Remove major corrhist

Remove major correction history and slightly increase all other
correction weights.

Passed STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 50080 W: 13171 L: 12959 D: 23950
Ptnml(0-2): 196, 5998, 12462, 6166, 218
https://tests.stockfishchess.org/tests/live_elo/67954526406a4efe9eb7d176

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 51504 W: 13188 L: 12995 D: 25321
Ptnml(0-2): 54, 5658, 14128, 5865, 47
https://tests.stockfishchess.org/tests/live_elo/67954961406a4efe9eb7d251

closes https://github.com/official-stockfish/Stockfish/pull/5822

Bench: 2081366

src/history.h

@@ -54,10 +54,6 @@ inline int pawn_structure_index(const Position& pos) {
     return pos.pawn_key() & ((T == Normal ? PAWN_HISTORY_SIZE : CORRECTION_HISTORY_SIZE) - 1);
 }
 
-inline int major_piece_index(const Position& pos) {
-    return pos.major_piece_key() & (CORRECTION_HISTORY_SIZE - 1);
-}
-
 inline int minor_piece_index(const Position& pos) {
     return pos.minor_piece_key() & (CORRECTION_HISTORY_SIZE - 1);
 }
@@ -136,7 +132,6 @@ using PawnHistory = Stats<std::int16_t, 8192, PAWN_HISTORY_SIZE, PIECE_NB, SQUAR
 // see https://www.chessprogramming.org/Static_Evaluation_Correction_History
 enum CorrHistType {
     Pawn,          // By color and pawn structure
-    Major,         // By color and positions of major pieces (Queen, Rook) and King
     Minor,         // By color and positions of minor pieces (Knight, Bishop) and King
     NonPawn,       // By Non-pawn material positions and color
     PieceTo,       // By [piece][to] move

src/position.cpp

@@ -335,7 +335,6 @@ void Position::set_check_info() const {
 void Position::set_state() const {
 
     st->key = st->materialKey = 0;
-    st->majorPieceKey = st->minorPieceKey = 0;
     st->nonPawnKey[WHITE] = st->nonPawnKey[BLACK] = 0;
     st->pawnKey                                   = Zobrist::noPawns;
     st->nonPawnMaterial[WHITE] = st->nonPawnMaterial[BLACK] = VALUE_ZERO;
@@ -360,16 +359,12 @@ void Position::set_state() const {
             {
                 st->nonPawnMaterial[color_of(pc)] += PieceValue[pc];
 
-                if (type_of(pc) >= ROOK)
+                if (type_of(pc) <= BISHOP)
-                    st->majorPieceKey ^= Zobrist::psq[pc][s];
-
-                else
                     st->minorPieceKey ^= Zobrist::psq[pc][s];
             }
 
             else
             {
-                st->majorPieceKey ^= Zobrist::psq[pc][s];
                 st->minorPieceKey ^= Zobrist::psq[pc][s];
             }
         }
@@ -742,7 +737,6 @@ void Position::do_move(Move                      m,
         do_castling<true>(us, from, to, rfrom, rto);
 
         k ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto];
-        st->majorPieceKey ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto];
         st->nonPawnKey[us] ^= Zobrist::psq[captured][rfrom] ^ Zobrist::psq[captured][rto];
         captured = NO_PIECE;
     }
@@ -773,10 +767,7 @@ void Position::do_move(Move                      m,
             st->nonPawnMaterial[them] -= PieceValue[captured];
             st->nonPawnKey[them] ^= Zobrist::psq[captured][capsq];
 
-            if (type_of(captured) >= ROOK)
+            if (type_of(captured) <= BISHOP)
-                st->majorPieceKey ^= Zobrist::psq[captured][capsq];
-
-            else
                 st->minorPieceKey ^= Zobrist::psq[captured][capsq];
         }
 
@@ -858,10 +849,7 @@ void Position::do_move(Move                      m,
             st->materialKey ^=
               Zobrist::psq[promotion][pieceCount[promotion] - 1] ^ Zobrist::psq[pc][pieceCount[pc]];
 
-            if (promotionType >= ROOK)
+            if (promotionType <= BISHOP)
-                st->majorPieceKey ^= Zobrist::psq[promotion][to];
-
-            else
                 st->minorPieceKey ^= Zobrist::psq[promotion][to];
 
             // Update material
@@ -881,14 +869,10 @@ void Position::do_move(Move                      m,
 
         if (type_of(pc) == KING)
         {
-            st->majorPieceKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
             st->minorPieceKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
         }
 
