Add history heuristics, reorder killer move to come after captures

src/search/move_ordering.rs

@@ -1,25 +1,36 @@
-use crate::{board::mailbox::Mailbox, movegen::r#move::Move};
+use crate::{
+    board::{board::Color, mailbox::Mailbox},
+    movegen::r#move::Move,
+};
 
+use super::MAX_HISTORY;
+
+// ttmove: -100, mvvlva: [-32, 5], killer:6, quiet[7, ..]
 pub fn score_move(
     mailbox: &Mailbox,
     mv: Move,
     killer_move: Option<Move>,
+    color: Color,
+    history_heuristic: &[[[i16; 64]; 64]; 2],
     tt_move: Option<Move>,
 ) -> i16 {
     if Some(mv) == tt_move {
         return -100;
     }
 
+    if mv.is_capture() {
+        let aggressor = mailbox.piece_at(mv.src()).unwrap();
+        if let Some(victim) = mailbox.piece_at(mv.dst()) {
+            return aggressor.0.idx() as i16 - 8 * victim.0.idx() as i16;
+        }
+        return 0; //en passant
+    }
+
     if Some(mv) == killer_move {
-        return -90;
+        return 6;
     }
 
-    let aggressor = mailbox.piece_at(mv.src()).expect("No aggressor found.");
-    if let Some(victim) = mailbox.piece_at(mv.dst()) {
-        return (aggressor.0.idx() - 8 * victim.0.idx()) as i16;
-    }
-
-    100
+    -history_heuristic[color][mv.src()][mv.dst()] + MAX_HISTORY + 6 + 1
 }
 
 #[cfg(test)]
@@ -41,11 +52,29 @@ mod tests {
         let castle = Move::new_with_type(Square::E1, Square::C1, MoveType::QueenCastle);
 
         let mut moves = vec![castle, queen_takes_pawn, pawn_takes_queen];
-        moves.sort_unstable_by_key(|mv| score_move(&game.mailbox, *mv, None, None));
+        moves.sort_unstable_by_key(|mv| {
+            score_move(
+                &game.mailbox,
+                *mv,
+                None,
+                game.current_player(),
+                &[[[0; 64]; 64]; 2],
+                None,
+            )
+        });
 
         assert_eq!(moves, vec![pawn_takes_queen, queen_takes_pawn, castle]);
 
-        moves.sort_unstable_by_key(|mv| score_move(&game.mailbox, *mv, None, Some(castle)));
+        moves.sort_unstable_by_key(|mv| {
+            score_move(
+                &game.mailbox,
+                *mv,
+                None,
+                game.current_player(),
+                &[[[0; 64]; 64]; 2],
+                Some(castle),
+            )
+        });
 
         assert_eq!(moves, vec![castle, pawn_takes_queen, queen_takes_pawn]);