Compute checkers from scratch

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index bc04d306815657a7944b4ad39b8efb133f9a32a8..efc71db89e015a4c8df6746fca181b4c9aa0a985 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -687,10 +687,10 @@ bool Position::gives_check(Move m, const CheckInfo& ci) const {
 void Position::do_move(Move m, StateInfo& newSt) {
 
   CheckInfo ci(*this);
-  do_move(m, newSt, ci, gives_check(m, ci));
+  do_move(m, newSt, gives_check(m, ci));
 }
 
-void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool givesCheck) {
+void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
 
   assert(is_ok(m));
   assert(&newSt != st);
@@ -848,32 +848,8 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool gives
   // Update the key with the final value
   st->key = k;
 
-  // Update checkers bitboard: piece must be already moved due to attacks_from()
-  st->checkersBB = 0;
-
-  if (givesCheck)
-  {
-      if (type_of(m) != NORMAL)
-          st->checkersBB = attackers_to(king_square(them)) & pieces(us);
-      else
-      {
-          // Direct checks
-          if (ci.checkSq[pt] & to)
-              st->checkersBB |= to;
-
-          // Discovered checks
-          if (ci.dcCandidates && (ci.dcCandidates & from))
-          {
-              assert(pt != QUEEN);
-
-              if (pt != ROOK)
-                  st->checkersBB |= attacks_from<ROOK>(king_square(them)) & pieces(us, QUEEN, ROOK);
-
-              if (pt != BISHOP)
-                  st->checkersBB |= attacks_from<BISHOP>(king_square(them)) & pieces(us, QUEEN, BISHOP);
-          }
-      }
-  }
+  // Calculate checkers bitboard (if move is check)
+  st->checkersBB = givesCheck ? attackers_to(king_square(them)) & pieces(us) : 0;
 
   sideToMove = ~sideToMove;