X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=cf7e411d8504e2c2cba05869d91aaccdafcd137a;hp=4738b27b2bb980fb4202b988a9c47f740caf91d5;hb=6aa9308f08bc76b0e3615dde65de7782a6761fa3;hpb=d4af15f682c1967450233ab62cba1a6c5d601df6 diff --git a/src/search.cpp b/src/search.cpp index 4738b27b..cf7e411d 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -40,7 +40,6 @@ namespace Search { SignalsType Signals; LimitsType Limits; - StateStackPtr SetupStates; } namespace Tablebases { @@ -61,22 +60,22 @@ using namespace Search; namespace { - // Different node types, used as template parameter - enum NodeType { Root, PV, NonPV }; + // Different node types, used as a template parameter + enum NodeType { NonPV, PV }; // Razoring and futility margin based on depth const int razor_margin[4] = { 483, 570, 603, 554 }; - Value futility_margin(Depth d) { return Value(200 * d); } + Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); } // Futility and reductions lookup tables, initialized at startup - int FutilityMoveCounts[2][16]; // [improving][depth] - Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] + int FutilityMoveCounts[2][16]; // [improving][depth] + int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] template Depth reduction(bool i, Depth d, int mn) { - return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)]; + return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY; } - // Skill struct is used to implement strength limiting + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} bool enabled() const { return level < 20; } @@ -88,8 +87,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager struct is used to detect a so called 'easy move'; when PV is - // stable across multiple search iterations we can fast return the best move. + // EasyMoveManager structure is used to detect an 'easy move'. When the PV is + // stable across multiple search iterations, we can quickly return the best move. struct EasyMoveManager { void clear() { @@ -106,7 +105,7 @@ namespace { assert(newPv.size() >= 3); - // Keep track of how many times in a row 3rd ply remains stable + // Keep track of how many times in a row the 3rd ply remains stable stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0; if (!std::equal(newPv.begin(), newPv.begin() + 3, pv)) @@ -114,8 +113,8 @@ namespace { std::copy(newPv.begin(), newPv.begin() + 3, pv); StateInfo st[2]; - pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0], CheckInfo(pos))); - pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1], CheckInfo(pos))); + pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0])); + pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1])); expectedPosKey = pos.key(); pos.undo_move(newPv[1]); pos.undo_move(newPv[0]); @@ -127,9 +126,38 @@ namespace { Move pv[3]; }; + // Set of rows with half bits set to 1 and half to 0. It is used to allocate + // the search depths across the threads. + typedef std::vector Row; + + const Row HalfDensity[] = { + {0, 1}, + {1, 0}, + {0, 0, 1, 1}, + {0, 1, 1, 0}, + {1, 1, 0, 0}, + {1, 0, 0, 1}, + {0, 0, 0, 1, 1, 1}, + {0, 0, 1, 1, 1, 0}, + {0, 1, 1, 1, 0, 0}, + {1, 1, 1, 0, 0, 0}, + {1, 1, 0, 0, 0, 1}, + {1, 0, 0, 0, 1, 1}, + {0, 0, 0, 0, 1, 1, 1, 1}, + {0, 0, 0, 1, 1, 1, 1, 0}, + {0, 0, 1, 1, 1, 1, 0 ,0}, + {0, 1, 1, 1, 1, 0, 0 ,0}, + {1, 1, 1, 1, 0, 0, 0 ,0}, + {1, 1, 1, 0, 0, 0, 0 ,1}, + {1, 1, 0, 0, 0, 0, 1 ,1}, + {1, 0, 0, 0, 0, 1, 1 ,1}, + }; + + const size_t HalfDensitySize = std::extent::value; + EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; - CounterMovesHistoryStats CounterMovesHistory; + CounterMoveHistoryStats CounterMoveHistory; template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); @@ -140,7 +168,8 @@ namespace { Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); - void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt); + void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus); + void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus); void check_time(); } // namespace @@ -150,22 +179,21 @@ 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)); + Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0); - // 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) + Reductions[NonPV][imp][d][mc]++; + } for (int d = 0; d < 16; ++d) { @@ -175,29 +203,31 @@ void Search::init() { } -/// Search::clear() resets to zero search state, to obtain reproducible results +/// Search::clear() resets search state to zero, to obtain reproducible results void Search::clear() { TT.clear(); - CounterMovesHistory.clear(); + CounterMoveHistory.clear(); for (Thread* th : Threads) { th->history.clear(); th->counterMoves.clear(); + th->fromTo.clear(); } + + Threads.main()->previousScore = VALUE_INFINITE; } /// Search::perft() is our utility to verify move