Fixed a bug in PV extraction from the transposition table: The

previous used move_is_legal to verify that the move from the TT
was legal, and the old version of move_is_legal only works when
the side to move is not in check. Fixed this by adding a separate,
slower version of move_is_legal which works even when the side to
move is in check.

diff --git a/src/movegen.cpp b/src/movegen.cpp
index 079918e96279ddaab10a35ac4e533c87e0180cf1..eb65e7b9f18977dc1bcb9f730aab1e175ced4d61 100644 (file)
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -567,6 +567,29 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
 }
 
 
 }
 
 

+/// Another version of move_is_legal(), which takes only a position and a move
+/// as input. This function does not require that the side to move is not in
+/// check. It is not optimized for speed, and is only used for verifying move
+/// legality when building a PV from the transposition table.
+
+bool move_is_legal(const Position& pos, const Move m) {
+
+  Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
+  if (!pos.is_check())
+      return move_is_legal(pos, m, pinned);
+  else
+  {
+      Position p(pos);
+      MoveStack moves[64];
+      int n = generate_evasions(p, moves, pinned);
+      for (int i = 0; i < n; i++)
+          if (moves[i].move == m)
+              return true;
+      return false;
+  }
+}
+
+

 namespace {
 
   template<PieceType Piece>
 namespace {
 
   template<PieceType Piece>

diff --git a/src/movegen.h b/src/movegen.h
index e16a8ab5a80cfad0a665bb9a21694194471dcc75..991b0de30294e4eac09f07c696f2e0eedc3849e7 100644 (file)
--- a/src/movegen.h
+++ b/src/movegen.h
@@ -38,6 +38,7 @@ extern int generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bi
 extern int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned);
 extern int generate_legal_moves(const Position& pos, MoveStack* mlist);
 extern bool move_is_legal(const Position& pos, const Move m, Bitboard pinned);
 extern int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned);
 extern int generate_legal_moves(const Position& pos, MoveStack* mlist);
 extern bool move_is_legal(const Position& pos, const Move m, Bitboard pinned);

+extern bool move_is_legal(const Position& pos, const Move m);

 
 
 #endif // !defined(MOVEGEN_H_INCLUDED)
 
 
 #endif // !defined(MOVEGEN_H_INCLUDED)

diff --git a/src/tt.cpp b/src/tt.cpp
index c1a8b1b950b24edbc514fdb43baaae2dc6909288..1e98aa24901549c888a3704576b5215619f6a6bf 100644 (file)
--- a/src/tt.cpp
+++ b/src/tt.cpp
@@ -207,7 +207,7 @@ void TranspositionTable::extract_pv(const Position& pos, Move pv[]) {
        tte && tte->move() != MOVE_NONE && !stop;
        tte = retrieve(p.get_key()), ply++)
   {
        tte && tte->move() != MOVE_NONE && !stop;
        tte = retrieve(p.get_key()), ply++)
   {

-      if (!move_is_legal(p, tte->move(), p.pinned_pieces(p.side_to_move())))
+      if (!move_is_legal(p, tte->move()))

           break;
       pv[ply] = tte->move();
       p.do_move(pv[ply], st[ply]);
           break;
       pv[ply] = tte->move();
       p.do_move(pv[ply], st[ply]);