X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=b9acc645847471f42e4a8101d1d439c2634fdb73;hp=c9da8d8b56e25e5df22b9610e59fde0524b3f58a;hb=3141490374182551ed26f39ba4e3efb59589f057;hpb=8094b2add88cd681f3cdc7896990633b54c6ff48

diff --git a/src/position.cpp b/src/position.cpp
index c9da8d8b..b9acc645 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -30,7 +30,6 @@
 #include "rkiss.h"
 #include "thread.h"
 #include "tt.h"
-#include "ucioption.h"
 
 using std::string;
 using std::cout;
@@ -42,7 +41,7 @@ Key Position::zobCastle[16];
 Key Position::zobSideToMove;
 Key Position::zobExclusion;
 
-Score Position::PieceSquareTable[16][64];
+Score Position::pieceSquareTable[16][64];
 
 // Material values arrays, indexed by Piece
 const Value PieceValueMidgame[17] = {
@@ -78,12 +77,11 @@ namespace {
 
 CheckInfo::CheckInfo(const Position& pos) {
 
-  Color us = pos.side_to_move();
-  Color them = opposite_color(us);
+  Color them = flip(pos.side_to_move());
   Square ksq = pos.king_square(them);
 
-  dcCandidates = pos.discovered_check_candidates(us);
-  pinned = pos.pinned_pieces(us);
+  pinned = pos.pinned_pieces();
+  dcCandidates = pos.discovered_check_candidates();
 
   checkSq[PAWN]   = pos.attacks_from<PAWN>(ksq, them);
   checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
@@ -101,9 +99,10 @@ CheckInfo::CheckInfo(const Position& pos) {
 Position::Position(const Position& pos, int th) {
 
   memcpy(this, &pos, sizeof(Position));
-  detach(); // Always detach() in copy c'tor to avoid surprises
   threadID = th;
   nodes = 0;
+
+  assert(is_ok());
 }
 
 Position::Position(const string& fen, bool isChess960, int th) {
@@ -113,23 +112,11 @@ Position::Position(const string& fen, bool isChess960, int th) {
 }
 
 
-/// Position::detach() copies the content of the current state and castling
-/// masks inside the position itself. This is needed when the st pointee could
-/// become stale, as example because the caller is about to going out of scope.
-
-void Position::detach() {
-
-  startState = *st;
-  st = &startState;
-  st->previous = NULL; // As a safe guard
-}
-
-
 /// Position::from_fen() initializes the position object with the given FEN
 /// string. This function is not very robust - make sure that input FENs are
 /// correct (this is assumed to be the responsibility of the GUI).
 
-void Position::from_fen(const string& fen, bool isChess960) {
+void Position::from_fen(const string& fenStr, bool isChess960) {
 /*
    A FEN string defines a particular position using only the ASCII character set.
 
@@ -161,13 +148,13 @@ void Position::from_fen(const string& fen, bool isChess960) {
   char col, row, token;
   size_t p;
   Square sq = SQ_A8;
-  std::istringstream ss(fen);
+  std::istringstream fen(fenStr);
 
   clear();
-  ss >> std::noskipws;
+  fen >> std::noskipws;
 
   // 1. Piece placement
-  while ((ss >> token) && !isspace(token))
+  while ((fen >> token) && !isspace(token))
   {
       if (token == '/')
           sq -= Square(16); // Jump back of 2 rows
@@ -183,31 +170,35 @@ void Position::from_fen(const string& fen, bool isChess960) {
   }
 
   // 2. Active color
-  ss >> token;
+  fen >> token;
   sideToMove = (token == 'w' ? WHITE : BLACK);
-  ss >> token;
+  fen >> token;
 
   // 3. Castling availability
-  while ((ss >> token) && !isspace(token))
+  while ((fen >> token) && !isspace(token))
       set_castling_rights(token);
 
   // 4. En passant square. Ignore if no pawn capture is possible
-  if (   ((ss >> col) && (col >= 'a' && col <= 'h'))
-      && ((ss >> row) && (row == '3' || row == '6')))
+  if (   ((fen >> col) && (col >= 'a' && col <= 'h'))
+      && ((fen >> row) && (row == '3' || row == '6')))
   {
       st->epSquare = make_square(File(col - 'a'), Rank(row - '1'));
-      Color them = opposite_color(sideToMove);
+      Color them = flip(sideToMove);
 
       if (!(attacks_from<PAWN>(st->epSquare, them) & pieces(PAWN, sideToMove)))
           st->epSquare = SQ_NONE;
   }
 
   // 5-6. Halfmove clock and fullmove number
-  ss >> std::skipws >> st->rule50 >> fullMoves;
+  fen >> std::skipws >> st->rule50 >> startPosPly;
+
+  // Convert from fullmove starting from 1 to ply starting from 0,
+  // handle also common incorrect FEN with fullmove = 0.
+  startPosPly = Max(2 * (startPosPly - 1), 0) + int(sideToMove == BLACK);
 
   // Various initialisations
   chess960 = isChess960;
-  find_checkers();
+  st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(flip(sideToMove));
 
   st->key = compute_key();
   st->pawnKey = compute_pawn_key();
@@ -215,6 +206,8 @@ void Position::from_fen(const string& fen, bool isChess960) {
   st->value = compute_value();
   st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
   st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
+
+  assert(is_ok());
 }
 
 
@@ -245,7 +238,7 @@ void Position::set_castling_rights(char token) {
     Square sqH = relative_square(c, SQ_H1);
     Square rsq, ksq = king_square(c);
 
-    token = toupper(token);
+    token = char(toupper(token));
 
     if (token == 'K')
         for (rsq = sqH; piece_on(rsq) != make_piece(c, ROOK); rsq--) {}
@@ -258,7 +251,7 @@ void Position::set_castling_rights(char token) {
 
     else return;
 
-    if (square_file(rsq) < square_file(ksq))
+    if (file_of(rsq) < file_of(ksq))
         set_castle(WHITE_OOO << c, ksq, rsq);
     else
         set_castle(WHITE_OO << c, ksq, rsq);
@@ -270,54 +263,60 @@ void Position::set_castling_rights(char token) {
 
 const string Position::to_fen() const {
 
-  string fen;
+  std::ostringstream fen;
   Square sq;
-  char emptyCnt;
+  int emptyCnt;
 
-  for (Rank rank = RANK_8; rank >= RANK_1; rank--, fen += '/')
+  for (Rank rank = RANK_8; rank >= RANK_1; rank--)
   {
-      emptyCnt = '0';
+      emptyCnt = 0;
 
       for (File file = FILE_A; file <= FILE_H; file++)
       {
           sq = make_square(file, rank);
 
