X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=ed8d9ff76d19a6327b4093ca6ef4457dedfd301e;hp=ffe361268e6b0a113468e15b4ac18b758e32c977;hb=1b5b900a290631f04e4c8683e68eb9a9ba682196;hpb=f8f5dcbb682830a66a37f68f3c192bbbfc84a33a diff --git a/src/search.cpp b/src/search.cpp index ffe36126..ed8d9ff7 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -37,11 +37,8 @@ namespace Search { - volatile SignalsType Signals; + SignalsType Signals; LimitsType Limits; - RootMoveVector RootMoves; - Position RootPos; - Time::point SearchTime; StateStackPtr SetupStates; } @@ -66,62 +63,84 @@ namespace { // Different node types, used as template parameter enum NodeType { Root, PV, NonPV }; - // Dynamic razoring margin based on depth - inline Value razor_margin(Depth d) { return Value(512 + 32 * d); } + // 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); } - // Futility lookup tables (initialized at startup) and their access functions - int FutilityMoveCounts[2][16]; // [improving][depth] + // Futility and reductions lookup tables, initialized at startup + int FutilityMoveCounts[2][16]; // [improving][depth] + Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] - inline Value futility_margin(Depth d) { - return Value(200 * d); + template Depth reduction(bool i, Depth d, int mn) { + return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)]; } - // Reduction lookup tables (initialized at startup) and their access function - int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] + // Skill struct is used to implement strength limiting + struct Skill { + Skill(int l) : level(l) {} + bool enabled() const { return level < 20; } + bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; } + Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); } + Move pick_best(size_t multiPV); - template inline Depth reduction(bool i, Depth d, int mn) { - return (Depth) Reductions[PvNode][i][std::min(int(d), 63)][std::min(mn, 63)]; - } + int level; + 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. + struct EasyMoveManager { + + void clear() { + stableCnt = 0; + expectedPosKey = 0; + pv[0] = pv[1] = pv[2] = MOVE_NONE; + } + + Move get(Key key) const { + return expectedPosKey == key ? pv[2] : MOVE_NONE; + } + + void update(Position& pos, const std::vector& newPv) { + + assert(newPv.size() >= 3); + + // Keep track of how many times in a row 3rd ply remains stable + stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0; + + if (!std::equal(newPv.begin(), newPv.begin() + 3, pv)) + { + 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))); + expectedPosKey = pos.key(); + pos.undo_move(newPv[1]); + pos.undo_move(newPv[0]); + } + } + + int stableCnt; + Key expectedPosKey; + Move pv[3]; + }; - size_t PVIdx; - TimeManager TimeMgr; - double BestMoveChanges; + EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; - HistoryStats History; - GainsStats Gains; - MovesStats Countermoves, Followupmoves; + CounterMovesHistoryStats CounterMovesHistory; - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - void id_loop(Position& pos); 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); - string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta); - - struct Skill { - Skill(int l, size_t rootSize) : level(l), - candidates(l < 20 ? std::min(4, (int)rootSize) : 0), - best(MOVE_NONE) {} - ~Skill() { - if (candidates) // Swap best PV line with the sub-optimal one - std::swap(RootMoves[0], *std::find(RootMoves.begin(), - RootMoves.end(), best ? best : pick_move())); - } - - size_t candidates_size() const { return candidates; } - bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; } - Move pick_move(); - - int level; - size_t candidates; - Move best; - }; + void check_time(); } // namespace @@ -130,25 +149,23 @@ namespace { void Search::init() { - // Init reductions array - for (int d = 1; d < 64; ++d) - for (int mc = 1; mc < 64; ++mc) - { - double pvRed = 0.00 + log(double(d)) * log(double(mc)) / 3.00; - double nonPVRed = 0.33 + log(double(d)) * log(double(mc)) / 2.25; + const double K[][2] = {{ 0.799, 2.281 }, { 0.484, 3.023 }}; - Reductions[1][1][d][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0); - Reductions[0][1][d][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0); + 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]; - Reductions[1][0][d][mc] = Reductions[1][1][d][mc]; - Reductions[0][0][d][mc] = Reductions[0][1][d][mc]; + if (r >= 1.5) + Reductions[pv][imp][d][mc] = int(r) * ONE_PLY; - // Increase reduction when eval is not improving - if (Reductions[0][0][d][mc] >= 2) - Reductions[0][0][d][mc] += 1; - } + // 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; + } - // Init futility move count array for (int d = 0; d < 16; ++d) { FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8)); @@ -157,6 +174,21 @@ void Search::init() { } +/// Search::clear() resets to zero search state, to obtain reproducible results + +void Search::clear() { + + TT.clear(); + CounterMovesHistory.clear(); + + for (Thread* th : Threads) + { + th->history.clear(); + th->counterMoves.clear(); + } +} + + /// 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. template @@ -167,37 +199,38 @@ uint64_t Search::perft(Position& pos, Depth depth) { CheckInfo ci(pos); const bool leaf = (depth == 2 * ONE_PLY); - for (MoveList it(pos); *it; ++it) + for (const auto& m : MoveList(pos)) { if (Root && depth <= ONE_PLY) cnt = 1, nodes++; else { - pos.do_move(*it, st, pos.gives_check(*it, ci)); + pos.do_move(m, st, pos.gives_check(m, ci)); cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); nodes += cnt; - pos.undo_move(*it); + pos.undo_move(m); } if (Root) - sync_cout << UCI::move(*it, pos.is_chess960()) << ": " << cnt << sync_endl; + sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl; } return nodes; } -template uint64_t Search::perft(Position& pos, Depth depth); +template uint64_t Search::perft(Position&, Depth); -/// Search::think() is the external interface to Stockfish's search, and is -/// called by the main thread when the program receives the UCI 'go' command. It -/// searches from RootPos and at the end prints the "bestmove" to output. +/// 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. -void Search::think() { +void MainThread::search() { - TimeMgr.init(Limits, RootPos.side_to_move(), RootPos.game_ply()); + Color us = rootPos.side_to_move(); + Time.init(Limits, us, rootPos.game_ply()); int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns - DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(contempt); - DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(contempt); + DrawValue[ us] = VALUE_DRAW - Value(contempt); + DrawValue[~us] = VALUE_DRAW + Value(contempt); TB::Hits = 0; TB::RootInTB = false; @@ -212,21 +245,21 @@ void Search::think() { TB::ProbeDepth = DEPTH_ZERO; } - if (RootMoves.empty()) + if (rootMoves.empty()) { - RootMoves.push_back(MOVE_NONE); + rootMoves.push_back(RootMove(MOVE_NONE)); sync_cout << "info depth 0 score " - << UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << UCI::value(rootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; } else { - if (TB::Cardinality >= RootPos.count(WHITE) - + RootPos.count(BLACK)) + 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); + TB::RootInTB = Tablebases::root_probe(rootPos, rootMoves, TB::Score); if (TB::RootInTB) TB::Cardinality = 0; // Do not probe tablebases during the search @@ -234,7 +267,7 @@ void Search::think() { 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); + TB::RootInTB = Tablebases::root_probe_wdl(rootPos, rootMoves, TB::Score); // Only probe during search if winning if (TB::Score <= VALUE_DRAW) @@ -243,7 +276,7 @@ void Search::think() { if (TB::RootInTB) { - TB::Hits = RootMoves.size(); + TB::Hits = rootMoves.size(); if (!TB::UseRule50) TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 @@ -252,17 +285,26 @@ void Search::think() { } } - for (size_t i = 0; i < Threads.size(); ++i) - Threads[i]->maxPly = 0; - - Threads.timer->run = true; - Threads.timer->notify_one(); // Wake up the recurring timer - - id_loop(RootPos); // Let's start searching ! + 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(); + } + } - Threads.timer->run = false; + Thread::search(); // Let's start searching! } + // When playing in 'nodes as time' mode, subtract the searched nodes from + // the available ones before to exit. + if (Limits.npmsec) + Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); + // When we reach the maximum depth, we can arrive here without a raise of // Signals.stop. However, if we are pondering or in an infinite search, // the UCI protocol states that we shouldn't print the best move before the @@ -271,182 +313,269 @@ void Search::think() { if (!Signals.stop && (Limits.ponder || Limits.infinite)) { Signals.stopOnPonderhit = true; - RootPos.this_thread()->wait_for(Signals.stop); + wait(Signals.stop); } - sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960()); + // Stop the threads if not already stopped + Signals.stop = true; + + // Wait until all threads have finished + for (Thread* th : Threads) + if (th != this) + th->wait_for_search_finished(); + + // Check if there are threads with a better score than main thread + Thread* bestThread = this; + if ( !this->easyMovePlayed + && Options["MultiPV"] == 1 + && !Skill(Options["Skill Level"]).enabled()) + { + for (Thread* th : Threads) + if ( th->completedDepth > bestThread->completedDepth + && th->rootMoves[0].score > bestThread->rootMoves[0].score) + bestThread = th; + } - if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos)) - std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960()); + // Send new PV when needed + if (bestThread != this) + sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl; + + sync_cout << "bestmove " << UCI::move(bestThread->rootMoves[0].pv[0], rootPos.is_chess960()); + + if (bestThread->rootMoves[0].pv.size() > 1 || bestThread->rootMoves[0].extract_ponder_from_tt(rootPos)) + std::cout << " ponder " << UCI::move(bestThread->rootMoves[0].pv[1], rootPos.is_chess960()); std::cout << sync_endl; } -namespace { +// 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. - // id_loop() 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. +void Thread::search() { - void id_loop(Position& pos) { + Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) + Value bestValue, alpha, beta, delta; + Move easyMove = MOVE_NONE; + MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) - Depth depth; - Value bestValue, alpha, beta, delta; + std::memset(ss-2, 0, 5 * sizeof(Stack)); - std::memset(ss-2, 0, 5 * sizeof(Stack)); + bestValue = delta = alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; + completedDepth = DEPTH_ZERO; - depth = DEPTH_ZERO; - BestMoveChanges = 0; - bestValue = delta = alpha = -VALUE_INFINITE; - beta = VALUE_INFINITE; + if (mainThread) + { + easyMove = EasyMove.get(rootPos.key()); + EasyMove.clear(); + mainThread->easyMovePlayed = mainThread->failedLow = false; + mainThread->bestMoveChanges = 0; + TT.new_search(); + } - TT.new_search(); - History.clear(); - Gains.clear(); - Countermoves.clear(); - Followupmoves.clear(); + size_t multiPV = Options["MultiPV"]; + Skill skill(Options["Skill Level"]); - size_t multiPV = Options["MultiPV"]; - Skill skill(Options["Skill Level"], RootMoves.size()); + // When playing with strength handicap enable MultiPV search that we will + // use behind the scenes to retrieve a set of possible moves. + if (skill.enabled()) + multiPV = std::max(multiPV, (size_t)4); - // Do we have to play with skill handicap? In this case enable MultiPV search - // that we will use behind the scenes to retrieve a set of possible moves. - multiPV = std::max(multiPV, skill.candidates_size()); + multiPV = std::min(multiPV, rootMoves.size()); - // Iterative deepening loop until requested to stop or target depth reached - while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) - { - // Age out PV variability metric - BestMoveChanges *= 0.5; + // Iterative deepening loop until requested to stop or target depth reached + while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= 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). + if (!mainThread) + { + int d = rootDepth + rootPos.game_ply(); - // Save the last iteration's scores before first PV line is searched and - // all the move scores except the (new) PV are set to -VALUE_INFINITE. - for (size_t i = 0; i < RootMoves.size(); ++i) - RootMoves[i].previousScore = RootMoves[i].score; + 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 + }; - // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx) - { - // Reset aspiration window starting size - if (depth >= 5 * ONE_PLY) - { - delta = Value(16); - alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); - beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); - } + if ((HalfDensityMap[idx - 7] >> (d % 6)) & 1) + continue; + } + } - // Start with a small aspiration window and, in the case of a fail - // high/low, re-search with a bigger window until we're not failing - // high/low anymore. - while (true) - { - bestValue = search(pos, ss, alpha, beta, depth, 