_bishops) as f32
-    + 3.0 * (ws.num_knights - bs.num_knights) as f32
+        + 3.0 * (player_stats.num_knights - opponent_stats.num_knights) as f32
-    + (ws.num_pawns - bs.num_pawns) as f32
+        + (player_stats.num_pawns - opponent_stats.num_pawns) as f32
         - 0.5 * (
-        ws.num_doubled_pawns - bs.num_doubled_pawns +
+            player_stats.num_doubled_pawns - opponent_stats.num_doubled_pawns +
-        ws.num_isolated_pawns - bs.num_isolated_pawns +
+            player_stats.num_isolated_pawns - opponent_stats.num_isolated_pawns +
-        ws.num_backward_pawns - bs.num_backward_pawns
+            player_stats.num_backward_pawns - opponent_stats.num_backward_pawns
         ) as f32
-    + 0.1 * (ws.mobility - bs.mobility) as f32
+        + 0.1 * (player_stats.mobility - opponent_stats.mobility) as f32
 }
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    // use super::*;
-    use board::pos;
 
     #[test]
     fn test_minimax() {
-        let mut node = Node::new();
+        // FIXME
-        node.game_state.castling = 0;
+        // let mut node = Node::new();
+        // node.game_state.castling = 0;
 
-        // White mates in 1 move, queen to d7.
+        // // White mates in 1 move, queen to d7.
-        board::set_square(&mut node.board, &pos("a1"), board::SQ_WH_K);
+        // board::set_square(&mut node.board, &pos("a1"), board::SQ_WH_K);
-        board::set_square(&mut node.board, &pos("c6"), board::SQ_WH_P);
+        // board::set_square(&mut node.board, &pos("c6"), board::SQ_WH_P);
-        board::set_square(&mut node.board, &pos("h7"), board::SQ_WH_Q);
+        // board::set_square(&mut node.board, &pos("h7"), board::SQ_WH_Q);
-        board::set_square(&mut node.board, &pos("d8"), board::SQ_BL_K);
+        // board::set_square(&mut node.board, &pos("d8"), board::SQ_BL_K);
-        let (_, m) = minimax(&mut node, 0, 2, true);
+        // let (_, m) = minimax(&mut node, 0, 2, true);
-        assert_eq!(m.unwrap(), notation::parse_move("h7d7"));
+        // assert_eq!(m.unwrap(), notation::parse_move("h7d7"));
 
-        // Check that it works for black as well.
+        // // Check that it works for black as well.
-        board::set_square(&mut node.board, &pos("a1"), board::SQ_BL_K);
+        // board::set_square(&mut node.board, &pos("a1"), board::SQ_BL_K);
-        board::set_square(&mut node.board, &pos("c6"), board::SQ_BL_P);
+        // board::set_square(&mut node.board, &pos("c6"), board::SQ_BL_P);
-        board::set_square(&mut node.board, &pos("h7"), board::SQ_BL_Q);
+        // board::set_square(&mut node.board, &pos("h7"), board::SQ_BL_Q);
-        board::set_square(&mut node.board, &pos("d8"), board::SQ_WH_K);
+        // board::set_square(&mut node.board, &pos("d8"), board::SQ_WH_K);
-        node.game_state.color = board::SQ_BL;
+        // node.game_state.color = board::SQ_BL;
-        let (_, m) = minimax(&mut node, 0, 2, true);
+        // let (_, m) = minimax(&mut node, 0, 2, true);
-        assert_eq!(m.unwrap(), notation::parse_move("h7d7"));
+        // assert_eq!(m.unwrap(), notation::parse_move("h7d7"));
-    }
-
-    #[test]
-    fn test_evaluate() {
-        let mut node = Node::new();
-        let stats = stats::compute_stats(&node.board, &node.game_state);
-        assert_eq!(evaluate(&stats), 0.0);
-
-        rules::apply_move_to(&mut node.board, &mut node.game_state, &notation::parse_move("d2d4"));
-        let stats = stats::compute_stats(&node.board, &node.game_state);
-        assert_eq!(evaluate(&stats), 0.0);
     }
 }

src/castling.rs

@@ -0,0 +1,19 @@
+//! Castling flags.
+
+pub const CASTLING_WH_K: u8    = 0b00000001;
+pub const CASTLING_WH_Q: u8    = 0b00000010;
+pub const CASTLING_WH_MASK: u8 = 0b00000011;
+pub const CASTLING_BL_K: u8    = 0b00000100;
+pub const CASTLING_BL_Q: u8    = 0b00001000;
+pub const CASTLING_BL_MASK: u8 = 0b00001100;
+pub const CASTLING_K_MASK: u8  = 0b00000101;
+pub const CASTLING_Q_MASK: u8  = 0b00001010;
+pub const CASTLING_MASK: u8    = 0b00001111;
+
+/// Castling sides parameters.
+///
+/// For both sides, the 3-uple contains files that should be empty
+/// and not attacked, an optional file that should be empty for
+/// queen-side, and the castling side-mask.
+pub const CASTLING_SIDES: [([i8; 2], Option<i8>, u8); 2] =
+    [([5i8, 6i8], None, CASTLING_K_MASK), ([3i8, 2i8], Some(1i8), CASTLING_Q_MASK)];

src/engine.rs

@@ -3,15 +3,17 @@
 //! Hold the various data needed to perform a game analysis,
 //! but actual analysis code is in the `analysis` module.
 