generation. All the leaf nodes -/// up to the given depth are generated and counted and the sum returned. +/// up to the given depth are generated and counted, and the sum is returned. template uint64_t Search::perft(Position& pos, Depth depth) { StateInfo st; uint64_t cnt, nodes = 0; - CheckInfo ci(pos); const bool leaf = (depth == 2 * ONE_PLY); for (const auto& m : MoveList(pos)) @@ -206,7 +236,7 @@ uint64_t Search::perft(Position& pos, Depth depth) { cnt = 1, nodes++; else { - pos.do_move(m, st, pos.gives_check(m, ci)); + pos.do_move(m, st, pos.gives_check(m)); cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); nodes += cnt; pos.undo_move(m); @@ -221,8 +251,7 @@ template uint64_t Search::perft(Position&, Depth); /// MainThread::search() is called by the main thread when the program receives -/// the UCI 'go' command. It searches from root position and at the end prints -/// the "bestmove" to output. +/// the UCI 'go' command. It searches from the root position and outputs the "bestmove". void MainThread::search() { @@ -233,19 +262,6 @@ 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)); @@ -255,54 +271,15 @@ void MainThread::search() { } else { - if (TB::Cardinality >= rootPos.count(WHITE) - + rootPos.count(BLACK)) - { - // If the current root position is in the tablebases then RootMoves - // contains only moves that preserve the draw or 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 a draw or 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! } // When playing in 'nodes as time' mode, subtract the searched nodes from - // the available ones before to exit. + // the available ones before exiting. if (Limits.npmsec) Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); @@ -329,7 +306,9 @@ 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 @@ -337,6 +316,8 @@ void MainThread::search() { bestThread = th; } + previousScore = bestThread->rootMoves[0].score; + // Send new PV when needed if (bestThread != this) sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl; @@ -352,16 +333,16 @@ void MainThread::search() { // Thread::search() is the main iterative deepening loop. It calls search() // repeatedly with increasing depth until the allocated thinking time has been -// consumed, user stops the search, or the maximum search depth is reached. +// consumed, the user stops the search, or the maximum search depth is reached. 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; @@ -386,31 +367,18 @@ void Thread::search() { multiPV = std::min(multiPV, rootMoves.size()); - // Iterative deepening loop until requested to stop or target depth reached - while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= Limits.depth)) + // Iterative deepening loop until requested to stop or the target depth is reached + while ( (rootDepth += ONE_PLY) < DEPTH_MAX + && !Signals.stop + && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth)) { - // Set up the new depth for the helper threads skipping in average each - // 2nd ply (using a half density map similar to a Hadamard matrix). + // Set up the new depths for the helper threads skipping on average every + // 2nd ply (using a half-density matrix). if (!mainThread) { - int d = rootDepth + rootPos.game_ply(); - - if (idx <= 6 || idx > 24) - { - if (((d + idx) >> (msb(idx + 1) - 1)) % 2) - continue; - } - else - { - // Table of values of 6 bits with 3 of them set - static const int HalfDensityMap[] = { - 0x07, 0x0b, 0x0d, 0x0e, 0x13, 0x16, 0x19, 0x1a, 0x1c, - 0x23, 0x25, 0x26, 0x29, 0x2c, 0x31, 0x32, 0x34, 0x38 - }; - - if ((HalfDensityMap[idx - 7] >> (d % 6)) & 1) - continue; - } + const Row& row = HalfDensity[(idx - 1) % HalfDensitySize]; + if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()]) + continue; } // Age out PV variability metric @@ -438,7 +406,7 @@ void Thread::search() { // high/low anymore. while (true) { - bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); // Bring the best move to the front. It is critical that sorting // is done with a stable algorithm because all the values but the @@ -448,14 +416,9 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // Write PV back to 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 + // 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 previous iteration. + // valid, although it refers to the previous iteration. if (Signals.stop) break; @@ -497,7 +460,7 @@ 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() @@ -528,18 +491,22 @@ void Thread::search() { { if (!Signals.stop && !Signals.stopOnPonderhit) { - // Take some extra time if the best move has changed - if (rootDepth > 4 * ONE_PLY && multiPV == 1) - Time.pv_instability(mainThread->bestMoveChanges); - - // Stop the search if only one legal move is available or all - // of the available time has been used or we matched an easyMove + // 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 int F[] = { mainThread->failedLow, + bestValue - mainThread->previousScore }; + + 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() * 5 / 42; + if ( rootMoves.size() == 1 - || Time.elapsed() > Time.available() * (mainThread->failedLow ? 