Connectivity Score S(3,1) is stronger than S(2,2)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 8e6d827eef25f27537cfc4a6e55615e054b03ce6..f6764b18466ae4ad010f3ec57b7ed105b1314f04 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -165,16 +165,18 @@ namespace {
   // Assorted bonuses and penalties
   const Score BishopPawns       = S(  8, 12);
   const Score CloseEnemies      = S(  7,  0);
+  const Score Connectivity      = S(  3,  1);
   const Score Hanging           = S( 52, 30);
   const Score HinderPassedPawn  = S(  8,  1);
+  const Score KnightOnQueen     = S( 21, 11);
   const Score LongRangedBishop  = S( 22,  0);
   const Score MinorBehindPawn   = S( 16,  0);
   const Score PawnlessFlank     = S( 20, 80);
   const Score RookOnPawn        = S(  8, 24);
+  const Score SliderOnQueen     = S( 42, 21);
   const Score ThreatByPawnPush  = S( 47, 26);
   const Score ThreatByRank      = S( 16,  3);
   const Score ThreatBySafePawn  = S(175,168);
-  const Score ThreatOnQueen     = S( 42, 21);
   const Score TrappedBishopA1H1 = S( 50, 50);
   const Score TrappedRook       = S( 92,  0);
   const Score WeakQueen         = S( 50, 10);
@@ -210,7 +212,7 @@ namespace {
 
     // attackedBy[color][piece type] is a bitboard representing all squares
     // attacked by a given color and piece type. Special "piece types" which
-    // are also calculated are QUEEN_DIAGONAL and ALL_PIECES.
+    // is also calculated is ALL_PIECES.
     Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
 
     // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
@@ -296,9 +298,6 @@ namespace {
 
     attackedBy[Us][Pt] = 0;
 
-    if (Pt == QUEEN)
-        attackedBy[Us][QUEEN_DIAGONAL] = 0;
-
     while ((s = *pl++) != SQ_NONE)
     {
         // Find attacked squares, including x-ray attacks for bishops and rooks
@@ -313,9 +312,6 @@ namespace {
         attackedBy[Us][Pt] |= b;
         attackedBy[Us][ALL_PIECES] |= b;
 
-        if (Pt == QUEEN)
-            attackedBy[Us][QUEEN_DIAGONAL] |= b & PseudoAttacks[BISHOP][s];
-
         if (b & kingRing[Them])
         {
             kingAttackersCount[Us]++;
@@ -482,22 +478,20 @@ namespace {
             score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
         }
     }
-    // Penalty when our king is on a pawnless flank
-    if (!(pos.pieces(PAWN) & KingFlank[file_of(ksq)]))
-        score -= PawnlessFlank;
 
-    // King tropism: firstly, find attacked squares in our king flank
-    b = attackedBy[Them][ALL_PIECES] & KingFlank[file_of(ksq)] & Camp;
+    Bitboard kf = KingFlank[file_of(ksq)];
 
-    assert(((Us == WHITE ? b << 4 : b >> 4) & b) == 0);
-    assert(popcount(Us == WHITE ? b << 4 : b >> 4) == popcount(b));
+    // Penalty when our king is on a pawnless flank
+    if (!(pos.pieces(PAWN) & kf))
+        score -= PawnlessFlank;
 
-    // Secondly, add the squares which are attacked twice in that flank and
-    // which are not defended by our pawns.
-    b =  (Us == WHITE ? b << 4 : b >> 4)
-       | (b & attackedBy2[Them] & ~attackedBy[Us][PAWN]);
+    // 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];
 
-    score -= CloseEnemies * popcount(b);
+    // King tropism, to anticipate slow motion attacks on our king
+    score -= CloseEnemies * (popcount(b1) + popcount(b2));
 
     if (T)
         Trace::add(KING, Us, score);
@@ -590,12 +584,25 @@ namespace {
 
     score += ThreatByPawnPush * popcount(b);
 
-    // Bonus for safe slider threats on the next move toward enemy queen
-    safeThreats = ~pos.pieces(Us) & ~attackedBy2[Them] & attackedBy2[Us];
-    b =  (attackedBy[Us][BISHOP] & attackedBy[Them][QUEEN_DIAGONAL])
-       | (attackedBy[Us][ROOK  ] & attackedBy[Them][QUEEN] & ~attackedBy[Them][QUEEN_DIAGONAL]);
+    // Bonus for threats on the next moves against enemy queen
+    if (pos.count<QUEEN>(Them) == 1)
+    {
+        Square s = pos.square<QUEEN>(Them);
+        safeThreats = mobilityArea[Us] & ~stronglyProtected;
 
-    score += ThreatOnQueen * popcount(b & safeThreats);
+        b = attackedBy[Us][KNIGHT] & pos.attacks_from<KNIGHT>(s);
+
+        score += KnightOnQueen * popcount(b & safeThreats);
+
+        b =  (attackedBy[Us][BISHOP] & pos.attacks_from<BISHOP>(s))
+           | (attackedBy[Us][ROOK  ] & pos.attacks_from<ROOK  >(s));
+
+        score += SliderOnQueen * popcount(b & safeThreats & attackedBy2[Us]);
+    }
+
+    // Connectivity: ensure that knights, bishops, rooks, and queens are protected
+    b = (pos.pieces(Us) ^ pos.pieces(Us, PAWN, KING)) & attackedBy[Us][ALL_PIECES];
+    score += Connectivity * popcount(b);
 
     if (T)
         Trace::add(THREAT, Us, score);
@@ -728,12 +735,9 @@ namespace {
     behind |= (Us == WHITE ? behind >>  8 : behind <<  8);
     behind |= (Us == WHITE ? behind >> 16 : behind << 16);
 
-    // Since SpaceMask[Us] is fully on our half of the board...
-    assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
-
-    // ...count safe + (behind & safe) with a single popcount.
-    int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
+    int bonus = popcount(safe) + popcount(behind & safe);
     int weight = pos.count<ALL_PIECES>(Us) - 2 * pe->open_files();
+
     Score score = make_score(bonus * weight * weight / 16, 0);
 
     if (T)