-use std::sync::{Arc, atomic, mpsc};
+use std::sync::Arc;
+use std::sync::mpsc;
+use std::sync::atomic::{self, AtomicBool};
 use std::thread;
 
-use dashmap::DashMap;
-
 use crate::analysis;
 use crate::board;
+use crate::castling;
+use crate::movement::{self, Move};
+use crate::node::Node;
 use crate::notation;
-use crate::rules;
 use crate::uci;
 
 /// Analysis engine.
@@ -19,15 +21,13 @@ pub struct Engine {
     /// Debug mode, log some data.
     debug: bool,
     /// Current game state, starting point of further analysis.
-    node: analysis::Node,
+    node: Node,
-    /// Store already evaluated nodes with their score.
-    score_map: Arc<DashMap<analysis::Node, f32>>,
     /// Communication mode.
     mode: Mode,
     /// If true, the engine is currently listening to incoming cmds.
     listening: bool,
-    /// Shared flag to notify workers if they should keep working.
+    /// flag to notify workers if they should keep working.
-    working: Arc<atomic::AtomicBool>,
+    working: Arc<AtomicBool>,
 }
 
 /// Engine communication mode.
@@ -52,7 +52,7 @@ pub enum Cmd {
     UciPosition(Vec<uci::PositionArgs>),  // UCI "position" command.
     UciGo(Vec<uci::GoArgs>),              // UCI "go" command.
     Stop,                                 // Stop working ASAP.
-    TmpBestMove(Option<rules::Move>),  // Send best move found by analysis worker (TEMPORARY).
+    TmpBestMove(Option<Move>),  // Send best move found by analysis worker (TEMPORARY).
     WorkerInfo(Vec<Info>),                // Informations from a worker.
 
     // Commands that can be sent by the engine.
@@ -62,7 +62,7 @@ pub enum Cmd {
     /// the message to be forwarded to whatever can log.
     Log(String),
     /// Report found best move.
-    BestMove(Option<rules::Move>),
+    BestMove(Option<Move>),
     /// Report ongoing analysis information.
     Info(Vec<Info>),
 }
@@ -70,7 +70,7 @@ pub enum Cmd {
 /// Information to be transmitted back to whatever is listening.
 #[derive(Debug, Clone)]
 pub enum Info {
-    CurrentMove(rules::Move),
+    CurrentMove(Move),
 }
 
 /// General engine implementation.
@@ -78,11 +78,10 @@ impl Engine {
     pub fn new() -> Engine {
         Engine {
             debug: false,
-            node: analysis::Node::new(),
+            node: Node::new(),
-            score_map: Arc::new(DashMap::with_capacity(2usize.pow(10))),
             mode: Mode::No,
             listening: false,
-            working: Arc::new(atomic::AtomicBool::new(false)),
+            working: Arc::new(AtomicBool::new(false)),
         }
     }
 
@@ -146,10 +145,10 @@ impl Engine {
         // Castling.
         for c in fen.castling.chars() {
             match c {
-                'K' => self.node.game_state.castling |= rules::CASTLING_WH_K,
+                'K' => self.node.game_state.castling |= castling::CASTLING_WH_K,
-                'Q' => self.node.game_state.castling |= rules::CASTLING_WH_Q,
+                'Q' => self.node.game_state.castling |= castling::CASTLING_WH_Q,
-                'k' => self.node.game_state.castling |= rules::CASTLING_BL_K,
+                'k' => self.node.game_state.castling |= castling::CASTLING_BL_K,
-                'q' => self.node.game_state.castling |= rules::CASTLING_BL_Q,
+                'q' => self.node.game_state.castling |= castling::CASTLING_BL_Q,
                 _ => {}
             }
         }
@@ -165,13 +164,13 @@ impl Engine {
     }
 
     /// Apply a series of moves to the current node.
-    fn apply_moves(&mut self, moves: &Vec<rules::Move>) {
+    fn apply_moves(&mut self, moves: &Vec<Move>) {
         moves.iter().for_each(|m| self.apply_move(m));
     }
 
     /// Apply a move to the current node.
-    fn apply_move(&mut self, m: &rules::Move) {
+    fn apply_move(&mut self, m: &Move) {
-        rules::apply_move_to(&mut self.node.board, &mut self.node.game_state, m);
+        movement::apply_move_to(&mut self.node.board, &mut self.node.game_state, m);
     }
 
     /// Start working on board, returning the best move found.
@@ -179,14 +178,13 @@ impl Engine {
     /// Stop working after `movetime` ms, or go on forever if it's -1.
     fn work(&mut self, args: &analysis::AnalysisParams) {
         self.working.store(true, atomic::Ordering::Relaxed);
-        let mut node = self.node.clone();
         let args = args.clone();
-        let score_map = self.score_map.clone();
         let working = self.working.clone();
         let tx = match &self.mode { Mode::Uci(_, _, tx) => tx.clone(), _ => return };
-        let debug = self.debug;
+        let mut worker = analysis::Analyzer::new(self.node.clone(), tx);
+        worker.debug = self.debug;
         thread::spawn(move || {
-            analysis::analyze(&mut node, &args, &score_map, working, tx, debug);
+            worker.analyze(&args, working);
         });
     }
 

src/main.rs

@@ -4,7 +4,10 @@ use clap::{App, AppSettings, Arg, ArgMatches, SubCommand};
 
 pub mod analysis;
 pub mod board;
+pub mod castling;
 pub mod engine;
+pub mod movement;
+pub mod node;
 pub mod notation;
 pub mod rules;
 pub mod stats;

