Candidate passed pawns

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6e33bb7215d0579e035915d20c40811dac8c8ae9..d9aae3d32bd3667a2b7daa415afeaf7c38b9380e 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -606,10 +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);
 
@@ -622,7 +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));
@@ -683,6 +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)];
     }
 
@@ -844,8 +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)