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 - // first and eventually the new best one are set to -VALUE_INFINITE - // and we want to keep the same order for all the moves except the - // new PV that goes to the front. Note that in case of MultiPV - // 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(pos); - - // 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. - if (Signals.stop) - break; - - // When failing high/low give some update (without cluttering - // the UI) before a re-search. - if ( multiPV == 1 - && (bestValue <= alpha || bestValue >= beta) - && Time::now() - SearchTime > 3000) - sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; - - // In case of failing low/high increase aspiration window and - // re-search, otherwise exit the loop. - if (bestValue <= alpha) - { - beta = (alpha + beta) / 2; - alpha = std::max(bestValue - delta, -VALUE_INFINITE); - - Signals.failedLowAtRoot = true; - Signals.stopOnPonderhit = false; - } - else if (bestValue >= beta) - { - alpha = (alpha + beta) / 2; - beta = std::min(bestValue + delta, VALUE_INFINITE); - } - else - break; - - delta += delta / 2; - - assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); - } + // Age out PV variability metric + if (mainThread) + mainThread->bestMoveChanges *= 0.505, mainThread->failedLow = false; - // Sort the PV lines searched so far and update the GUI - std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); + // Save the last iteration's scores before first PV line is searched and + // all the move scores except the (new) PV are set to -VALUE_INFINITE. + for (RootMove& rm : rootMoves) + rm.previousScore = rm.score; - if (Signals.stop) - sync_cout << "info nodes " << RootPos.nodes_searched() - << " time " << Time::now() - SearchTime << sync_endl; + // MultiPV loop. We perform a full root search for each PV line + for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx) + { + // Reset aspiration window starting size + if (rootDepth >= 5 * ONE_PLY) + { + delta = Value(18); + alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); + beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); + } - else if ( PVIdx + 1 == std::min(multiPV, RootMoves.size()) - || Time::now() - SearchTime > 3000) - sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; - } + // Start with a small aspiration window and, in the case of a fail + // high/low, re-search with a bigger window until we're not failing + // high/low anymore. + while (true) + { + 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 + // first and eventually the new best one are set to -VALUE_INFINITE + // and we want to keep the same order for all the moves except the + // new PV that goes to the front. Note that in case of MultiPV + // 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 + // writing PV back to TT is safe because RootMoves is still + // valid, although it refers to previous iteration. + if (Signals.stop) + break; - // If skill levels are enabled and time is up, pick a sub-optimal best move - if (skill.candidates_size() && skill.time_to_pick(depth)) - skill.pick_move(); + // When failing high/low give some update (without cluttering + // the UI) before a re-search. + if ( mainThread + && multiPV == 1 + && (bestValue <= alpha || bestValue >= beta) + && Time.elapsed() > 3000) + sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; + + // In case of failing low/high increase aspiration window and + // re-search, otherwise exit the loop. + if (bestValue <= alpha) + { + beta = (alpha + beta) / 2; + alpha = std::max(bestValue - delta, -VALUE_INFINITE); - // Have we found a "mate in x"? - if ( Limits.mate - && bestValue >= VALUE_MATE_IN_MAX_PLY - && VALUE_MATE - bestValue <= 2 * Limits.mate) - Signals.stop = true; + if (mainThread) + { + mainThread->failedLow = true; + Signals.stopOnPonderhit = false; + } + } + else if (bestValue >= beta) + { + alpha = (alpha + beta) / 2; + beta = std::min(bestValue + delta, VALUE_INFINITE); + } + else + break; - // Do we have time for the next iteration? Can we stop searching now? - if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit) - { - // Take some extra time if the best move has changed - if (depth > 4 * ONE_PLY && multiPV == 1) - TimeMgr.pv_instability(BestMoveChanges); - - // Stop the search if only one legal move is available or all - // of the available time has been used. - if ( RootMoves.size() == 1 - || Time::now() - SearchTime > TimeMgr.available_time()) - { - // If we are allowed to ponder do not stop the search now but - // keep pondering until the GUI sends "ponderhit" or "stop". - if (Limits.ponder) - Signals.stopOnPonderhit = true; - else - Signals.stop = true; - } - } - } + delta += delta / 4 + 5; + + assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); + } + + // Sort the PV lines searched so far and update the GUI + std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1); + + if (!mainThread) + break; + + if (Signals.stop) + sync_cout << "info nodes " << Threads.nodes_searched() + << " time " << Time.elapsed() << sync_endl; + + else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000) + sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; + } + + if (!Signals.stop) + completedDepth = rootDepth; + + if (!mainThread) + continue; + + // If skill level is enabled and time is up, pick a sub-optimal best move + if (skill.enabled() && skill.time_to_pick(rootDepth)) + skill.pick_best(multiPV); + + // Have we found a "mate in x"? + if ( Limits.mate + && bestValue >= VALUE_MATE_IN_MAX_PLY + && VALUE_MATE - bestValue <= 2 * Limits.mate) + Signals.stop = true; + + // Do we have time for the next iteration? Can we stop searching now? + if (Limits.use_time_management()) + { + 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 + // from the previous search and just did a fast verification. + 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))) + { + // If we are allowed to ponder do not stop the search now but + // keep pondering until the GUI sends "ponderhit" or "stop". + if (Limits.ponder) + Signals.stopOnPonderhit = true; + else + Signals.stop = true; + } + } + + if (rootMoves[0].pv.size() >= 3) + EasyMove.update(rootPos, rootMoves[0].pv); + else + EasyMove.clear(); + } } + if (!mainThread) + return; + + // Clear any candidate easy move that wasn't stable for the last search + // iterations; the second condition prevents consecutive fast moves. + if (EasyMove.stableCnt < 6 || mainThread->easyMovePlayed) + EasyMove.clear(); - // search<>() is the main search function for both PV and non-PV nodes and for - // normal and SplitPoint