feat: correctly evaluate pawns at higher ranks

1 files changed, 24 insertions, 2 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index a4b72eb..06369f5 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -88,8 +88,30 @@ impl Board {
             } else {
                 -1.
             };
-            let multiplier = piece_type.static_eval();
-            eval += sign * multiplier * pop_count(*bitboard) as f32;
+
+            eval += sign * match piece_type {
+                PieceType::Pawn => {
+                    serialize_bitboard(*bitboard).iter().fold(0., |acc, square| {
+                        acc + match (*square).rank() {
+                            6 => 3.,
+                            5 => 2.,
+                            _ => 1.,
+                        }
+                    })
+                }
+                PieceType::PawnBlack => {
+                    serialize_bitboard(*bitboard).iter().fold(0., |acc, square| {
+                        acc + match (*square).rank() {
+                            1 => 3.,
+                            2 => 2.,
+                            _ => 1.,
+                        }
+                    })
+                }
+                _ => {
+                    piece_type.static_eval() * pop_count(*bitboard) as f32
+                }
+            };
         }
         eval
     }