// Different node types, used as template parameter
enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
- // Lookup table to check if a Piece is a slider and its access function
- const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
- inline bool piece_is_slider(Piece p) { return Slidings[p]; }
-
// Dynamic razoring margin based on depth
inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- template <NodeType NT>
+ template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
void id_loop(Position& pos);
- bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta);
- bool connected_moves(const Position& pos, Move m1, Move m2);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- bool connected_threat(const Position& pos, Move m, Move threat);
+ bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta);
+ 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;
}
- if (Options["OwnBook"] && !Limits.infinite)
+ if (Options["OwnBook"] && !Limits.infinite && !Limits.mate)
{
Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]);
if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])
{
int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns
- cf = cf * MaterialTable::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase
+ cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase
DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
}
if (Options["Use Search Log"])
{
Log log(Options["Search Log Filename"]);
- log << "\nSearching: " << RootPos.to_fen()
+ log << "\nSearching: " << RootPos.fen()
<< "\ninfinite: " << Limits.infinite
<< " ponder: " << Limits.ponder
<< " time: " << Limits.time[RootColor]
// but if we are pondering or in infinite search, we shouldn't print the best
// move before we are told to do so.
if (!Signals.stop && (Limits.ponder || Limits.infinite))
- RootPos.this_thread()->wait_for_stop_or_ponderhit();
+ {
+ Signals.stopOnPonderhit = true;
+ RootPos.this_thread()->wait_for_stop();
+ }
// Best move could be MOVE_NONE when searching on a stalemate position
sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960())
}
// Sort the PV lines searched so far and update the GUI
- sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx);
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
+ if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
// Do we need to pick now the sub-optimal best move ?
if (depth > 2 && BestMoveChanges)
bestMoveNeverChanged = false;
+ // Do we have found a "mate in x"?
+ if ( Limits.mate
+ && bestValue >= VALUE_MATE_IN_MAX_PLY
+ && VALUE_MATE - bestValue <= 2 * Limits.mate)
+ Signals.stop = true;
+
// Do we have time for the next iteration? Can we stop searching now?
if (Limits.use_time_management() && !Signals.stopOnPonderhit)
{
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)
{
else if (tte)
{
- // Following asserts are valid only in single thread condition because
- // TT access is always racy and its contents cannot be trusted.
- assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
- assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE || Threads.size() > 1);
-
- ss->staticEval = eval = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
-
- if (eval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
+ // Never assume anything on values stored in TT
+ if ( (ss->staticEval = eval = tte->static_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->static_value_margin()) == VALUE_NONE)
eval = ss->staticEval = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
&& !pos.pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
+ Value v = qsearch<NonPV, false>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
pos.do_null_move<true>(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R);
(ss+1)->skipNullMove = false;
pos.do_null_move<false>(st);
// 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
- && connected_moves(pos, (ss-1)->currentMove, threatMove))
- return beta - 1;
+ && allows_move(pos, (ss-1)->currentMove, threatMove))
+ threatExtension = true;
}
}
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000)
+ if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000)
sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << move_to_uci(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
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 || !connected_threat(pos, move, threatMove)))
+ && (!threatMove || !prevents_move(pos, move, threatMove)))
{
if (SpNode)
sp->mutex.lock();
}
// Check for legality only before to do the move
- if (!pos.pl_move_is_legal(move, ci.pinned))
+ if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned))
{
moveCount--;
continue;
}
- pvMove = PvNode ? moveCount == 1 : false;
+ pvMove = PvNode && moveCount == 1;
ss->currentMove = move;
if (!SpNode && !captureOrPromotion && playedMoveCount < 64)
movesSearched[playedMoveCount++] = move;
if (doFullDepthSearch)
{
alpha = SpNode ? sp->alpha : alpha;
- value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ value = newDepth < ONE_PLY ?
+ givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
: - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
}
// high, in the latter case search only if value < beta, otherwise let the
// parent node to fail low with value <= alpha and to try another move.
if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta))))
- value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ value = newDepth < ONE_PLY ?
+ givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
-
// Step 17. Undo move
pos.undo_move(move);
if (value > bestValue)
{
- bestValue = value;
- if (SpNode) sp->bestValue = value;
+ bestValue = SpNode ? sp->bestValue = value : value;
if (value > alpha)
{
- bestMove = move;
- if (SpNode) sp->bestMove = move;
+ bestMove = SpNode ? sp->bestMove = move : move;
- if (PvNode && value < beta)
- {
- alpha = value; // Update alpha here! Always alpha < beta
- if (SpNode) sp->alpha = value;
- }
- else // Fail high
+ if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ alpha = SpNode ? sp->alpha = value : value;
+ else
{
- if (SpNode) sp->cutoff = true;
+ assert(value >= beta); // Fail high
+
+ if (SpNode)
+ sp->cutoff = true;
+
break;
}
}
// Step 19. Check for splitting the search
if ( !SpNode
&& depth >= Threads.min_split_depth()
- && bestValue < beta
&& Threads.available_slave_exists(thisThread))
{
+ assert(bestValue < beta);
+
bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
depth, threatMove, moveCount, mp, NT);
- break;
+ if (bestValue >= beta)
+ break;
}
}
// search function when the remaining depth is zero (or, to be more precise,
// less than ONE_PLY).
- template <NodeType NT>
+ template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
const bool PvNode = (NT == PV);
assert(NT == PV || NT == NonPV);
+ assert(InCheck == !!pos.checkers());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
const TTEntry* tte;
Key posKey;
Move ttMove, move, bestMove;
- Value bestValue, value, ttValue, futilityValue, futilityBase;
- bool inCheck, givesCheck, enoughMaterial, evasionPrunable;
+ Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
+ bool givesCheck, enoughMaterial, evasionPrunable;
Depth ttDepth;
- inCheck = pos.in_check();
+ // To flag BOUND_EXACT a node with eval above alpha and no available moves
+ if (PvNode)
+ oldAlpha = alpha;
+
ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
// Decide whether or not to include checks, this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
- ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+ ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
if ( tte
&& tte->depth() >= ttDepth
}
// Evaluate the position statically
- if (inCheck)
+ if (InCheck)
{
ss->staticEval = ss->evalMargin = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
{
if (tte)
{
- assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
-
- ss->staticEval = bestValue = tte->static_value();
- ss->evalMargin = tte->static_value_margin();
-
- if (ss->staticEval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
+ // Never assume anything on values stored in TT
+ if ( (ss->staticEval = bestValue = tte->static_value()) == VALUE_NONE
+ ||(ss->evalMargin = tte->static_value_margin()) == VALUE_NONE)
ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
}
else
// Futility pruning
if ( !PvNode
- && !inCheck
+ && !InCheck
&& !givesCheck
&& move != ttMove
&& enoughMaterial
if (futilityValue < beta)
{
- if (futilityValue > bestValue)
- bestValue = futilityValue;
-
+ bestValue = std::max(bestValue, futilityValue);
continue;
}
if ( futilityBase < beta
&& depth < DEPTH_ZERO
&& pos.see(move) <= 0)
+ {
+ bestValue = std::max(bestValue, futilityBase);
continue;
+ }
}
// Detect non-capture evasions that are candidate to be pruned
evasionPrunable = !PvNode
- && inCheck
+ && InCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY
&& !pos.is_capture(move)
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
if ( !PvNode
- && (!inCheck || evasionPrunable)
+ && (!InCheck || evasionPrunable)
&& move != ttMove
&& type_of(move) != PROMOTION
&& pos.see_sign(move) < 0)
// Don't search useless checks
if ( !PvNode
- && !inCheck
+ && !InCheck
&& givesCheck
&& move != ttMove
&& !pos.is_capture_or_promotion(move)
// Make and search the move
pos.do_move(move, st, ci, givesCheck);
- value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
+ value = givesCheck ? -qsearch<NT, true>(pos, ss+1, -beta, -alpha, depth - ONE_PLY)
+ : -qsearch<NT, false>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (inCheck && bestValue == -VALUE_INFINITE)
+ if (InCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
TT.store(posKey, value_to_tt(bestValue, ss->ply),
- PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
ttDepth, bestMove, ss->staticEval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // connected_moves() tests whether two moves are 'connected' in the sense
- // that the first move somehow made the second move possible (for instance
- // if the moving piece is the same in both moves). The first move is assumed
- // to be the move that was made to reach the current position, while the
- // second move is assumed to be a move from the current position.