641 : 315) / 640 - || (mainThread->easyMovePlayed = ( rootMoves[0].pv[0] == easyMove - && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.available() / 8))) + || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628 + || (mainThread->easyMovePlayed = doEasyMove)) { // If we are allowed to ponder do not stop the search now but // keep pondering until the GUI sends "ponderhit" or "stop". @@ -579,12 +546,14 @@ namespace { template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { - const bool RootNode = NT == Root; - const bool PvNode = NT == PV || NT == Root; + const bool PvNode = NT == PV; + const bool rootNode = PvNode && (ss-1)->ply == 0; assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); + assert(!(PvNode && cutNode)); + assert(depth / ONE_PLY * ONE_PLY == depth); Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; @@ -592,9 +561,10 @@ 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 @@ -604,7 +574,7 @@ namespace { bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; - // Check for available remaining time + // Check for the available remaining time if (thisThread->resetCalls.load(std::memory_order_relaxed)) { thisThread->resetCalls = false; @@ -622,7 +592,7 @@ namespace { if (PvNode && thisThread->maxPly < ss->ply) thisThread->maxPly = ss->ply; - if (!RootNode) + if (!rootNode) { // Step 2. Check for aborted search and immediate draw if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) @@ -644,6 +614,7 @@ 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; @@ -654,7 +625,7 @@ namespace { posKey = excludedMove ? pos.exclusion_key() : pos.key(); tte = TT.probe(posKey, ttHit); ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - ttMove = RootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] + ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; // At non-PV nodes we check for an early TT cutoff @@ -668,20 +639,36 @@ namespace { ss->currentMove = ttMove; // Can be MOVE_NONE // If ttMove is quiet, update killers, history, counter move on TT hit - if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove)) - update_stats(pos, ss, ttMove, depth, nullptr, 0); + if (ttValue >= beta && ttMove) + { + int d = depth / ONE_PLY; + + if (!pos.capture_or_promotion(ttMove)) + { + Value bonus = Value(d * d + 2 * d - 2); + update_stats(pos, ss, ttMove, nullptr, 0, bonus); + } + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece_type()) + { + Value penalty = Value(d * d + 4 * d + 1); + Square prevSq = to_sq((ss-1)->currentMove); + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); + } + } return ttValue; } // Step 4a. Tablebase probe - if (!RootNode && TB::Cardinality) + if (!rootNode && TB::Cardinality) { int piecesCnt = pos.count(WHITE) + pos.count(BLACK); if ( piecesCnt <= TB::Cardinality && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) - && pos.rule50_count() == 0) + && pos.rule50_count() == 0 + && !pos.can_castle(ANY_CASTLING)) { int found, v = Tablebases::probe_wdl(pos, &found); @@ -738,21 +725,21 @@ namespace { // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && eval + razor_margin[depth] <= alpha + && eval + razor_margin[depth / ONE_PLY] <= alpha && ttMove == MOVE_NONE) { if ( depth <= ONE_PLY && eval + razor_margin[3 * ONE_PLY] <= alpha) return qsearch(pos, ss, alpha, beta, DEPTH_ZERO); - Value ralpha = alpha - razor_margin[depth]; + Value ralpha = alpha - razor_margin[depth / ONE_PLY]; Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); if (v <= ralpha) return v; } // Step 7. Futility pruning: child node (skipped when in check) - if ( !RootNode + if ( !rootNode && depth < 7 * ONE_PLY && eval - futility_margin(depth) >= beta && eval < VALUE_KNOWN_WIN // Do not return unproven wins @@ -761,16 +748,17 @@ namespace { // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode - && depth >= 2 * ONE_PLY && eval >= beta + && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY) && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; + ss->counterMoves = nullptr; assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value - Depth R = ((823 + 67 * depth) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; + Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; pos.do_null_move(st); (ss+1)->skipEarlyPruning = true; @@ -800,9 +788,8 @@ namespace { } // Step 9. ProbCut (skipped when in check) - // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type]) - // and a reduced search returns a value much above beta, we can (almost) - // safely prune the previous move. + // If we have a good enough capture and a reduced search returns a value + // much above beta, we can (almost) safely prune the previous move. if ( !PvNode && depth >= 5 * ONE_PLY && abs(beta) < VALUE_MATE_IN_MAX_PLY) @@ -814,14 +801,14 @@ 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()]); - CheckInfo ci(pos); + MovePicker mp(pos, ttMove, rbeta - ss->staticEval); while ((move = mp.next_move()) != MOVE_NONE) - if (pos.legal(move, ci.pinned)) + if (pos.legal(move)) { ss->currentMove = move; - pos.do_move(move, st, pos.gives_check(move, ci)); + ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)]; + pos.do_move(move, st, pos.gives_check(move)); value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); pos.undo_move(move); if (value >= rbeta) @@ -830,13 +817,13 @@ namespace { } // Step 10. Internal iterative deepening (skipped when in check) - if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) + if ( depth >= 6 * ONE_PLY && !ttMove && (PvNode || ss->staticEval + 256 >= beta)) { - Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); + Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY; 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); @@ -845,18 +832,17 @@ 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 CounterMovesStats& cmh = CounterMovesHistory[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); - CheckInfo ci(pos); + MovePicker mp(pos, ttMove, depth, ss); 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 + singularExtensionNode = !rootNode && depth >= 8 * ONE_PLY && ttMove != MOVE_NONE /* && ttValue != VALUE_NONE Already implicit in the next condition */ @@ -877,13 +863,13 @@ moves_loop: // When in check search starts from here // At root obey the "searchmoves" option and skip moves not listed in Root // Move List. As a consequence any illegal move is also skipped. In MultiPV // mode we also skip PV moves which have been already searched. - if (RootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, + if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, thisThread->rootMoves.end(), move)) continue; ss->moveCount = ++moveCount; - if (RootNode && thisThread == Threads.main() && Time.elapsed() > 3000) + if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000) sync_cout << "info depth " << depth / ONE_PLY << " currmove " << UCI::move(move, pos.is_chess960()) << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl; @@ -893,13 +879,19 @@ 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); + givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates() + ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move) + : pos.gives_check(move); + + moveCountPruning = depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY]; // 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 @@ -910,12 +902,13 @@ moves_loop: // When in check search starts from here if ( singularExtensionNode && move == ttMove && !extension - && pos.legal(move, ci.pinned)) + && pos.legal(move)) { Value rBeta = ttValue - 2 * depth / ONE_PLY; + Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY; ss->excludedMove = move; ss->skipEarlyPruning = true; - value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); + value = search(pos, ss, rBeta - 1, rBeta, d, cutNode); ss->skipEarlyPruning = false; ss->excludedMove = MOVE_NONE; @@ -927,7 +920,7 @@ moves_loop: // When in check search starts from here newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth - if ( !RootNode + if ( !rootNode && !captureOrPromotion && !inCheck && !givesCheck @@ -935,47 +928,48 @@ 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 - if ( depth <= 4 * ONE_PLY + predictedDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO); + + // Countermoves based pruning + if ( predictedDepth < 3 * 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); - // Futility pruning: parent node - if (predictedDepth < 7 * ONE_PLY) + if ( predictedDepth < 7 * ONE_PLY + && ss->staticEval + 256 + 200 * predictedDepth / ONE_PLY <= alpha) + continue; + + // Prune moves with negative SEE at low depths and below a decreasing + // threshold at higher depths. + if (predictedDepth < 8 * ONE_PLY) { - futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256; + Value see_v = predictedDepth < 4 * ONE_PLY ? VALUE_ZERO + : -PawnValueMg * 2 * int(predictedDepth - 3 * ONE_PLY) / ONE_PLY; - if (futilityValue <= alpha) - { - bestValue = std::max(bestValue, futilityValue); + if (pos.see_sign(move) < see_v) continue; - } } - - // Prune moves with negative SEE at low depths - if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO) - continue; } // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); // Check for legality just before making the move - if (!RootNode && !pos.legal(move, ci.pinned)) + if (!rootNode && !pos.legal(move)) { ss->moveCount = --moveCount; continue; } ss->currentMove = move; + ss->counterMoves = &CounterMoveHistory[moved_piece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -984,38 +978,47 @@ moves_loop: // When in check search starts from here // re-searched at full depth. if ( depth >= 3 * ONE_PLY && moveCount > 1 - && !captureOrPromotion) + && (!captureOrPromotion || moveCountPruning)) { Depth r = reduction(improving, depth, moveCount); - // 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 reduction for moves with a good history - if ( 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 = std::max(DEPTH_ZERO, r - ONE_PLY); - - // Decrease reduction for moves that escape a capture - 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); + if (captureOrPromotion) + r -= r ? ONE_PLY : DEPTH_ZERO; + else + { + // 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. + 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 + 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) + + thisThread->fromTo.get(~pos.side_to_move(), move); + int rHist = (val - 8000) / 20000; + r = std::max(DEPTH_ZERO, (r / ONE_PLY - rHist) * ONE_PLY); + } Depth d = std::max(newDepth - r, ONE_PLY); value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); - doFullDepthSearch = (value > alpha && r != DEPTH_ZERO); + doFullDepthSearch = (value > alpha && d != newDepth); } else doFullDepthSearch = !PvNode || moveCount > 1; - // Step 16. Full depth search, when LMR is skipped or fails high + // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) value = newDepth < ONE_PLY ? givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) @@ -1024,8 +1027,8 @@ moves_loop: // When in check search starts from here // For PV nodes only, do a full PV search on the first move or after a fail // high (in the latter case search only if value < beta), otherwise let the - // parent node fail low with value <= alpha and to try another move. - if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta)))) + // parent node fail low with value <= alpha and try another move. + if (PvNode && (moveCount == 1 || (value > alpha && (rootNode || value < beta)))) { (ss+1)->pv = pv; (ss+1)->pv[0] = MOVE_NONE; @@ -1041,14 +1044,14 @@ moves_loop: // When in check search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 18. Check for new best move + // Step 18. Check for a new best move // Finished searching the move. If a stop occurred, the return value of // the search cannot be trusted, and we return immediately without // updating best move, PV and TT. if (Signals.stop.load(std::memory_order_relaxed)) return VALUE_ZERO; - if (RootNode) + if (rootNode) { RootMove& rm = *std::find(thisThread->rootMoves.begin(), thisThread->rootMoves.end(), move); @@ -1092,7 +1095,7 @@ moves_loop: // When in check search starts from here bestMove = move; - if (PvNode && !RootNode) // Update pv even in fail-high case + if (PvNode && !rootNode) // Update pv even in fail-high case update_pv(ss->pv, move, (ss+1)->pv); if (PvNode && value < beta) // Update alpha! Always alpha < beta @@ -1109,7 +1112,7 @@ moves_loop: // When in check search starts from here quietsSearched[quietCount++] = move; } - // Following condition would detect a stop only after move loop has been + // The following condition would detect a stop only after move loop has been // completed. But in this case bestValue is valid because we have fully // searched our subtree, and we can anyhow save the result in TT. /* @@ -1119,28 +1122,39 @@ moves_loop: // When in check search starts from here // Step 20. Check for mate and stalemate // All legal moves have been searched and if there are no legal moves, it - // must be mate or stalemate. If we are in a singular extension search then + // must be a mate or a stalemate. If we are in a singular extension search then // return a fail low score. if (!moveCount) bestValue = excludedMove ? alpha : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; + else if (bestMove) + { + int d = depth / ONE_PLY; - // Quiet best move: update killers, history and countermoves - else if (bestMove && !pos.capture_or_promotion(bestMove)) - update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount); + // Quiet best move: update killers, history and countermoves + if (!pos.capture_or_promotion(bestMove)) + { + Value bonus = Value(d * d + 2 * d - 2); + update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus); + } + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece_type()) + { + Value penalty = Value(d * d + 4 * d + 1); + Square prevSq = to_sq((ss-1)->currentMove); + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); + } + } // 