Use arrays

for safe checks, outposts and king protectors in evaluate.cpp

Tested for non regression on the safe checks
https://tests.stockfishchess.org/tests/view/5ef8b75c020eec13834a9596
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 22256 W: 4283 L: 4143 D: 13830
Ptnml(0-2): 291, 2439, 5588, 2459, 351

Tested for non regression on the safe checks, outposts and king protectors
https://tests.stockfishchess.org/tests/view/5ef8e543020eec13834a95e7
LLR: 2.95 (-2.94,2.94) {-1.50,0.50}
Total: 28400 W: 5382 L: 5253 D: 17765
Ptnml(0-2): 394, 3078, 7119, 3223, 386

closes https://github.com/official-stockfish/Stockfish/pull/2785

No functional change

src/evaluate.cpp

@@ -80,11 +80,11 @@ namespace {
   // KingAttackWeights[PieceType] contains king attack weights by piece type
   constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 };
 
-  // Penalties for enemy's safe checks
+  // SafeCheck[PieceType][single/multiple] contains safe check bonus by piece type,
-  constexpr int QueenSafeCheck  = 772;
+  // higher if multiple safe checks are possible for that piece type.
-  constexpr int RookSafeCheck   = 1084;
+  constexpr int SafeCheck[][2] = {
-  constexpr int BishopSafeCheck = 645;
+      {}, {}, {792, 1283}, {645, 967}, {1084, 1897}, {772, 1119}
-  constexpr int KnightSafeCheck = 792;
+  };
 
 #define S(mg, eg) make_score(mg, eg)
 
@@ -106,6 +106,18 @@ namespace {
       S(110,182), S(114,182), S(114,192), S(116,219) }
   };
 
+  // KingProtector[knight/bishop] contains penalty for each distance unit to own king
+  constexpr Score KingProtector[] = { S(8, 9), S(6, 9) };
+
+  // Outpost[knight/bishop] contains bonuses for each knight or bishop occupying a
+  // pawn protected square on rank 4 to 6 which is also safe from a pawn attack.
+  constexpr Score Outpost[] = { S(56, 36), S(30, 23) };
+
+  // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
+  constexpr Score PassedRank[RANK_NB] = {
+    S(0, 0), S(10, 28), S(17, 33), S(15, 41), S(62, 72), S(168, 177), S(276, 260)
+  };
+
   // RookOnFile[semiopen/open] contains bonuses for each rook when there is
   // no (friendly) pawn on the rook file.
   constexpr Score RookOnFile[] = { S(19, 7), S(48, 29) };
@@ -121,23 +133,14 @@ namespace {
     S(0, 0), S(3, 46), S(37, 68), S(42, 60), S(0, 38), S(58, 41)
   };
 
-  // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
-  constexpr Score PassedRank[RANK_NB] = {
-    S(0, 0), S(10, 28), S(17, 33), S(15, 41), S(62, 72), S(168, 177), S(276, 260)
-  };
-
   // Assorted bonuses and penalties
-  constexpr Score BishopKingProtector = S(  6,  9);
   constexpr Score BishopOnKingRing    = S( 24,  0);
-  constexpr Score BishopOutpost       = S( 30, 23);
   constexpr Score BishopPawns         = S(  3,  7);
   constexpr Score BishopXRayPawns     = S(  4,  5);
   constexpr Score CorneredBishop      = S( 50, 50);
   constexpr Score FlankAttacks        = S(  8,  0);
   constexpr Score Hanging             = S( 69, 36);
-  constexpr Score KnightKingProtector = S(  8,  9);
   constexpr Score KnightOnQueen       = S( 16, 11);
-  constexpr Score KnightOutpost       = S( 56, 36);
   constexpr Score LongDiagonalBishop  = S( 45,  0);
   constexpr Score MinorBehindPawn     = S( 18,  3);
   constexpr Score PassedFile          = S( 11,  8);
@@ -308,7 +311,7 @@ namespace {
             // Bonus if piece is on an outpost square or can reach one
             bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them);
             if (bb & s)
-                score += (Pt == KNIGHT) ? KnightOutpost : BishopOutpost;
+                score += Outpost[Pt == BISHOP];
             else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us))
                 score += ReachableOutpost;
 