-        else if (type_of(pc) >= ROOK)
+        else if (type_of(pc) <= BISHOP)
-            st->majorPieceKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
-
-        else
             st->minorPieceKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
     }
 

src/position.h

@@ -43,7 +43,6 @@ struct StateInfo {
     // Copied when making a move
     Key    materialKey;
     Key    pawnKey;
-    Key    majorPieceKey;
     Key    minorPieceKey;
     Key    nonPawnKey[COLOR_NB];
     Value  nonPawnMaterial[COLOR_NB];
@@ -154,7 +153,6 @@ class Position {
     Key key() const;
     Key material_key() const;
     Key pawn_key() const;
-    Key major_piece_key() const;
     Key minor_piece_key() const;
     Key non_pawn_key(Color c) const;
 
@@ -305,8 +303,6 @@ inline Key Position::pawn_key() const { return st->pawnKey; }
 
 inline Key Position::material_key() const { return st->materialKey; }
 
-inline Key Position::major_piece_key() const { return st->majorPieceKey; }
-
 inline Key Position::minor_piece_key() const { return st->minorPieceKey; }
 
 inline Key Position::non_pawn_key(Color c) const { return st->nonPawnKey[c]; }

src/search.cpp

@@ -87,7 +87,6 @@ int correction_value(const Worker& w, const Position& pos, const Stack* ss) {
     const Color us    = pos.side_to_move();
     const auto  m     = (ss - 1)->currentMove;
     const auto  pcv   = w.pawnCorrectionHistory[us][pawn_structure_index<Correction>(pos)];
-    const auto  macv  = w.majorPieceCorrectionHistory[us][major_piece_index(pos)];
     const auto  micv  = w.minorPieceCorrectionHistory[us][minor_piece_index(pos)];
     const auto  wnpcv = w.nonPawnCorrectionHistory[WHITE][non_pawn_index<WHITE>(pos)][us];
     const auto  bnpcv = w.nonPawnCorrectionHistory[BLACK][non_pawn_index<BLACK>(pos)][us];
@@ -95,7 +94,7 @@ int correction_value(const Worker& w, const Position& pos, const Stack* ss) {
       m.is_ok() ? (*(ss - 2)->continuationCorrectionHistory)[pos.piece_on(m.to_sq())][m.to_sq()]
                  : 0;
 
-    return (6922 * pcv + 3837 * macv + 6238 * micv + 7490 * (wnpcv + bnpcv) + 6270 * cntcv);
+    return (7000 * pcv + 6300 * micv + 7550 * (wnpcv + bnpcv) + 6320 * cntcv);
 }
 
 // Add correctionHistory value to raw staticEval and guarantee evaluation
@@ -516,7 +515,6 @@ void Search::Worker::clear() {
     captureHistory.fill(-631);
     pawnHistory.fill(-1210);
     pawnCorrectionHistory.fill(0);
-    majorPieceCorrectionHistory.fill(0);
     minorPieceCorrectionHistory.fill(0);
     nonPawnCorrectionHistory[WHITE].fill(0);
     nonPawnCorrectionHistory[BLACK].fill(0);
@@ -1439,7 +1437,6 @@ moves_loop:  // When in check, search starts here
                                 -CORRECTION_HISTORY_LIMIT / 4, CORRECTION_HISTORY_LIMIT / 4);
         thisThread->pawnCorrectionHistory[us][pawn_structure_index<Correction>(pos)]
           << bonus * 114 / 128;
-        thisThread->majorPieceCorrectionHistory[us][major_piece_index(pos)] << bonus * 163 / 128;
         thisThread->minorPieceCorrectionHistory[us][minor_piece_index(pos)] << bonus * 146 / 128;
         thisThread->nonPawnCorrectionHistory[WHITE][non_pawn_index<WHITE>(pos)][us]
           << bonus * nonPawnWeight / 128;

src/search.h

@@ -288,7 +288,6 @@ class Worker {
     PawnHistory           pawnHistory;
 
     CorrectionHistory<Pawn>         pawnCorrectionHistory;
-    CorrectionHistory<Major>        majorPieceCorrectionHistory;
     CorrectionHistory<Minor>        minorPieceCorrectionHistory;
     CorrectionHistory<NonPawn>      nonPawnCorrectionHistory[COLOR_NB];
     CorrectionHistory<Continuation> continuationCorrectionHistory;