From: Stéphane Nicolet <Stephane.Nicolet@u-paris2.fr>
Date: Tue, 28 Jul 2020 08:08:09 +0000 (+0200)
Subject: Improve handling of queen imbalance
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=33f3cfae0093b934563e1eca78486261f18e4650

Improve handling of queen imbalance

We double the bonus for potential threats by minors and rooks against
our queen, in case of "queen vs pieces imbalance". Hopefully this will
improve a little bit the evaluation for this well-known Stockfish weakness.

passed STC:
LLR: 2.93 (-2.94,2.94) {-0.50,1.50}
Total: 72976 W: 14003 L: 13710 D: 45263
Ptnml(0-2): 1218, 8370, 17094, 8513, 1293
https://tests.stockfishchess.org/tests/view/5efa50eb020eec13834a977d

passed LTC:
LLR: 2.93 (-2.94,2.94) {0.25,1.75}
Total: 22232 W: 2779 L: 2560 D: 16893
Ptnml(0-2): 129, 1885, 6896, 2050, 156
https://tests.stockfishchess.org/tests/view/5f1fdd2dc09435d870cb9f13

closes https://github.com/official-stockfish/Stockfish/pull/2864

Bench: 4367349
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index d16648a8..b34d82f6 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -579,17 +579,21 @@ namespace {
     // Bonus for threats on the next moves against enemy queen
     if (pos.count<QUEEN>(Them) == 1)
     {
+        bool queenImbalance = pos.count<QUEEN>() == 1;
+
         Square s = pos.square<QUEEN>(Them);
-        safe = mobilityArea[Us] & ~stronglyProtected;
+        safe =   mobilityArea[Us]
+              & ~pos.pieces(Us, PAWN)
+              & ~stronglyProtected;
 
         b = attackedBy[Us][KNIGHT] & attacks_bb<KNIGHT>(s);
 
-        score += KnightOnQueen * popcount(b & safe);
+        score += KnightOnQueen * popcount(b & safe) * (1 + queenImbalance);
 
         b =  (attackedBy[Us][BISHOP] & attacks_bb<BISHOP>(s, pos.pieces()))
            | (attackedBy[Us][ROOK  ] & attacks_bb<ROOK  >(s, pos.pieces()));
 
-        score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]);
+        score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]) * (1 + queenImbalance);
     }
 
     if (T)