-          if (square_is_occupied(sq))
+          if (!square_is_empty(sq))
           {
-              if (emptyCnt != '0')
+              if (emptyCnt)
               {
-                  fen += emptyCnt;
-                  emptyCnt = '0';
+                  fen << emptyCnt;
+                  emptyCnt = 0;
               }
-              fen += PieceToChar[piece_on(sq)];
-          } else
+              fen << PieceToChar[piece_on(sq)];
+          }
+          else
               emptyCnt++;
       }
 
-      if (emptyCnt != '0')
-          fen += emptyCnt;
+      if (emptyCnt)
+          fen << emptyCnt;
+
+      if (rank > RANK_1)
+          fen << '/';
   }
 
-  fen += (sideToMove == WHITE ? " w " : " b ");
+  fen << (sideToMove == WHITE ? " w " : " b ");
 
   if (st->castleRights != CASTLES_NONE)
   {
       if (can_castle(WHITE_OO))
-          fen += chess960 ? char(toupper(file_to_char(square_file(castle_rook_square(WHITE_OO))))) : 'K';
+          fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE_OO))))) : 'K');
 
       if (can_castle(WHITE_OOO))
-          fen += chess960 ? char(toupper(file_to_char(square_file(castle_rook_square(WHITE_OOO))))) : 'Q';
+          fen << (chess960 ? char(toupper(file_to_char(file_of(castle_rook_square(WHITE_OOO))))) : 'Q');
 
       if (can_castle(BLACK_OO))
-          fen += chess960 ? file_to_char(square_file(castle_rook_square(BLACK_OO))) : 'k';
+          fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK_OO))) : 'k');
 
       if (can_castle(BLACK_OOO))
-          fen += chess960 ? file_to_char(square_file(castle_rook_square(BLACK_OOO))) : 'q';
+          fen << (chess960 ? file_to_char(file_of(castle_rook_square(BLACK_OOO))) : 'q');
   } else
-      fen += '-';
+      fen << '-';
 
-  fen += (ep_square() == SQ_NONE ? " -" : " " + square_to_string(ep_square()));
-  return fen;
+  fen << (ep_square() == SQ_NONE ? " -" : " " + square_to_string(ep_square()))
+      << " " << st->rule50 << " " << 1 + (startPosPly - int(sideToMove == BLACK)) / 2;
+
+  return fen.str();
 }
 
 
@@ -331,7 +330,7 @@ void Position::print(Move move) const {
   if (move)
   {
       Position p(*this, thread());
-      string dd = (piece_color(piece_on(move_from(move))) == BLACK ? ".." : "");
+      string dd = (sideToMove == BLACK ? ".." : "");
       cout << "\nMove is: " << dd << move_to_san(p, move);
   }
 
@@ -343,10 +342,10 @@ void Position::print(Move move) const {
           Square sq = make_square(file, rank);
           Piece piece = piece_on(sq);
 
-          if (piece == PIECE_NONE && square_color(sq) == DARK)
+          if (piece == PIECE_NONE && color_of(sq) == DARK)
               piece = PIECE_NONE_DARK_SQ;
 
-          char c = (piece_color(piece_on(sq)) == BLACK ? '=' : ' ');
+          char c = (color_of(piece_on(sq)) == BLACK ? '=' : ' ');
           cout << c << PieceToChar[piece] << c << '|';
       }
   }
@@ -355,36 +354,28 @@ void Position::print(Move move) const {
 
 
 /// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
-/// king) pieces for the given color and for the given pinner type. Or, when
-/// template parameter FindPinned is false, the pieces of the given color
-/// candidate for a discovery check against the enemy king.
-/// Bitboard checkersBB must be already updated when looking for pinners.
+/// king) pieces for the given color. Or, when template parameter FindPinned is
+/// false, the function return the pieces of the given color candidate for a
+/// discovery check against the enemy king.
 
 template<bool FindPinned>
-Bitboard Position::hidden_checkers(Color c) const {
-
-  Bitboard result = EmptyBoardBB;
-  Bitboard pinners = pieces_of_color(FindPinned ? opposite_color(c) : c);
+Bitboard Position::hidden_checkers() const {
 
-  // Pinned pieces protect our king, dicovery checks attack
-  // the enemy king.
-  Square ksq = king_square(FindPinned ? c : opposite_color(c));
+  // Pinned pieces protect our king, dicovery checks attack the enemy king
+  Bitboard b, result = EmptyBoardBB;
+  Bitboard pinners = pieces(FindPinned ? flip(sideToMove) : sideToMove);
+  Square ksq = king_square(FindPinned ? sideToMove : flip(sideToMove));
 
-  // Pinners are sliders, not checkers, that give check when candidate pinned is removed
-  pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
-
-  if (FindPinned && pinners)
-      pinners &= ~st->checkersBB;
+  // Pinners are sliders, that give check when candidate pinned is removed
+  pinners &=  (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq])
+            | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
 
   while (pinners)
   {
-      Square s = pop_1st_bit(&pinners);
-      Bitboard b = squares_between(s, ksq) & occupied_squares();
-
-      assert(b);
+      b = squares_between(ksq, pop_1st_bit(&pinners)) & occupied_squares();
 
-      if (  !(b & (b - 1)) // Only one bit set?
-          && (b & pieces_of_color(c))) // Is an our piece?
+      // Only one bit set and is an our piece?
+      if (b && !(b & (b - 1)) && (b & pieces(sideToMove)))
           result |= b;
   }
   return result;
@@ -392,23 +383,21 @@ Bitboard Position::hidden_checkers(Color c) const {
 
 
 /// Position:pinned_pieces() returns a bitboard of all pinned (against the
-/// king) pieces for the given color. Note that checkersBB bitboard must
-/// be already updated.
+/// king) pieces for the side to move.
 
-Bitboard Position::pinned_pieces(Color c) const {
+Bitboard Position::pinned_pieces() const {
 
-  return hidden_checkers<true>(c);
+  return hidden_checkers<true>();
 }
 
 
 /// Position:discovered_check_candidates() returns a bitboard containing all
-/// pieces for the given side which are candidates for giving a discovered
-/// check. Contrary to pinned_pieces() here there is no need of checkersBB
-/// to be already updated.
+/// pieces for the side to move which are candidates for giving a discovered
+/// check.
 
