Split up search and eval

1 files changed, 5 insertions, 227 deletions

diff --git a/engine/src/eval.rs b/engine/src/eval.rs
index 01f07f6..eaae0a4 100644
--- a/engine/src/eval.rs
+++ b/engine/src/eval.rs
@@ -37,8 +37,8 @@ impl Neg for Evaluation {
 }
 
 impl Evaluation {
-	const NULL_MAX: Self = Self(i16::MAX);
-	const NULL_MIN: Self = Self(i16::MIN + 1);
+	pub(crate) const NULL_MAX: Self = Self(i16::MAX);
+	pub(crate) const NULL_MIN: Self = Self(i16::MIN + 1);
 
 	pub const WIN: Self = Self(i16::MAX - 1);
 	pub const DRAW: Self = Self(0);
@@ -91,7 +91,7 @@ impl Evaluation {
 		}
 	}
 
-	fn increment(self) -> Self {
+	pub fn increment(self) -> Self {
 		if self.is_force_win() {
 			Self(self.0 - 1)
 		} else if self.is_force_loss() {
@@ -101,7 +101,7 @@ impl Evaluation {
 		}
 	}
 
-	fn add(self, rhs: f32) -> Self {
+	pub fn add(self, rhs: f32) -> Self {
 		let Some(eval) = self.to_f32() else {
 			return self;
 		};
@@ -110,7 +110,7 @@ impl Evaluation {
 	}
 }
 
-fn eval_position(board: CheckersBitBoard) -> Evaluation {
+pub fn eval_position(board: CheckersBitBoard) -> Evaluation {
 	let light_pieces = board.pieces_bits() & !board.color_bits();
 	let dark_pieces = board.pieces_bits() & board.color_bits();
 
@@ -134,228 +134,6 @@ fn eval_position(board: CheckersBitBoard) -> Evaluation {
 	}
 }
 
