Add move ordering heuristic MVV/LVA

src/search/quiescence.rs

@@ -4,6 +4,8 @@ use crate::{
     movegen::r#move::{Move, MoveType},
 };
 
+use super::move_ordering::score_by_mvv_lva;
+
 pub fn quiescence(game: &mut Game, mut alpha: i32, beta: i32) -> (Option<Move>, i32) {
     let color = game.current_player();
     let stand_pat = evaluate_position(&game.board);
@@ -16,11 +18,14 @@ pub fn quiescence(game: &mut Game, mut alpha: i32, beta: i32) -> (Option<Move>,
         alpha = stand_pat;
     }
 
-    let captures = game
-        .board
-        .pseudo_moves_all()
-        .into_iter()
-        .filter(|m| !matches!(m.move_type, MoveType::Quiet));
+    let mut captures: Vec<_> = game.board.pseudo_moves_all().into_iter().filter(|m| {
+        matches!(
+            m.move_type,
+            MoveType::Capture | MoveType::PromotionCapture(_)
+        )
+    }).collect();
+
+    captures.sort_unstable_by_key(|mv| score_by_mvv_lva(&game.board, *mv));
 
     for mv in captures {
         let move_parameters = MoveParameters::build(&game.board, &mv);
@@ -41,5 +46,5 @@ pub fn quiescence(game: &mut Game, mut alpha: i32, beta: i32) -> (Option<Move>,
         alpha = alpha.max(move_score);
     }
 
-    (None, 0)
+    (None, alpha)
 }