-Bitboard Position::discovered_check_candidates(Color c) const {
+Bitboard Position::discovered_check_candidates() const {
 
-  return hidden_checkers<false>(c);
+  return hidden_checkers<false>();
 }
 
 /// Position::attackers_to() computes a bitboard containing all pieces which
@@ -469,13 +458,13 @@ Bitboard Position::attacks_from(Piece p, Square s, Bitboard occ) {
 
 bool Position::move_attacks_square(Move m, Square s) const {
 
-  assert(move_is_ok(m));
+  assert(is_ok(m));
   assert(square_is_ok(s));
 
   Bitboard occ, xray;
   Square f = move_from(m), t = move_to(m);
 
-  assert(square_is_occupied(f));
+  assert(!square_is_empty(f));
 
   if (bit_is_set(attacks_from(piece_on(f), t), s))
       return true;
@@ -485,7 +474,7 @@ bool Position::move_attacks_square(Move m, Square s) const {
   do_move_bb(&occ, make_move_bb(f, t));
   xray = ( (rook_attacks_bb(s, occ)   & pieces(ROOK, QUEEN))
           |(bishop_attacks_bb(s, occ) & pieces(BISHOP, QUEEN)))
-         & pieces_of_color(piece_color(piece_on(f)));
+         & pieces(color_of(piece_on(f)));
 
   // If we have attacks we need to verify that are caused by our move
   // and are not already existent ones.
@@ -493,41 +482,27 @@ bool Position::move_attacks_square(Move m, Square s) const {
 }
 
 
-/// Position::find_checkers() computes the checkersBB bitboard, which
-/// contains a nonzero bit for each checking piece (0, 1 or 2). It
-/// currently works by calling Position::attackers_to, which is probably
-/// inefficient. Consider rewriting this function to use the last move
-/// played, like in non-bitboard versions of Glaurung.
-
-void Position::find_checkers() {
-
-  Color us = side_to_move();
-  st->checkersBB = attackers_to(king_square(us)) & pieces_of_color(opposite_color(us));
-}
-
-
 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
 
 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
 
-  assert(is_ok());
-  assert(move_is_ok(m));
-  assert(pinned == pinned_pieces(side_to_move()));
+  assert(is_ok(m));
+  assert(pinned == pinned_pieces());
 
   Color us = side_to_move();
   Square from = move_from(m);
 
-  assert(piece_color(piece_on(from)) == us);
+  assert(color_of(piece_on(from)) == us);
   assert(piece_on(king_square(us)) == make_piece(us, KING));
 
-  // En passant captures are a tricky special case. Because they are
-  // rather uncommon, we do it simply by testing whether the king is attacked
-  // after the move is made
-  if (move_is_ep(m))
+  // En passant captures are a tricky special case. Because they are rather
+  // uncommon, we do it simply by testing whether the king is attacked after
+  // the move is made.
+  if (is_enpassant(m))
   {
-      Color them = opposite_color(us);
+      Color them = flip(us);
       Square to = move_to(m);
-      Square capsq = make_square(square_file(to), square_rank(from));
+      Square capsq = to + pawn_push(them);
       Square ksq = king_square(us);
       Bitboard b = occupied_squares();
 
@@ -547,8 +522,8 @@ bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
   // If the moving piece is a king, check whether the destination
   // square is attacked by the opponent. Castling moves are checked
   // for legality during move generation.
-  if (piece_type(piece_on(from)) == KING)
-      return move_is_castle(m) || !(attackers_to(move_to(m)) & pieces_of_color(opposite_color(us)));
+  if (type_of(piece_on(from)) == KING)
+      return is_castle(m) || !(attackers_to(move_to(m)) & pieces(flip(us)));
 
   // A non-king move is legal if and only if it is not pinned or it
   // is moving along the ray towards or away from the king.
@@ -558,42 +533,35 @@ bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
 }
 
 
-/// Position::move_is_pl_slow() takes a move and tests whether the move
-/// is pseudo legal. This version is not very fast and should be used
-/// only in non time-critical paths.
-
-bool Position::move_is_pl_slow(const Move m) const {
-
-  MoveStack mlist[MAX_MOVES];
-  MoveStack *cur, *last;
+/// Position::move_is_legal() takes a random move and tests whether the move
+/// is legal. This version is not very fast and should be used only
+/// in non time-critical paths.
 
-  last = in_check() ? generate<MV_EVASION>(*this, mlist)
-                    : generate<MV_NON_EVASION>(*this, mlist);
+bool Position::move_is_legal(const Move m) const {
 
-  for (cur = mlist; cur != last; cur++)
-      if (cur->move == m)
+  for (MoveList<MV_LEGAL> ml(*this); !ml.end(); ++ml)
+      if (ml.move() == m)
           return true;
 
   return false;
 }
 
 
-/// Fast version of Position::move_is_pl() that takes a move and a bitboard
-/// of pinned pieces as input, and tests whether the move is pseudo legal.
+/// Position::is_pseudo_legal() takes a random move and tests whether the move
+/// is pseudo legal. It is used to validate moves from TT that can be corrupted
+/// due to SMP concurrent access or hash position key aliasing.
 
-bool Position::move_is_pl(const Move m) const {
-
-  assert(is_ok());
+bool Position::is_pseudo_legal(const Move m) const {
 
   Color us = sideToMove;
-  Color them = opposite_color(sideToMove);
+  Color them = flip(sideToMove);
   Square from = move_from(m);
   Square to = move_to(m);
   Piece pc = piece_on(from);
 
   // Use a slower but simpler function for uncommon cases
-  if (move_is_special(m))
-      return move_is_pl_slow(m);
+  if (is_special(m))
+      return move_is_legal(m);
 
   // Is not a promotion, so promotion piece must be empty
   if (promotion_piece_type(m) - 2 != PIECE_TYPE_NONE)
@@ -601,15 +569,15 @@ bool Position::move_is_pl(const Move m) const {
 
   // If the from square is not occupied by a piece belonging to the side to
   // move, the move is obviously not legal.
-  if (pc == PIECE_NONE || piece_color(pc) != us)
+  if (pc == PIECE_NONE || color_of(pc) != us)
       return false;
 
   // The destination square cannot be occupied by a friendly piece
-  if (piece_color(piece_on(to)) == us)
+  if (color_of(piece_on(to)) == us)
       return false;
 
   // Handle the special case of a pawn move
-  if (piece_type(pc) == PAWN)
+  if (type_of(pc) == PAWN)
   {
       // Move direction must be compatible with pawn color
       int direction = to - from;
@@ -618,7 +586,7 @@ bool Position::move_is_pl(const Move m) const {
 
       // We have already handled promotion moves, so destination
       // cannot be on the 8/1th rank.
-      if (square_rank(to) == RANK_8 || square_rank(to) == RANK_1)
+      if (rank_of(to) == RANK_8 || rank_of(to) == RANK_1)
           return false;
 
       // Proceed according to the square delta between the origin and
@@ -631,11 +599,11 @@ bool Position::move_is_pl(const Move m) const {
       case DELTA_SE:
       // Capture. The destination square must be occupied by an enemy
       // piece (en passant captures was handled earlier).
-      if (piece_color(piece_on(to)) != them)
+      if (color_of(piece_on(to)) != them)
           return false;
 
       // From and to files must be one file apart, avoids a7h5
-      if (abs(square_file(from) - square_file(to)) != 1)
+      if (abs(file_of(from) - file_of(to)) != 1)
           return false;
       break;
 