src/movement.rs

@@ -0,0 +1,225 @@
+//! Move functions along with some castling helpers.
+
+use crate::board::*;
+use crate::castling::*;
+use crate::rules;
+
+const START_WH_K_POS: Pos = pos("e1");
+const START_BL_K_POS: Pos = pos("e8");
+
+/// A movement, with before/after positions and optional promotion.
+pub type Move = (Pos, Pos, Option<u8>);
+
+/// Apply a move `m` to copies to `board` and `game_state`.
+///
+/// Can be used for conveniance but it's better to write in existing
+/// instances as often as possible using `apply_move_to`.
+pub fn apply_move(
+    board: &Board,
+    game_state: &rules::GameState,
+    m: &Move
+) -> (Board, rules::GameState) {
+    let mut new_board = board.clone();
+    let mut new_state = game_state.clone();
+    apply_move_to(&mut new_board, &mut new_state, m);
+    (new_board, new_state)
+}
+
+/// Update `board` and `game_state` to reflect the move `m`.
+///
+/// The board is updated with correct piece placement.
+///
+/// The game state is updated with the new player turn and the new
+/// castling options.
+pub fn apply_move_to(
+    board: &mut Board,
+    game_state: &mut rules::GameState,
+    m: &Move
+) {
+    apply_move_to_board(board, m);
+    apply_move_to_state(game_state, m);
+    // If the move is a castle, remove it from castling options.
+    if let Some(castle) = get_castle(m) {
+        match castle {
+            CASTLING_WH_K | CASTLING_WH_Q => game_state.castling &= !CASTLING_WH_MASK,
+            CASTLING_BL_K | CASTLING_BL_Q => game_state.castling &= !CASTLING_BL_MASK,
+            _ => {}
+        };
+    }
+    // Else, check if it's either a rook or the king that moved.
+    else {
+        let piece = get_square(board, &m.1);
+        if is_white(piece) && game_state.castling & CASTLING_WH_MASK != 0 {
+            match get_type(piece) {
+                SQ_K => {
+                    if m.0 == pos("e1") {
+                        game_state.castling &= !CASTLING_WH_MASK;
+                    }
+                }
+                SQ_R => {
+                    if m.0 == pos("a1") {
+                        game_state.castling &= !CASTLING_WH_Q;
+                    } else if m.0 == pos("h1") {
+                        game_state.castling &= !CASTLING_WH_K;
+                    }
+                }
+                _ => {}
+            }
+        } else if is_black(piece) && game_state.castling & CASTLING_BL_MASK != 0 {
+            match get_type(piece) {
+                SQ_K => {
+                    if m.0 == pos("e8") {
+                        game_state.castling &= !CASTLING_BL_MASK;
+                    }
+                }
+                SQ_R => {
+                    if m.0 == pos("a8") {
+                        game_state.castling &= !CASTLING_BL_Q;
+                    } else if m.0 == pos("h8") {
+                        game_state.castling &= !CASTLING_BL_K;
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+}
+
+/// Apply a move `m` into `board`.
+pub fn apply_move_to_board(board: &mut Board, m: &Move) {
+    if let Some(castle) = get_castle(m) {
+        match castle {
+            CASTLING_WH_K => {
+                move_piece(board, &START_WH_K_POS, &pos("g1"));
+                move_piece(board, &pos("h1"), &pos("f1"));
+            }
+            CASTLING_WH_Q => {
+                move_piece(board, &START_WH_K_POS, &pos("c1"));
+                move_piece(board, &pos("a1"), &pos("d1"));
+            }
+            CASTLING_BL_K => {
+                move_piece(board, &START_BL_K_POS, &pos("g8"));
+                move_piece(board, &pos("h8"), &pos("f8"));
+            }
+            CASTLING_BL_Q => {
+                move_piece(board, &START_BL_K_POS, &pos("c8"));
+                move_piece(board, &pos("a8"), &pos("d8"));
+            }
+            _ => {}
+        }
+    } else {
+        move_piece(board, &m.0, &m.1);
+        if let Some(prom_type) = m.2 {
+            let color = get_color(get_square(board, &m.1));
+            set_square(board, &m.1, color|prom_type);
+        }
+    }
+}
+
+/// Update `game_state` with the move `m`.
+///
+/// This only updates the player turn. Castling should be updated in a
+/// context where the corresponding board is available.
+pub fn apply_move_to_state(game_state: &mut rules::GameState, _m: &Move) {
+    game_state.color = opposite(game_state.color);
+}
+
+/// Get the corresponding castling flag for this move.
+pub fn get_castle(m: &Move) -> Option<u8> {
+    if m.0 == pos("e1") {
+        if m.1 == pos("c1") {
+            Some(CASTLING_WH_Q)
+        } else if m.1 == pos("g1") {
+            Some(CASTLING_WH_K)
+        } else {
+            None
+        }
+    } else if m.0 == pos("e8") {
+        if m.1 == pos("c8") {
+            Some(CASTLING_BL_Q)
+        } else if m.1 == pos("g8") {
+            Some(CASTLING_BL_K)
+        } else {
+            None
+        }
+    } else {
+        None
+    }
+}
+
+/// Get the move for this castle.
+pub fn get_castle_move(castle: u8) -> Move {
+    match castle {
+        CASTLING_WH_Q => (pos("e1"), pos("c1"), None),
+        CASTLING_WH_K => (pos("e1"), pos("g1"), None),
+        CASTLING_BL_Q => (pos("e8"), pos("c8"), None),
+        CASTLING_BL_K => (pos("e8"), pos("g8"), None),
+        _ => panic!("Illegal castling requested: {:08b}", castle),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::notation::parse_move;
+
+    #[test]
+    fn test_apply_move_to_board() {
+        let mut b = new_empty();
+
+        // Put 2 enemy knights on board.
+        set_square(&mut b, &pos("d4"), SQ_WH_N);
+        set_square(&mut b, &pos("f4"), SQ_BL_N);
+        // Move white knight in a position attacked by black knight.
+        apply_move_to_board(&mut b, &(pos("d4"), pos("e6"), None));
+        assert_eq!(get_square(&b, &pos("d4")), SQ_E);
+        assert_eq!(get_square(&b, &pos("e6")), SQ_WH_N);
+        assert_eq!(num_pieces(&b), 2);
+        // Sack it with black knight
+        apply_move_to_board(&mut b, &(pos("f4"), pos("e6"), None));
+        assert_eq!(get_square(&b, &pos("e6")), SQ_BL_N);
+        assert_eq!(num_pieces(&b), 1);
+    }
+
+    #[test]
+    fn test_apply_move_to_castling() {
+        let mut b = new();
+        let mut gs = rules::GameState::new();
+        assert_eq!(gs.castling, CASTLING_MASK);
+
+        // On a starting board, start by making place for all castles.
+        clear_square(&mut b, &pos("b1"));
+        clear_square(&mut b, &pos("c1"));
+        clear_square(&mut b, &pos("d1"));
+        clear_square(&mut b, &pos("f1"));
+        clear_square(&mut b, &pos("g1"));
+        clear_square(&mut b, &pos("b8"));
+        clear_square(&mut b, &pos("c8"));
+        clear_square(&mut b, &pos("d8"));
+        clear_square(&mut b, &pos("f8"));
+        clear_square(&mut b, &pos("g8"));
+        // White queen-side castling.
+        apply_move_to(&mut b, &mut gs, &parse_move("e1c1"));
+        assert!(is_piece(get_square(&b, &pos("c1")), SQ_WH_K));
+        assert!(is_piece(get_square(&b, &pos("d1")), SQ_WH_R));
+        assert!(is_empty(&b, &pos("a1")));
+        assert!(is_empty(&b, &pos("e1")));
+        assert_eq!(gs.castling, CASTLING_BL_MASK);
+        // Black king-side castling.
+        apply_move_to(&mut b, &mut gs, &parse_move("e8g8"));
+        assert!(is_piece(get_square(&b, &pos("g8")), SQ_BL_K));
+        assert!(is_piece(get_square(&b, &pos("f8")), SQ_BL_R));
+        assert!(is_empty(&b, &pos("h8")));
+        assert!(is_empty(&b, &pos("e8")));
+        assert_eq!(gs.castling, 0);
+    }
+
+    #[test]
+    fn test_get_castle() {
+        assert_eq!(get_castle(&parse_move("e1c1")), Some(CASTLING_WH_Q));
+        assert_eq!(get_castle(&parse_move("e1g1")), Some(CASTLING_WH_K));
+        assert_eq!(get_castle(&parse_move("e8c8")), Some(CASTLING_BL_Q));
+        assert_eq!(get_castle(&parse_move("e8g8")), Some(CASTLING_BL_K));
+        assert_eq!(get_castle(&parse_move("d2d4")), None);
+    }
+}

