From: Gary Linscott <glinscott@gmail.com>
Date: Mon, 11 Feb 2013 15:26:18 +0000 (-0500)
Subject: Bishop pins only
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=a7cdf7299a771949332f8c7ef77ae8fd125d0f08;hp=-c

Bishop pins only
---

a7cdf7299a771949332f8c7ef77ae8fd125d0f08
diff --combined src/evaluate.cpp
index e29b9b0f,49dc07fe..183f166a
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@@ -577,16 -577,22 +577,15 @@@ Value do_evaluate(const Position& pos, 
  
          mobility += MobilityBonus[Piece][mob];
  
-         if (Piece == BISHOP && (PseudoAttacks[Piece][pos.king_square(Them)] & s)) {
-              const Bitboard between = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
-              if (!more_than_one(between))
-                  score += make_score(25, 25);
 -        // Add a bonus if a slider is pinning an enemy piece
 -        if (   (Piece == BISHOP || Piece == ROOK || Piece == QUEEN)
 -            && (PseudoAttacks[Piece][pos.king_square(Them)] & s))
 -        {
 -            b = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
 -
 -            assert(b);
 -
 -            if (!more_than_one(b) && (b & pos.pieces(Them)))
 -                score += ThreatBonus[Piece][type_of(pos.piece_on(lsb(b)))];
--        }
--
          // Decrease score if we are attacked by an enemy pawn. Remaining part
          // of threat evaluation must be done later when we have full attack info.
          if (ei.attackedBy[Them][PAWN] & s)
              score -= ThreatenedByPawnPenalty[Piece];
++        else if (Piece == BISHOP && (PseudoAttacks[Piece][pos.king_square(Them)] & s)) {
++             const Bitboard between = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
++             if (!more_than_one(between))
++                 score += make_score(15, 25);
++        }
  
          // Bishop and knight outposts squares
          if (    (Piece == BISHOP || Piece == KNIGHT)
@@@ -693,7 -699,8 +692,8 @@@
                        & ~ei.attackedBy[Them][0];
  
      if (undefendedMinors)
-         score += UndefendedMinorPenalty;
+         score += more_than_one(undefendedMinors) ? UndefendedMinorPenalty * 2
+                                                  : UndefendedMinorPenalty;
  
      // Enemy pieces not defended by a pawn and under our attack
      weakEnemies =  pos.pieces(Them)