nodes. When called just after a split point the search - // is simpler because we have already probed the hash table, done a null move - // search, and searched the first move before splitting, so we don't have to - // repeat all this work again. We also don't need to store anything to the hash - // table here: This is taken care of after we return from the split point. + // If skill level is enabled, swap best PV line with the sub-optimal one + if (skill.enabled()) + std::swap(rootMoves[0], *std::find(rootMoves.begin(), + rootMoves.end(), skill.best_move(multiPV))); +} + + +namespace { + + // search<>() is the main search function for both PV and non-PV nodes - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { const bool RootNode = NT == Root; @@ -454,42 +583,39 @@ namespace { assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); - assert(depth > DEPTH_ZERO); + assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; TTEntry* tte; - SplitPoint* splitPoint; Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth, predictedDepth; Value bestValue, value, ttValue, eval, nullValue, futilityValue; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, dangerous, doFullDepthSearch; + bool captureOrPromotion, doFullDepthSearch; int moveCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); + moveCount = quietCount = ss->moveCount = 0; + bestValue = -VALUE_INFINITE; + ss->ply = (ss-1)->ply + 1; - if (SpNode) + // Check for available remaining time + if (thisThread->resetCalls.load(std::memory_order_relaxed)) { - splitPoint = ss->splitPoint; - bestMove = splitPoint->bestMove; - bestValue = splitPoint->bestValue; - tte = NULL; - ttHit = false; - ttMove = excludedMove = MOVE_NONE; - ttValue = VALUE_NONE; - - assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0); - - goto moves_loop; + thisThread->resetCalls = false; + thisThread->callsCnt = 0; } + if (++thisThread->callsCnt > 4096) + { + for (Thread* th : Threads) + th->resetCalls = true; - moveCount = quietCount = 0; - bestValue = -VALUE_INFINITE; - ss->ply = (ss-1)->ply + 1; + check_time(); + } // Used to send selDepth info to GUI if (PvNode && thisThread->maxPly < ss->ply) @@ -498,8 +624,9 @@ namespace { if (!RootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop || pos.is_draw() || ss->ply >= MAX_PLY) - return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; + if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) + return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) + : DrawValue[pos.side_to_move()]; // Step 3. Mate distance pruning. Even if we mate at the next move our score // would be at best mate_in(ss->ply+1), but if alpha is already bigger because @@ -515,32 +642,33 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); - ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - (ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO; + ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + (ss+1)->skipEarlyPruning = false; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; - // Step 4. Transposition table lookup - // We don't want the score of a partial search to overwrite a previous full search - // TT value, so we use a different position key in case of an excluded move. + // Step 4. Transposition table lookup. We don't want the score of a partial + // search to overwrite a previous full search TT value, so we use a different + // position key in case of an excluded move. excludedMove = ss->excludedMove; posKey = excludedMove ? pos.exclusion_key() : pos.key(); tte = TT.probe(posKey, ttHit); - ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; + ttMove = RootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] + : ttHit ? tte->move() : MOVE_NONE; - // At non-PV nodes we check for a fail high/low. We don't probe at PV nodes + // At non-PV nodes we check for an early TT cutoff if ( !PvNode && ttHit && tte->depth() >= depth - && ttValue != VALUE_NONE // Only in case of TT access race + && ttValue != VALUE_NONE // Possible in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) { ss->currentMove = ttMove; // Can be MOVE_NONE - // If ttMove is quiet, update killers, history, counter move and followup move on TT hit - if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove) && !inCheck) - update_stats(pos, ss, ttMove, depth, NULL, 0); + // 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); return ttValue; } @@ -575,7 +703,7 @@ namespace { } } - // Step 5. Evaluate the position statically and update parent's gain statistics + // Step 5. Evaluate the position statically if (inCheck) { ss->staticEval = eval = VALUE_NONE; @@ -596,37 +724,27 @@ namespace { else { eval = ss->staticEval = - (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo; + (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) + : -(ss-1)->staticEval + 2 * Eval::Tempo; - tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation()); + tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, + ss->staticEval, TT.generation()); } if (ss->skipEarlyPruning) goto moves_loop; - if ( !pos.captured_piece_type() - && ss->staticEval != VALUE_NONE - && (ss-1)->staticEval != VALUE_NONE - && (move = (ss-1)->currentMove) != MOVE_NULL - && move != MOVE_NONE - && type_of(move) == NORMAL) - { - Square to = to_sq(move); - Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval); - } - // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && eval + razor_margin(depth) <= alpha - && ttMove == MOVE_NONE - && !pos.pawn_on_7th(pos.side_to_move())) + && eval + razor_margin[depth] <= alpha + && ttMove == MOVE_NONE) { if ( depth <= ONE_PLY - && eval + razor_margin(3 * ONE_PLY) <= alpha) + && 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]; Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); if (v <= ralpha) return v; @@ -656,7 +774,7 @@ namespace { pos.do_null_move(st); (ss+1)->skipEarlyPruning = true; nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); (ss+1)->skipEarlyPruning = false; pos.undo_null_move(); @@ -672,7 +790,7 @@ namespace { // Do verification search at high depths ss->skipEarlyPruning = true; Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta, DEPTH_ZERO) - : search(pos, ss, beta-1, beta, depth-R, false); + : search(pos, ss, beta-1, beta, depth-R, false); ss->skipEarlyPruning = false; if (v >= beta) @@ -682,8 +800,8 @@ 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. + // 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) @@ -695,15 +813,15 @@ namespace { assert((ss-1)->currentMove != MOVE_NONE); assert((ss-1)->currentMove != MOVE_NULL); - MovePicker