Remove ThreatByHangingPawn bonus (#1356)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 08796159bde5e8cc1860a512c5e541e2dd8df7ee..fa3b0a720b2face4a2ac66d6085370f3b8e77e43 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, 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
@@ -220,7 +220,6 @@ namespace {
   const Score WeakQueen             = S( 50, 10);
   const Score CloseEnemies          = S(  7,  0);
   const Score PawnlessFlank         = S( 20, 80);
-  const Score ThreatByHangingPawn   = S( 71, 61);
   const Score ThreatBySafePawn      = S(192,175);
   const Score ThreatByRank          = S( 16,  3);
   const Score Hanging               = S( 48, 27);
@@ -310,8 +309,8 @@ namespace {
     while ((s = *pl++) != SQ_NONE)
     {
         // Find attacked squares, including x-ray attacks for bishops and rooks
-        b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
-          : Pt ==   ROOK ? attacks_bb<  ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
+        b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
+          : Pt ==   ROOK ? attacks_bb<  ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
                          : pos.attacks_from<Pt>(s);
 
         if (pos.pinned_pieces(Us) & s)
@@ -423,13 +422,11 @@ namespace {
   Score Evaluation<T>::evaluate_king() {
 
     const Color     Them = (Us == WHITE ? BLACK : WHITE);
-    const Direction Up   = (Us == WHITE ? NORTH : SOUTH);
     const Bitboard  Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
                                         : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
     Bitboard weak, b, b1, b2, safe, unsafeChecks;
-    int kingDanger;
 
     // King shelter and enemy pawns storm
     Score score = pe->king_safety<Us>(pos, ksq);
@@ -442,7 +439,7 @@ namespace {
               & ~attackedBy2[Us]
               & (attackedBy[Us][KING] | attackedBy[Us][QUEEN] | ~attackedBy[Us][ALL_PIECES]);
 
-        kingDanger = unsafeChecks = 0;
+        int kingDanger = unsafeChecks = 0;
 
         // Analyse the safe enemy's checks which are possible on next move
         safe  = ~pos.pieces(Them);
@@ -478,9 +475,8 @@ namespace {
             unsafeChecks |= b;
 
         // Unsafe or occupied checking squares will also be considered, as long as
-        // the square is not defended by our pawns or occupied by a blocked pawn.
-        unsafeChecks &= ~(   attackedBy[Us][PAWN]
-                          | (pos.pieces(Them, PAWN) & shift<Up>(pos.pieces(PAWN))));
+        // the square is in the attacker's mobility area.
+        unsafeChecks &= mobilityArea[Them];
 
         kingDanger +=        kingAttackersCount[Them] * kingAttackersWeight[Them]
                      + 102 * kingAdjacentZoneAttacksCount[Them]
@@ -546,9 +542,6 @@ namespace {
         safeThreats = (shift<Right>(b) | shift<Left>(b)) & weak;
 
         score += ThreatBySafePawn * popcount(safeThreats);
-
-        if (weak ^ safeThreats)
-            score += ThreatByHangingPawn;
     }
 
     // Squares strongly protected by the opponent, either because they attack the
@@ -894,7 +887,7 @@ namespace {
         Trace::add(TOTAL, score);
     }
 
-    return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
+    return pos.side_to_move() == WHITE ? v : -v; // Side to move point of view
   }
 
 } // namespace
@@ -906,7 +899,7 @@ Score Eval::Contempt = SCORE_ZERO;
 
 Value Eval::evaluate(const Position& pos)
 {
-   return Evaluation<>(pos).value();
+   return Evaluation<>(pos).value() + Eval::Tempo;
 }
 
 /// trace() is like evaluate(), but instead of returning a value, it returns
@@ -917,7 +910,7 @@ std::string Eval::trace(const Position& pos) {
 
   std::memset(scores, 0, sizeof(scores));
 
-  Value v = Evaluation<TRACE>(pos).value();
+  Value v = Evaluation<TRACE>(pos).value() + Eval::Tempo;
   v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
 
   std::stringstream ss;