// 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 yields_to_threat(const Position& pos, Move move, Move threat);
+ bool prevents_threat(const Position& pos, Move move, Move threat);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
struct Skill {
}
// Sort the PV lines searched so far and update the GUI
- sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx);
+ sort<RootMove>(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
&& !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);
if ( depth < 5 * ONE_PLY
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
- && connected_moves(pos, (ss-1)->currentMove, threatMove))
+ && yields_to_threat(pos, (ss-1)->currentMove, threatMove))
return beta - 1;
}
}
// Move count based pruning
if ( depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[depth]
- && (!threatMove || !connected_threat(pos, move, threatMove)))
+ && (!threatMove || !prevents_threat(pos, move, threatMove)))
{
if (SpNode)
sp->mutex.lock();
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);
&& depth >= Threads.min_split_depth()
&& bestValue < beta
&& Threads.available_slave_exists(thisThread))
- {
bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, &bestMove,
depth, threatMove, moveCount, mp, NT);
- break;
- }
}
if (SpNode)
// 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.in_check());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
Key posKey;
Move ttMove, move, bestMove;
Value bestValue, value, ttValue, futilityValue, futilityBase;
- bool inCheck, givesCheck, enoughMaterial, evasionPrunable;
+ bool givesCheck, enoughMaterial, evasionPrunable;
Depth ttDepth;
- inCheck = pos.in_check();
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;
// Futility pruning
if ( !PvNode
- && !inCheck
+ && !InCheck
&& !givesCheck
&& move != ttMove
&& enoughMaterial
// 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),
}
- // 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) {
+ // 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.
- Square f1, t1, f2, t2;
- Piece p1, p2;
- Square ksq;
+ bool yields_to_threat(const Position& pos, Move move, Move threat) {
- assert(is_ok(m1));
- assert(is_ok(m2));
+ assert(is_ok(move));
+ assert(is_ok(threat));
+ assert(color_of(pos.piece_on(from_sq(threat))) == ~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 mfrom = from_sq(move);
+ Square mto = to_sq(move);
+ Square tfrom = from_sq(threat);
+ Square tto = to_sq(threat);
- // 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 threat's destination was vacated by the move
+ if (mto == tfrom || tto == mfrom)
return true;
- // Case 3: Moving through the vacated square
- p2 = pos.piece_on(f2);
- if (piece_is_slider(p2) && (between_bb(f2, t2) & f1))
+ // Threat moves through the vacated square
+ if (between_bb(tfrom, tto) & mfrom)
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)
+ // 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)
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))
+ // Threat gives a discovered check through the move's checking piece
+ if (matt & pos.king_square(pos.side_to_move()))
+ {
+ assert(between_bb(mto, pos.king_square(pos.side_to_move())) & tfrom);
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_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.
- bool connected_threat(const Position& pos, Move m, Move threat) {
+ bool prevents_threat(const Position& pos, Move move, Move threat) {
- assert(is_ok(m));
+ assert(is_ok(move));
assert(is_ok(threat));
- assert(!pos.is_capture_or_promotion(m));
- assert(!pos.is_passed_pawn_push(m));
+ assert(!pos.is_capture_or_promotion(move));
+ assert(!pos.is_passed_pawn_push(move));
- Square mfrom = from_sq(m);
- Square mto = to_sq(m);
+ Square mfrom = from_sq(move);
+ Square mto = to_sq(move);
Square tfrom = from_sq(threat);
Square tto = to_sq(threat);
- // Case 1: Don't prune moves which move the threatened piece
+ // Don't prune moves of the threatened piece
if (mfrom == tto)
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 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))
{
- // Update occupancy as if the piece is moving
- Bitboard occ = pos.pieces() ^ mfrom ^ mto;
+ // Update occupancy as if the piece and the threat are moving
+ Bitboard occ = pos.pieces() ^ mfrom ^ mto ^ tfrom;
Piece piece = pos.piece_on(mfrom);
// The moved piece attacks the square 'tto' ?
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(tfrom, tto) & mto) && pos.see_sign(move) >= 0)
return true;
return false;
projects / stockfish / blobdiff