mp(pos, ttMove, History, pos.captured_piece_type()); + MovePicker mp(pos, ttMove, thisThread->history, PieceValue[MG][pos.captured_piece_type()]); CheckInfo ci(pos); - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) if (pos.legal(move, ci.pinned)) { ss->currentMove = move; pos.do_move(move, st, pos.gives_check(move, ci)); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); pos.undo_move(move); if (value >= rbeta) return value; @@ -715,26 +833,22 @@ namespace { && !ttMove && (PvNode || ss->staticEval + 256 >= beta)) { - Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2); + Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d / 2, true); + search(pos, ss, alpha, beta, d, true); ss->skipEarlyPruning = false; tte = TT.probe(posKey, ttHit); ttMove = ttHit ? tte->move() : MOVE_NONE; } -moves_loop: // When in check and at SpNode search starts from here +moves_loop: // When in check search starts from here - Square prevMoveSq = to_sq((ss-1)->currentMove); - Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first, - Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second }; + 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]; - Square prevOwnMoveSq = to_sq((ss-2)->currentMove); - Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first, - Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second }; - - MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss); + MovePicker mp(pos, ttMove, depth, thisThread->history, cmh, cm, ss); CheckInfo ci(pos); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc improving = ss->staticEval >= (ss-2)->staticEval @@ -742,7 +856,6 @@ moves_loop: // When in check and at SpNode search starts from here ||(ss-2)->staticEval == VALUE_NONE; singularExtensionNode = !RootNode - && !SpNode && depth >= 8 * ONE_PLY && ttMove != MOVE_NONE /* && ttValue != VALUE_NONE Already implicit in the next condition */ @@ -753,7 +866,7 @@ moves_loop: // When in check and at SpNode search starts from here // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); @@ -763,45 +876,27 @@ moves_loop: // When in check and at SpNode 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(RootMoves.begin() + PVIdx, RootMoves.end(), move)) + if (RootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, + thisThread->rootMoves.end(), move)) continue; - if (SpNode) - { - // Shared counter cannot be decremented later if the move turns out to be illegal - if (!pos.legal(move, ci.pinned)) - continue; - - moveCount = ++splitPoint->moveCount; - splitPoint->mutex.unlock(); - } - else - ++moveCount; + ss->moveCount = ++moveCount; - if (RootNode) - { - Signals.firstRootMove = (moveCount == 1); - - if (thisThread == Threads.main() && Time::now() - SearchTime > 3000) - sync_cout << "info depth " << depth / ONE_PLY - << " currmove " << UCI::move(move, pos.is_chess960()) - << " currmovenumber " << moveCount + PVIdx << sync_endl; - } + 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; if (PvNode) - (ss+1)->pv = NULL; + (ss+1)->pv = nullptr; extension = DEPTH_ZERO; captureOrPromotion = pos.capture_or_promotion(move); givesCheck = type_of(move) == NORMAL && !ci.dcCandidates - ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) + ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) : pos.gives_check(move, ci); - dangerous = givesCheck - || type_of(move) != NORMAL - || pos.advanced_pawn_push(move); - // Step 12. Extend checks if (givesCheck && pos.see_sign(move) >= VALUE_ZERO) extension = ONE_PLY; @@ -819,7 +914,7 @@ moves_loop: // When in check and at SpNode search starts from here Value rBeta = ttValue - 2 * depth / 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, depth / 2, cutNode); ss->skipEarlyPruning = false; ss->excludedMove = MOVE_NONE; @@ -834,64 +929,52 @@ moves_loop: // When in check and at SpNode search starts from here if ( !RootNode && !captureOrPromotion && !inCheck - && !dangerous + && !givesCheck + && !pos.advanced_pawn_push(move) && bestValue > VALUE_MATED_IN_MAX_PLY) { // Move count based pruning if ( depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth]) - { - if (SpNode) - splitPoint->mutex.lock(); + continue; + // History 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) continue; - } predictedDepth = newDepth - reduction(improving, depth, moveCount); // Futility pruning: parent node if (predictedDepth < 7 * ONE_PLY) { - futilityValue = ss->staticEval + futility_margin(predictedDepth) - + 128 + Gains[pos.moved_piece(move)][to_sq(move)]; + futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256; if (futilityValue <= alpha) { bestValue = std::max(bestValue, futilityValue); - - if (SpNode) - { - splitPoint->mutex.lock(); - if (bestValue > splitPoint->bestValue) - splitPoint->bestValue = bestValue; - } continue; } } // Prune moves with negative SEE at low depths if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO) - { - if (SpNode) - splitPoint->mutex.lock(); - continue; - } } // Speculative prefetch as early as possible - prefetch((char*)TT.first_entry(pos.key_after(move))); + prefetch(TT.first_entry(pos.key_after(move))); // Check for legality just before making the move - if (!RootNode && !SpNode && !pos.legal(move, ci.pinned)) + if (!RootNode && !pos.legal(move, ci.pinned)) { - moveCount--; + ss->moveCount = --moveCount; continue; } ss->currentMove = move; - if (!SpNode && !captureOrPromotion && quietCount < 64) - quietsSearched[quietCount++] = move; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -900,56 +983,43 @@ moves_loop: // When in check and at SpNode search starts from here // re-searched at full depth. if ( depth >= 3 * ONE_PLY && moveCount > 1 - && !captureOrPromotion - && move != ss->killers[0] - && move != ss->killers[1]) + && !captureOrPromotion) { - ss->reduction = reduction(improving, depth, moveCount); + Depth r = reduction(improving, depth, moveCount); + // Increase reduction for cut nodes and moves with a bad history if ( (!PvNode && cutNode) - || History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO) - ss->reduction += ONE_PLY; + || ( 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; - if (move == countermoves[0] || move == countermoves[1]) - ss->reduction = std::max(DEPTH_ZERO, ss->reduction - 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 ( ss->reduction + 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) - ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); - - Depth d = std::max(newDepth - ss->reduction, ONE_PLY); - if (SpNode) - alpha = splitPoint->alpha; + r = std::max(DEPTH_ZERO, r - ONE_PLY); - value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + Depth d = std::max(newDepth - r, ONE_PLY); - // Re-search at intermediate depth if reduction is very high - if (value > alpha && ss->reduction >= 4 * ONE_PLY) - { - Depth d2 = std::max(newDepth - 2 * ONE_PLY, ONE_PLY); - value = -search(pos, ss+1, -(alpha+1), -alpha, d2, true); - } + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); - doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); - ss->reduction = DEPTH_ZERO; + doFullDepthSearch = (value > alpha && r != DEPTH_ZERO); } else doFullDepthSearch = !PvNode || moveCount > 1; // Step 16. Full depth search, when LMR is skipped or fails high if (doFullDepthSearch) - { - if (SpNode) - alpha = splitPoint->alpha; - value = newDepth < ONE_PLY ? givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); - } + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); // 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 @@ -962,7 +1032,7 @@ moves_loop: // When in check and at SpNode search starts from here value = newDepth < ONE_PLY ? givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth, false); + : - search(pos, ss+1, -beta, -alpha, newDepth, false); } // Step 17. Undo move @@ -971,22 +1041,16 @@ moves_loop: // When in check and at SpNode search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); // Step 18. Check for new best move - if (SpNode) - { - splitPoint->mutex.lock(); - bestValue = splitPoint->bestValue; - alpha = splitPoint->alpha; - } - - // Finished searching the move. If a stop or a cutoff occurred, the return - // value of the search cannot be trusted, and we return immediately without + // 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 || thisThread->cutoff_occurred()) + if (Signals.stop.load(std::memory_order_relaxed)) return VALUE_ZERO; if (RootNode) { - RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); + RootMove& rm = *std::find(thisThread->rootMoves.begin(), + thisThread->rootMoves.end(), move); // PV move or new best move ? if (moveCount == 1 || value > alpha) @@ -1002,8 +1066,8 @@ moves_loop: // When in check and at SpNode search starts from here // We record how often the best move has been changed in each // iteration. This information is used for time management: When // the best move changes frequently, we allocate some more time. - if (moveCount > 1) - ++BestMoveChanges; + if (moveCount > 1 && thisThread == Threads.main()) + ++static_cast(thisThread)->bestMoveChanges; } else // All other moves but the PV are set to the lowest value: this is @@ -1014,58 +1078,41 @@ moves_loop: // When in check and at SpNode search starts from here if (value > bestValue) { - bestValue = SpNode ? splitPoint->bestValue = value : value; + bestValue = value; if (value > alpha) { - bestMove = SpNode ? splitPoint->bestMove = move : move; + // If there is an easy move for this position, clear it if unstable + if ( PvNode + && thisThread == Threads.main() + && EasyMove.get(pos.key()) + && (move != EasyMove.get(pos.key()) || moveCount > 1)) + EasyMove.clear(); + + bestMove = move; if (PvNode && !RootNode) // Update pv even in fail-high case - update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv); + update_pv(ss->pv, move, (ss+1)->pv); if (PvNode && value < beta) // Update alpha! Always alpha < beta - alpha = SpNode ? splitPoint->alpha = value : value; + alpha = value; else { assert(value >= beta); // Fail high - - if (SpNode) - splitPoint->cutoff = true; - break; } } } - // Step 19. Check for splitting the search - if ( !SpNode - && Threads.size() >= 2 - && depth >= Threads.minimumSplitDepth - && ( !thisThread->activeSplitPoint - || !thisThread->activeSplitPoint->allSlavesSearching) - && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD) - { - assert(bestValue > -VALUE_INFINITE && bestValue < beta); - - thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove, - depth, moveCount, &mp, NT, cutNode); - - if (Signals.stop || thisThread->cutoff_occurred()) - return VALUE_ZERO; - - if (bestValue >= beta) - break; - } + if (!captureOrPromotion && move != bestMove && quietCount < 64) + quietsSearched[quietCount++] = move; } - if (SpNode) - return bestValue; - - // Following condition would detect a stop or a cutoff set 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. + // 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. /* - if (Signals.stop || thisThread->cutoff_occurred()) + if (Signals.stop) return VALUE_DRAW; */ @@ -1077,9 +1124,23 @@ moves_loop: // When in check and at SpNode search starts from here bestValue = excludedMove ? alpha : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; - // Quiet best move: update killers, history, countermoves and followupmoves - else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck) - update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1); + // Quiet best move: update killers, history and countermoves + else if (bestMove && !pos.capture_or_promotion(bestMove)) + update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount); + + // 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)) + { + 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); + } tte->save(posKey, value_to_tt(bestValue, ss->ply), bestValue >= beta ? BOUND_LOWER : @@ -1128,7 +1189,8 @@ moves_loop: // When in check and at SpNode search starts from here // Check for an instant draw or if the maximum ply has been reached if (pos.is_draw() || ss->ply >= MAX_PLY) - return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; + return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) + : DrawValue[pos.side_to_move()]; assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -1176,7 +1238,8 @@ moves_loop: // When in check and at SpNode search starts from here } else ss->staticEval = bestValue = - (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo; + (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) + : -(ss-1)->staticEval + 2 * Eval::Tempo; // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) @@ -1198,16 +1261,16 @@ moves_loop: // When in check and at SpNode 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, History, to_sq((ss-1)->currentMove)); + MovePicker mp(pos, ttMove, depth, pos.this_thread()->history, to_sq((ss-1)->currentMove)); CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); givesCheck = type_of(move) == NORMAL && !ci.dcCandidates - ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) + ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) : pos.gives_check(move, ci); // Futility pruning @@ -1236,8 +1299,7 @@ moves_loop: // When in check and at SpNode search starts from here // Detect non-capture