1 files changed, 171 insertions, 160 deletions
diff --git a/engine/src/eval.rs b/engine/src/eval.rs
index 94849ce..a666913 100644..100755
--- a/engine/src/eval.rs
+++ b/engine/src/eval.rs
@@ -1,160 +1,171 @@
-use std::fmt::{self, Display};
-use std::ops::Neg;
-
-use model::CheckersBitBoard;
-
-const KING_WORTH: u32 = 2;
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
-pub struct Evaluation(i16);
-
-impl Display for Evaluation {
-	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-		if self.is_force_win() {
-			write!(f, "+M{}", self.force_sequence_length().unwrap())
-		} else if self.is_force_loss() {
-			write!(f, "-M{}", self.force_sequence_length().unwrap())
-		} else {
-			write!(f, "{:+}", self.to_f32().unwrap())
-		}
-	}
-}
-
-impl Neg for Evaluation {
-	type Output = Self;
-
-	fn neg(self) -> Self::Output {
-		Self(-self.0)
-	}
-}
-
-impl Evaluation {
-	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);
-	pub const LOSS: Self = Self(i16::MIN + 2);
-
-	// last fourteen bits set to 1
-	const FORCE_WIN_THRESHOLD: i16 = 0x3FFF;
-
-	pub fn new(eval: f32) -> Self {
-		if eval >= 1.0 {
-			return Self::WIN;
-		} else if eval <= -1.0 {
-			return Self::LOSS;
-		}
-
-		Self((eval * 16384.0) as i16)
-	}
-
-	pub fn to_f32(self) -> Option<f32> {
-		if self.is_force_sequence() {
-			return None;
-		}
-
-		Some(self.0 as f32 / 16384.0)
-	}
-
-	pub fn is_force_win(self) -> bool {
-		self.0 > Self::FORCE_WIN_THRESHOLD
-	}
-
-	pub fn is_force_loss(self) -> bool {
-		self.0 < -Self::FORCE_WIN_THRESHOLD
-	}
-
-	pub fn is_force_sequence(self) -> bool {
-		self.is_force_win() || self.is_force_loss()
-	}
-
-	pub fn force_sequence_length(self) -> Option<u8> {
-		if self == Self::NULL_MAX || self == Self::NULL_MIN {
-			return None;
-		}
-
-		if self.is_force_win() {
-			Some((Self::WIN.0 - self.0) as u8)
-		} else if self.is_force_loss() {
-			Some((self.0 - Self::LOSS.0) as u8)
-		} else {
-			None
-		}
-	}
-
-	pub fn increment(self) -> Self {
-		if self.is_force_win() {
-			Self(self.0 - 1)
-		} else if self.is_force_loss() {
-			Self(self.0 + 1)
-		} else {
-			self
-		}
-	}
-
-	pub fn add_f32(self, rhs: f32) -> Self {
-		let Some(eval) = self.to_f32() else {
-			return self;
-		};
-
-		Self::new(eval + rhs)
-	}
-}
-
-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();
-
-	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 {
-		Evaluation::new((dark_eval - light_eval) / (dark_eval + light_eval))
-	} else {
-		Evaluation::DRAW
-	}
-}
-
-#[cfg(test)]
-mod tests {
-	use super::*;
-
-	#[test]
-	fn zero_eval() {
-		let draw = Evaluation::new(0.0);
-		assert_eq!(draw, Evaluation::DRAW);
-		assert_eq!(draw.to_f32(), Some(0.0));
-		assert_eq!(draw.to_string(), "+0");
-	}
-
-	#[test]
-	fn comparisons() {
-		assert!(Evaluation::NULL_MAX > Evaluation::WIN);
-		assert!(Evaluation::WIN > Evaluation::new(0.5));
-		assert!(Evaluation::new(0.5) > Evaluation::DRAW);
-		assert!(Evaluation::DRAW > Evaluation::new(-0.5));
-		assert!(Evaluation::new(-0.5) > Evaluation::LOSS);
-		assert!(Evaluation::LOSS > Evaluation::NULL_MIN);
-	}
-
-	#[test]
-	fn negations() {
-		assert_eq!(-Evaluation::NULL_MAX, Evaluation::NULL_MIN);
-		assert_eq!(-Evaluation::NULL_MIN, Evaluation::NULL_MAX);
-		assert_eq!(-Evaluation::WIN, Evaluation::LOSS);
-		assert_eq!(-Evaluation::LOSS, Evaluation::WIN);
-		assert_eq!(-Evaluation::DRAW, Evaluation::DRAW);
-		assert_eq!(-Evaluation::new(0.5), Evaluation::new(-0.5));
-	}
-}
+use std::fmt::{self, Display};
+use std::ops::Neg;
+
