In official-stockfish#6391 multiple histories were changed together.

See if the ones indexed by move from_to() were better previously.
bench: 3012156

Author: mstembera

src/history.h

@@ -98,11 +98,11 @@ using Stats = MultiArray<StatsEntry<T, D>, Sizes...>;
 // during the current search, and is used for reduction and move ordering decisions.
 // It uses 2 tables (one for each color) indexed by the move's from and to squares,
 // see https://www.chessprogramming.org/Butterfly_Boards
-using ButterflyHistory = Stats<std::int16_t, 7183, COLOR_NB, UINT_16_HISTORY_SIZE>;
+using ButterflyHistory = Stats<std::int16_t, 7183, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)>;
 
 // LowPlyHistory is addressed by play and move's from and to squares, used
 // to improve move ordering near the root
-using LowPlyHistory = Stats<std::int16_t, 7183, LOW_PLY_HISTORY_SIZE, UINT_16_HISTORY_SIZE>;
+using LowPlyHistory = Stats<std::int16_t, 7183, LOW_PLY_HISTORY_SIZE, int(SQUARE_NB) * int(SQUARE_NB)>;
 
 // CapturePieceToHistory is addressed by a move's [piece][to][captured piece type]
 using CapturePieceToHistory = Stats<std::int16_t, 10692, PIECE_NB, SQUARE_NB, PIECE_TYPE_NB>;

src/movepick.cpp

@@ -158,7 +158,7 @@ ExtMove* MovePicker::score(MoveList<Type>& ml) {
         else if constexpr (Type == QUIETS)
         {
             // histories
-            m.value = 2 * (*mainHistory)[us][m.raw()];
+            m.value = 2 * (*mainHistory)[us][m.from_to()];
             m.value += 2 * (*pawnHistory)[pawn_history_index(pos)][pc][to];
             m.value += (*continuationHistory[0])[pc][to];
             m.value += (*continuationHistory[1])[pc][to];
@@ -176,7 +176,7 @@ ExtMove* MovePicker::score(MoveList<Type>& ml) {
 
 
             if (ply < LOW_PLY_HISTORY_SIZE)
-                m.value += 8 * (*lowPlyHistory)[ply][m.raw()] / (1 + ply);
+                m.value += 8 * (*lowPlyHistory)[ply][m.from_to()] / (1 + ply);
         }
 
         else  // Type == EVASIONS
@@ -185,9 +185,9 @@ ExtMove* MovePicker::score(MoveList<Type>& ml) {
                 m.value = PieceValue[capturedPiece] + (1 << 28);
             else
             {
-                m.value = (*mainHistory)[us][m.raw()] + (*continuationHistory[0])[pc][to];
+                m.value = (*mainHistory)[us][m.from_to()] + (*continuationHistory[0])[pc][to];
                 if (ply < LOW_PLY_HISTORY_SIZE)
-                    m.value += (*lowPlyHistory)[ply][m.raw()];
+                    m.value += (*lowPlyHistory)[ply][m.from_to()];
             }
         }
     }

src/search.cpp

@@ -824,7 +824,7 @@ Value Search::Worker::search(
     if (((ss - 1)->currentMove).is_ok() && !(ss - 1)->inCheck && !priorCapture)
     {
         int evalDiff = std::clamp(-int((ss - 1)->staticEval + ss->staticEval), -200, 156) + 58;
-        mainHistory[~us][((ss - 1)->currentMove).raw()] << evalDiff * 9;
+        mainHistory[~us][((ss - 1)->currentMove).from_to()] << evalDiff * 9;
         if (!ttHit && type_of(pos.piece_on(prevSq)) != PAWN
             && ((ss - 1)->currentMove).type_of() != PROMOTION)
             pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq] << evalDiff * 14;
@@ -1068,7 +1068,7 @@ Value Search::Worker::search(
                 if (history < -4312 * depth)
                     continue;
 
-                history += 76 * mainHistory[us][move.raw()] / 32;
+                history += 76 * mainHistory[us][move.from_to()] / 32;
 
                 // (*Scaler): Generally, lower divisors scales well
                 lmrDepth += history / 3220;
@@ -1198,7 +1198,7 @@ Value Search::Worker::search(
             ss->statScore = 803 * int(PieceValue[pos.captured_piece()]) / 128
                           + captureHistory[movedPiece][move.to_sq()][type_of(pos.captured_piece())];
         else
-            ss->statScore = 2 * mainHistory[us][move.raw()]
+            ss->statScore = 2 * mainHistory[us][move.from_to()]
                           + (*contHist[0])[movedPiece][move.to_sq()]
                           + (*contHist[1])[movedPiece][move.to_sq()];
 
@@ -1415,7 +1415,7 @@ Value Search::Worker::search(
         update_continuation_histories(ss - 1, pos.piece_on(prevSq), prevSq,
                                       scaledBonus * 400 / 32768);
 
-        mainHistory[~us][((ss - 1)->currentMove).raw()] << scaledBonus * 220 / 32768;
+        mainHistory[~us][((ss - 1)->currentMove).from_to()] << scaledBonus * 220 / 32768;
 
         if (type_of(pos.piece_on(prevSq)) != PAWN && ((ss - 1)->currentMove).type_of() != PROMOTION)
             pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq]
@@ -1862,10 +1862,10 @@ void update_quiet_histories(
   const Position& pos, Stack* ss, Search::Worker& workerThread, Move move, int bonus) {
 
     Color us = pos.side_to_move();
-    workerThread.mainHistory[us][move.raw()] << bonus;  // Untuned to prevent duplicate effort
+    workerThread.mainHistory[us][move.from_to()] << bonus;  // Untuned to prevent duplicate effort
 
     if (ss->ply < LOW_PLY_HISTORY_SIZE)
-        workerThread.lowPlyHistory[ss->ply][move.raw()] << bonus * 761 / 1024;
+        workerThread.lowPlyHistory[ss->ply][move.from_to()] << bonus * 761 / 1024;
 
     update_continuation_histories(ss, pos.moved_piece(move), move.to_sq(), bonus * 955 / 1024);
 

src/types.h

@@ -448,6 +448,8 @@ class Move {
         return Square(data & 0x3F);
     }
 
+    constexpr int from_to() const { return data & 0xFFF; }
+
     constexpr MoveType type_of() const { return MoveType(data & (3 << 14)); }
 
     constexpr PieceType promotion_type() const { return PieceType(((data >> 12) & 3) + KNIGHT); }