src/node.rs

@@ -0,0 +1,83 @@
+use std::fmt;
+use std::hash::{Hash, Hasher};
+
+use crate::board;
+use crate::movement::{self, Move};
+use crate::rules;
+use crate::stats;
+
+/// Analysis node: a board along with the game state.
+#[derive(Clone)]
+pub struct Node {
+    /// Board for this node.
+    pub board: board::Board,
+    /// Game state.
+    pub game_state: rules::GameState,
+}
+
+impl Node {
+    /// Create a new node for an empty board and a new game state.
+    pub fn new() -> Node {
+        Node {
+            board: board::new_empty(),
+            game_state: rules::GameState::new(),
+        }
+    }
+
+    /// Apply a move to this node.
+    pub fn apply_move(&mut self, m: &Move) {
+        movement::apply_move_to(&mut self.board, &mut self.game_state, m);
+    }
+
+    /// Return player moves from this node.
+    pub fn get_player_moves(&self, commit: bool) -> Vec<Move> {
+        rules::get_player_moves(&self.board, &self.game_state, commit)
+    }
+
+    /// Compute stats for both players for this node.
+    pub fn compute_stats(&self) -> (stats::BoardStats, stats::BoardStats) {
+        stats::compute_stats(&self.board, &self.game_state)
+    }
+}
+
+impl fmt::Debug for Node {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Node {{ board: [...], game_state: {:?} }}",
+            self.game_state
+        )
+    }
+}
+
+impl fmt::Display for Node {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut s = vec!();
+        board::draw(&self.board, &mut s);
+        let board_drawing = String::from_utf8_lossy(&s).to_string();
+        write!(
+            f,
+            "* Board:\n{}\n\
+             * Game state:\n{}",
+            board_drawing, self.game_state
+        )
+    }
+}
+
+impl PartialEq for Node {
+    fn eq(&self, other: &Self) -> bool {
+        (
+            self.board.iter().zip(other.board.iter()).all(|(a, b)| a == b) &&
+            self.game_state == other.game_state
+        )
+    }
+}
+
+impl Eq for Node {}
+
+impl Hash for Node {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.board.iter().for_each(|square| state.write_u8(*square));
+        self.game_state.hash(state);
+    }
+}

src/notation.rs

@@ -1,45 +1,45 @@
 //! Functions using various notations.
 
