From 8baa56b3cf74a241b830d794ae9f4943ffba3fd1 Mon Sep 17 00:00:00 2001
From: MinetaS <skdty87@gmail.com>
Date: Mon, 28 Oct 2024 04:20:39 +0900
Subject: [PATCH] Assert moveCountPruning properly

moveCountPruning should not be set to false again once it is set to
true, otherwise it will break the internal logics of MovePicker. There
have been a few tests which overlooked this.

Examples:
https://tests.stockfishchess.org/tests/view/671e7c0486d5ee47d953d226
https://tests.stockfishchess.org/tests/view/66a1de7b4ff211be9d4eccea

No functional change
---
 src/search.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 6e513b458ff..f7f137a3e30 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -49,6 +49,13 @@
 #include "uci.h"
 #include "ucioption.h"
 
+#define WRITE_TRUE_ONCE(var, x) \
+    do \
+    { \
+        assert(!(var) || !!(x)); \
+        (var) = (x); \
+    } while (0)
+
 namespace Stockfish {
 
 namespace TB = Tablebases;
@@ -996,7 +1003,7 @@ Value Search::Worker::search(
         if (!rootNode && pos.non_pawn_material(us) && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
         {
             // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~8 Elo)
-            moveCountPruning = moveCount >= futility_move_count(improving, depth);
+            WRITE_TRUE_ONCE(moveCountPruning, moveCount >= futility_move_count(improving, depth));
 
             // Reduced depth of the next LMR search
             int lmrDepth = newDepth - r;