-unsafe fn sort_moves(
-	a: &Move,
-	board: CheckersBitBoard,
-	table: TranspositionTableRef,
-) -> Evaluation {
-	table
-		.get_any_depth(a.apply_to(board))
-		.unwrap_or(Evaluation::DRAW)
-}
-
-pub fn negamax(
-	depth: u8,
-	mut alpha: Evaluation,
-	beta: Evaluation,
-	board: CheckersBitBoard,
-	allowed_moves: Option<Arc<[Move]>>,
-	cancel_flag: &AtomicBool,
-	task: &EvaluationTask,
-) -> (Evaluation, Option<Move>) {
-	task.nodes_explored
-		.fetch_add(1, std::sync::atomic::Ordering::Release);
-
-	if depth < 1 {
-		if board.turn() == PieceColor::Dark {
-			(eval_position(board), None)
-		} else {
-			(-eval_position(board), None)
-		}
-	} else {
-		let table = task.transposition_table;
-		if let Some(entry) = table.get(board, depth) {
-			return (entry, None);
-		}
-
-		let turn = board.turn();
-		let mut best_eval = Evaluation::NULL_MIN;
-		let mut best_move = None;
-
-		let sort_fn = |m: &Move| unsafe { sort_moves(m, board, table) };
-		let sorter: LazySort<Move, _, Evaluation, { PossibleMoves::MAX_POSSIBLE_MOVES }> =
-			if let Some(moves) = allowed_moves {
-				LazySort::new(moves.iter().cloned(), sort_fn)
-			} else {
-				let moves = PossibleMoves::moves(board);
-				LazySort::new(moves, sort_fn)
-			};
-
-		if sorter.is_empty() {
-			return (Evaluation::LOSS, None);
-		}
-
-		for current_move in sorter.into_iter() {
-			if cancel_flag.load(std::sync::atomic::Ordering::Acquire) {
-				return (best_eval, best_move);
-			}
-
-			let board = unsafe { current_move.apply_to(board) };
-			let current_eval = if board.turn() == turn {
-				negamax(depth - 1, alpha, beta, board, None, cancel_flag, task)
-					.0
-					.increment()
-			} else {
-				-negamax(depth - 1, -beta, -alpha, board, None, cancel_flag, task)
-					.0
-					.increment()
-			};
-
-			if best_eval < current_eval {
-				best_eval = current_eval;
-				best_move = Some(current_move);
-			}
-
-			if alpha < best_eval {
-				alpha = best_eval;
-			}
-
-			if alpha >= beta {
-				return (best_eval, best_move);
-			}
-		}
-
-		table.insert(board, best_eval, unsafe { NonZeroU8::new_unchecked(depth) });
-
-		(best_eval, best_move)
-	}
-}
-
-pub fn evaluate(task: Arc<EvaluationTask>, frontend: &dyn Frontend) -> Evaluation {
-	let board = task.position;
-	let cancel_flag = &task.cancel_flag;
-
-	let allowed_moves = task.allowed_moves.clone();
-	let limits = task.limits;
-	let max_depth = limits.depth;
-	let max_nodes = limits.nodes;
-	let max_time = limits.time.map(|d| Instant::now() + d.div_f32(2.0));
-
-	let mut alpha = Evaluation::NULL_MIN;
-	let mut beta = Evaluation::NULL_MAX;
-	let mut depth = 0;
-	let mut eval = Evaluation::DRAW;
-	let mut best_move = None;
-	loop {
-		if let Some(max_depth) = max_depth {
-			if depth > max_depth.get() {
-				break;
-			}
-		}
-
-		if let Some(max_time) = max_time {
-			if Instant::now() > max_time {
-				break;
-			}
-		}
-
-		if let Some(max_nodes) = max_nodes {
-			if task
-				.nodes_explored
-				.load(std::sync::atomic::Ordering::Acquire)
-				> max_nodes.get()
-			{
-				break;
-			}
-		}
-
-		let em = negamax(
-			depth,
-			alpha,
-			beta,
-			board,
-			allowed_moves.clone(),
-			cancel_flag,
-			&task,
-		);
-
-		// prevent incomplete search from overwriting evaluation
-		if cancel_flag.load(std::sync::atomic::Ordering::Acquire) {
-			break;
-		}
-
-		eval = em.0;
-		best_move = em.1;
-
-		while (eval <= alpha) || (eval >= beta) {
-			let em = negamax(
-				depth,
-				alpha,
-				beta,
-				board,
-				allowed_moves.clone(),
-				cancel_flag,
-				&task,
-			);
-
-			// prevent incomplete search from overwriting evaluation
-			if cancel_flag.load(std::sync::atomic::Ordering::Acquire) {
-				break;
-			}
-
-			eval = em.0;
-			best_move = em.1;
-
-			if eval <= alpha {
-				alpha = Evaluation::NULL_MIN;
-			} else if eval >= beta {
-				beta = Evaluation::NULL_MAX;
-			}
-		}
-
-		if alpha.is_force_loss() {
-			alpha = Evaluation::NULL_MIN;
-		} else {
-			alpha = eval.add(-0.125);
-		}
-
-		if beta.is_force_win() {
-			beta = Evaluation::NULL_MAX;
-		} else {
-			beta = eval.add(0.125);
-		}
-
-		depth += 1;
-	}
-
-	// ponder
-	if let Some(best_move) = best_move {
-		// If the best move has not been found yet, then no move will be
-		// reported. This should be very rare. This technically is not allowed
-		// by the UCI specification, but if someone stops it this quickly, they
-		// probably didn't care about the best move anyway.
-		frontend.report_best_move(best_move);
-
-		if task.ponder {
-			let board = unsafe { best_move.apply_to(board) };
-
-			let mut depth = 0;
-			loop {
-				if task
-					.end_ponder_flag
-					.load(std::sync::atomic::Ordering::Acquire)
-				{
-					break;
-				}
-
-				negamax(
-					depth,
-					Evaluation::NULL_MIN,
-					Evaluation::NULL_MAX,
-					board,
-					None,
-					&task.end_ponder_flag,
-					&task,
-				);
-
-				depth += 1;
-			}
-		}
-	}
-
-	eval
-}
-
 #[cfg(test)]
 mod tests {
 	use super::*;