Fix reported DTZ for mate-in-1-ply positions

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 3e0533b20c7d8c730c08976bb5c016f39746b742..69a36cf5ee4659a43b80050925054d2e71b3c223 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -171,6 +171,7 @@ namespace {
   constexpr Score KnightOnQueen      = S( 21, 11);
   constexpr Score LongDiagonalBishop = S( 22,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
+  constexpr Score Overload           = S( 10,  5);
   constexpr Score PawnlessFlank      = S( 20, 80);
   constexpr Score RookOnPawn         = S(  8, 24);
   constexpr Score SliderOnQueen      = S( 42, 21);
@@ -300,6 +301,7 @@ namespace {
     Bitboard b, bb;
     Square s;
     Score score = SCORE_ZERO;
+    int mob;
 
     attackedBy[Us][Pt] = 0;
 
@@ -324,7 +326,8 @@ namespace {
             kingAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
         }
 
-        int mob = popcount(b & mobilityArea[Us]);
+        mob = (Pt == KNIGHT || Pt == BISHOP) ? popcount(b & mobilityArea[Us] & ~pos.pieces(Us, QUEEN))
+                                             : popcount(b & mobilityArea[Us]);
 
         mobility[Us] += MobilityBonus[Pt - 2][mob];
 
@@ -518,19 +521,15 @@ namespace {
     Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
     Score score = SCORE_ZERO;
 
-    // Non-pawn enemies attacked by a pawn
+    // Non-pawn enemies
     nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
-    weak = nonPawnEnemies & attackedBy[Us][PAWN];
 
-    if (weak)
-    {
-        // Our safe or protected pawns
-        b =  pos.pieces(Us, PAWN)
-           & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
+    // Our safe or protected pawns
+    b =   pos.pieces(Us, PAWN)
+       & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
 
-        safeThreats = pawn_attacks_bb<Us>(b) & weak;
-        score += ThreatBySafePawn * popcount(safeThreats);
-    }
+    safeThreats = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
+    score += ThreatBySafePawn * popcount(safeThreats);
 
     // Squares strongly protected by the enemy, either because they defend the
     // square with a pawn, or because they defend the square twice and we don't.
@@ -610,6 +609,12 @@ namespace {
     b = (pos.pieces(Us) ^ pos.pieces(Us, PAWN, KING)) & attackedBy[Us][ALL_PIECES];
     score += Connectivity * popcount(b);
 
+    // Bonus for overload (non-pawn enemies attacked and defended exactly once)
+    b =  nonPawnEnemies
+       & attackedBy[Us][ALL_PIECES]   & ~attackedBy2[Us]
+       & attackedBy[Them][ALL_PIECES] & ~attackedBy2[Them];
+    score += Overload * popcount(b);
+
     if (T)
         Trace::add(THREAT, Us, score);
 
@@ -733,8 +738,7 @@ namespace {
     // pawn, or if it is undefended and attacked by an enemy piece.
     Bitboard safe =   SpaceMask
                    & ~pos.pieces(Us, PAWN)
-                   & ~attackedBy[Them][PAWN]
-                   & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
+                   & ~attackedBy[Them][PAWN];
 
     // Find all squares which are at most three squares behind some friendly pawn
     Bitboard behind = pos.pieces(Us, PAWN);