From 7a9f67747f23e837a8691ba9e6e4f0d1fdafff73 Mon Sep 17 00:00:00 2001
From: mstembera <MissingEmail@email>
Date: Tue, 4 Apr 2023 19:44:09 -0700
Subject: [PATCH] Reduce Position::pieces() overloads

Reduce the number of overloads for pieces() by using a more general template implementation.
Secondly simplify some code in search.cpp using the new general functionality.

TC https://tests.stockfishchess.org/tests/view/642ce27877ff3301150dc193
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 269640 W: 71775 L: 71809 D: 126056
Ptnml(0-2): 687, 27294, 78885, 27274, 680

closes https://github.com/official-stockfish/Stockfish/pull/4501

No functional change.
---
 src/position.h | 19 ++++++++-----------
 src/search.cpp | 12 +++++++-----
 2 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/src/position.h b/src/position.h
index bb45c44a..a736f3e6 100644
--- a/src/position.h
+++ b/src/position.h
@@ -92,10 +92,9 @@ public:
 
   // Position representation
   Bitboard pieces(PieceType pt) const;
-  Bitboard pieces(PieceType pt1, PieceType pt2) const;
+  template<typename ...PieceTypes> Bitboard pieces(PieceType pt, PieceTypes... pts) const;
   Bitboard pieces(Color c) const;
-  Bitboard pieces(Color c, PieceType pt) const;
-  Bitboard pieces(Color c, PieceType pt1, PieceType pt2) const;
+  template<typename ...PieceTypes> Bitboard pieces(Color c, PieceTypes... pts) const;
   Piece piece_on(Square s) const;
   Square ep_square() const;
   bool empty(Square s) const;
@@ -229,20 +228,18 @@ inline Bitboard Position::pieces(PieceType pt = ALL_PIECES) const {
   return byTypeBB[pt];
 }
 
-inline Bitboard Position::pieces(PieceType pt1, PieceType pt2) const {
-  return pieces(pt1) | pieces(pt2);
+template<typename ...PieceTypes>
+inline Bitboard Position::pieces(PieceType pt, PieceTypes... pts) const {
+  return pieces(pt) | pieces(pts...);
 }
 
 inline Bitboard Position::pieces(Color c) const {
   return byColorBB[c];
 }
 
-inline Bitboard Position::pieces(Color c, PieceType pt) const {
-  return pieces(c) & pieces(pt);
-}
-
-inline Bitboard Position::pieces(Color c, PieceType pt1, PieceType pt2) const {
-  return pieces(c) & (pieces(pt1) | pieces(pt2));
+template<typename ...PieceTypes>
+inline Bitboard Position::pieces(Color c, PieceTypes... pts) const {
+  return pieces(c) & pieces(pts...);
 }
 
 template<PieceType Pt> inline int Position::count(Color c) const {
diff --git a/src/search.cpp b/src/search.cpp
index 4463b42a..4187117b 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1018,16 +1018,18 @@ moves_loop: // When in check, search starts here
               {
                   if (depth < 2 - capture)
                       continue;
-                  // don't prune move if a heavy enemy piece (KQR) is under attack after the exchanges
-                  Bitboard leftEnemies = (pos.pieces(~us, QUEEN, ROOK) | pos.pieces(~us, KING)) & occupied;
+                  // Don't prune the move if opp. King/Queen/Rook is attacked by a slider after the exchanges.
+                  // Since in see_ge we don't update occupied when the king recaptures, we also don't prune the
+                  // move when the opp. King gets a discovered slider attack DURING the exchanges.
+                  Bitboard leftEnemies = pos.pieces(~us, ROOK, QUEEN, KING) & occupied;
                   Bitboard attacks = 0;
                   occupied |= to_sq(move);
                   while (leftEnemies && !attacks)
                   {
                       Square sq = pop_lsb(leftEnemies);
-                      attacks |= pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
-                      // exclude Queen/Rook(s) which were already threatened before SEE
-                      if (attacks && (sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))))
+                      attacks = pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
+                      // Exclude Queen/Rook(s) which were already threatened before SEE
+                      if (attacks && sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us)))
                           attacks = 0;
                   }
                   if (!attacks)
-- 
2.39.2