From: Stéphane Nicolet <cassio@free.fr>
Date: Mon, 30 Jan 2017 21:05:43 +0000 (+0100)
Subject: Simplify away QueenContactChecks
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=ddecdc97d71e07536d1b1a23ffca7b0475a5b480

Simplify away QueenContactChecks

Changing the definition of safe checks to include
squares protected only by the king, but twice
attacked by the opponent.

STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 8691 W: 1683 L: 1541 D: 5467
http://tests.stockfishchess.org/tests/view/588f53b50ebc5915193f7dc7

LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 31266 W: 4150 L: 4043 D: 23073
http://tests.stockfishchess.org/tests/view/588f68ab0ebc5915193f7dda

Bench : 5885815
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index d9aae3d3..2414d5a0 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -209,7 +209,6 @@ namespace {
   const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
 
   // Penalties for enemy's safe checks
-  const int QueenContactCheck = 997;
   const int QueenCheck        = 745;
   const int RookCheck         = 688;
   const int BishopCheck       = 588;
@@ -430,15 +429,9 @@ namespace {
                     - 717 * !pos.count<QUEEN>(Them)
                     -   7 * mg_value(score) / 5 - 5;
 
-        // Analyse the enemy's safe queen contact checks. Firstly, find the
-        // undefended squares around our king reachable by the enemy queen...
-        b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
-
-        // ...and keep squares supported by another enemy piece.
-        kingDanger += QueenContactCheck * popcount(b & ei.attackedBy2[Them]);
-
         // Analyse the safe enemy's checks which are possible on next move
-        safe  = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
+        safe  = ~pos.pieces(Them);
+        safe &= ~ei.attackedBy[Us][ALL_PIECES] | (undefended & ei.attackedBy2[Them]);
 
         b1 = pos.attacks_from<ROOK  >(ksq);
         b2 = pos.attacks_from<BISHOP>(ksq);