From: mstembera <MissingEmail@email>
Date: Sat, 23 Oct 2021 03:01:05 +0000 (-0700)
Subject: Fix sometimes incorrect key for prefetches
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=385deefd807b512a1c404f5cc4c2045f265a800d

Fix sometimes incorrect key for prefetches

STC
https://tests.stockfishchess.org/tests/view/61737b4f6ce927be32558401
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 138712 W: 34914 L: 34942 D: 68856
Ptnml(0-2): 421, 14817, 38894, 14817, 407

Very minor tweak since Position::key() depends on the 50 move rule counter.
Comments: https://github.com/mstembera/Stockfish/commit/cddde31eed505cdf0c4fc8ff96b89f6e39c797e1

closes https://github.com/official-stockfish/Stockfish/pull/3759

No functional change
---

diff --git a/src/position.cpp b/src/position.cpp
index 0686d245..ae1da017 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1013,9 +1013,9 @@ void Position::do_null_move(StateInfo& newSt) {
   }
 
   st->key ^= Zobrist::side;
+  ++st->rule50;
   prefetch(TT.first_entry(key()));
 
-  ++st->rule50;
   st->pliesFromNull = 0;
 
   sideToMove = ~sideToMove;