Further simplify unstoppable (#938)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6cf7e4da58bf9a469512cf9179cfc4c2a74cffd7..19bfc9fe299820f3c4a95beeb2845f77892a2e47 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -197,7 +197,6 @@ namespace {
   const Score WeakQueen           = S(50, 10);
   const Score Hanging             = S(48, 27);
   const Score ThreatByPawnPush    = S(38, 22);
-  const Score Unstoppable         = S( 0, 20);
   const Score PawnlessFlank       = S(20, 80);
   const Score HinderPassedPawn    = S( 7,  0);
   const Score ThreatByRank        = S(16,  3);
@@ -678,6 +677,10 @@ namespace {
                 mbonus += rr + r * 2, ebonus += rr + r * 2;
         } // rr != 0
 
+        // Assign a small bonus when no pieces left (unstoppable)
+        if (!pos.non_pawn_material(Us) && !pos.non_pawn_material(Them))
+            ebonus += 20;
+
         score += make_score(mbonus, ebonus) + PassedFile[file_of(s)];
     }
 
@@ -852,17 +855,6 @@ Value Eval::evaluate(const Position& pos) {
   score +=  evaluate_passed_pawns<WHITE, DoTrace>(pos, ei)
           - evaluate_passed_pawns<BLACK, DoTrace>(pos, ei);
 
-  // If both sides have only pawns, score for potential unstoppable pawns
-  if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
-  {
-      Bitboard b;
-      if ((b = ei.pi->passed_pawns(WHITE)) != 0)
-          score += Unstoppable * int(relative_rank(WHITE, frontmost_sq(WHITE, b)));
-
-      if ((b = ei.pi->passed_pawns(BLACK)) != 0)
-          score -= Unstoppable * int(relative_rank(BLACK, frontmost_sq(BLACK, b)));
-  }
-
   // Evaluate space for both sides, only during opening
   if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 12222)
       score +=  evaluate_space<WHITE>(pos, ei)