feat: add basic draw evaluation

1 files changed, 32 insertions, 0 deletions

diff --git a/src/grossmeister/evaluation.rs b/src/grossmeister/evaluation.rs
index 572fa63..4512dcc 100644
--- a/src/grossmeister/evaluation.rs
+++ b/src/grossmeister/evaluation.rs
@@ -125,8 +125,40 @@ impl Grossmeister {
         }
     }
 
+    pub fn is_dead_position(&self) -> bool {
+        let non_minor_exists = [
+            Piece::Pawn,
+            Piece::PawnBlack,
+            Piece::Rook,
+            Piece::RookBlack,
+            Piece::Queen,
+            Piece::QueenBlack
+        ].iter().any(|&piece| {
+            self.board.piece_sets[piece as usize].pop_count() > 0
+        });
+
+        if non_minor_exists {
+            return false;
+        }
+
+        let minor_pieces = [
+            Piece::Knight,
+            Piece::KnightBlack,
+            Piece::Bishop,
+            Piece::BishopBlack
+        ].iter().fold(0, |acc, &piece| {
+            acc + self.board.piece_sets[piece as usize].pop_count()
+        });
+
+        minor_pieces <= 1
+    }
+
     /// Evaluate a position relative to the current player
     pub fn evaluate(&self) -> f32 {
+        if self.is_dead_position() {
+            return 0.0
+        }
+
         let color = self.board.color();
         let opponent_color = color.flip();