Document index[] and pieceList[] are not invariants

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index 025a2d722af3ab15a5a3b2cd57fdf1356474b55b..c673225737b2906d428743b8a6f034d60d75d1c9 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -829,6 +829,10 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
       set_bit(&(byTypeBB[promotion]), to);
       board[to] = piece_of_color_and_type(us, promotion);
 
+      // Update material key
+      st->materialKey ^= zobMaterial[us][PAWN][pieceCount[us][PAWN]];
+      st->materialKey ^= zobMaterial[us][promotion][pieceCount[us][promotion]+1];
+
       // Update piece counts
       pieceCount[us][PAWN]--;
       pieceCount[us][promotion]++;
@@ -845,10 +849,6 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
       key ^= zobrist[us][PAWN][to] ^ zobrist[us][promotion][to];
       st->pawnKey ^= zobrist[us][PAWN][to];
 
-      // Update material key
-      st->materialKey ^= zobMaterial[us][PAWN][pieceCount[us][PAWN]];
-      st->materialKey ^= zobMaterial[us][promotion][pieceCount[us][promotion]+1];
-
       // Partially revert and update incremental scores
       st->mgValue -= pst<MidGame>(us, PAWN, to);
       st->mgValue += pst<MidGame>(us, promotion, to);
@@ -886,6 +886,8 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
 
   st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
   st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
+
+  assert(is_ok());
 }
 
 
@@ -937,6 +939,12 @@ void Position::do_capture_move(Bitboard& key, PieceType capture, Color them, Squ
     pieceCount[them][capture]--;
 
     // Update piece list, move the last piece at index[capsq] position
+    //
+    // WARNING: this is a not perfectly revresible operation. When we
+    // will reinsert the captured piece in undo_move() we will put it
+    // at the end of the list and not in its original place, it means
+    // index[] and pieceList[] are not guaranteed to be invariant to a
+    // do_move() + undo_move() sequence.
     Square lastPieceSquare = pieceList[them][capture][pieceCount[them][capture]];
     index[lastPieceSquare] = index[capsq];
     pieceList[them][capture][index[lastPieceSquare]] = lastPieceSquare;
@@ -953,7 +961,6 @@ void Position::do_capture_move(Bitboard& key, PieceType capture, Color them, Squ
 
 void Position::do_castle_move(Move m) {
 
-  assert(is_ok());
   assert(move_is_ok(m));
   assert(move_is_castle(m));
 
@@ -1042,6 +1049,8 @@ void Position::do_castle_move(Move m) {
 
   st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
   st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
+
+  assert(is_ok());
 }
 
 
@@ -1146,6 +1155,8 @@ void Position::undo_move(Move m) {
 
   // Finally point our state pointer back to the previous state
   st = st->previous;
+
+  assert(is_ok());
 }
 
 
@@ -1210,6 +1221,8 @@ void Position::undo_castle_move(Move m) {
 
   // Finally point our state pointer back to the previous state
   st = st->previous;
+
+  assert(is_ok());
 }
 
 
@@ -1689,7 +1702,7 @@ bool Position::is_mate() const {
 
   MoveStack moves[256];
 
-  return is_check() && !generate_evasions(*this, moves, pinned_pieces(sideToMove));
+  return is_check() && (generate_evasions(*this, moves, pinned_pieces(sideToMove)) == moves);
 }
 
 
@@ -1709,20 +1722,18 @@ bool Position::has_mate_threat(Color c) {
       do_null_move(st1);
 
   MoveStack mlist[120];
-  int count;
   bool result = false;
   Bitboard dc = discovered_check_candidates(sideToMove);
   Bitboard pinned = pinned_pieces(sideToMove);
 
   // Generate pseudo-legal non-capture and capture check moves
-  count = generate_non_capture_checks(*this, mlist, dc);
-  count += generate_captures(*this, mlist + count);
+  MoveStack* last = generate_non_capture_checks(*this, mlist, dc);
+  last = generate_captures(*this, last);
 
   // Loop through the moves, and see if one of them is mate
-  for (int i = 0; i < count; i++)
+  for (MoveStack* cur = mlist; cur != last; cur++)
   {
-      Move move = mlist[i].move;
-
+      Move move = cur->move;
       if (!pl_move_is_legal(move, pinned))
           continue;