Remove recaptures stage in qsearch

[stockfish] / src / movepick.h

diff --git a/src/movepick.h b/src/movepick.h
index f210f5387fcb222bb8a0728e4a9e413a2a7b583b..7828fa19d975fb9f5e12f4e8a652d487037e6804 100644 (file)
--- a/src/movepick.h
+++ b/src/movepick.h
@@ -32,7 +32,10 @@
 
 namespace Stockfish {
 
-constexpr int PAWN_HISTORY_SIZE = 512;
+constexpr int PAWN_HISTORY_SIZE = 512;  // has to be a power of 2
+
+static_assert((PAWN_HISTORY_SIZE & (PAWN_HISTORY_SIZE - 1)) == 0,
+              "PAWN_HISTORY_SIZE has to be a power of 2");
 
 inline int pawn_structure(const Position& pos) { return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1); }
 
@@ -55,7 +58,7 @@ class StatsEntry {
         assert(abs(bonus) <= D);  // Ensure range is [-D, D]
         static_assert(D <= std::numeric_limits<T>::max(), "D overflows T");
 
-        entry += (bonus * D - entry * abs(bonus)) / (D * 5 / 4);
+        entry += bonus - entry * abs(bonus) / D;
 
         assert(abs(entry) <= D);
     }
@@ -93,11 +96,10 @@ enum StatsType {
     Captures
 };
 
-// ButterflyHistory records how often quiet moves have been successful or
-// unsuccessful 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 www.chessprogramming.org/Butterfly_Boards
-// (~11 elo)
+// ButterflyHistory records how often quiet moves have been successful or unsuccessful
+// 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 www.chessprogramming.org/Butterfly_Boards (~11 elo)
 using ButterflyHistory = Stats<int16_t, 7183, COLOR_NB, int(SQUARE_NB) * int(SQUARE_NB)>;
 
 // CounterMoveHistory stores counter moves indexed by [piece][to] of the previous
@@ -116,7 +118,7 @@ using PieceToHistory = Stats<int16_t, 29952, PIECE_NB, SQUARE_NB>;
 // (~63 elo)
 using ContinuationHistory = Stats<PieceToHistory, NOT_USED, PIECE_NB, SQUARE_NB>;
 
-// PawnStructureHistory is addressed by the pawn structure and a move's [piece][to]
+// PawnHistory is addressed by the pawn structure and a move's [piece][to]
 using PawnHistory = Stats<int16_t, 8192, PAWN_HISTORY_SIZE, PIECE_NB, SQUARE_NB>;
 
 // MovePicker class is used to pick one pseudo-legal move at a time from the
@@ -141,7 +143,7 @@ class MovePicker {
                const ButterflyHistory*,
                const CapturePieceToHistory*,
                const PieceToHistory**,
-               const PawnHistory&,
+               const PawnHistory*,
                Move,
                const Move*);
     MovePicker(const Position&,
@@ -150,9 +152,8 @@ class MovePicker {
                const ButterflyHistory*,
                const CapturePieceToHistory*,
                const PieceToHistory**,
-               const PawnHistory&,
-               Square);
-    MovePicker(const Position&, Move, Value, const CapturePieceToHistory*, const PawnHistory&);
+               const PawnHistory*);
+    MovePicker(const Position&, Move, Value, const CapturePieceToHistory*);
     Move next_move(bool skipQuiets = false);
 
    private:
@@ -167,11 +168,10 @@ class MovePicker {
     const ButterflyHistory*      mainHistory;
     const CapturePieceToHistory* captureHistory;
     const PieceToHistory**       continuationHistory;
-    const PawnHistory&           pawnHistory;
+    const PawnHistory*           pawnHistory;
     Move                         ttMove;
     ExtMove                      refutations[3], *cur, *endMoves, *endBadCaptures;
     int                          stage;
-    Square                       recaptureSquare;
     Value                        threshold;
     Depth                        depth;
     ExtMove                      moves[MAX_MOVES];