Simplify tropism. (#1807)

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index daf0c1d74d7b2c1e1b5460b5714852ce94ec9e08..97218baa19f9627cb27ce59948c255e18cef0b81 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -127,7 +127,7 @@ namespace {
 
   // RookOnFile[semiopen/open] contains bonuses for each rook when there is
   // no (friendly) pawn on the rook file.
-  constexpr Score RookOnFile[] = { S(20, 7), S(45, 20) };
+  constexpr Score RookOnFile[] = { S(18, 7), S(44, 20) };
 
   // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
   // which piece type attacks which one. Attacks on lesser pieces which are
@@ -165,13 +165,13 @@ namespace {
   constexpr Score MinorBehindPawn    = S( 16,  0);
   constexpr Score Overload           = S( 13,  6);
   constexpr Score PawnlessFlank      = S( 19, 84);
-  constexpr Score RookOnPawn         = S( 10, 30);
+  constexpr Score RookOnPawn         = S( 10, 29);
   constexpr Score SliderOnQueen      = S( 42, 21);
   constexpr Score ThreatByKing       = S( 22, 78);
   constexpr Score ThreatByPawnPush   = S( 45, 40);
   constexpr Score ThreatByRank       = S( 16,  3);
   constexpr Score ThreatBySafePawn   = S(173,102);
-  constexpr Score TrappedRook        = S( 92,  0);
+  constexpr Score TrappedRook        = S( 96,  5);
   constexpr Score WeakQueen          = S( 50, 10);
   constexpr Score WeakUnopposedPawn  = S( 15, 19);
 
@@ -421,7 +421,7 @@ namespace {
     // 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];
+    b2 = b1 & attackedBy2[Them];
 
     int tropism = popcount(b1) + popcount(b2);
 
@@ -480,15 +480,12 @@ namespace {
                      +   4 * tropism
                      - 873 * !pos.count<QUEEN>(Them)
                      -   6 * mg_value(score) / 8
+                     +       mg_value(mobility[Them] - mobility[Us])
                      -   30;
 
         // Transform the kingDanger units into a Score, and subtract it from the evaluation
         if (kingDanger > 0)
-        {
-            int mobilityDanger = mg_value(mobility[Them] - mobility[Us]);
-            kingDanger = std::max(0, kingDanger + mobilityDanger);
             score -= make_score(kingDanger * kingDanger / 4096, kingDanger / 16);
-        }
     }
 
     // Penalty when our king is on a pawnless flank