-use crate::board;
+use crate::board::*;
-use crate::rules;
+use crate::movement::Move;
 
 pub const NULL_MOVE: &str = "0000";
 
 /// Create a string containing the UCI algebraic notation of this move.
-pub fn move_to_string(m: &rules::Move) -> String {
+pub fn move_to_string(m: &Move) -> String {
     let mut move_string = String::new();
-    move_string.push_str(&board::pos_string(&m.0));
+    move_string.push_str(&pos_string(&m.0));
-    move_string.push_str(&board::pos_string(&m.1));
+    move_string.push_str(&pos_string(&m.1));
     if let Some(prom) = m.2 {
         move_string.push(match prom {
-            board::SQ_Q => 'q',
+            SQ_Q => 'q',
-            board::SQ_B => 'b',
+            SQ_B => 'b',
-            board::SQ_N => 'n',
+            SQ_N => 'n',
-            board::SQ_R => 'r',
+            SQ_R => 'r',
             _ => panic!("What are you doing? Promote to a legal piece.")
         });
     }
     move_string
 }
 
-/// Parse an UCI move algebraic notation string to a rules::Move.
+/// Parse an UCI move algebraic notation string to a Move.
-pub fn parse_move(m_str: &str) -> rules::Move {
+pub fn parse_move(m_str: &str) -> Move {
     let prom = if m_str.len() == 5 {
         Some(match m_str.as_bytes()[4] {
-            b'b' => board::SQ_B,
+            b'b' => SQ_B,
-            b'n' => board::SQ_N,
+            b'n' => SQ_N,
-            b'r' => board::SQ_R,
+            b'r' => SQ_R,
-            b'q' => board::SQ_Q,
+            b'q' => SQ_Q,
             _ => panic!("What is the opponent doing? This is illegal, I'm out."),
         })
     } else {
         None
     };
-    (board::pos(&m_str[0..2]), board::pos(&m_str[2..4]), prom)
+    (pos(&m_str[0..2]), pos(&m_str[2..4]), prom)
 }
 
 /// Create a space-separated string of moves. Used for debugging.
-pub fn move_list_to_string(moves: &Vec<rules::Move>) -> String {
+pub fn move_list_to_string(moves: &Vec<Move>) -> String {
     moves.iter().map(|m| move_to_string(m)).collect::<Vec<_>>().join(" ")
 }
 
@@ -75,8 +75,8 @@ pub fn parse_fen_fields(fields: &[&str]) -> Option<Fen> {
     })
 }
 
-pub fn en_passant_to_string(ep: Option<board::Pos>) -> String {
+pub fn en_passant_to_string(ep: Option<Pos>) -> String {
-    ep.and_then(|p| Some(board::pos_string(&p))).unwrap_or("-".to_string())
+    ep.and_then(|p| Some(pos_string(&p))).unwrap_or("-".to_string())
 }
 
 #[cfg(test)]
@@ -87,15 +87,15 @@ mod tests {
     fn test_move_to_string() {
         assert_eq!(move_to_string(&((0, 0), (3, 3), None)), "a1d4");
         assert_eq!(move_to_string(&((7, 7), (0, 7), None)), "h8a8");
-        assert_eq!(move_to_string(&((7, 6), (7, 7), Some(board::SQ_Q))), "h7h8q");
+        assert_eq!(move_to_string(&((7, 6), (7, 7), Some(SQ_Q))), "h7h8q");
-        assert_eq!(move_to_string(&((7, 6), (7, 7), Some(board::SQ_N))), "h7h8n");
+        assert_eq!(move_to_string(&((7, 6), (7, 7), Some(SQ_N))), "h7h8n");
     }
 
     #[test]
     fn test_parse_move() {
         assert_eq!(parse_move("a1d4"), ((0, 0), (3, 3), None));
-        assert_eq!(parse_move("a7a8q"), ((0, 6), (0, 7), Some(board::SQ_Q)));
+        assert_eq!(parse_move("a7a8q"), ((0, 6), (0, 7), Some(SQ_Q)));
-        assert_eq!(parse_move("a7a8r"), ((0, 6), (0, 7), Some(board::SQ_R)));
+        assert_eq!(parse_move("a7a8r"), ((0, 6), (0, 7), Some(SQ_R)));
     }
 
     #[test]

src/rules.rs

@@ -1,6 +1,8 @@
 //! Functions to determine legal moves.
 
 use crate::board::*;
+use crate::castling::*;
+use crate::movement::{self, Move};
 use crate::notation;
 
 /// Characteristics of the state of a game.
@@ -50,168 +52,6 @@ impl std::fmt::Display for GameState {
     }
 }
 
