X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fevaluate.cpp;h=3ba405ccf28ff378192bed7b905ef1fc9f9686c9;hp=984a85a65e0492c3daaa46ddc72f06709ae32487;hb=9a1d5f0f1d8a12a85b198688d4f1d636a146eb7a;hpb=496c7497cb81de4383f7df42b1836af53e432ce3

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 984a85a6..3ba405cc 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -150,6 +150,8 @@ namespace {
 
   #undef S
 
+  const Score BishopPinBonus = make_score(66, 11);
+
   // Bonus for having the side to move (modified by Joona Kiiski)
   const Score Tempo = make_score(24, 11);
 
@@ -496,7 +498,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
 
     // Init king safety tables only if we are going to use them
     if (   pos.piece_count(Us, QUEEN)
-        && pos.non_pawn_material(Us) >= QueenValueMg + RookValueMg)
+        && pos.non_pawn_material(Us) > QueenValueMg + PawnValueMg)
     {
         ei.kingRing[Them] = (b | (Us == WHITE ? b >> 8 : b << 8));
         b &= ei.attackedBy[Us][PAWN];
@@ -582,6 +584,13 @@ Value do_evaluate(const Position& pos, Value& margin) {
         if (ei.attackedBy[Them][PAWN] & s)
             score -= ThreatenedByPawnPenalty[Piece];
 
+        // Otherwise give a bonus if we are a bishop and can pin a piece or
+        // can give a discovered check through an x-ray attack.
+        else if (    Piece == BISHOP
+                 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
+                 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
+                 score += BishopPinBonus;
+
         // Bishop and knight outposts squares
         if (    (Piece == BISHOP || Piece == KNIGHT)
             && !(pos.pieces(Them, PAWN) & attack_span_mask(Us, s)))