Knight threats on Queen

We give a S(21,11) bonus for knight threats on the next moves
against enemy queen. The threats are from squares which are
"not strongly protected" and which may be empty, contain enemy
pieces or even one of our piece at the moment (N,B,Q,R) -- hence
be two-steps threats in the later case because we will have to
move our piece and *then* attack the enemy queen with the knight.

STC: http://tests.stockfishchess.org/tests/view/5a9e442e0ebc590297cb6162
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 35129 W: 7346 L: 7052 D: 20731

LTC: http://tests.stockfishchess.org/tests/view/5a9e6e620ebc590297cb617f
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 42442 W: 6695 L: 6414 D: 29333

How to continue from there?

• Trying to refine the threat condition ("not strongly protected")
• Trying the two-steps idea for bishops or rooks threats against queen

Bench: 6051247

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 2b901bbd166777ad311a2a691bf69538084c48fb..1e5c588a31eb8a357bdf4e54591e8484cc97f1df 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -167,6 +167,7 @@ namespace {
   const Score CloseEnemies      = S(  7,  0);
   const Score Hanging           = S( 52, 30);
   const Score HinderPassedPawn  = S(  8,  1);
   const Score CloseEnemies      = S(  7,  0);
   const Score Hanging           = S( 52, 30);
   const Score HinderPassedPawn  = S(  8,  1);

+  const Score KnightOnQueen     = S( 21, 11);

   const Score LongRangedBishop  = S( 22,  0);
   const Score MinorBehindPawn   = S( 16,  0);
   const Score PawnlessFlank     = S( 20, 80);
   const Score LongRangedBishop  = S( 22,  0);
   const Score MinorBehindPawn   = S( 16,  0);
   const Score PawnlessFlank     = S( 20, 80);


@@ -489,7 +490,7 @@ namespace {
     if (!(pos.pieces(PAWN) & kf))
         score -= PawnlessFlank;
 
     if (!(pos.pieces(PAWN) & kf))
         score -= PawnlessFlank;
 

-    // Find the squares that opponent attacks in our king flank, and the squares  
+    // Find the squares that opponent attacks in our king flank, and the squares

     // which are attacked twice in that flank but not defended by our pawns.
     b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
     b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];
     // which are attacked twice in that flank but not defended by our pawns.
     b1 = attackedBy[Them][ALL_PIECES] & kf & Camp;
     b2 = b1 & attackedBy2[Them] & ~attackedBy[Us][PAWN];


@@ -595,6 +596,17 @@ namespace {
 
     score += ThreatOnQueen * popcount(b & safeThreats);
 
 
     score += ThreatOnQueen * popcount(b & safeThreats);
 

+    // Bonus for knight threats on the next moves against enemy queen
+    if (pos.count<QUEEN>(Them) == 1)
+    {
+        b =   pos.attacks_from<KNIGHT>(pos.square<QUEEN>(Them))
+           &  attackedBy[Us][KNIGHT]
+           & ~pos.pieces(Us, PAWN, KING)
+           & ~stronglyProtected;
+
+        score += KnightOnQueen * popcount(b);
+    }
+

     if (T)
         Trace::add(THREAT, Us, score);
 
     if (T)
         Trace::add(THREAT, Us, score);
 

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 29a987519182ed709d1b7889be21335866d1d2a5..67bf59d183325a52fd2cfc3a200a5d0e60d18f7b 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -237,7 +237,7 @@ template<Color Us>
 Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
 Value Entry::shelter_storm(const Position& pos, Square ksq) {
 
   constexpr Color Them = (Us == WHITE ? BLACK : WHITE);

-  constexpr Bitboard ShelterMask = 
+  constexpr Bitboard ShelterMask =

                 Us == WHITE ? make_bitboard(SQ_A2, SQ_B3, SQ_C2, SQ_F2, SQ_G3, SQ_H2)
                             : make_bitboard(SQ_A7, SQ_B6, SQ_C7, SQ_F7, SQ_G6, SQ_H7);
   constexpr Bitboard StormMask =
                 Us == WHITE ? make_bitboard(SQ_A2, SQ_B3, SQ_C2, SQ_F2, SQ_G3, SQ_H2)
                             : make_bitboard(SQ_A7, SQ_B6, SQ_C7, SQ_F7, SQ_G6, SQ_H7);
   constexpr Bitboard StormMask =