From 5237987cf62f8e031a979ba7945f11c710c28c57 Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Thu, 26 Jan 2023 16:33:29 +0300
Subject: feat: prioritize winning captures in move ordering

---
 src/board/engine.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/board/engine.rs b/src/board/engine.rs
index 8bd409b..1d01e06 100644
--- a/src/board/engine.rs
+++ b/src/board/engine.rs
@@ -109,6 +109,7 @@ impl Board {
     }
 
     /// Evaluate move for move ordering, prioritizing efficient captures
+    /// where low-value pieces capture high-value pieces
     fn eval_move(&self, m: Move) -> f32 {
         let [source_eval, target_eval] = [m.source, m.target]
             .map(|sq| self.piece_by_square(sq))
@@ -118,7 +119,7 @@ impl Board {
                     None => 0.,
                 }
             });
-        source_eval - target_eval
+        2. * target_eval - source_eval
     }
 
     pub fn negamax_search(&mut self, mut alpha: f32, beta: f32, depth_left: u8, deadline: Instant) -> (f32, Vec<Move>) {
@@ -130,7 +131,7 @@ impl Board {
         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)
+            a_eval.total_cmp(&b_eval).reverse()
         });
 
         match self.transposition_table[(self.hash % TTABLE_SIZE) as usize] {
@@ -210,7 +211,7 @@ impl Board {
         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)
+            a_eval.total_cmp(&b_eval).reverse()
         });
 
         match self.transposition_table[(self.hash % TTABLE_SIZE) as usize] {
-- 
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