Merge branch 'nmp'

src/search/negamax.rs

@@ -69,7 +69,13 @@ pub fn negamax(
         return Ok(eval);
     }
 
-    if plies != 0 && !in_check && depth >= 3 && do_nmp && game.board.non_pawn_materials() > 0 {
+    if alpha == beta - 1
+        && plies != 0
+        && !in_check
+        && depth >= 3
+        && do_nmp
+        && game.board.non_pawn_materials() > 0
+    {
         game.make_null_move();
         let score = -negamax(
             game,