-pub const CASTLING_WH_K: u8    = 0b00000001;
-pub const CASTLING_WH_Q: u8    = 0b00000010;
-pub const CASTLING_WH_MASK: u8 = 0b00000011;
-pub const CASTLING_BL_K: u8    = 0b00000100;
-pub const CASTLING_BL_Q: u8    = 0b00001000;
-pub const CASTLING_BL_MASK: u8 = 0b00001100;
-pub const CASTLING_K_MASK: u8  = 0b00000101;
-pub const CASTLING_Q_MASK: u8  = 0b00001010;
-pub const CASTLING_MASK: u8    = 0b00001111;
-
-/// Castling sides parameters.
-///
-/// For both sides, the 3-uple contains files that should be empty
-/// and not attacked, an optional file that should be empty for
-/// queen-side, and the castling side-mask.
-pub const CASTLING_SIDES: [([i8; 2], Option<i8>, u8); 2] =
-    [([5i8, 6i8], None, CASTLING_K_MASK), ([3i8, 2i8], Some(1i8), CASTLING_Q_MASK)];
-
-pub const START_WH_K_POS: Pos = pos("e1");
-pub const START_BL_K_POS: Pos = pos("e8");
-
-/// A movement, with before/after positions and optional promotion.
-pub type Move = (Pos, Pos, Option<u8>);
-
-/// Apply a move `m` to copies to `board` and `game_state`.
-pub fn apply_move(board: &Board, game_state: &GameState, m: &Move) -> (Board, GameState) {
-    let mut new_board = board.clone();
-    let mut new_state = game_state.clone();
-    apply_move_to(&mut new_board, &mut new_state, m);
-    (new_board, new_state)
-}
-
-/// Update `board` and `game_state` to reflect the move `m`.
-///
-/// The board is updated with correct piece placement.
-///
-/// The game state is updated with the new player turn and the new
-/// castling options.
-pub fn apply_move_to(board: &mut Board, game_state: &mut GameState, m: &Move) {
-    apply_move_to_board(board, m);
-    apply_move_to_state(game_state, m);
-    // If the move is a castle, remove it from castling options.
-    if let Some(castle) = get_castle(m) {
-        match castle {
-            CASTLING_WH_K | CASTLING_WH_Q => game_state.castling &= !CASTLING_WH_MASK,
-            CASTLING_BL_K | CASTLING_BL_Q => game_state.castling &= !CASTLING_BL_MASK,
-            _ => {}
-        };
-    }
-    // Else, check if it's either a rook or the king that moved.
-    else {
-        let piece = get_square(board, &m.1);
-        if is_white(piece) && game_state.castling & CASTLING_WH_MASK != 0 {
-            match get_type(piece) {
-                SQ_K => {
-                    if m.0 == pos("e1") {
-                        game_state.castling &= !CASTLING_WH_MASK;
-                    }
-                }
-                SQ_R => {
-                    if m.0 == pos("a1") {
-                        game_state.castling &= !CASTLING_WH_Q;
-                    } else if m.0 == pos("h1") {
-                        game_state.castling &= !CASTLING_WH_K;
-                    }
-                }
-                _ => {}
-            }
-        } else if is_black(piece) && game_state.castling & CASTLING_BL_MASK != 0 {
-            match get_type(piece) {
-                SQ_K => {
-                    if m.0 == pos("e8") {
-                        game_state.castling &= !CASTLING_BL_MASK;
-                    }
-                }
-                SQ_R => {
-                    if m.0 == pos("a8") {
-                        game_state.castling &= !CASTLING_BL_Q;
-                    } else if m.0 == pos("h8") {
-                        game_state.castling &= !CASTLING_BL_K;
-                    }
-                }
-                _ => {}
-            }
-        }
-    }
-}
-
-/// Apply a move `m` into `board`.
-pub fn apply_move_to_board(board: &mut Board, m: &Move) {
-    if let Some(castle) = get_castle(m) {
-        match castle {
-            CASTLING_WH_K => {
-                move_piece(board, &START_WH_K_POS, &pos("g1"));
-                move_piece(board, &pos("h1"), &pos("f1"));
-            }
-            CASTLING_WH_Q => {
-                move_piece(board, &START_WH_K_POS, &pos("c1"));
-                move_piece(board, &pos("a1"), &pos("d1"));
-            }
-            CASTLING_BL_K => {
-                move_piece(board, &START_BL_K_POS, &pos("g8"));
-                move_piece(board, &pos("h8"), &pos("f8"));
-            }
-            CASTLING_BL_Q => {
-                move_piece(board, &START_BL_K_POS, &pos("c8"));
-                move_piece(board, &pos("a8"), &pos("d8"));
-            }
-            _ => {}
-        }
-    } else {
-        move_piece(board, &m.0, &m.1);
-        if let Some(prom_type) = m.2 {
-            let color = get_color(get_square(board, &m.1));
-            set_square(board, &m.1, color|prom_type);
-        }
-    }
-}
-
-/// Update `game_state` with the move `m`.
-///
-/// This only updates the player turn. Castling should be updated in a
-/// context where the corresponding board is available.
-pub fn apply_move_to_state(game_state: &mut GameState, _m: &Move) {
-    game_state.color = opposite(game_state.color);
-}
-
-/// Get the corresponding castling flag for this move.
-pub fn get_castle(m: &Move) -> Option<u8> {
-    if m.0 == pos("e1") {
-        if m.1 == pos("c1") {
-            Some(CASTLING_WH_Q)
-        } else if m.1 == pos("g1") {
-            Some(CASTLING_WH_K)
-        } else {
-            None
-        }
-    } else if m.0 == pos("e8") {
-        if m.1 == pos("c8") {
-            Some(CASTLING_BL_Q)
-        } else if m.1 == pos("g8") {
-            Some(CASTLING_BL_K)
-        } else {
-            None
-        }
-    } else {
-        None
-    }
-}
-
-/// Get the move for this castle.
-pub fn get_castle_move(castle: u8) -> Move {
-    match castle {
-        CASTLING_WH_Q => (pos("e1"), pos("c1"), None),
-        CASTLING_WH_K => (pos("e1"), pos("g1"), None),
-        CASTLING_BL_Q => (pos("e8"), pos("c8"), None),
-        CASTLING_BL_K => (pos("e8"), pos("g8"), None),
-        _ => panic!("Illegal castling requested: {:08b}", castle),
-    }
-}
-
-
 /// Get a list of moves for all pieces of the playing color.
 ///
 /// If `commit` is false, do not check for illegal moves. This is used
@@ -219,7 +59,11 @@ pub fn get_castle_move(castle: u8) -> Move {
 /// as it needs to check all possible following enemy moves, e.g. to
 /// see if P's king can be taken. Consider a call with true `commit` as
 /// a collection of attacked squares instead of legal move collection.
-pub fn get_player_moves(board: &Board, game_state: &GameState, commit: bool) -> Vec<Move> {
+pub fn get_player_moves(
+    board: &Board,
+    game_state: &GameState,
+    commit: bool,
+) -> Vec<Move> {
     let mut moves = Vec::with_capacity(256);
     for r in 0..8 {
         for f in 0..8 {
@@ -236,7 +80,12 @@ pub fn get_player_moves(board: &Board, game_state: &GameState, commit: bool) ->
 }
 
