From: Marco Costalba <mcostalba@gmail.com>
Date: Fri, 27 Apr 2012 09:30:35 +0000 (+0100)
Subject: Fix wrong condition in PawnEntry::king_safety()
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=2aac860db3d04881103a3b0d09e864ac77b80697

Fix wrong condition in PawnEntry::king_safety()

Since revision 374c9e6b63d0e233371
we use also castling information to calculate king safety.
So before to reuse the cached king safety score we have to
veify not only king position, but also castling rights are
the same of the pre-calculated ones.

This is a very subtle bug, found only becuase even after
previous patch, consecutives runs of 'bench' _still_ showed
different numbers. Pawn tables are not cleared between 'bench'
runs and in the second run a king safety score, previously
evaluated under some castling rights, was reused by another
position with different castling rights instead of being
recalculated from scratch.

Bug spotted and tracked down by Balint Pfliegel

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

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 6897969c..6923d20b 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -260,6 +260,7 @@ template<Color Us>
 Score PawnEntry::update_safety(const Position& pos, Square ksq) {
 
   kingSquares[Us] = ksq;
+  castleRights[Us] = pos.can_castle(Us);
 
   if (relative_rank(Us, ksq) > RANK_4)
       return kingSafety[Us] = SCORE_ZERO;
diff --git a/src/pawns.h b/src/pawns.h
index 0376ce61..4fee9316 100644
--- a/src/pawns.h
+++ b/src/pawns.h
@@ -59,6 +59,7 @@ private:
   Bitboard passedPawns[2];
   Bitboard pawnAttacks[2];
   Square kingSquares[2];
+  int castleRights[2];
   Score value;
   int halfOpenFiles[2];
   Score kingSafety[2];
@@ -106,7 +107,8 @@ inline int PawnEntry::has_open_file_to_right(Color c, File f) const {
 
 template<Color Us>
 inline Score PawnEntry::king_safety(const Position& pos, Square ksq) {
-  return kingSquares[Us] == ksq ? kingSafety[Us] : update_safety<Us>(pos, ksq);
+  return kingSquares[Us] == ksq && castleRights[Us] == pos.can_castle(Us)
+       ? kingSafety[Us] : update_safety<Us>(pos, ksq);
 }
 
 #endif // !defined(PAWNS_H_INCLUDED)
diff --git a/src/position.h b/src/position.h
index 8f11a394..e67dfbd4 100644
--- a/src/position.h
+++ b/src/position.h
@@ -111,8 +111,8 @@ public:
   int piece_count(Color c, PieceType pt) const;
 
   // Castling
-  bool can_castle(CastleRight f) const;
-  bool can_castle(Color c) const;
+  int can_castle(CastleRight f) const;
+  int can_castle(Color c) const;
   bool castle_impeded(Color c, CastlingSide s) const;
   Square castle_rook_square(Color c, CastlingSide s) const;
 
@@ -297,11 +297,11 @@ inline Square Position::king_square(Color c) const {
   return pieceList[c][KING][0];
 }
 
-inline bool Position::can_castle(CastleRight f) const {
+inline int Position::can_castle(CastleRight f) const {
   return st->castleRights & f;
 }
 
-inline bool Position::can_castle(Color c) const {
+inline int Position::can_castle(Color c) const {
   return st->castleRights & ((WHITE_OO | WHITE_OOO) << c);
 }