From: Marco Costalba <mcostalba@gmail.com>
Date: Thu, 18 Jun 2009 13:22:39 +0000 (+0200)
Subject: Skip castle rights update when not needed
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=190f88e5324ffd048c5234e78b41748432dc7579

Skip castle rights update when not needed

Micro optimization in do_move(), a quick check
avoid us to update castle rights in almost 90%
of cases.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/position.cpp b/src/position.cpp
index 3ae7f50d..c17c5c57 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -796,11 +796,14 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
     pieceList[us][piece][index[from]] = to;
     index[to] = index[from];
 
-    // Update castle rights
-    st->key ^= zobCastle[st->castleRights];
-    st->castleRights &= castleRightsMask[from];
-    st->castleRights &= castleRightsMask[to];
-    st->key ^= zobCastle[st->castleRights];
+    // Update castle rights, try to shortcut a common case
+    if ((castleRightsMask[from] & castleRightsMask[to]) != ALL_CASTLES)
+    {
+        st->key ^= zobCastle[st->castleRights];
+        st->castleRights &= castleRightsMask[from];
+        st->castleRights &= castleRightsMask[to];
+        st->key ^= zobCastle[st->castleRights];
+    }
 
     // Update checkers bitboard, piece must be already moved
     st->checkersBB = EmptyBoardBB;