evasions that are candidates to be pruned evasionPrunable = InCheck && bestValue > VALUE_MATED_IN_MAX_PLY - && !pos.capture(move) - && !pos.can_castle(pos.side_to_move()); + && !pos.capture(move); // Don't search moves with negative SEE values if ( (!InCheck || evasionPrunable) @@ -1246,7 +1308,7 @@ moves_loop: // When in check and at SpNode search starts from here continue; // Speculative prefetch as early as possible - prefetch((char*)TT.first_entry(pos.key_after(move))); + prefetch(TT.first_entry(pos.key_after(move))); // Check for legality just before making the move if (!pos.legal(move, ci.pinned)) @@ -1272,7 +1334,7 @@ moves_loop: // When in check and at SpNode search starts from here if (PvNode) // Update pv even in fail-high case update_pv(ss->pv, move, (ss+1)->pv); - if (PvNode && value < beta) // Update alpha here! Always alpha < beta + if (PvNode && value < beta) // Update alpha here! { alpha = value; bestMove = move; @@ -1337,10 +1399,12 @@ moves_loop: // When in check and at SpNode search starts from here *pv = MOVE_NONE; } - // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high - // of a quiet move. - void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) { + // update_stats() updates killers, history, countermove and countermove + // 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) { if (ss->killers[0] != move) { @@ -1348,354 +1412,208 @@ moves_loop: // When in check and at SpNode search starts from here ss->killers[0] = move; } - // Increase history value of the cut-off move and decrease all the other - // played quiet moves. - Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY)); - History.update(pos.moved_piece(move), to_sq(move), bonus); - for (int i = 0; i < quietsCnt; ++i) + 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]; + Thread* thisThread = pos.this_thread(); + + thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); + + if (is_ok((ss-1)->currentMove)) { - Move m = quiets[i]; - History.update(pos.moved_piece(m), to_sq(m), -bonus); + thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); + cmh.update(pos.moved_piece(move), to_sq(move), bonus); } - if (is_ok((ss-1)->currentMove)) + // Decrease all the other played quiet moves + for (int i = 0; i < quietsCnt; ++i) { - Square prevMoveSq = to_sq((ss-1)->currentMove); - Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move); + 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 (is_ok((ss-2)->currentMove) && (ss-1)->currentMove == (ss-1)->ttMove) + // 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 prevOwnMoveSq = to_sq((ss-2)->currentMove); - Followupmoves.update(pos.piece_on(prevOwnMoveSq), prevOwnMoveSq, move); + 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); } } - // When playing with a strength handicap, choose best move among the first 'candidates' - // RootMoves using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. + // When playing with strength handicap, choose best move among a set of RootMoves + // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. - Move Skill::pick_move() { + Move Skill::pick_best(size_t multiPV) { - // PRNG sequence should be non-deterministic, so we seed it with the time at init - static PRNG rng(Time::now()); + const Search::RootMoveVector& rootMoves = Threads.main()->rootMoves; + static PRNG rng(now()); // PRNG sequence should be non-deterministic // RootMoves are already sorted by score in descending order - int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg); + Value topScore = rootMoves[0].score; + int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValueMg); int weakness = 120 - 2 * level; int maxScore = -VALUE_INFINITE; - best = MOVE_NONE; - // Choose best move. For each move score we add two terms both dependent on - // weakness. One deterministic and bigger for weaker moves, and one random, + // 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. - for (size_t i = 0; i < candidates; ++i) + for (size_t i = 0; i < multiPV; ++i) { - int score = RootMoves[i].score; - // This is our magic formula - score += ( weakness * int(RootMoves[0].score - score) - + variance * (rng.rand() % weakness)) / 128; + int push = ( weakness * int(topScore - rootMoves[i].score) + + delta * (rng.rand() % weakness)) / 128; - if (score > maxScore) + if (rootMoves[i].score + push > maxScore) { - maxScore = score; - best = RootMoves[i].pv[0]; + maxScore = rootMoves[i].score + push; + best = rootMoves[i].pv[0]; } } + return best; } - // uci_pv() formats PV information according to the UCI protocol. UCI - // requires that all (if any) unsearched PV lines are sent using a previous - // search score. + // check_time() is used to print debug info and, more importantly, to detect + // when we are out of available time and thus stop the search. - string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta) { + void check_time() { - std::stringstream ss; - Time::point elapsed = Time::now() - SearchTime + 1; - size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size()); - int selDepth = 0; + static TimePoint lastInfoTime = now(); - for (size_t i = 0; i < Threads.size(); ++i) - if (Threads[i]->maxPly > selDepth) - selDepth = Threads[i]->maxPly; + int elapsed = Time.elapsed(); + TimePoint tick = Limits.startTime + elapsed; - for (size_t i = 0; i < uciPVSize; ++i) + if (tick - lastInfoTime >= 1000) { - bool updated = (i <= PVIdx); - - if (depth == ONE_PLY && !updated) - continue; - - Depth d = updated ? depth : depth - ONE_PLY; - Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore; - - bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; - v = tb ? TB::Score : v; - - if (ss.rdbuf()->in_avail()) // Not at first line - ss << "\n"; - - ss << "info depth " << d / ONE_PLY - << " seldepth " << selDepth - << " multipv " << i + 1 - << " score " << UCI::value(v); - - if (!tb && i == PVIdx) - ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); - - ss << " nodes " << pos.nodes_searched() - << " nps " << pos.nodes_searched() * 1000 / elapsed; - - if (elapsed > 1000) // Earlier makes little sense - ss << " hashfull " << TT.hashfull(); - - ss << " tbhits " << TB::Hits - << " time " << elapsed - << " pv"; - - for (size_t j = 0; j < RootMoves[i].pv.size(); ++j) - ss << " " << UCI::move(RootMoves[i].pv[j], pos.is_chess960()); + lastInfoTime = tick; + dbg_print(); } - return ss.str(); - } + // An engine may not stop pondering until told so by the GUI + if (Limits.ponder) + return; -} // namespace - - -/// 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; - size_t idx = 0; - - for ( ; idx < pv.size(); ++idx) - { - bool