Candidate passed pawns

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ed1bcf49036915b708a55d182813c9fb0f1255ba..d9aae3d32bd3667a2b7daa415afeaf7c38b9380e 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -75,7 +75,6 @@ namespace {
 
     Material::Entry* me;
     Pawns::Entry* pe;
-    Bitboard pinnedPieces[COLOR_NB];
     Bitboard mobilityArea[COLOR_NB];
 
     // attackedBy[color][piece type] is a bitboard representing all squares
@@ -217,7 +216,7 @@ namespace {
   const int KnightCheck       = 924;
 
   // Threshold for lazy evaluation
-  const Value LazyEval = Value(1500);
+  const Value LazyThreshold = Value(1500);
 
   // eval_init() initializes king and attack bitboards for a given color
   // adding pawn attacks. To be done at the beginning of the evaluation.
@@ -230,8 +229,6 @@ namespace {
     const Square Down = (Us == WHITE ? SOUTH : NORTH);
     const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
 
-    ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
-
     // Find our pawns on the first two ranks, and those which are blocked
     Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
 
@@ -283,7 +280,7 @@ namespace {
           : Pt ==   ROOK ? attacks_bb<  ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
                          : pos.attacks_from<Pt>(s);
 
-        if (ei.pinnedPieces[Us] & s)
+        if (pos.pinned_pieces(Us) & s)
             b &= LineBB[pos.square<KING>(Us)][s];
 
         ei.attackedBy2[Us] |= ei.attackedBy[Us][ALL_PIECES] & b;
@@ -429,7 +426,7 @@ namespace {
         kingDanger =  std::min(807, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
                     + 101 * ei.kingAdjacentZoneAttacksCount[Them]
                     + 235 * popcount(undefended)
-                    + 134 * (popcount(b) + !!ei.pinnedPieces[Us])
+                    + 134 * (popcount(b) + !!pos.pinned_pieces(Us))
                     - 717 * !pos.count<QUEEN>(Them)
                     -   7 * mg_value(score) / 5 - 5;
 
@@ -609,10 +606,11 @@ namespace {
   }
 
 
-  // evaluate_passed_pawns() evaluates the passed pawns of the given color
+  // evaluate_passer_pawns() evaluates the passed pawns and candidate passed
+  // pawns of the given color.
 
   template<Color Us, bool DoTrace>
-  Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
+  Score evaluate_passer_pawns(const Position& pos, const EvalInfo& ei) {
 
     const Color Them = (Us == WHITE ? BLACK : WHITE);
 
@@ -625,7 +623,6 @@ namespace {
     {
         Square s = pop_lsb(&b);
 
-        assert(pos.pawn_passed(Us, s));
         assert(!(pos.pieces(PAWN) & forward_bb(Us, s)));
 
         bb = forward_bb(Us, s) & (ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
@@ -686,6 +683,11 @@ namespace {
         if (!pos.non_pawn_material(Them))
             ebonus += 20;
 
+        // Scale down bonus for candidate passers which need more than one pawn
+        // push to become passed.
+        if (!pos.pawn_passed(Us, s + pawn_push(Us)))
+            mbonus /= 2, ebonus /= 2;
+
         score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
     }
 
@@ -792,18 +794,6 @@ namespace {
     return sf;
   }
 
-
-  Value lazy_eval(Value mg, Value eg) {
-
-    if (mg > LazyEval && eg > LazyEval)
-        return  LazyEval + ((mg + eg) / 2 - LazyEval) / 4;
-
-    else if (mg < -LazyEval && eg < -LazyEval)
-        return -LazyEval + ((mg + eg) / 2 + LazyEval) / 4;
-
-    return VALUE_ZERO;
-  }
-
 } // namespace
 
 
@@ -816,6 +806,7 @@ Value Eval::evaluate(const Position& pos) {
   assert(!pos.checkers());
 
   Score mobility[COLOR_NB] = { SCORE_ZERO, SCORE_ZERO };
+  Value v;
   EvalInfo ei;
 
   // Probe the material hash table
@@ -835,11 +826,10 @@ Value Eval::evaluate(const Position& pos) {
   ei.pe = Pawns::probe(pos);
   score += ei.pe->pawns_score();
 
-  // We have taken into account all cheap evaluation terms.
-  // If score exceeds a threshold return a lazy evaluation.
-  Value lazy = lazy_eval(mg_value(score), eg_value(score));
-  if (lazy)
-      return pos.side_to_move() == WHITE ? lazy : -lazy;
+  // Early exit if score is high
+  v = (mg_value(score) + eg_value(score)) / 2;
+  if (abs(v) > LazyThreshold)
+     return pos.side_to_move() == WHITE ? v : -v;
 
   // Initialize attack and king safety bitboards
   eval_init<WHITE>(pos, ei);
@@ -859,8 +849,8 @@ Value Eval::evaluate(const Position& pos) {
           - evaluate_threats<BLACK, DoTrace>(pos, ei);
 
   // Evaluate passed pawns, we need full attack information including king
-  score +=  evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
-          - evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
+  score +=  evaluate_passer_pawns<WHITE, DoTrace>(pos, ei)
+          - evaluate_passer_pawns<BLACK, DoTrace>(pos, ei);
 
   // Evaluate space for both sides, only during opening
   if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
@@ -874,8 +864,8 @@ Value Eval::evaluate(const Position& pos) {
   ScaleFactor sf = evaluate_scale_factor(pos, ei, eg_value(score));
 
   // Interpolate between a middlegame and a (scaled by 'sf') endgame score
-  Value v =  mg_value(score) * int(ei.me->game_phase())
-           + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
+  v =  mg_value(score) * int(ei.me->game_phase())
+     + eg_value(score) * int(PHASE_MIDGAME - ei.me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
 
   v /= int(PHASE_MIDGAME);