@@ -317,8 +320,7 @@ namespace {
                 score += MinorBehindPawn;
 
             // Penalty if the piece is far from the king
-            score -= (Pt == KNIGHT ? KnightKingProtector
+            score -= KingProtector[Pt == BISHOP] * distance(pos.square<KING>(Us), s);
-                                   : BishopKingProtector) * distance(pos.square<KING>(Us), s);
 
             if (Pt == BISHOP)
             {
@@ -420,41 +422,33 @@ namespace {
     b2 = attacks_bb<BISHOP>(ksq, pos.pieces() ^ pos.pieces(Us, QUEEN));
 
     // Enemy rooks checks
-    rookChecks = b1 & safe & attackedBy[Them][ROOK];
+    rookChecks = b1 & attackedBy[Them][ROOK] & safe;
     if (rookChecks)
-        kingDanger += more_than_one(rookChecks) ? RookSafeCheck * 175/100
+        kingDanger += SafeCheck[ROOK][more_than_one(rookChecks)];
-                                                : RookSafeCheck;
     else
         unsafeChecks |= b1 & attackedBy[Them][ROOK];
 
-    // Enemy queen safe checks: we count them only if they are from squares from
+    // Enemy queen safe checks: count them only if the checks are from squares from
-    // which we can't give a rook check, because rook checks are more valuable.
+    // which opponent cannot give a rook check, because rook checks are more valuable.
-    queenChecks =  (b1 | b2)
+    queenChecks =  (b1 | b2) & attackedBy[Them][QUEEN] & safe
-                 & attackedBy[Them][QUEEN]
+                 & ~(attackedBy[Us][QUEEN] | rookChecks);
-                 & safe
-                 & ~attackedBy[Us][QUEEN]
-                 & ~rookChecks;
     if (queenChecks)
-        kingDanger += more_than_one(queenChecks) ? QueenSafeCheck * 145/100
+        kingDanger += SafeCheck[QUEEN][more_than_one(queenChecks)];
-                                                 : QueenSafeCheck;
 
-    // Enemy bishops checks: we count them only if they are from squares from
+    // Enemy bishops checks: count them only if they are from squares from which
-    // which we can't give a queen check, because queen checks are more valuable.
+    // opponent cannot give a queen check, because queen checks are more valuable.
-    bishopChecks =  b2
+    bishopChecks =  b2 & attackedBy[Them][BISHOP] & safe
-                  & attackedBy[Them][BISHOP]
-                  & safe
                   & ~queenChecks;
     if (bishopChecks)
-        kingDanger += more_than_one(bishopChecks) ? BishopSafeCheck * 3/2
+        kingDanger += SafeCheck[BISHOP][more_than_one(bishopChecks)];
-                                                  : BishopSafeCheck;
+
     else
         unsafeChecks |= b2 & attackedBy[Them][BISHOP];
 
     // Enemy knights checks
     knightChecks = attacks_bb<KNIGHT>(ksq) & attackedBy[Them][KNIGHT];
     if (knightChecks & safe)
-        kingDanger += more_than_one(knightChecks & safe) ? KnightSafeCheck * 162/100
+        kingDanger += SafeCheck[KNIGHT][more_than_one(knightChecks & safe)];
-                                                         : KnightSafeCheck;
     else
         unsafeChecks |= knightChecks;
 

src/pawns.cpp

@@ -38,7 +38,9 @@ namespace {
   constexpr Score WeakLever     = S( 0, 56);
   constexpr Score WeakUnopposed = S(13, 27);
 
-  constexpr Score BlockedStorm[RANK_NB]  = {S( 0, 0), S( 0, 0), S( 76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2)};
+  constexpr Score BlockedStorm[RANK_NB] = {
+    S(0, 0), S(0, 0), S(76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2)
+  };
 
   // Connected pawn bonus
   constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };