X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=97ab5918ae808090ca181aab078e35f15f8399d4;hp=d61fca1bca5a3d5d91749f9ad2f1a1966f1349e4;hb=ade3bb9a4e774aa9b760235f3b0ee42e0a0420d9;hpb=4f6aa152284e80094467ea0051bb58b004042555 diff --git a/src/search.cpp b/src/search.cpp index d61fca1b..97ab5918 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -40,7 +40,6 @@ namespace Search { SignalsType Signals; LimitsType Limits; - StateStackPtr SetupStates; } namespace Tablebases { @@ -179,22 +178,21 @@ namespace { void Search::init() { - const double K[][2] = {{ 0.799, 2.281 }, { 0.484, 3.023 }}; - - for (int pv = 0; pv <= 1; ++pv) - for (int imp = 0; imp <= 1; ++imp) - for (int d = 1; d < 64; ++d) - for (int mc = 1; mc < 64; ++mc) - { - double r = K[pv][0] + log(d) * log(mc) / K[pv][1]; + for (int imp = 0; imp <= 1; ++imp) + for (int d = 1; d < 64; ++d) + for (int mc = 1; mc < 64; ++mc) + { + double r = log(d) * log(mc) / 2; + if (r < 0.80) + continue; - if (r >= 1.5) - Reductions[pv][imp][d][mc] = int(r) * ONE_PLY; + Reductions[NonPV][imp][d][mc] = int(std::round(r)) * ONE_PLY; + Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - ONE_PLY, DEPTH_ZERO); - // Increase reduction when eval is not improving - if (!pv && !imp && Reductions[pv][imp][d][mc] >= 2 * ONE_PLY) - Reductions[pv][imp][d][mc] += ONE_PLY; - } + // Increase reduction for non-PV nodes when eval is not improving + if (!imp && Reductions[NonPV][imp][d][mc] >= 2 * ONE_PLY) + Reductions[NonPV][imp][d][mc] += ONE_PLY; + } for (int d = 0; d < 16; ++d) { @@ -263,19 +261,6 @@ void MainThread::search() { DrawValue[ us] = VALUE_DRAW - Value(contempt); DrawValue[~us] = VALUE_DRAW + Value(contempt); - TB::Hits = 0; - TB::RootInTB = false; - TB::UseRule50 = Options["Syzygy50MoveRule"]; - TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; - TB::Cardinality = Options["SyzygyProbeLimit"]; - - // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality - if (TB::Cardinality > TB::MaxCardinality) - { - TB::Cardinality = TB::MaxCardinality; - TB::ProbeDepth = DEPTH_ZERO; - } - if (rootMoves.empty()) { rootMoves.push_back(RootMove(MOVE_NONE)); @@ -285,49 +270,9 @@ void MainThread::search() { } else { - if ( TB::Cardinality >= rootPos.count(WHITE) - + rootPos.count(BLACK) - && !rootPos.can_castle(ANY_CASTLING)) - { - // If the current root position is in the tablebases, then RootMoves - // contains only moves that preserve the draw or the win. - TB::RootInTB = Tablebases::root_probe(rootPos, rootMoves, TB::Score); - - if (TB::RootInTB) - TB::Cardinality = 0; // Do not probe tablebases during the search - - else // If DTZ tables are missing, use WDL tables as a fallback - { - // Filter out moves that do not preserve the draw or the win. - TB::RootInTB = Tablebases::root_probe_wdl(rootPos, rootMoves, TB::Score); - - // Only probe during search if winning - if (TB::Score <= VALUE_DRAW) - TB::Cardinality = 0; - } - - if (TB::RootInTB) - { - TB::Hits = rootMoves.size(); - - if (!TB::UseRule50) - TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 - : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 - : VALUE_DRAW; - } - } - for (Thread* th : Threads) - { - th->maxPly = 0; - th->rootDepth = DEPTH_ZERO; if (th != this) - { - th->rootPos = Position(rootPos, th); - th->rootMoves = rootMoves; th->start_searching(); - } - } Thread::search(); // Let's start searching! } @@ -360,7 +305,9 @@ void MainThread::search() { Thread* bestThread = this; if ( !this->easyMovePlayed && Options["MultiPV"] == 1 - && !Skill(Options["Skill Level"]).enabled()) + && !Limits.depth + && !Skill(Options["Skill Level"]).enabled() + && rootMoves[0].pv[0] != MOVE_NONE) { for (Thread* th : Threads) if ( th->completedDepth > bestThread->completedDepth @@ -389,12 +336,12 @@ void MainThread::search() { void Thread::search() { - Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) + Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2) Value bestValue, alpha, beta, delta; Move easyMove = MOVE_NONE; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - std::memset(ss-2, 0, 5 * sizeof(Stack)); + std::memset(ss-5, 0, 8 * sizeof(Stack)); bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -420,7 +367,7 @@ void Thread::search() { multiPV = std::min(multiPV, rootMoves.size()); // Iterative deepening loop until requested to stop or the target depth is reached. - while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= Limits.depth)) + while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth <= Limits.depth)) { // Set up the new depths for the helper threads skipping on average every // 2nd ply (using a half-density matrix). @@ -466,11 +413,6 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // Write PV back to the transposition table in case the relevant - // entries have been overwritten during the search. - for (size_t i = 0; i <= PVIdx; ++i) - rootMoves[i].insert_pv_in_tt(rootPos); - // If search has been stopped, break immediately. Sorting and // writing PV back to TT is safe because RootMoves is still // valid, although it refers to the previous iteration. @@ -515,7 +457,7 @@ void Thread::search() { std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1); if (!mainThread) - break; + continue; if (Signals.stop) sync_cout << "info nodes " << Threads.nodes_searched() @@ -549,18 +491,18 @@ void Thread::search() { // Stop the search if only one legal move is available, or if all // of the available time has been used, or if we matched an easyMove // from the previous search and just did a fast verification. - const bool F[] = { !mainThread->failedLow, - bestValue >= mainThread->previousScore }; + const int F[] = { mainThread->failedLow, + bestValue - mainThread->previousScore }; - int improvingFactor = 640 - 160*F[0] - 126*F[1] - 124*F[0]*F[1]; + int improvingFactor = std::max(229, std::min(715, 357 + 119 * F[0] - 6 * F[1])); double unstablePvFactor = 1 + mainThread->bestMoveChanges; bool doEasyMove = rootMoves[0].pv[0] == easyMove && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.optimum() * 25 / 204; + && Time.elapsed() > Time.optimum() * 5 / 42; if ( rootMoves.size() == 1 - || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 634 + || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628 || (mainThread->easyMovePlayed = doEasyMove)) { // If we are allowed to ponder do not stop the search now but @@ -607,6 +549,7 @@ namespace { assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); + assert(!(PvNode && cutNode)); Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; @@ -614,9 +557,10 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth, predictedDepth; - Value bestValue, value, ttValue, eval, nullValue, futilityValue; + Value bestValue, value, ttValue, eval, nullValue; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning; + Piece moved_piece; int moveCount, quietCount; // Step 1. Initialize node @@ -666,6 +610,7 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->counterMoves = nullptr; (ss+1)->skipEarlyPruning = false; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; @@ -786,9 +731,11 @@ namespace { if ( !PvNode && depth >= 2 * ONE_PLY && eval >= beta + && (ss->staticEval >= beta || depth >= 12 * ONE_PLY) && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; + ss->counterMoves = nullptr; assert(eval - beta >= 0); @@ -837,13 +784,14 @@ namespace { assert((ss-1)->currentMove != MOVE_NONE); assert((ss-1)->currentMove != MOVE_NULL); - MovePicker mp(pos, ttMove, thisThread->history, PieceValue[MG][pos.captured_piece_type()]); + MovePicker mp(pos, ttMove, PieceValue[MG][pos.captured_piece_type()]); CheckInfo ci(pos); while ((move = mp.next_move()) != MOVE_NONE) if (pos.legal(move, ci.pinned)) { ss->currentMove = move; + ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)]; pos.do_move(move, st, pos.gives_check(move, ci)); value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); pos.undo_move(move); @@ -859,7 +807,7 @@ namespace { { Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d, true); + search(pos, ss, alpha, beta, d, cutNode); ss->skipEarlyPruning = false; tte = TT.probe(posKey, ttHit); @@ -868,15 +816,15 @@ namespace { moves_loop: // When in check search starts from here - Square prevSq = to_sq((ss-1)->currentMove); - Move cm = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]; - const CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq]; + const CounterMoveStats* cmh = (ss-1)->counterMoves; + const CounterMoveStats* fmh = (ss-2)->counterMoves; + const CounterMoveStats* fmh2 = (ss-4)->counterMoves; - MovePicker mp(pos, ttMove, depth, thisThread->history, cmh, cm, ss); + MovePicker mp(pos, ttMove, depth, ss); CheckInfo ci(pos); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc improving = ss->staticEval >= (ss-2)->staticEval - || ss->staticEval == VALUE_NONE + /* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */ ||(ss-2)->staticEval == VALUE_NONE; singularExtensionNode = !rootNode @@ -916,13 +864,19 @@ moves_loop: // When in check search starts from here extension = DEPTH_ZERO; captureOrPromotion = pos.capture_or_promotion(move); + moved_piece = pos.moved_piece(move); givesCheck = type_of(move) == NORMAL && !ci.dcCandidates ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) : pos.gives_check(move, ci); + moveCountPruning = depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[improving][depth]; + // Step 12. Extend checks - if (givesCheck && pos.see_sign(move) >= VALUE_ZERO) + if ( givesCheck + && !moveCountPruning + && pos.see_sign(move) >= VALUE_ZERO) extension = ONE_PLY; // Singular extension search. If all moves but one fail low on a search of @@ -958,30 +912,23 @@ moves_loop: // When in check search starts from here && bestValue > VALUE_MATED_IN_MAX_PLY) { // Move count based pruning - if ( depth < 16 * ONE_PLY - && moveCount >= FutilityMoveCounts[improving][depth]) + if (moveCountPruning) continue; - // History based pruning + // Countermoves based pruning if ( depth <= 4 * ONE_PLY && move != ss->killers[0] - && thisThread->history[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO - && cmh[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO) + && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO) + && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO) + && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh))) continue; - predictedDepth = newDepth - reduction(improving, depth, moveCount); + predictedDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO); // Futility pruning: parent node - if (predictedDepth < 7 * ONE_PLY) - { - futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256; - - if (futilityValue <= alpha) - { - bestValue = std::max(bestValue, futilityValue); - continue; - } - } + if ( predictedDepth < 7 * ONE_PLY + && ss->staticEval + futility_margin(predictedDepth) + 256 <= alpha) + continue; // Prune moves with negative SEE at low depths if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO) @@ -999,6 +946,7 @@ moves_loop: // When in check search starts from here } ss->currentMove = move; + ss->counterMoves = &CounterMoveHistory[moved_piece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -1010,27 +958,27 @@ moves_loop: // When in check search starts from here && !captureOrPromotion) { Depth r = reduction(improving, depth, moveCount); + Value val = thisThread->history[moved_piece][to_sq(move)] + + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO) + + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO) + + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO); - // Increase reduction for cut nodes and moves with a bad history - if ( (!PvNode && cutNode) - || ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO - && cmh[pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO)) - r += ONE_PLY; - - // Decrease/increase reduction for moves with a good/bad history - int rHist = ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] - + cmh[pos.piece_on(to_sq(move))][to_sq(move)]) / 14980; - r = std::max(DEPTH_ZERO, r - rHist * ONE_PLY); + // Increase reduction for cut nodes + if (cutNode) + r += 2 * ONE_PLY; // Decrease reduction for moves that escape a capture. Filter out // castling moves, because they are coded as "king captures rook" and // hence break make_move(). Also use see() instead of see_sign(), // because the destination square is empty. - if ( r - && type_of(move) == NORMAL - && type_of(pos.piece_on(to_sq(move))) != PAWN - && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO) - r = std::max(DEPTH_ZERO, r - ONE_PLY); + else if ( type_of(move) == NORMAL + && type_of(pos.piece_on(to_sq(move))) != PAWN + && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO) + r -= 2 * ONE_PLY; + + // Decrease/increase reduction for moves with a good/bad history + int rHist = (val - 10000) / 20000; + r = std::max(DEPTH_ZERO, r - rHist * ONE_PLY); Depth d = std::max(newDepth - r, ONE_PLY); @@ -1158,15 +1106,19 @@ moves_loop: // When in check search starts from here // Bonus for prior countermove that caused the fail low else if ( depth >= 3 * ONE_PLY && !bestMove - && !inCheck && !pos.captured_piece_type() - && is_ok((ss - 1)->currentMove) - && is_ok((ss - 2)->currentMove)) + && is_ok((ss-1)->currentMove)) { - Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); - Square prevPrevSq = to_sq((ss - 2)->currentMove); - CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; - prevCmh.update(pos.piece_on(prevSq), prevSq, bonus); + Square prevSq = to_sq((ss-1)->currentMove); + Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + 2 * depth / ONE_PLY - 2); + if ((ss-2)->counterMoves) + (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); + + if ((ss-3)->counterMoves) + (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); + + if ((ss-5)->counterMoves) + (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); } tte->save(posKey, value_to_tt(bestValue, ss->ply), @@ -1287,7 +1239,7 @@ moves_loop: // When in check search starts from here // to search the moves. Because the depth is <= 0 here, only captures, // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will // be generated. - MovePicker mp(pos, ttMove, depth, pos.this_thread()->history, to_sq((ss-1)->currentMove)); + MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove)); CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs @@ -1426,8 +1378,8 @@ moves_loop: // When in check search starts from here } - // update_stats() updates killers, history, countermove and countermove - // history when a new quiet best move is found. + // update_stats() updates killers, history, countermove and countermove plus + // follow-up move history when a new quiet best move is found. void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) { @@ -1438,37 +1390,54 @@ moves_loop: // When in check search starts from here ss->killers[0] = move; } - Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); + Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + 2 * depth / ONE_PLY - 2); Square prevSq = to_sq((ss-1)->currentMove); - CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq]; + CounterMoveStats* cmh = (ss-1)->counterMoves; + CounterMoveStats* fmh = (ss-2)->counterMoves; + CounterMoveStats* fmh2 = (ss-4)->counterMoves; Thread* thisThread = pos.this_thread(); thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); - if (is_ok((ss-1)->currentMove)) + if (cmh) { thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); - cmh.update(pos.moved_piece(move), to_sq(move), bonus); + cmh->update(pos.moved_piece(move), to_sq(move), bonus); } + if (fmh) + fmh->update(pos.moved_piece(move), to_sq(move), bonus); + + if (fmh2) + fmh2->update(pos.moved_piece(move), to_sq(move), bonus); + // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); - if (is_ok((ss-1)->currentMove)) - cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + if (cmh) + cmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + + if (fmh) + fmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + + if (fmh2) + fmh2->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ( (ss-1)->moveCount == 1 - && !pos.captured_piece_type() - && is_ok((ss-2)->currentMove)) + if ((ss-1)->moveCount == 1 && !pos.captured_piece_type()) { - Square prevPrevSq = to_sq((ss-2)->currentMove); - CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; - prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); + if ((ss-2)->counterMoves) + (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1); + + if ((ss-3)->counterMoves) + (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1); + + if ((ss-5)->counterMoves) + (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1); } } @@ -1478,7 +1447,7 @@ moves_loop: // When in check search starts from here Move Skill::pick_best(size_t multiPV) { - const Search::RootMoveVector& rootMoves = Threads.main()->rootMoves; + const RootMoves& rootMoves = Threads.main()->rootMoves; static PRNG rng(now()); // PRNG sequence should be non-deterministic // RootMoves are already sorted by score in descending order @@ -1543,7 +1512,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { std::stringstream ss; int elapsed = Time.elapsed() + 1; - const Search::RootMoveVector& rootMoves = pos.this_thread()->rootMoves; + const RootMoves& rootMoves = pos.this_thread()->rootMoves; size_t PVIdx = pos.this_thread()->PVIdx; size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size()); uint64_t nodes_searched = Threads.nodes_searched(); @@ -1591,33 +1560,6 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { } -/// RootMove::insert_pv_in_tt() is called at the end of a search iteration, and -/// inserts the PV back into the TT. This makes sure the old PV moves are searched -/// first, even if the old TT entries have been overwritten. - -void RootMove::insert_pv_in_tt(Position& pos) { - - StateInfo state[MAX_PLY], *st = state; - bool ttHit; - - for (Move m : pv) - { - assert(MoveList(pos).contains(m)); - - TTEntry* tte = TT.probe(pos.key(), ttHit); - - if (!ttHit || tte->move() != m) // Don't overwrite correct entries - tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, - m, VALUE_NONE, TT.generation()); - - pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos))); - } - - for (size_t i = pv.size(); i > 0; ) - pos.undo_move(pv[--i]); -} - - /// RootMove::extract_ponder_from_tt() is called in case we have no ponder move /// before exiting the search, for instance, in case we stop the search during a /// fail high at root. We try hard to have a ponder move to return to the GUI, @@ -1643,3 +1585,49 @@ bool RootMove::extract_ponder_from_tt(Position& pos) return false; } + +void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) { + + Hits = 0; + RootInTB = false; + UseRule50 = Options["Syzygy50MoveRule"]; + ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; + Cardinality = Options["SyzygyProbeLimit"]; + + // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality + if (Cardinality > MaxCardinality) + { + Cardinality = MaxCardinality; + ProbeDepth = DEPTH_ZERO; + } + + if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING)) + return; + + // If the current root position is in the tablebases, then RootMoves + // contains only moves that preserve the draw or the win. + RootInTB = root_probe(pos, rootMoves, TB::Score); + + if (RootInTB) + Cardinality = 0; // Do not probe tablebases during the search + + else // If DTZ tables are missing, use WDL tables as a fallback + { + // Filter out moves that do not preserve the draw or the win. + RootInTB = root_probe_wdl(pos, rootMoves, TB::Score); + + // Only probe during search if winning + if (TB::Score <= VALUE_DRAW) + Cardinality = 0; + } + + if (RootInTB) + { + Hits = rootMoves.size(); + + if (!UseRule50) + TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 + : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 + : VALUE_DRAW; + } +}