@@ -650,7 +618,7 @@ bool Position::move_is_pl(const Move m) const {
       // Double white pawn push. The destination square must be on the fourth
       // rank, and both the destination square and the square between the
       // source and destination squares must be empty.
-      if (   square_rank(to) != RANK_4
+      if (   rank_of(to) != RANK_4
           || !square_is_empty(to)
           || !square_is_empty(from + DELTA_N))
           return false;
@@ -660,7 +628,7 @@ bool Position::move_is_pl(const Move m) const {
       // Double black pawn push. The destination square must be on the fifth
       // rank, and both the destination square and the square between the
       // source and destination squares must be empty.
-      if (   square_rank(to) != RANK_5
+      if (   rank_of(to) != RANK_5
           || !square_is_empty(to)
           || !square_is_empty(from + DELTA_S))
           return false;
@@ -677,11 +645,11 @@ bool Position::move_is_pl(const Move m) const {
   {
       // In case of king moves under check we have to remove king so to catch
       // as invalid moves like b1a1 when opposite queen is on c1.
-      if (piece_type(piece_on(from)) == KING)
+      if (type_of(piece_on(from)) == KING)
       {
           Bitboard b = occupied_squares();
           clear_bit(&b, from);
-          if (attackers_to(move_to(m), b) & pieces_of_color(opposite_color(us)))
+          if (attackers_to(move_to(m), b) & pieces(flip(us)))
               return false;
       }
       else
@@ -703,18 +671,17 @@ bool Position::move_is_pl(const Move m) const {
 }
 
 
-/// Position::move_gives_check() tests whether a pseudo-legal move is a check
+/// Position::move_gives_check() tests whether a pseudo-legal move gives a check
 
 bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
 
-  assert(is_ok());
-  assert(move_is_ok(m));
-  assert(ci.dcCandidates == discovered_check_candidates(side_to_move()));
-  assert(piece_color(piece_on(move_from(m))) == side_to_move());
+  assert(is_ok(m));
+  assert(ci.dcCandidates == discovered_check_candidates());
+  assert(color_of(piece_on(move_from(m))) == side_to_move());
 
   Square from = move_from(m);
   Square to = move_to(m);
-  PieceType pt = piece_type(piece_on(from));
+  PieceType pt = type_of(piece_on(from));
 
   // Direct check ?
   if (bit_is_set(ci.checkSq[pt], to))
@@ -725,20 +692,20 @@ bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
   {
       // For pawn and king moves we need to verify also direction
       if (  (pt != PAWN && pt != KING)
-          || !squares_aligned(from, to, king_square(opposite_color(side_to_move()))))
+          || !squares_aligned(from, to, king_square(flip(side_to_move()))))
           return true;
   }
 
   // Can we skip the ugly special cases ?
-  if (!move_is_special(m))
+  if (!is_special(m))
       return false;
 
   Color us = side_to_move();
   Bitboard b = occupied_squares();
-  Square ksq = king_square(opposite_color(us));
+  Square ksq = king_square(flip(us));
 
   // Promotion with check ?
-  if (move_is_promotion(m))
+  if (is_promotion(m))
   {
       clear_bit(&b, from);
 
@@ -761,9 +728,9 @@ bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
   // of direct checks and ordinary discovered check, the only case we
   // need to handle is the unusual case of a discovered check through
   // the captured pawn.
-  if (move_is_ep(m))
+  if (is_enpassant(m))
   {
-      Square capsq = make_square(square_file(to), square_rank(from));
+      Square capsq = make_square(file_of(to), rank_of(from));
       clear_bit(&b, from);
       clear_bit(&b, capsq);
       set_bit(&b, to);
@@ -772,7 +739,7 @@ bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
   }
 
   // Castling with check ?
-  if (move_is_castle(m))
+  if (is_castle(m))
   {
       Square kfrom, kto, rfrom, rto;
       kfrom = from;
@@ -797,30 +764,6 @@ bool Position::move_gives_check(Move m, const CheckInfo& ci) const {
 }
 
 
-/// Position::do_setup_move() makes a permanent move on the board. It should
-/// be used when setting up a position on board. You can't undo the move.
-
-void Position::do_setup_move(Move m) {
-
-  StateInfo newSt;
-
-  // Update the number of full moves after black's move
-  if (sideToMove == BLACK)
-      fullMoves++;
-
-  do_move(m, newSt);
-
-  // Reset "game ply" in case we made a non-reversible move.
-  // "game ply" is used for repetition detection.
-  if (st->rule50 == 0)
-      st->gamePly = 0;
-
-  // Our StateInfo newSt is about going out of scope so copy
-  // its content before it disappears.
-  detach();
-}
-
-
 /// Position::do_move() makes a move, and saves all information necessary
 /// to a StateInfo object. The move is assumed to be legal. Pseudo-legal
 /// moves should be filtered out before this function is called.
@@ -833,8 +776,7 @@ void Position::do_move(Move m, StateInfo& newSt) {
 
 void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
 
-  assert(is_ok());
-  assert(move_is_ok(m));
+  assert(is_ok(m));
   assert(&newSt != st);
 
   nodes++;
@@ -845,10 +787,10 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   // pointer to point to the new, ready to be updated, state.
   struct ReducedStateInfo {
     Key pawnKey, materialKey;
-    int castleRights, rule50, gamePly, pliesFromNull;
-    Square epSquare;
-    Score value;
     Value npMaterial[2];
+    int castleRights, rule50, pliesFromNull;
+    Score value;
+    Square epSquare;
   };
 
   memcpy(&newSt, st, sizeof(ReducedStateInfo));
@@ -856,10 +798,6 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   newSt.previous = st;
   st = &newSt;
 
-  // Save the current key to the history[] array, in order to be able to
-  // detect repetition draws.
-  history[st->gamePly++] = key;
-
   // Update side to move
   key ^= zobSideToMove;
 
@@ -868,7 +806,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   st->rule50++;
   st->pliesFromNull++;
 
-  if (move_is_castle(m))
+  if (is_castle(m))
   {
       st->key = key;
       do_castle_move(m);
@@ -876,18 +814,18 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   }
 
   Color us = side_to_move();
-  Color them = opposite_color(us);
+  Color them = flip(us);
   Square from = move_from(m);
   Square to = move_to(m);
-  bool ep = move_is_ep(m);
-  bool pm = move_is_promotion(m);
+  bool ep = is_enpassant(m);
+  bool pm = is_promotion(m);
 
   Piece piece = piece_on(from);
-  PieceType pt = piece_type(piece);
-  PieceType capture = ep ? PAWN : piece_type(piece_on(to));
+  PieceType pt = type_of(piece);
+  PieceType capture = ep ? PAWN : type_of(piece_on(to));
 
-  assert(piece_color(piece_on(from)) == us);
-  assert(piece_color(piece_on(to)) == them || square_is_empty(to));
+  assert(color_of(piece_on(from)) == us);
+  assert(color_of(piece_on(to)) == them || square_is_empty(to));
   assert(!(ep || pm) || piece == make_piece(us, PAWN));
   assert(!pm || relative_rank(us, to) == RANK_8);
 
