Re-introduce "keep pawns on both flanks"

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 55ceadfdbf403c8a1252bc04ba8be4044c73c82a..4a4ae2ad982b430d941dbcaca85af66a0eb0bf12 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -158,15 +158,15 @@ namespace {
   constexpr Score BishopPawns        = S(  3,  7);
   constexpr Score CloseEnemies       = S(  6,  0);
   constexpr Score CorneredBishop     = S( 50, 50);
-  constexpr Score Hanging            = S( 52, 30);
+  constexpr Score Hanging            = S( 57, 32);
   constexpr Score HinderPassedPawn   = S(  8,  0);
   constexpr Score KingProtector      = S(  6,  6);
   constexpr Score KnightOnQueen      = S( 21, 11);
-  constexpr Score LongDiagonalBishop = S( 22,  0);
+  constexpr Score LongDiagonalBishop = S( 46,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
   constexpr Score Overload           = S( 13,  6);
-  constexpr Score PawnlessFlank      = S( 20, 80);
-  constexpr Score RookOnPawn         = S(  8, 24);
+  constexpr Score PawnlessFlank      = S( 19, 84);
+  constexpr Score RookOnPawn         = S( 10, 30);
   constexpr Score SliderOnQueen      = S( 42, 21);
   constexpr Score ThreatByKing       = S( 23, 76);
   constexpr Score ThreatByPawnPush   = S( 45, 40);
@@ -351,7 +351,7 @@ namespace {
                                      * (1 + popcount(blocked & CenterFiles));
 
                 // Bonus for bishop on a long diagonal which can "see" both center squares
-                if (more_than_one(Center & (attacks_bb<BISHOP>(s, pos.pieces(PAWN)) | s)))
+                if (more_than_one(attacks_bb<BISHOP>(s, pos.pieces(PAWN)) & Center))
                     score += LongDiagonalBishop;
             }
 
@@ -413,11 +413,19 @@ namespace {
                                            : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
-    Bitboard weak, b, b1, b2, safe, unsafeChecks;
+    Bitboard kingFlank, weak, b, b1, b2, safe, unsafeChecks;
 
     // King shelter and enemy pawns storm
     Score score = pe->king_safety<Us>(pos, ksq);
 
+    // Find the squares that opponent attacks in our king flank, and the squares
+    // which are attacked twice in that flank but not defended by our pawns.
+    kingFlank = KingFlank[file_of(ksq)];
+    b1 = attackedBy[Them][ALL_PIECES] & kingFlank & Camp;
+    b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
+
+    int tropism = popcount(b1) + popcount(b2);
+
     // Main king safety evaluation
     if (kingAttackersCount[Them] > 1 - pos.count<QUEEN>(Them))
     {
@@ -470,9 +478,10 @@ namespace {
                      +  69 * kingAttacksCount[Them]
                      + 185 * popcount(kingRing[Us] & weak)
                      + 129 * popcount(pos.blockers_for_king(Us) | unsafeChecks)
+                     +   4 * tropism
                      - 873 * !pos.count<QUEEN>(Them)
                      -   6 * mg_value(score) / 8
-                     -   2 ;
+                     -   30;
 
         // Transform the kingDanger units into a Score, and subtract it from the evaluation
         if (kingDanger > 0)
@@ -483,19 +492,12 @@ namespace {
         }
     }
 
-    Bitboard kf = KingFlank[file_of(ksq)];
-
     // Penalty when our king is on a pawnless flank
-    if (!(pos.pieces(PAWN) & kf))
+    if (!(pos.pieces(PAWN) & kingFlank))
         score -= PawnlessFlank;
 
-    // Find the squares that opponent attacks in our king flank, and the squares
-    // which are attacked twice in that flank but not defended by our pawns.
-    b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
-    b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
-
-    // King tropism, to anticipate slow motion attacks on our king
-    score -= CloseEnemies * (popcount(b1) + popcount(b2));
+    // King tropism bonus, to anticipate slow motion attacks on our king
+    score -= CloseEnemies * tropism;
 
     if (T)
         Trace::add(KING, Us, score);
@@ -716,14 +718,14 @@ namespace {
   template<Tracing T> template<Color Us>
   Score Evaluation<T>::space() const {
 
+    if (pos.non_pawn_material() < SpaceThreshold)
+        return SCORE_ZERO;
+
     constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
     constexpr Bitboard SpaceMask =
       Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
                   : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
 
-    if (pos.non_pawn_material() < SpaceThreshold)
-        return SCORE_ZERO;
-
     // Find the available squares for our pieces inside the area defined by SpaceMask
     Bitboard safe =   SpaceMask
                    & ~pos.pieces(Us, PAWN)
@@ -756,7 +758,7 @@ namespace {
     int outflanking =  distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
                      - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
 
-    bool pawnsOnBothFlanks =   (pos.pieces(PAWN) & QueenSide)
+    bool pawnsOnBothFlanks =   (pos.pieces(PAWN) & QueenSide)          
                             && (pos.pieces(PAWN) & KingSide);
 
     // Compute the initiative bonus for the attacking side
@@ -765,7 +767,7 @@ namespace {
                     + 12 * outflanking
                     + 16 * pawnsOnBothFlanks
                     + 48 * !pos.non_pawn_material()
-                    -136 ;
+                    -118 ;
 
     // Now apply the bonus: note that we find the attacking side by extracting
     // the sign of the endgame value, and that we carefully cap the bonus so