Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta);
- bool yields_to_threat(const Position& pos, Move move, Move threat);
- bool prevents_threat(const Position& pos, Move move, Move threat);
+ bool allows_move(const Position& pos, Move first, Move second);
+ bool prevents_move(const Position& pos, Move first, Move second);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
struct Skill {
{
RootMoves.push_back(MOVE_NONE);
sync_cout << "info depth 0 score "
- << score_to_uci(RootPos.in_check() ? -VALUE_MATE : VALUE_DRAW)
+ << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
goto finalize;
Value bestValue, value, ttValue;
Value eval, nullValue, futilityValue;
bool inCheck, givesCheck, pvMove, singularExtensionNode;
- bool captureOrPromotion, dangerous, doFullDepthSearch;
+ bool captureOrPromotion, dangerous, doFullDepthSearch, threatExtension;
int moveCount, playedMoveCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
moveCount = playedMoveCount = 0;
- inCheck = pos.in_check();
+ threatExtension = false;
+ inCheck = pos.checkers();
if (SpNode)
{
// The null move failed low, which means that we may be faced with
// some kind of threat. If the previous move was reduced, check if
// the move that refuted the null move was somehow connected to the
- // move which was reduced. If a connection is found, return a fail
- // low score (which will cause the reduced move to fail high in the
- // parent node, which will trigger a re-search with full depth).
+ // move which was reduced. If a connection is found extend moves that
+ // defend against threat.
threatMove = (ss+1)->currentMove;
if ( depth < 5 * ONE_PLY
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
- && yields_to_threat(pos, (ss-1)->currentMove, threatMove))
- return beta - 1;
+ && allows_move(pos, (ss-1)->currentMove, threatMove))
+ threatExtension = true;
}
}
if (PvNode && dangerous)
ext = ONE_PLY;
+ else if (threatExtension && prevents_move(pos, move, threatMove))
+ ext = ONE_PLY;
+
else if (givesCheck && pos.see_sign(move) >= 0)
ext = ONE_PLY / 2;
// Move count based pruning
if ( depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[depth]
- && (!threatMove || !prevents_threat(pos, move, threatMove)))
+ && (!threatMove || !prevents_move(pos, move, threatMove)))
{
if (SpNode)
sp->mutex.lock();
const bool PvNode = (NT == PV);
assert(NT == PV || NT == NonPV);
- assert(InCheck == pos.in_check());
+ assert(InCheck == !!pos.checkers());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
}
- // yields_to_threat() tests whether the move at previous ply yields to the so
- // called threat move (the best move returned from a null search that fails
- // low). Here 'yields to' means that the move somehow made the threat possible
- // for instance if the moving piece is the same in both moves.
+ // allows_move() tests whether the move at previous ply (first) somehow makes a
+ // second move possible, for instance if the moving piece is the same in both
+ // moves. Normally the second move is the threat move (the best move returned
+ // from a null search that fails low).
- bool yields_to_threat(const Position& pos, Move move, Move threat) {
+ bool allows_move(const Position& pos, Move first, Move second) {
- assert(is_ok(move));
- assert(is_ok(threat));
- assert(color_of(pos.piece_on(from_sq(threat))) == ~pos.side_to_move());
+ assert(is_ok(first));
+ assert(is_ok(second));
+ assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move());
+ assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move());
- Square mfrom = from_sq(move);
- Square mto = to_sq(move);
- Square tfrom = from_sq(threat);
- Square tto = to_sq(threat);
+ Square m1from = from_sq(first);
+ Square m2from = from_sq(second);
+ Square m1to = to_sq(first);
+ Square m2to = to_sq(second);
- // The piece is the same or threat's destination was vacated by the move
- if (mto == tfrom || tto == mfrom)
+ // The piece is the same or second's destination was vacated by the first move
+ if (m1to == m2from || m2to == m1from)
return true;
- // Threat moves through the vacated square
- if (between_bb(tfrom, tto) & mfrom)
+ // Second one moves through the square vacated by first one
+ if (between_bb(m2from, m2to) & m1from)
return true;
- // Threat's destination is defended by the move's piece
- Bitboard matt = pos.attacks_from(pos.piece_on(mto), mto, pos.pieces() ^ tfrom);
- if (matt & tto)
+ // Second's destination is defended by the first move's piece
+ Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from);
+ if (m1att & m2to)
return true;
- // Threat gives a discovered check through the move's checking piece
- if (matt & pos.king_square(pos.side_to_move()))
+ // Second move gives a discovered check through the first's checking piece
+ if (m1att & pos.king_square(pos.side_to_move()))
{
- assert(between_bb(mto, pos.king_square(pos.side_to_move())) & tfrom);
+ assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
return true;
}
}
- // prevents_threat() tests whether a move is able to defend against the so
- // called threat move (the best move returned from a null search that fails
- // low). In this case will not be pruned.
+ // prevents_move() tests whether a move (first) is able to defend against an
+ // opponent's move (second). In this case will not be pruned. Normally the
+ // second move is the threat move (the best move returned from a null search
+ // that fails low).
- bool prevents_threat(const Position& pos, Move move, Move threat) {
+ bool prevents_move(const Position& pos, Move first, Move second) {
- assert(is_ok(move));
- assert(is_ok(threat));
- assert(!pos.is_capture_or_promotion(move));
- assert(!pos.is_passed_pawn_push(move));
+ assert(is_ok(first));
+ assert(is_ok(second));
+ assert(!pos.is_capture_or_promotion(first));
+ assert(!pos.is_passed_pawn_push(first));
- Square mfrom = from_sq(move);
- Square mto = to_sq(move);
- Square tfrom = from_sq(threat);
- Square tto = to_sq(threat);
+ Square m1from = from_sq(first);
+ Square m2from = from_sq(second);
+ Square m1to = to_sq(first);
+ Square m2to = to_sq(second);
// Don't prune moves of the threatened piece
- if (mfrom == tto)
+ if (m1from == m2to)
return true;
// If the threatened piece has value less than or equal to the value of the
// threat piece, don't prune moves which defend it.
- if ( pos.is_capture(threat)
- && ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)]
- || type_of(pos.piece_on(tfrom)) == KING))
+ if ( pos.is_capture(second)
+ && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)]
+ || type_of(pos.piece_on(m2from)) == KING))
{
// Update occupancy as if the piece and the threat are moving
- Bitboard occ = pos.pieces() ^ mfrom ^ mto ^ tfrom;
- Piece piece = pos.piece_on(mfrom);
+ Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from;
+ Piece piece = pos.piece_on(m1from);
// The moved piece attacks the square 'tto' ?
- if (pos.attacks_from(piece, mto, occ) & tto)
+ if (pos.attacks_from(piece, m1to, occ) & m2to)
return true;
// Scan for possible X-ray attackers behind the moved piece
- Bitboard xray = (attacks_bb< ROOK>(tto, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
- | (attacks_bb<BISHOP>(tto, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
+ Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
+ | (attacks_bb<BISHOP>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
// Verify attackers are triggered by our move and not already existing
- if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(tto))))
+ if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(m2to))))
return true;
}
// Don't prune safe moves which block the threat path
- if ((between_bb(tfrom, tto) & mto) && pos.see_sign(move) >= 0)
+ if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
return true;
return false;
projects / stockfish / blobdiff