Rewrite CTF bonus

Consider paths instead of just the distance between squares.

racingkings STC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 413 W: 205 L: 116 D: 92
http://www.variantfishtest.org:6543/tests/view/5e94459d6e23db4f73614c65

racingkings LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 387 W: 181 L: 97 D: 109
http://www.variantfishtest.org:6543/tests/view/5e944f3c6e23db4f73614c72

kingofthehill STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 1416 W: 701 L: 587 D: 128
http://www.variantfishtest.org:6543/tests/view/5e9445b86e23db4f73614c69

kingofthehill LTC
LLR: 2.96 (-2.94,2.94) [0.00,10.00]
Total: 1130 W: 553 L: 445 D: 132
http://www.variantfishtest.org:6543/tests/view/5e944f5a6e23db4f73614c75

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 8b7f065..f478716 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -905,20 +905,27 @@ namespace {
     // Capture the flag
     if (pos.capture_the_flag(Us))
     {
-        bool isKingCTF = pos.capture_the_flag_piece() == KING;
+        PieceType ptCtf = pos.capture_the_flag_piece();
         Bitboard ctfPieces = pos.pieces(Us, pos.capture_the_flag_piece());
-        int scale = pos.count(Us, pos.capture_the_flag_piece());
-        while (ctfPieces)
+        Bitboard ctfTargets = pos.capture_the_flag(Us) & pos.board_bb();
+        Bitboard onHold = 0;
+        Bitboard processed = 0;
+        // Traverse all paths of the CTF pieces to the CTF targets.
+        // Put squares that are attacked or occupied on hold for one iteration.
+        for (int dist = 0; ctfPieces && (ctfTargets & ~processed); dist++)
         {
-            Square s1 = pop_lsb(&ctfPieces);
-            Bitboard target_squares = pos.capture_the_flag(Us) & pos.board_bb();
-            while (target_squares)
+            score += make_score(2500, 2500) * popcount(ctfTargets & ctfPieces) / (1 + dist * dist);
+            Bitboard current = ctfPieces;
+            processed |= ctfPieces;
+            ctfPieces = onHold & ~processed;
+            onHold = 0;
+            while (current)
             {
-                Square s2 = pop_lsb(&target_squares);
-                int dist =  distance(s1, s2)
-                          + (isKingCTF || pos.flag_move() ? popcount(pos.attackers_to(s2, Them)) : 0)
-                          + !!(pos.pieces(Us) & s2);
-                score += make_score(2500, 2500) / (1 + scale * dist * dist);
+                Square s = pop_lsb(&current);
+                Bitboard attacks = (  (PseudoAttacks[Us][ptCtf][s] & pos.pieces())
+                                    | (PseudoMoves[Us][ptCtf][s] & ~pos.pieces())) & ~processed & pos.board_bb();
+                ctfPieces |= attacks & ~pos.pieces(Us) & ~attackedBy[Them][ALL_PIECES];
+                onHold |= attacks;
             }
         }
     }