Count unsafe captures in antichess threat evaluation

giveaway STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 543 W: 258 L: 167 D: 118
http://www.variantfishtest.org:6543/tests/view/5ed2d2266e23db36d55f2cb3

giveaway LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 663 W: 280 L: 192 D: 191
http://www.variantfishtest.org:6543/tests/view/5ed3b2ba6e23db36d55f2cd7

losers STC
LLR: 2.99 (-2.94,2.94) [-10.00,5.00]
Total: 856 W: 407 L: 351 D: 98
http://www.variantfishtest.org:6543/tests/view/5ed393136e23db36d55f2cce

losers LTC
LLR: 2.98 (-2.94,2.94) [-10.00,5.00]
Total: 3105 W: 1364 L: 1325 D: 416
http://www.variantfishtest.org:6543/tests/view/5ed3b2c26e23db36d55f2cd9

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6ca09bb..a11be4b 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -621,8 +621,9 @@ namespace {
     if (pos.must_capture())
     {
         // Penalties for possible captures
-        if (attackedBy[Us][ALL_PIECES] & pos.pieces(Them))
-            score -= make_score(1000, 1000) / popcount(attackedBy[Us][ALL_PIECES] & pos.pieces(Them));
+        Bitboard captures = attackedBy[Us][ALL_PIECES] & pos.pieces(Them);
+        if (captures)
+            score -= make_score(2000, 2000) / (1 + popcount(captures & attackedBy[Them][ALL_PIECES] & ~attackedBy2[Us]));
 
         // Bonus if we threaten to force captures
         Bitboard moves = 0, piecebb = pos.pieces(Us);