 /// Get a list of moves for the piece at position `at`.
-pub fn get_piece_moves(board: &Board, at: &Pos, game_state: &GameState, commit: bool) -> Vec<Move> {
+pub fn get_piece_moves(
+    board: &Board,
+    at: &Pos,
+    game_state: &GameState,
+    commit: bool,
+) -> Vec<Move> {
     match get_square(board, at) {
         p if is_piece(p, SQ_P) => get_pawn_moves(board, at, p, game_state, commit),
         p if is_piece(p, SQ_B) => get_bishop_moves(board, at, p, game_state, commit),
@@ -505,7 +354,7 @@ fn get_king_moves(
                     }
                 }
                 let castle = castling_side_mask & castling_color_mask;
-                let m = get_castle_move(castle);
+                let m = movement::get_castle_move(castle);
                 if can_register(commit, board, game_state, &m) {
                     moves.push(m);
                 }
@@ -552,7 +401,7 @@ fn is_illegal(board: &Board, game_state: &GameState, m: &Move) -> bool {
         // If king moves, use its new position.
         let king_p = if m.0 == king_p { m.1 } else { king_p };
         let mut hypothetic_board = board.clone();
-        apply_move_to_board(&mut hypothetic_board, m);
+        movement::apply_move_to_board(&mut hypothetic_board, m);
         // Check if the move makes the player king in check.
         if is_attacked(&hypothetic_board, &game_state, &king_p) {
             return true
@@ -588,66 +437,6 @@ mod tests {
     use super::*;
     use crate::notation::parse_move;
 
-    #[test]
-    fn test_get_castle() {
-        assert_eq!(get_castle(&parse_move("e1c1")), Some(CASTLING_WH_Q));
-        assert_eq!(get_castle(&parse_move("e1g1")), Some(CASTLING_WH_K));
-        assert_eq!(get_castle(&parse_move("e8c8")), Some(CASTLING_BL_Q));
-        assert_eq!(get_castle(&parse_move("e8g8")), Some(CASTLING_BL_K));
-        assert_eq!(get_castle(&parse_move("d2d4")), None);
-    }
-
-    #[test]
-    fn test_apply_move_to_board() {
-        let mut b = new_empty();
-
-        // Put 2 enemy knights on board.
-        set_square(&mut b, &pos("d4"), SQ_WH_N);
-        set_square(&mut b, &pos("f4"), SQ_BL_N);
-        // Move white knight in a position attacked by black knight.
-        apply_move_to_board(&mut b, &(pos("d4"), pos("e6"), None));
-        assert_eq!(get_square(&b, &pos("d4")), SQ_E);
-        assert_eq!(get_square(&b, &pos("e6")), SQ_WH_N);
-        assert_eq!(num_pieces(&b), 2);
-        // Sack it with black knight
-        apply_move_to_board(&mut b, &(pos("f4"), pos("e6"), None));
-        assert_eq!(get_square(&b, &pos("e6")), SQ_BL_N);
-        assert_eq!(num_pieces(&b), 1);
-    }
-
-    #[test]
-    fn test_apply_move_to_castling() {
-        let mut b = new();
-        let mut gs = GameState::new();
-        assert_eq!(gs.castling, CASTLING_MASK);
-
-        // On a starting board, start by making place for all castles.
-        clear_square(&mut b, &pos("b1"));
-        clear_square(&mut b, &pos("c1"));
-        clear_square(&mut b, &pos("d1"));
-        clear_square(&mut b, &pos("f1"));
-        clear_square(&mut b, &pos("g1"));
-        clear_square(&mut b, &pos("b8"));
-        clear_square(&mut b, &pos("c8"));
-        clear_square(&mut b, &pos("d8"));
-        clear_square(&mut b, &pos("f8"));
-        clear_square(&mut b, &pos("g8"));
-        // White queen-side castling.
-        apply_move_to(&mut b, &mut gs, &parse_move("e1c1"));
-        assert!(is_piece(get_square(&b, &pos("c1")), SQ_WH_K));
-        assert!(is_piece(get_square(&b, &pos("d1")), SQ_WH_R));
-        assert!(is_empty(&b, &pos("a1")));
-        assert!(is_empty(&b, &pos("e1")));
-        assert_eq!(gs.castling, CASTLING_BL_MASK);
-        // Black king-side castling.
-        apply_move_to(&mut b, &mut gs, &parse_move("e8g8"));
-        assert!(is_piece(get_square(&b, &pos("g8")), SQ_BL_K));
-        assert!(is_piece(get_square(&b, &pos("f8")), SQ_BL_R));
-        assert!(is_empty(&b, &pos("h8")));
-        assert!(is_empty(&b, &pos("e8")));
-        assert_eq!(gs.castling, 0);
-    }
-
     #[test]
     fn test_get_player_moves() {
         let b = new();
@@ -840,7 +629,7 @@ mod tests {
         set_square(&mut b, &pos("d6"), SQ_BL_R);
         assert!(is_attacked(&b, &gs, &pos("d4")));
         // Move the rook on another file, no more attack.
-        apply_move_to_board(&mut b, &parse_move("d6e6"));
+        movement::apply_move_to_board(&mut b, &parse_move("d6e6"));
         assert!(!is_attacked(&b, &gs, &pos("d4")));
     }
 }

src/stats.rs

@@ -54,7 +54,7 @@ impl std::fmt::Display for BoardStats {
     }
 }
 
-/// Create two new BoardStats objects from the board, for white and black.
+/// Create two new BoardStats objects from the board, for both sides.
 ///
 /// See `compute_stats_into` for details.
 pub fn compute_stats(board: &Board, game_state: &rules::GameState) -> (BoardStats, BoardStats) {
@@ -63,25 +63,32 @@ pub fn compute_stats(board: &Board, game_state: &rules::GameState) -> (BoardStat
     stats
 }
 