@@ -918,9 +856,9 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
 
   // Move the piece
   Bitboard move_bb = make_move_bb(from, to);
-  do_move_bb(&(byColorBB[us]), move_bb);
-  do_move_bb(&(byTypeBB[pt]), move_bb);
-  do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
+  do_move_bb(&byColorBB[us], move_bb);
+  do_move_bb(&byTypeBB[pt], move_bb);
+  do_move_bb(&byTypeBB[0], move_bb); // HACK: byTypeBB[0] == occupied squares
 
   board[to] = board[from];
   board[from] = PIECE_NONE;
@@ -943,7 +881,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
       // Set en passant square, only if moved pawn can be captured
       if ((to ^ from) == 16)
       {
-          if (attacks_from<PAWN>(from + (us == WHITE ? DELTA_N : DELTA_S), us) & pieces(PAWN, them))
+          if (attacks_from<PAWN>(from + pawn_push(us), us) & pieces(PAWN, them))
           {
               st->epSquare = Square((int(from) + int(to)) / 2);
               key ^= zobEp[st->epSquare];
@@ -957,8 +895,8 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
           assert(promotion >= KNIGHT && promotion <= QUEEN);
 
           // Insert promoted piece instead of pawn
-          clear_bit(&(byTypeBB[PAWN]), to);
-          set_bit(&(byTypeBB[promotion]), to);
+          clear_bit(&byTypeBB[PAWN], to);
+          set_bit(&byTypeBB[promotion], to);
           board[to] = make_piece(us, promotion);
 
           // Update piece counts
@@ -1010,7 +948,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   if (moveIsCheck)
   {
       if (ep | pm)
-          st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
+          st->checkersBB = attackers_to(king_square(them)) & pieces(us);
       else
       {
           // Direct checks
@@ -1030,7 +968,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
   }
 
   // Finish
-  sideToMove = opposite_color(sideToMove);
+  sideToMove = flip(sideToMove);
   st->value += (sideToMove == WHITE ?  TempoValue : -TempoValue);
 
   assert(is_ok());
@@ -1052,10 +990,10 @@ void Position::do_capture_move(Key& key, PieceType capture, Color them, Square t
     {
         if (ep) // en passant ?
         {
-            capsq = (them == BLACK)? (to - DELTA_N) : (to - DELTA_S);
+            capsq = to + pawn_push(them);
 
             assert(to == st->epSquare);
-            assert(relative_rank(opposite_color(them), to) == RANK_6);
+            assert(relative_rank(flip(them), to) == RANK_6);
             assert(piece_on(to) == PIECE_NONE);
             assert(piece_on(capsq) == make_piece(them, PAWN));
 
@@ -1067,9 +1005,9 @@ void Position::do_capture_move(Key& key, PieceType capture, Color them, Square t
         st->npMaterial[them] -= PieceValueMidgame[capture];
 
     // Remove captured piece
-    clear_bit(&(byColorBB[them]), capsq);
-    clear_bit(&(byTypeBB[capture]), capsq);
-    clear_bit(&(byTypeBB[0]), capsq);
+    clear_bit(&byColorBB[them], capsq);
+    clear_bit(&byTypeBB[capture], capsq);
+    clear_bit(&byTypeBB[0], capsq);
 
     // Update hash key
     key ^= zobrist[them][capture][capsq];
@@ -1107,18 +1045,15 @@ void Position::do_capture_move(Key& key, PieceType capture, Color them, Square t
 
 void Position::do_castle_move(Move m) {
 
-  assert(move_is_ok(m));
-  assert(move_is_castle(m));
+  assert(is_ok(m));
+  assert(is_castle(m));
 
   Color us = side_to_move();
-  Color them = opposite_color(us);
-
-  // Reset capture field
-  st->capturedType = PIECE_TYPE_NONE;
+  Color them = flip(us);
 
   // Find source squares for king and rook
   Square kfrom = move_from(m);
-  Square rfrom = move_to(m);  // HACK: See comment at beginning of function
+  Square rfrom = move_to(m);
   Square kto, rto;
 
   assert(piece_on(kfrom) == make_piece(us, KING));
@@ -1129,28 +1064,30 @@ void Position::do_castle_move(Move m) {
   {
       kto = relative_square(us, SQ_G1);
       rto = relative_square(us, SQ_F1);
-  } else { // O-O-O
+  }
+  else // O-O-O
+  {
       kto = relative_square(us, SQ_C1);
       rto = relative_square(us, SQ_D1);
   }
 
-  // Remove pieces from source squares:
-  clear_bit(&(byColorBB[us]), kfrom);
-  clear_bit(&(byTypeBB[KING]), kfrom);
-  clear_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
-  clear_bit(&(byColorBB[us]), rfrom);
-  clear_bit(&(byTypeBB[ROOK]), rfrom);
-  clear_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
-
-  // Put pieces on destination squares:
-  set_bit(&(byColorBB[us]), kto);
-  set_bit(&(byTypeBB[KING]), kto);
-  set_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
-  set_bit(&(byColorBB[us]), rto);
-  set_bit(&(byTypeBB[ROOK]), rto);
-  set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
-
-  // Update board array
+  // Remove pieces from source squares
+  clear_bit(&byColorBB[us], kfrom);
+  clear_bit(&byTypeBB[KING], kfrom);
+  clear_bit(&byTypeBB[0], kfrom);
+  clear_bit(&byColorBB[us], rfrom);
+  clear_bit(&byTypeBB[ROOK], rfrom);
+  clear_bit(&byTypeBB[0], rfrom);
+
+  // Put pieces on destination squares
+  set_bit(&byColorBB[us], kto);
+  set_bit(&byTypeBB[KING], kto);
+  set_bit(&byTypeBB[0], kto);
+  set_bit(&byColorBB[us], rto);
+  set_bit(&byTypeBB[ROOK], rto);
+  set_bit(&byTypeBB[0], rto);
+
+  // Update board
   Piece king = make_piece(us, KING);
   Piece rook = make_piece(us, ROOK);
   board[kfrom] = board[rfrom] = PIECE_NONE;
@@ -1160,10 +1097,13 @@ void Position::do_castle_move(Move m) {
   // Update piece lists
   pieceList[us][KING][index[kfrom]] = kto;
   pieceList[us][ROOK][index[rfrom]] = rto;
-  int tmp = index[rfrom]; // In Chess960 could be rto == kfrom
+  int tmp = index[rfrom]; // In Chess960 could be kto == rfrom
   index[kto] = index[kfrom];
   index[rto] = tmp;
 
+  // Reset capture field
+  st->capturedType = PIECE_TYPE_NONE;
+
   // Update incremental scores
   st->value += pst_delta(king, kfrom, kto);
   st->value += pst_delta(rook, rfrom, rto);
@@ -1188,10 +1128,10 @@ void Position::do_castle_move(Move m) {
   st->rule50 = 0;
 
