feat: improved scoring for (semi)dead positions

1 files changed, 16 insertions, 4 deletions

diff --git a/src/grossmeister/search.rs b/src/grossmeister/search.rs
index 2d20e3a..cad2b99 100644
--- a/src/grossmeister/search.rs
+++ b/src/grossmeister/search.rs
@@ -71,16 +71,16 @@ impl Grossmeister {
             }
         }
 
-        if depth_left == 0 {
-            return (self.quiscence(alpha, beta, root_distance), principal_variation);
-        }
-
         // Mate distance pruning
         let mating_score = Grossmeister::MDP(&mut alpha, &mut beta, root_distance);
         if mating_score != 0.0 {
             return (mating_score, principal_variation)
         }
 
+        if depth_left == 0 {
+            return (self.quiscence(alpha, beta, root_distance), principal_variation);
+        }
+
         let mut should_pv_search = true;
         let mut legal_move_found = false;
 
@@ -509,4 +509,16 @@ mod tests {
         dbg!(score, pv);
         assert_eq!(SCORE_MATE - score, 3.0); // Mate in 3 plies
     }
+
+    #[test]
+    fn unwinnable() {
+        let fen = String::from("8/8/2P1k3/1K1n4/8/8/8/8 b - - 0 55");
+        let board = Board::from_FEN(fen);
+
+        let mut gm = Grossmeister::new(board);
+        gm.debug = true;
+        let (score, pv) = gm.iterative_deepening(5);
+        dbg!(score, pv);
+        assert!(score <= 0.0);
+    }
 }