-
- bool connected_moves(const Position& pos, Move m1, Move m2) {
+ // 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).
- Square f1, t1, f2, t2;
- Piece p1, p2;
- Square ksq;
+ bool allows_move(const Position& pos, Move first, Move second) {
- assert(is_ok(m1));
- assert(is_ok(m2));
+ 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());
- // Case 1: The moving piece is the same in both moves
- f2 = from_sq(m2);
- t1 = to_sq(m1);
- if (f2 == t1)
- return true;
+ Square m1from = from_sq(first);
+ Square m2from = from_sq(second);
+ Square m1to = to_sq(first);
+ Square m2to = to_sq(second);
- // Case 2: The destination square for m2 was vacated by m1
- t2 = to_sq(m2);
- f1 = from_sq(m1);
- if (t2 == f1)
+ // The piece is the same or second's destination was vacated by the first move
+ if (m1to == m2from || m2to == m1from)
return true;
- // Case 3: Moving through the vacated square
- p2 = pos.piece_on(f2);
- if (piece_is_slider(p2) && (between_bb(f2, t2) & f1))
+ // Second one moves through the square vacated by first one
+ if (between_bb(m2from, m2to) & m1from)
return true;
- // Case 4: The destination square for m2 is defended by the moving piece in m1
- p1 = pos.piece_on(t1);
- if (pos.attacks_from(p1, t1) & t2)
+ // 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;
- // Case 5: Discovered check, checking piece is the piece moved in m1
- ksq = pos.king_square(pos.side_to_move());
- if ( piece_is_slider(p1)
- && (between_bb(t1, ksq) & f2)
- && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq))
+ // Second move gives a discovered check through the first's checking piece
+ if (m1att & pos.king_square(pos.side_to_move()))
+ {
+ assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
return true;
+ }
return false;
}
- // connected_threat() tests whether it is safe to forward prune a move or if
- // is somehow connected to the threat move returned by null search.
+ // 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 connected_threat(const Position& pos, Move m, Move threat) {
+ bool prevents_move(const Position& pos, Move first, Move second) {
- assert(is_ok(m));
- assert(is_ok(threat));
- assert(!pos.is_capture_or_promotion(m));
- assert(!pos.is_passed_pawn_push(m));
+ assert(is_ok(first));
+ assert(is_ok(second));
- Square mfrom = from_sq(m);
- Square mto = to_sq(m);
- 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);
- // Case 1: Don't prune moves which move the threatened piece
- if (mfrom == tto)
+ // Don't prune moves of the threatened piece
+ if (m1from == m2to)
return true;
- // Case 2: If the threatened piece has value less than or equal to the
- // value of the threatening 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 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(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;
}
- // Case 3: If the moving piece in the threatened move is a slider, don't
- // prune safe moves which block its ray.
- if ( piece_is_slider(pos.piece_on(tfrom))
- && (between_bb(tfrom, tto) & mto)
- && pos.see_sign(m) >= 0)
+ // Don't prune safe moves which block the threat path
+ if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
return true;
return false;
do {
pv.push_back(m);
- assert(pos.move_is_legal(pv[ply]));
+ assert(MoveList<LEGAL>(pos).contains(pv[ply]));
+
pos.do_move(pv[ply++], *st++);
tte = TT.probe(pos.key());
StateInfo state[MAX_PLY_PLUS_2], *st = state;
TTEntry* tte;
int ply = 0;
- Value v, m;
do {
tte = TT.probe(pos.key());
if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries
- {
- if (pos.in_check())
- v = m = VALUE_NONE;
- else
- v = evaluate(pos, m);
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE, VALUE_NONE);
- TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m);
- }
+ assert(MoveList<LEGAL>(pos).contains(pv[ply]));
- assert(pos.move_is_legal(pv[ply]));
pos.do_move(pv[ply++], *st++);
} while (pv[ply] != MOVE_NONE);
&& !sp->slavesMask)
{
assert(!sp->master->is_searching);
- sp->master->wake_up();
+ sp->master->notify_one();
}
// After releasing the lock we cannot access anymore any SplitPoint