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); - CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; - prevCmh.update(pos.piece_on(prevSq), prevSq, bonus); + int d = depth / ONE_PLY; + Value bonus = Value(d * d + 2 * d - 2); + Square prevSq = to_sq((ss-1)->currentMove); + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus); } tte->save(posKey, value_to_tt(bestValue, ss->ply), @@ -1163,11 +1177,11 @@ moves_loop: // When in check search starts from here 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); + assert(depth / ONE_PLY * ONE_PLY == depth); Move pv[MAX_PLY+1]; StateInfo st; @@ -1262,17 +1276,16 @@ 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)); - CheckInfo ci(pos); + MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove)); // Loop through the moves until no moves remain or a beta cutoff occurs while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(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); + givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates() + ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move) + : pos.gives_check(move); // Futility pruning if ( !InCheck @@ -1312,7 +1325,7 @@ moves_loop: // When in check search starts from here prefetch(TT.first_entry(pos.key_after(move))); // Check for legality just before making the move - if (!pos.legal(move, ci.pinned)) + if (!pos.legal(move)) continue; ss->currentMove = move; @@ -1325,7 +1338,7 @@ moves_loop: // When in check search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Check for new best move + // Check for a new best move if (value > bestValue) { bestValue = value; @@ -1401,11 +1414,30 @@ 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_cm_stats() updates countermove and follow-up move history + + void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) { + + CounterMoveStats* cmh = (ss-1)->counterMoves; + CounterMoveStats* fmh1 = (ss-2)->counterMoves; + CounterMoveStats* fmh2 = (ss-4)->counterMoves; + + if (cmh) + cmh->update(pc, s, bonus); + + if (fmh1) + fmh1->update(pc, s, bonus); + + if (fmh2) + fmh2->update(pc, s, bonus); + } + + + // 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) { + Move* quiets, int quietsCnt, Value bonus) { if (ss->killers[0] != move) { @@ -1413,37 +1445,24 @@ 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); - - Square prevSq = to_sq((ss-1)->currentMove); - CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq]; + Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - + thisThread->fromTo.update(c, move, bonus); thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); + update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); - if (is_ok((ss-1)->currentMove)) + if ((ss-1)->counterMoves) { + Square prevSq = to_sq((ss-1)->currentMove); thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); - cmh.update(pos.moved_piece(move), to_sq(move), bonus); } // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { + thisThread->fromTo.update(c, quiets[i], -bonus); 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); - } - - // 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)) - { - Square prevPrevSq = to_sq((ss-2)->currentMove); - CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; - prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); + update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } } @@ -1453,7 +1472,7 @@ 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 @@ -1463,8 +1482,8 @@ moves_loop: // When in check search starts from here int maxScore = -VALUE_INFINITE; // Choose best move. For each move score we add two terms, both dependent on - // weakness. One deterministic and bigger for weaker levels, and one random, - // then we choose the move with the resulting highest score. + // weakness. One is deterministic and bigger for weaker levels, and one is + // random. Then we choose the move with the resulting highest score. for (size_t i = 0; i < multiPV; ++i) { // This is our magic formula @@ -1518,7 +1537,7 @@ 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(); @@ -1566,35 +1585,8 @@ 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 +/// 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, /// otherwise in case of 'ponder on' we have nothing to think on. @@ -1605,16 +1597,62 @@ bool RootMove::extract_ponder_from_tt(Position& pos) assert(pv.size() == 1); - pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos))); + pos.do_move(pv[0], st, pos.gives_check(pv[0])); TTEntry* tte = TT.probe(pos.key(), ttHit); - pos.undo_move(pv[0]); if (ttHit) { Move m = tte->move(); // Local copy to be SMP safe if (MoveList(pos).contains(m)) - return pv.push_back(m), true; + pv.push_back(m); } - return false; + pos.undo_move(pv[0]); + return pv.size() > 1; +} + +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; + } }