   // Update checkers BB
-  st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
+  st->checkersBB = attackers_to(king_square(them)) & pieces(us);
 
   // Finish
-  sideToMove = opposite_color(sideToMove);
+  sideToMove = flip(sideToMove);
   st->value += (sideToMove == WHITE ?  TempoValue : -TempoValue);
 
   assert(is_ok());
@@ -1203,28 +1143,27 @@ void Position::do_castle_move(Move m) {
 
 void Position::undo_move(Move m) {
 
-  assert(is_ok());
-  assert(move_is_ok(m));
+  assert(is_ok(m));
 
-  sideToMove = opposite_color(sideToMove);
+  sideToMove = flip(sideToMove);
 
-  if (move_is_castle(m))
+  if (is_castle(m))
   {
       undo_castle_move(m);
       return;
   }
 
   Color us = side_to_move();
-  Color them = opposite_color(us);
+  Color them = flip(us);
   Square from = move_from(m);
   Square to = move_to(m);
-  bool ep = move_is_ep(m);
-  bool pm = move_is_promotion(m);
+  bool ep = is_enpassant(m);
+  bool pm = is_promotion(m);
 
-  PieceType pt = piece_type(piece_on(to));
+  PieceType pt = type_of(piece_on(to));
 
   assert(square_is_empty(from));
-  assert(piece_color(piece_on(to)) == us);
+  assert(color_of(piece_on(to)) == us);
   assert(!pm || relative_rank(us, to) == RANK_8);
   assert(!ep || to == st->previous->epSquare);
   assert(!ep || relative_rank(us, to) == RANK_6);
@@ -1239,8 +1178,8 @@ void Position::undo_move(Move m) {
       assert(piece_on(to) == make_piece(us, promotion));
 
       // Replace promoted piece with a pawn
-      clear_bit(&(byTypeBB[promotion]), to);
-      set_bit(&(byTypeBB[PAWN]), to);
+      clear_bit(&byTypeBB[promotion], to);
+      set_bit(&byTypeBB[PAWN], to);
 
       // Update piece counts
       pieceCount[us][promotion]--;
@@ -1257,9 +1196,9 @@ void Position::undo_move(Move m) {
 
   // Put the piece back at the source square
   Bitboard move_bb = make_move_bb(to, from);
-  do_move_bb(&(byColorBB[us]), move_bb);
-  do_move_bb(&(byTypeBB[pt]), move_bb);
-  do_move_bb(&(byTypeBB[0]), move_bb); // HACK: byTypeBB[0] == occupied squares
+  do_move_bb(&byColorBB[us], move_bb);
+  do_move_bb(&byTypeBB[pt], move_bb);
+  do_move_bb(&byTypeBB[0], move_bb); // HACK: byTypeBB[0] == occupied squares
 
   board[from] = make_piece(us, pt);
   board[to] = PIECE_NONE;
@@ -1273,15 +1212,15 @@ void Position::undo_move(Move m) {
       Square capsq = to;
 
       if (ep)
-          capsq = (us == WHITE)? (to - DELTA_N) : (to - DELTA_S);
+          capsq = to - pawn_push(us);
 
       assert(st->capturedType != KING);
       assert(!ep || square_is_empty(capsq));
 
       // Restore the captured piece
-      set_bit(&(byColorBB[them]), capsq);
-      set_bit(&(byTypeBB[st->capturedType]), capsq);
-      set_bit(&(byTypeBB[0]), capsq);
+      set_bit(&byColorBB[them], capsq);
+      set_bit(&byTypeBB[st->capturedType], capsq);
+      set_bit(&byTypeBB[0], capsq);
 
       board[capsq] = make_piece(them, st->capturedType);
 
@@ -1307,17 +1246,17 @@ void Position::undo_move(Move m) {
 
 void Position::undo_castle_move(Move m) {
 
-  assert(move_is_ok(m));
-  assert(move_is_castle(m));
+  assert(is_ok(m));
+  assert(is_castle(m));
 
   // When we have arrived here, some work has already been done by
-  // Position::undo_move.  In particular, the side to move has been switched,
+  // Position::undo_move. In particular, the side to move has been switched,
   // so the code below is correct.
   Color us = side_to_move();
 
   // Find source squares for king and rook
   Square kfrom = move_from(m);
-  Square rfrom = move_to(m);  // HACK: See comment at beginning of function
+  Square rfrom = move_to(m);
   Square kto, rto;
 
   // Find destination squares for king and rook
@@ -1325,7 +1264,9 @@ void Position::undo_castle_move(Move m) {
   {
       kto = relative_square(us, SQ_G1);
       rto = relative_square(us, SQ_F1);
-  } else { // O-O-O
+  }
+  else // O-O-O
+  {
       kto = relative_square(us, SQ_C1);
       rto = relative_square(us, SQ_D1);
   }
@@ -1333,26 +1274,28 @@ void Position::undo_castle_move(Move m) {
   assert(piece_on(kto) == make_piece(us, KING));
   assert(piece_on(rto) == make_piece(us, ROOK));
 
-  // Remove pieces from destination squares:
-  clear_bit(&(byColorBB[us]), kto);
-  clear_bit(&(byTypeBB[KING]), kto);
-  clear_bit(&(byTypeBB[0]), kto); // HACK: byTypeBB[0] == occupied squares
-  clear_bit(&(byColorBB[us]), rto);
-  clear_bit(&(byTypeBB[ROOK]), rto);
-  clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
-
-  // Put pieces on source squares:
-  set_bit(&(byColorBB[us]), kfrom);
-  set_bit(&(byTypeBB[KING]), kfrom);
-  set_bit(&(byTypeBB[0]), kfrom); // HACK: byTypeBB[0] == occupied squares
-  set_bit(&(byColorBB[us]), rfrom);
-  set_bit(&(byTypeBB[ROOK]), rfrom);
-  set_bit(&(byTypeBB[0]), rfrom); // HACK: byTypeBB[0] == occupied squares
+  // Remove pieces from destination squares
+  clear_bit(&byColorBB[us], kto);
+  clear_bit(&byTypeBB[KING], kto);
+  clear_bit(&byTypeBB[0], kto);
+  clear_bit(&byColorBB[us], rto);
+  clear_bit(&byTypeBB[ROOK], rto);
+  clear_bit(&byTypeBB[0], rto);
+
+  // Put pieces on source squares
+  set_bit(&byColorBB[us], kfrom);
+  set_bit(&byTypeBB[KING], kfrom);
+  set_bit(&byTypeBB[0], kfrom);
+  set_bit(&byColorBB[us], rfrom);
+  set_bit(&byTypeBB[ROOK], rfrom);
+  set_bit(&byTypeBB[0], rfrom);
 
