feat: implement move ordering

1 files changed, 20 insertions, 0 deletions

diff --git a/src/board/engine.rs b/src/board/engine.rs
index 4fe8652..75a505e 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -1,3 +1,4 @@
+use std::cmp::Ordering;
 use crate::{bitboard::pop_count, board::*};
 
 use super::ttable::{NodeType, TranspositionTableItem};
@@ -107,6 +108,19 @@ impl Board {
         material_advantage + 0.1 * mobility_advantage
     }
 
+    /// Evaluate move for move ordering, prioritizing efficient captures
+    fn eval_move(&self, m: Move) -> f32 {
+        let [source_eval, target_eval] = [m.source, m.target]
+            .map(|sq| self.piece_by_square(sq))
+            .map(|p| {
+                match p {
+                    Some(p) => p.static_eval(),
+                    None => 0.,
+                }
+            });
+        source_eval - target_eval
+    }
+
     pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8) -> (f32, Vec<Move>) {
         let transposition = self.transposition_table[(self.hash % TTABLE_SIZE) as usize];
 
@@ -115,6 +129,12 @@ impl Board {
 
         let mut moves = self.generate_pseudolegal_moves(color);
 
+        moves.sort_unstable_by(|a, b| {
+            let a_eval = self.eval_move(*a);
+            let b_eval = self.eval_move(*b);
+            a_eval.total_cmp(&b_eval)
+        });
+
         if transposition.is_some() {
             match transposition {
                 Some(item) => {