From 1b379403ab971e188483df5d580c39695db7f44a Mon Sep 17 00:00:00 2001
From: Micha White <botahamec@outlook.com>
Date: Wed, 27 Sep 2023 09:35:50 -0400
Subject: Big changes

---
 ai/src/lib.rs | 174 ++--------------------------------------------------------
 1 file changed, 6 insertions(+), 168 deletions(-)

(limited to 'ai/src/lib.rs')

diff --git a/ai/src/lib.rs b/ai/src/lib.rs
index 8c49ba7..06f0818 100644
--- a/ai/src/lib.rs
+++ b/ai/src/lib.rs
@@ -1,171 +1,9 @@
-use crate::transposition_table::TranspositionTableReference;
+#![feature(new_uninit)]
+#![feature(get_mut_unchecked)]
+
+pub use eval::negamax;
 pub use model::{CheckersBitBoard, Move, PieceColor, PossibleMoves};
-use parking_lot::{Mutex, RwLock};
-use rayon::prelude::*;
-use std::mem::MaybeUninit;
+pub use transposition_table::{TranspositionTable, TranspositionTableRef};
 
+mod eval;
 mod transposition_table;
-
-const KING_WORTH: u32 = 2;
-
-fn eval_position(board: CheckersBitBoard) -> f32 {
-	let light_pieces = board.pieces_bits() & !board.color_bits();
-	let dark_pieces = board.pieces_bits() & board.color_bits();
-
-	let light_peasants = light_pieces & !board.king_bits();
-	let dark_peasants = dark_pieces & !board.king_bits();
-
-	let light_kings = light_pieces & board.king_bits();
-	let dark_kings = dark_pieces & board.king_bits();
-
-	// if we assume the black player doesn't exist, how good is this for white?
-	let light_eval =
-		(light_peasants.count_ones() as f32) + ((light_kings.count_ones() * KING_WORTH) as f32);
-	let dark_eval =
-		(dark_peasants.count_ones() as f32) + ((dark_kings.count_ones() * KING_WORTH) as f32);
-
-	// avoiding a divide by zero error
-	if dark_eval + light_eval != 0.0 {
-		dark_eval / (dark_eval + light_eval)
-	} else {
-		0.5
-	}
-}
-
-pub fn eval_singlethreaded(
-	depth: usize,
-	mut alpha: f32,
-	beta: f32,
-	board: CheckersBitBoard,
-) -> f32 {
-	if depth <= 1 {
-		if board.turn() == PieceColor::Dark {
-			eval_position(board)
-		} else {
-			1.0 - eval_position(board)
-		}
-	} else {
-		let table = TranspositionTableReference::new();
-		if let Some(eval) = table.get(board, depth as u8) {
-			return eval;
-		}
-
-		let turn = board.turn();
-		let mut best_eval = f32::NEG_INFINITY;
-		let moves = PossibleMoves::moves(board);
-
-		if moves.is_empty() {
-			return 0.0;
-		}
-
-		for current_move in PossibleMoves::moves(board) {
-			let board = unsafe { current_move.apply_to(board) };
-			let current_eval = if board.turn() != turn {
-				1.0 - eval_singlethreaded(depth - 1, 1.0 - beta, 1.0 - alpha, board)
-			} else {
-				eval_singlethreaded(depth - 1, alpha, beta, board)
-			};
-
-			let table = TranspositionTableReference::new();
-			table.insert(board, current_eval, depth as u8);
-
-			if current_eval >= beta {
-				return beta;
-			}
-
-			if best_eval < current_eval {
-				best_eval = current_eval;
-			}
-			if alpha < best_eval {
-				alpha = best_eval;
-			}
-		}
-
-		best_eval
-	}
-}
-
-pub fn eval_multithreaded(depth: usize, alpha: f32, beta: f32, board: CheckersBitBoard) -> f32 {
-	if depth <= 1 {
-		if board.turn() == PieceColor::Dark {
-			eval_position(board)
-		} else {
-			1.0 - eval_position(board)
-		}
-	} else {
-		let turn = board.turn();
-		let best_eval = Mutex::new(f32::NEG_INFINITY);
-		let keep_going = RwLock::new(true);
-		let alpha = RwLock::new(alpha);
-
-		let is_still_going = || *keep_going.read();
-		let get_alpha = || *alpha.read();
-
-		let moves = PossibleMoves::moves(board);
-
-		if moves.is_empty() {
-			let pos_eval = if board.turn() == PieceColor::Dark {
-				eval_position(board)
-			} else {
-				1.0 - eval_position(board)
-			};
-			return if pos_eval < f32::EPSILON || pos_eval > 1.0 - f32::EPSILON {
-				pos_eval
-			} else {
-				0.5
-			};
-		}
-
-		moves.into_iter().par_bridge().for_each(|current_move| {
-			if is_still_going() {
-				let board = unsafe { current_move.apply_to(board) };
-				let current_eval = if board.turn() != turn {
-					1.0 - eval_singlethreaded(depth - 1, 1.0 - beta, 1.0 - get_alpha(), board)
-				} else {
-					eval_singlethreaded(depth - 1, get_alpha(), beta, board)
-				};
-
-				let mut best = best_eval.lock();
-				if current_eval >= beta {
-					*best = beta;
-					let mut going_val = keep_going.write();
-					*going_val = false;
-				}
-
-				if *best < current_eval {
-					*best = current_eval;
-				}
-				if get_alpha() < *best {
-					let mut alpha = alpha.write();
-					*alpha = *best;
-				}
-			}
-		});
-
-		best_eval.into_inner()
-	}
-}
-
-pub fn best_move(depth: usize, board: CheckersBitBoard) -> Move {
-	let mut best_eval = 0.0;
-	let mut best_move = MaybeUninit::uninit();
-	let moves = PossibleMoves::moves(board);
-
-	if moves.is_empty() {
-		panic!("No moves are available")
-	}
-
-	for current_move in PossibleMoves::moves(board) {
-		let new_board = unsafe { current_move.apply_to(board) };
-		let mut current_eval = eval_multithreaded(depth - 1, best_eval, 1.0, new_board);
-		if new_board.turn() != board.turn() {
-			current_eval = 1.0 - current_eval;
-		}
-		if current_eval > best_eval {
-			best_eval = current_eval;
-			best_move.write(current_move);
-		}
-	}
-
-	unsafe { best_move.assume_init() }
-}
-- 
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