   // Update board
-  board[rto] = board[kto] = PIECE_NONE;
-  board[rfrom] = make_piece(us, ROOK);
-  board[kfrom] = make_piece(us, KING);
+  Piece king = make_piece(us, KING);
+  Piece rook = make_piece(us, ROOK);
+  board[kto] = board[rto] = PIECE_NONE;
+  board[kfrom] = king;
+  board[rfrom] = rook;
 
   // Update piece lists
   pieceList[us][KING][index[kto]] = kfrom;
@@ -1373,7 +1316,6 @@ void Position::undo_castle_move(Move m) {
 
 void Position::do_null_move(StateInfo& backupSt) {
 
-  assert(is_ok());
   assert(!in_check());
 
   // Back up the information necessary to undo the null move to the supplied
@@ -1387,10 +1329,6 @@ void Position::do_null_move(StateInfo& backupSt) {
   backupSt.pliesFromNull = st->pliesFromNull;
   st->previous = &backupSt;
 
-  // Save the current key to the history[] array, in order to be able to
-  // detect repetition draws.
-  history[st->gamePly++] = st->key;
-
   // Update the necessary information
   if (st->epSquare != SQ_NONE)
       st->key ^= zobEp[st->epSquare];
@@ -1398,11 +1336,13 @@ void Position::do_null_move(StateInfo& backupSt) {
   st->key ^= zobSideToMove;
   prefetch((char*)TT.first_entry(st->key));
 
-  sideToMove = opposite_color(sideToMove);
+  sideToMove = flip(sideToMove);
   st->epSquare = SQ_NONE;
   st->rule50++;
   st->pliesFromNull = 0;
   st->value += (sideToMove == WHITE) ?  TempoValue : -TempoValue;
+
+  assert(is_ok());
 }
 
 
@@ -1410,7 +1350,6 @@ void Position::do_null_move(StateInfo& backupSt) {
 
 void Position::undo_null_move() {
 
-  assert(is_ok());
   assert(!in_check());
 
   // Restore information from the our backup StateInfo object
@@ -1422,9 +1361,10 @@ void Position::undo_null_move() {
   st->pliesFromNull = backupSt->pliesFromNull;
 
   // Update the necessary information
-  sideToMove = opposite_color(sideToMove);
+  sideToMove = flip(sideToMove);
   st->rule50--;
-  st->gamePly--;
+
+  assert(is_ok());
 }
 
 
@@ -1436,7 +1376,7 @@ void Position::undo_null_move() {
 
 int Position::see_sign(Move m) const {
 
-  assert(move_is_ok(m));
+  assert(is_ok(m));
 
   Square from = move_from(m);
   Square to = move_to(m);
@@ -1458,26 +1398,26 @@ int Position::see(Move m) const {
   PieceType capturedType, pt;
   Color stm;
 
-  assert(move_is_ok(m));
+  assert(is_ok(m));
 
   // As castle moves are implemented as capturing the rook, they have
   // SEE == RookValueMidgame most of the times (unless the rook is under
   // attack).
-  if (move_is_castle(m))
+  if (is_castle(m))
       return 0;
 
   from = move_from(m);
   to = move_to(m);
-  capturedType = piece_type(piece_on(to));
+  capturedType = type_of(piece_on(to));
   occupied = occupied_squares();
 
   // Handle en passant moves
-  if (st->epSquare == to && piece_type(piece_on(from)) == PAWN)
+  if (st->epSquare == to && type_of(piece_on(from)) == PAWN)
   {
-      Square capQq = (side_to_move() == WHITE ? to - DELTA_N : to - DELTA_S);
+      Square capQq = to - pawn_push(side_to_move());
 
       assert(capturedType == PIECE_TYPE_NONE);
-      assert(piece_type(piece_on(capQq)) == PAWN);
+      assert(type_of(piece_on(capQq)) == PAWN);
 
       // Remove the captured pawn
       clear_bit(&occupied, capQq);
@@ -1490,8 +1430,8 @@ int Position::see(Move m) const {
   attackers = attackers_to(to, occupied);
 
   // If the opponent has no attackers we are finished
-  stm = opposite_color(piece_color(piece_on(from)));
-  stmAttackers = attackers & pieces_of_color(stm);
+  stm = flip(color_of(piece_on(from)));
+  stmAttackers = attackers & pieces(stm);
   if (!stmAttackers)
       return PieceValueMidgame[capturedType];
 
@@ -1502,7 +1442,7 @@ int Position::see(Move m) const {
   // capture with the least valuable piece. After each capture, we look for
   // new X-ray attacks from behind the capturing piece.
   swapList[0] = PieceValueMidgame[capturedType];
-  capturedType = piece_type(piece_on(from));
+  capturedType = type_of(piece_on(from));
 
   do {
       // Locate the least valuable attacker for the side to move. The loop
@@ -1528,8 +1468,8 @@ int Position::see(Move m) const {
       // Remember the value of the capturing piece, and change the side to
       // move before beginning the next iteration.
       capturedType = pt;
-      stm = opposite_color(stm);
-      stmAttackers = attackers & pieces_of_color(stm);
+      stm = flip(stm);
+      stmAttackers = attackers & pieces(stm);
 
       // Stop before processing a king capture
       if (capturedType == KING && stmAttackers)
@@ -1573,7 +1513,6 @@ void Position::clear() {
       castleRightsMask[sq] = ALL_CASTLES;
   }
   sideToMove = WHITE;
-  fullMoves = 1;
   nodes = 0;
 }
 
@@ -1583,8 +1522,8 @@ void Position::clear() {
 
 void Position::put_piece(Piece p, Square s) {
 
-  Color c = piece_color(p);
-  PieceType pt = piece_type(p);
+  Color c = color_of(p);
+  PieceType pt = type_of(p);
 
   board[s] = p;
   index[s] = pieceCount[c][pt]++;
@@ -1606,8 +1545,8 @@ Key Position::compute_key() const {
   Key result = zobCastle[st->castleRights];
 
   for (Square s = SQ_A1; s <= SQ_H8; s++)
-      if (square_is_occupied(s))
-          result ^= zobrist[piece_color(piece_on(s))][piece_type(piece_on(s))][s];
+      if (!square_is_empty(s))
+          result ^= zobrist[color_of(piece_on(s))][type_of(piece_on(s))][s];
 
   if (ep_square() != SQ_NONE)
       result ^= zobEp[ep_square()];
@@ -1714,9 +1653,24 @@ bool Position::is_draw() const {
 
