feat: more efficiently order moves

1 files changed, 13 insertions, 8 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index 05cb1e7..feb3368 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -187,11 +187,14 @@ impl Board {
         0.0
     }
 
-    pub fn order_moves(&self, moves: &mut Vec<Move>) {
-        moves.sort_unstable_by(|a, b| {
-            let a_eval = self.eval_move(*a);
-            let b_eval = self.eval_move(*b);
-            if a_eval == 0.0 && b_eval == 0.0 {
+    pub fn order_moves(&self, moves: Vec<Move>) -> Vec<Move> {
+        let mut moves_with_eval: Vec<(Move, f32)> = moves
+            .iter()
+            .map(|m| (*m, self.eval_move(*m)))
+            .collect();
+
+        moves_with_eval.sort_unstable_by(|(a, a_eval), (b, b_eval)| {
+            if *a_eval == 0.0 && *b_eval == 0.0 {
                 // Prioritize equal captures over non-captures
                 if a.is_tactical() && !b.is_tactical() {
                     return Ordering::Less
@@ -200,8 +203,10 @@ impl Board {
                     return Ordering::Greater
                 }
             }
-            a_eval.total_cmp(&b_eval).reverse()
+            a_eval.total_cmp(b_eval).reverse()
         });
+
+        moves_with_eval.iter_mut().map(|(m, _)| *m).collect()
     }
 
     pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8, deadline: Instant) -> (f32, Vec<Move>) {
@@ -209,7 +214,7 @@ impl Board {
         let color = self.color();
 
         let mut moves = self.generate_pseudolegal_moves(color);
-        self.order_moves(&mut moves);
+        moves = self.order_moves(moves);
 
         match self.transposition_table[(self.hash % TTABLE_SIZE) as usize] {
             Some(item) => {
@@ -285,7 +290,7 @@ impl Board {
     pub fn quiscence(&mut self, mut alpha: f32, beta: f32) -> f32 {
         let color = self.color();
         let mut moves = self.generate_pseudolegal_moves(color);
-        self.order_moves(&mut moves);
+        moves = self.order_moves(moves);
 
         match self.transposition_table[(self.hash % TTABLE_SIZE) as usize] {
             Some(item) => {