// 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)); }
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 yields_to_threat(const Position& pos, Move move, Move threat);
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["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]
// Sort the PV lines searched so far and update the GUI
sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ 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 ?
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)
{
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
ss->staticEval = ss->evalMargin = eval = VALUE_NONE;
-
- else if (tte)
+ else
{
- // 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
- eval = ss->staticEval = evaluate(pos, ss->evalMargin);
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
// Can ttValue be used as a better position evaluation?
- if (ttValue != VALUE_NONE)
+ if (tte && ttValue != VALUE_NONE)
+ {
if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
|| ((tte->type() & BOUND_UPPER) && ttValue < eval))
eval = ttValue;
- }
- else
- {
- eval = ss->staticEval = evaluate(pos, ss->evalMargin);
- TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
- ss->staticEval, ss->evalMargin);
+ }
}
// Update gain for the parent non-capture move given the static position
// 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;
}
}
{
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;
alpha = value; // Update alpha here! Always alpha < beta
if (SpNode) sp->alpha = value;
}
- else // Fail high
+ else
{
+ 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);
+ if (bestValue >= beta)
+ break;
+ }
}
if (SpNode)
if (bestValue >= beta) // Failed high
{
- TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth,
- bestMove, ss->staticEval, ss->evalMargin);
+ TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, bestMove);
if (!pos.is_capture_or_promotion(bestMove) && !inCheck)
{
else // Failed low or PV search
TT.store(posKey, value_to_tt(bestValue, ss->ply),
PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval, ss->evalMargin);
+ depth, bestMove);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
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);
const TTEntry* tte;
Key posKey;
Move ttMove, move, bestMove;
- Value bestValue, value, ttValue, futilityValue, futilityBase;
- bool givesCheck, enoughMaterial, evasionPrunable;
+ Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
+ bool givesCheck, enoughMaterial, evasionPrunable, fromNull;
Depth ttDepth;
+ // 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;
+ fromNull = (ss-1)->currentMove == MOVE_NULL;
// Check for an instant draw or maximum ply reached
if (pos.is_draw<false, false>() || ss->ply > MAX_PLY)
}
else
{
- if (tte)
+ if (fromNull)
{
- 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
- ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
+ // Approximated score. Real one is slightly higher due to tempo
+ ss->staticEval = bestValue = -(ss-1)->staticEval;
+ ss->evalMargin = VALUE_ZERO;
}
else
ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
if (bestValue >= beta)
{
if (!tte)
- TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
- DEPTH_NONE, MOVE_NONE, ss->staticEval, ss->evalMargin);
+ TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE);
return bestValue;
}
// Futility pruning
if ( !PvNode
&& !InCheck
+ && !fromNull
&& !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
}
else // Fail high
{
- TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
- ttDepth, move, ss->staticEval, ss->evalMargin);
-
+ TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, ttDepth, move);
return value;
}
}
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,
- ttDepth, bestMove, ss->staticEval, ss->evalMargin);
+ PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // 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.
-
- bool yields_to_threat(const Position& pos, Move move, Move threat) {
+ // 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).
- assert(is_ok(move));
- assert(is_ok(threat));
+ bool allows_move(const Position& pos, Move first, Move second) {
- Square t1 = to_sq(move);
- Square f1 = from_sq(move);
- Square t2 = to_sq(threat);
- Square f2 = from_sq(threat);
+ 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());
- // We are suposed to be called upon returning from a null search
- assert(color_of(pos.piece_on(f2)) == ~pos.side_to_move());
+ 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 (t1 == f2 || t2 == f1)
+ // 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(f2, t2) & f1)
+ // 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 t1_att = pos.attacks_from(pos.piece_on(t1), t1, pos.pieces() ^ f2);
- if (t1_att & 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;
- // Threat gives a discovered check through the move's checking piece
- if (t1_att & 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(t1, pos.king_square(pos.side_to_move())) & f2);
+ assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
return true;
}
}
- // 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]);
- 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);