speed up for legal

official-pikafish · Oct 1, 2022 · 3c764c1 · 3c764c1
1 parent d699bdf
commit 3c764c1
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Showing 3 changed files with 21 additions and 19 deletions.
diff --git a/src/movegen.cpp b/src/movegen.cpp
@@ -184,21 +184,13 @@ ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
 template<>
 ExtMove* generate<LEGAL>(const Position& pos, ExtMove* moveList) {
 
-  Color us = pos.side_to_move();
-  Bitboard pinned = pos.blockers_for_king(us) & pos.pieces(us);
-  Square ksq = pos.square<KING>(us);
   ExtMove* cur = moveList;
 
-  // We have to take special cares about the cannon and checks
-  bool inCheck = pos.checkers();
-  bool notOk = inCheck || (attacks_bb<ROOK>(ksq) & pos.pieces(~us, CANNON));
-
-  moveList = inCheck ? generate<EVASIONS>(pos, moveList)
-                     : generate<PSEUDO_LEGAL>(pos, moveList);
+  moveList = pos.checkers() ? generate<EVASIONS>(pos, moveList)
+                            : generate<PSEUDO_LEGAL>(pos, moveList);
 
   while (cur != moveList)
-      // A move is always legal when not moving the king or a pinned piece
-      if ((notOk || (pinned && pinned & from_sq(*cur)) || from_sq(*cur) == ksq) && !pos.legal(*cur))
+      if (!pos.legal(*cur))
           *cur = (--moveList)->move;
       else
           ++cur;

diff --git a/src/position.cpp b/src/position.cpp
@@ -173,15 +173,20 @@ Position& Position::set(const string& fenStr, StateInfo* si, Thread* th) {
 
 void Position::set_check_info(StateInfo* si) const {
 
-  si->blockersForKing[WHITE] = blockers_for_king(pieces(BLACK), square<KING>(WHITE), si->pinners[BLACK]);
-  si->blockersForKing[BLACK] = blockers_for_king(pieces(WHITE), square<KING>(BLACK), si->pinners[WHITE]);
+  Color  us   = sideToMove;
+  Square uksq = square<KING>( us);
+  Square oksq = square<KING>(~us);
 
-  Square ksq = square<KING>(~sideToMove);
+  si->blockersForKing[ us] = blockers_for_king(pieces(~us), uksq, si->pinners[~us]);
+  si->blockersForKing[~us] = blockers_for_king(pieces( us), oksq, si->pinners[ us]);
+
+  // We have to take special cares about the cannon and checks
+  si->needSlowCheck = checkers() || (attacks_bb<ROOK>(uksq) & pieces(~us, CANNON));
 
-  si->checkSquares[PAWN]   = pawn_attacks_to_bb(sideToMove, ksq);
-  si->checkSquares[KNIGHT] = attacks_bb<KNIGHT_TO>(ksq, pieces());
-  si->checkSquares[CANNON] = attacks_bb<CANNON>(ksq, pieces());
-  si->checkSquares[ROOK]   = attacks_bb<ROOK>(ksq, pieces());
+  si->checkSquares[PAWN]   = pawn_attacks_to_bb(sideToMove, oksq);
+  si->checkSquares[KNIGHT] = attacks_bb<KNIGHT_TO>(oksq, pieces());
+  si->checkSquares[CANNON] = attacks_bb<CANNON>(oksq, pieces());
+  si->checkSquares[ROOK]   = attacks_bb<ROOK>(oksq, pieces());
   si->checkSquares[KING]   = si->checkSquares[ADVISOR] = si->checkSquares[BISHOP] = 0;
 }
 
@@ -323,12 +328,16 @@ bool Position::legal(Move m) const {
   Square from = from_sq(m);
   Square to = to_sq(m);
   Bitboard occupied = (pieces() ^ from) | to;
+  Square ksq = type_of(moved_piece(m)) == KING ? to : square<KING>(us);
 
   assert(color_of(moved_piece(m)) == us);
   assert(piece_on(square<KING>(us)) == make_piece(us, KING));
 
+  // A non-king move is always legal when not moving the king or a pinned piece if we don't need slow check
+  if (!st->needSlowCheck && ksq != to && !(blockers_for_king(us) & from))
+      return true;
+
   // Flying general rule
-  Square ksq = type_of(moved_piece(m)) == KING ? to : square<KING>(us);
   if (attacks_bb<ROOK>(ksq, occupied) & pieces(~us, KING))
       return false;
 

diff --git a/src/position.h b/src/position.h
@@ -48,6 +48,7 @@ struct StateInfo {
   Bitboard   blockersForKing[COLOR_NB];
   Bitboard   pinners[COLOR_NB];
   Bitboard   checkSquares[PIECE_TYPE_NB];
+  bool       needSlowCheck;
   Piece      capturedPiece;
   uint16_t   chased;
   Move       move;