+use model::CheckersBitBoard;
+
+const KING_WORTH: u32 = 2;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Evaluation(i16);
+
+impl Display for Evaluation {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+		if self.is_force_win() {
+			write!(f, "+W{}", self.force_sequence_length().unwrap())
+		} else if self.is_force_loss() {
+			write!(f, "-W{}", self.force_sequence_length().unwrap())
+		} else {
+			write!(f, "{:+}", self.to_f32().unwrap())
+		}
+	}
+}
+
+impl Neg for Evaluation {
+	type Output = Self;
+
+	fn neg(self) -> Self::Output {
+		Self(-self.0)
+	}
+}
+
+impl Evaluation {
+	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);
+	pub const LOSS: Self = Self(i16::MIN + 2);
+
+	// last fourteen bits set to 1
+	const FORCE_WIN_THRESHOLD: i16 = 0x3FFF;
+	// divisor for converting to a float
+	const MAX_FLOAT: f32 = 16384.0;
+
+	pub fn new(eval: f32) -> Self {
+		if eval >= 1.0 {
+			return Self::WIN;
+		} else if eval <= -1.0 {
+			return Self::LOSS;
+		}
+
+		Self((eval * 16384.0) as i16)
+	}
+
+	pub fn to_f32(self) -> Option<f32> {
+		if self.is_force_sequence() {
+			return None;
+		}
+
+		Some(self.0 as f32 / Self::MAX_FLOAT)
+	}
+
+	/// Converts to an `f32` without checking to see if the game if a force
+	/// sequence.
+	///
+	/// # Safety
+	/// Results in undefined behavior if the evaluation is a force sequence
+	pub unsafe fn to_f32_unchecked(self) -> f32 {
+		self.0 as f32 / Self::MAX_FLOAT
+	}
+
+	pub fn is_force_win(self) -> bool {
+		self.0 > Self::FORCE_WIN_THRESHOLD
+	}
+
+	pub fn is_force_loss(self) -> bool {
+		self.0 < -Self::FORCE_WIN_THRESHOLD
+	}
+
+	pub fn is_force_sequence(self) -> bool {
+		self.is_force_win() || self.is_force_loss()
+	}
+
+	pub fn force_sequence_length(self) -> Option<u8> {
+		if self == Self::NULL_MAX || self == Self::NULL_MIN {
+			return None;
+		}
+
+		if self.is_force_win() {
+			Some((Self::WIN.0 - self.0) as u8)
+		} else if self.is_force_loss() {
+			Some((self.0 - Self::LOSS.0) as u8)
+		} else {
+			None
+		}
+	}
+
+	pub fn increment(self) -> Self {
+		if self.is_force_win() {
+			Self(self.0 - 1)
+		} else if self.is_force_loss() {
+			Self(self.0 + 1)
+		} else {
+			self
+		}
+	}
+
+	pub fn add_f32(self, rhs: f32) -> Self {
+		let Some(eval) = self.to_f32() else {
+			return self;
+		};
+
+		Self::new(eval + rhs)
+	}
+}
+
+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();
+
+	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 {
+		Evaluation::new((dark_eval - light_eval) / (dark_eval + light_eval))
+	} else {
+		Evaluation::DRAW
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn zero_eval() {
+		let draw = Evaluation::new(0.0);
+		assert_eq!(draw, Evaluation::DRAW);
+		assert_eq!(draw.to_f32(), Some(0.0));
+		assert_eq!(draw.to_string(), "+0");
+	}
+
+	#[test]
+	fn comparisons() {
+		assert!(Evaluation::NULL_MAX > Evaluation::WIN);
+		assert!(Evaluation::WIN > Evaluation::new(0.5));
+		assert!(Evaluation::new(0.5) > Evaluation::DRAW);
+		assert!(Evaluation::DRAW > Evaluation::new(-0.5));
+		assert!(Evaluation::new(-0.5) > Evaluation::LOSS);
+		assert!(Evaluation::LOSS > Evaluation::NULL_MIN);
+	}
+
+	#[test]
+	fn negations() {
+		assert_eq!(-Evaluation::NULL_MAX, Evaluation::NULL_MIN);
+		assert_eq!(-Evaluation::NULL_MIN, Evaluation::NULL_MAX);
+		assert_eq!(-Evaluation::WIN, Evaluation::LOSS);
+		assert_eq!(-Evaluation::LOSS, Evaluation::WIN);
+		assert_eq!(-Evaluation::DRAW, Evaluation::DRAW);
+		assert_eq!(-Evaluation::new(0.5), Evaluation::new(-0.5));
+	}
+}