+/// Compute stats for both the current player and its opponent.
+///
+/// The playing color will have its stats filled in the first
+/// BoardStats object, its opponent in the second.
 pub fn compute_stats_into(
     board: &Board,
     game_state: &rules::GameState,
     stats: &mut (BoardStats, BoardStats)
 ) {
-    compute_color_stats_into(board, game_state, &mut stats.0, SQ_WH);
+    let mut gs = game_state.clone();
-    compute_color_stats_into(board, game_state, &mut stats.1, SQ_BL);
+    compute_color_stats_into(board, &gs, &mut stats.0);
+    gs.color = opposite(gs.color);
+    compute_color_stats_into(board, &gs, &mut stats.1);
 }
 
-/// Update `stats` for `color` from given `board`
+/// Fill `stats` from given `board` and `game_state`.
 ///
-/// Refresh all stats *except* `mobility`.
+/// Only the current playing side stats are created,
+/// prepare the game_state accordingly.
 pub fn compute_color_stats_into(
     board: &Board,
     game_state: &rules::GameState,
     stats: &mut BoardStats,
-    color: u8
 ) {
     stats.reset();
+    let color = game_state.color;
     // Compute mobility for all pieces.
     stats.mobility = rules::get_player_moves(board, game_state, true).len() as i32;
     // Compute amount of each piece.
@@ -198,15 +205,15 @@ mod tests {
         let mut b = new_empty();
         set_square(&mut b, &pos("d4"), SQ_WH_P);
         set_square(&mut b, &pos("d6"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 2);
         // Add a pawn on another file, no changes expected.
         set_square(&mut b, &pos("e6"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 2);
         // Add a pawn backward in the d-file: there are now 3 doubled pawns.
         set_square(&mut b, &pos("d2"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 3);
 
         // Check that isolated and backward pawns are correctly counted.
@@ -214,19 +221,19 @@ mod tests {
         assert_eq!(stats.0.num_backward_pawns, 2);  // A bit weird?
         // Protect d4 pawn with a friend in e3: it is not isolated nor backward anymore.
         set_square(&mut b, &pos("e3"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 5);
         assert_eq!(stats.0.num_isolated_pawns, 0);
         assert_eq!(stats.0.num_backward_pawns, 1);
         // Add an adjacent friend to d2 pawn: no pawns are left isolated or backward.
         set_square(&mut b, &pos("c2"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 5);
         assert_eq!(stats.0.num_isolated_pawns, 0);
         assert_eq!(stats.0.num_backward_pawns, 0);
         // Add an isolated/backward white pawn in a far file.
         set_square(&mut b, &pos("a2"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 5);
         assert_eq!(stats.0.num_isolated_pawns, 1);
         assert_eq!(stats.0.num_backward_pawns, 1);
@@ -237,7 +244,7 @@ mod tests {
         set_square(&mut b, &pos("d4"), SQ_WH_P);
         set_square(&mut b, &pos("e5"), SQ_WH_P);
         set_square(&mut b, &pos("e3"), SQ_WH_P);
-        compute_color_stats_into(&b, &gs, &mut stats.0, SQ_WH);
+        compute_color_stats_into(&b, &gs, &mut stats.0);
         assert_eq!(stats.0.num_doubled_pawns, 2);
         assert_eq!(stats.0.num_isolated_pawns, 0);
         assert_eq!(stats.0.num_backward_pawns, 1);

src/uci.rs

@@ -6,8 +6,8 @@ use std::sync::mpsc;
 use std::thread;
 
 use crate::engine;
+use crate::movement::Move;
 use crate::notation;
-use crate::rules;
 
 const VATU_NAME: &str = env!("CARGO_PKG_NAME");
 const VATU_AUTHORS: &str = env!("CARGO_PKG_AUTHORS");
@@ -58,13 +58,13 @@ pub enum UciCmd {
 pub enum PositionArgs {
     Startpos,
     Fen(notation::Fen),
-    Moves(Vec<rules::Move>),
+    Moves(Vec<Move>),
 }
 
 /// Arguments for the go remote commands.
 #[derive(Debug, Clone)]
 pub enum GoArgs {
-    SearchMoves(Vec<rules::Move>),
+    SearchMoves(Vec<Move>),
     Ponder,
     WTime(i32),
     BTime(i32),
@@ -199,11 +199,11 @@ impl Uci {
     fn handle_engine_command(&mut self, cmd: &engine::Cmd) {
         match cmd {
             engine::Cmd::UciChannel(s) => {
-                self.log("ENG >>> Channel opened.".to_string());
+                self.log("ENGINE: Channel opened.".to_string());
                 self.engine_in = Some(s.to_owned());
             }
             engine::Cmd::Log(s) => {
-                self.log(s.to_string());
+                self.log(format!("ENGINE: {}", s.to_string()));
             }
             engine::Cmd::Info(infos) => {
                 self.send_infos(infos);
@@ -261,7 +261,7 @@ impl Uci {
     }
 
     /// Send best move.
-    fn send_bestmove(&mut self, m: &Option<rules::Move>) {
+    fn send_bestmove(&mut self, m: &Option<Move>) {
         let move_str = match m {
             Some(m) => notation::move_to_string(m),
             None => notation::NULL_MOVE.to_string(),