   // Draw by repetition?
   if (!SkipRepetition)
-      for (int i = 4, e = Min(Min(st->gamePly, st->rule50), st->pliesFromNull); i <= e; i += 2)
-          if (history[st->gamePly - i] == st->key)
-              return true;
+  {
+      int i = 4, e = Min(st->rule50, st->pliesFromNull);
+
+      if (i <= e)
+      {
+          StateInfo* stp = st->previous->previous;
+
+          do {
+              stp = stp->previous->previous;
+
+              if (stp->key == st->key)
+                  return true;
+
+              i +=2;
+
+          } while (i <= e);
+      }
+  }
 
   return false;
 }
@@ -1731,8 +1685,7 @@ template bool Position::is_draw<true>() const;
 
 bool Position::is_mate() const {
 
-  MoveStack moves[MAX_MOVES];
-  return in_check() && generate<MV_LEGAL>(*this, moves) == moves;
+  return in_check() && !MoveList<MV_LEGAL>(*this).size();
 }
 
 
@@ -1740,7 +1693,7 @@ bool Position::is_mate() const {
 /// startup the various arrays used to compute hash keys and the piece
 /// square tables. The latter is a two-step operation: First, the white
 /// halves of the tables are copied from the MgPST[][] and EgPST[][] arrays.
-/// Second, the black halves of the tables are initialized by mirroring
+/// Second, the black halves of the tables are initialized by flipping
 /// and changing the sign of the corresponding white scores.
 
 void Position::init() {
@@ -1761,22 +1714,19 @@ void Position::init() {
   zobSideToMove = rk.rand<Key>();
   zobExclusion  = rk.rand<Key>();
 
-  for (Square s = SQ_A1; s <= SQ_H8; s++)
-      for (Piece p = WP; p <= WK; p++)
-          PieceSquareTable[p][s] = make_score(MgPST[p][s], EgPST[p][s]);
-
-  for (Square s = SQ_A1; s <= SQ_H8; s++)
-      for (Piece p = BP; p <= BK; p++)
-          PieceSquareTable[p][s] = -PieceSquareTable[p-8][flip_square(s)];
+  for (Piece p = WP; p <= WK; p++)
+      for (Square s = SQ_A1; s <= SQ_H8; s++)
+      {
+          pieceSquareTable[p][s] = make_score(MgPST[p][s], EgPST[p][s]);
+          pieceSquareTable[p+8][flip(s)] = -pieceSquareTable[p][s];
+      }
 }
 
 
-/// Position::flip() flips position with the white and black sides reversed. This
+/// Position::flip_me() flips position with the white and black sides reversed. This
 /// is only useful for debugging especially for finding evaluation symmetry bugs.
 
-void Position::flip() {
-
-  assert(is_ok());
+void Position::flip_me() {
 
   // Make a copy of current position before to start changing
   const Position pos(*this, threadID);
@@ -1787,27 +1737,27 @@ void Position::flip() {
   // Board
   for (Square s = SQ_A1; s <= SQ_H8; s++)
       if (!pos.square_is_empty(s))
-          put_piece(Piece(pos.piece_on(s) ^ 8), flip_square(s));
+          put_piece(Piece(pos.piece_on(s) ^ 8), flip(s));
 
   // Side to move
-  sideToMove = opposite_color(pos.side_to_move());
+  sideToMove = flip(pos.side_to_move());
 
   // Castling rights
   if (pos.can_castle(WHITE_OO))
-      set_castle(BLACK_OO,  king_square(BLACK), flip_square(pos.castle_rook_square(WHITE_OO)));
+      set_castle(BLACK_OO,  king_square(BLACK), flip(pos.castle_rook_square(WHITE_OO)));
   if (pos.can_castle(WHITE_OOO))
-      set_castle(BLACK_OOO, king_square(BLACK), flip_square(pos.castle_rook_square(WHITE_OOO)));
+      set_castle(BLACK_OOO, king_square(BLACK), flip(pos.castle_rook_square(WHITE_OOO)));
   if (pos.can_castle(BLACK_OO))
-      set_castle(WHITE_OO,  king_square(WHITE), flip_square(pos.castle_rook_square(BLACK_OO)));
+      set_castle(WHITE_OO,  king_square(WHITE), flip(pos.castle_rook_square(BLACK_OO)));
   if (pos.can_castle(BLACK_OOO))
-      set_castle(WHITE_OOO, king_square(WHITE), flip_square(pos.castle_rook_square(BLACK_OOO)));
+      set_castle(WHITE_OOO, king_square(WHITE), flip(pos.castle_rook_square(BLACK_OOO)));
 
   // En passant square
   if (pos.st->epSquare != SQ_NONE)
-      st->epSquare = flip_square(pos.st->epSquare);
+      st->epSquare = flip(pos.st->epSquare);
 
   // Checkers
-  find_checkers();
+  st->checkersBB = attackers_to(king_square(sideToMove)) & pieces(flip(sideToMove));
 
   // Hash keys
   st->key = compute_key();
@@ -1867,8 +1817,8 @@ bool Position::is_ok(int* failedStep) const {
   {
       int kingCount[2] = {0, 0};
       for (Square s = SQ_A1; s <= SQ_H8; s++)
-          if (piece_type(piece_on(s)) == KING)
-              kingCount[piece_color(piece_on(s))]++;
+          if (type_of(piece_on(s)) == KING)
+              kingCount[color_of(piece_on(s))]++;
 
       if (kingCount[0] != 1 || kingCount[1] != 1)
           return false;
@@ -1879,9 +1829,9 @@ bool Position::is_ok(int* failedStep) const {
   if (debugKingCapture)
   {
       Color us = side_to_move();
-      Color them = opposite_color(us);
+      Color them = flip(us);
       Square ksq = king_square(them);
-      if (attackers_to(ksq) & pieces_of_color(us))
+      if (attackers_to(ksq) & pieces(us))
           return false;
   }
 
@@ -1895,12 +1845,12 @@ bool Position::is_ok(int* failedStep) const {
   if (debugBitboards)
   {
       // The intersection of the white and black pieces must be empty
-      if ((pieces_of_color(WHITE) & pieces_of_color(BLACK)) != EmptyBoardBB)
+      if ((pieces(WHITE) & pieces(BLACK)) != EmptyBoardBB)
           return false;
 
       // The union of the white and black pieces must be equal to all
       // occupied squares
-      if ((pieces_of_color(WHITE) | pieces_of_color(BLACK)) != occupied_squares())
+      if ((pieces(WHITE) | pieces(BLACK)) != occupied_squares())
           return false;
 
       // Separate piece type bitboards must have empty intersections
@@ -1965,10 +1915,10 @@ bool Position::is_ok(int* failedStep) const {
           for (PieceType pt = PAWN; pt <= KING; pt++)
               for (int i = 0; i < pieceCount[c][pt]; i++)
               {
-                  if (piece_on(piece_list(c, pt, i)) != make_piece(c, pt))
+                  if (piece_on(piece_list(c, pt)[i]) != make_piece(c, pt))
                       return false;
 
-                  if (index[piece_list(c, pt, i)] != i)
+                  if (index[piece_list(c, pt)[i]] != i)
                       return false;
               }