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);
}
// 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 (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);
// 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),
// 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)
+ if (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & t2)
return true;
// Case 5: Discovered check, checking piece is the piece moved in m1
assert(!pos.is_capture_or_promotion(m));
assert(!pos.is_passed_pawn_push(m));
- Square mfrom, mto, tfrom, tto;
-
- mfrom = from_sq(m);
- mto = to_sq(m);
- tfrom = from_sq(threat);
- tto = to_sq(threat);
+ Square mfrom = from_sq(m);
+ Square mto = to_sq(m);
+ Square tfrom = from_sq(threat);
+ Square tto = to_sq(threat);
// Case 1: Don't prune moves which move the threatened piece
if (mfrom == tto)
// 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)
+ if ( pos.is_capture(threat)
&& ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)]
- || type_of(pos.piece_on(tfrom)) == KING)
- && pos.move_attacks_square(m, tto))
- return true;
+ || type_of(pos.piece_on(tfrom)) == 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);
+
+ // The moved piece attacks the square 'tto' ?
+ if (pos.attacks_from(piece, mto, occ) & tto)
+ 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));
+
+ // Verify attackers are triggered by our move and not already existing
+ if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(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.