ttHit; - TTEntry* tte = TT.probe(pos.key(), ttHit); - - if (!ttHit || tte->move() != pv[idx]) // Don't overwrite correct entries - tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE, TT.generation()); - - assert(MoveList(pos).contains(pv[idx])); - - pos.do_move(pv[idx], *st++); + if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10) + || (Limits.movetime && elapsed >= Limits.movetime) + || (Limits.nodes && Threads.nodes_searched() >= Limits.nodes)) + Signals.stop = true; } - while (idx) pos.undo_move(pv[--idx]); -} - - -/// 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, otherwise in case of -/// 'ponder on' we have nothing to think on. - -Move RootMove::extract_ponder_from_tt(Position& pos) -{ - StateInfo st; - bool found; - - assert(pv.size() == 1); - - pos.do_move(pv[0], st); - TTEntry* tte = TT.probe(pos.key(), found); - Move m = found ? tte->move() : MOVE_NONE; - if (!MoveList(pos).contains(m)) - m = MOVE_NONE; - - pos.undo_move(pv[0]); - pv.push_back(m); - return m; -} - +} // namespace -/// Thread::idle_loop() is where the thread is parked when it has no work to do -void Thread::idle_loop() { +/// UCI::pv() formats PV information according to the UCI protocol. UCI requires +/// that all (if any) unsearched PV lines are sent using a previous search score. - // Pointer 'this_sp' is not null only if we are called from split(), and not - // at the thread creation. This means we are the split point's master. - SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL; +string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { - assert(!this_sp || (this_sp->masterThread == this && searching)); + std::stringstream ss; + int elapsed = Time.elapsed() + 1; + const Search::RootMoveVector& 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(); - while (!exit) + for (size_t i = 0; i < multiPV; ++i) { - // If this thread has been assigned work, launch a search - while (searching) - { - Threads.mutex.lock(); - - assert(activeSplitPoint); - SplitPoint* sp = activeSplitPoint; - - Threads.mutex.unlock(); - - Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) - Position pos(*sp->pos, this); - - std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack)); - ss->splitPoint = sp; - - sp->mutex.lock(); - - assert(activePosition == NULL); - - activePosition = &pos; - - if (sp->nodeType == NonPV) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else if (sp->nodeType == PV) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else if (sp->nodeType == Root) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else - assert(false); + bool updated = (i <= PVIdx); - assert(searching); + if (depth == ONE_PLY && !updated) + continue; - searching = false; - activePosition = NULL; - sp->slavesMask.reset(idx); - sp->allSlavesSearching = false; - sp->nodes += pos.nodes_searched(); + Depth d = updated ? depth : depth - ONE_PLY; + Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore; - // Wake up the master thread so to allow it to return from the idle - // loop in case we are the last slave of the split point. - if ( this != sp->masterThread - && sp->slavesMask.none()) - { - assert(!sp->masterThread->searching); - sp->masterThread->notify_one(); - } + bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; + v = tb ? TB::Score : v; - // After releasing the lock we can't access any SplitPoint related data - // in a safe way because it could have been released under our feet by - // the sp master. - sp->mutex.unlock(); + if (ss.rdbuf()->in_avail()) // Not at first line + ss << "\n"; - // Try to late join to another split point if none of its slaves has - // already finished. - if (Threads.size() > 2) - for (size_t i = 0; i < Threads.size(); ++i) - { - const int size = Threads[i]->splitPointsSize; // Local copy - sp = size ? &Threads[i]->splitPoints[size - 1] : NULL; + ss << "info" + << " depth " << d / ONE_PLY + << " seldepth " << pos.this_thread()->maxPly + << " multipv " << i + 1 + << " score " << UCI::value(v); - if ( sp - && sp->allSlavesSearching - && available_to(Threads[i])) - { - // Recheck the conditions under lock protection - Threads.mutex.lock(); - sp->mutex.lock(); - - if ( sp->allSlavesSearching - && available_to(Threads[i])) - { - sp->slavesMask.set(idx); - activeSplitPoint = sp; - searching = true; - } - - sp->mutex.unlock(); - Threads.mutex.unlock(); - - break; // Just a single attempt - } - } - } + if (!tb && i == PVIdx) + ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); - // Grab the lock to avoid races with Thread::notify_one() - mutex.lock(); + ss << " nodes " << nodes_searched + << " nps " << nodes_searched * 1000 / elapsed; - // If we are master and all slaves have finished then exit idle_loop - if (this_sp && this_sp->slavesMask.none()) - { - assert(!searching); - mutex.unlock(); - break; - } + if (elapsed > 1000) // Earlier makes little sense + ss << " hashfull " << TT.hashfull(); - // If we are not searching, wait for a condition to be signaled instead of - // wasting CPU time polling for work. - if (!searching && !exit) - sleepCondition.wait(mutex); + ss << " tbhits " << TB::Hits + << " time " << elapsed + << " pv"; - mutex.unlock(); + for (Move m : rootMoves[i].pv) + ss << " " << UCI::move(m, pos.is_chess960()); } + + return ss.str(); } -/// check_time() is called by the timer thread when the timer triggers. It is -/// used to print debug info and, more importantly, to detect when we are out of -/// available time and thus stop the search. +/// 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 check_time() { +void RootMove::insert_pv_in_tt(Position& pos) { - static Time::point lastInfoTime = Time::now(); - Time::point elapsed = Time::now() - SearchTime; + StateInfo state[MAX_PLY], *st = state; + bool ttHit; - if (Time::now() - lastInfoTime >= 1000) + for (Move m : pv) { - lastInfoTime = Time::now(); - dbg_print(); - } + assert(MoveList(pos).contains(m)); - // An engine may not stop pondering until told so by the GUI - if (Limits.ponder) - return; + TTEntry* tte = TT.probe(pos.key(), ttHit); - if (Limits.use_time_management()) - { - bool stillAtFirstMove = Signals.firstRootMove - && !Signals.failedLowAtRoot - && elapsed > TimeMgr.available_time() * 75 / 100; + 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()); - if ( stillAtFirstMove - || elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution) - Signals.stop = true; + pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos))); } - else if (Limits.movetime && elapsed >= Limits.movetime) - Signals.stop = true; - else if (Limits.nodes) - { - Threads.mutex.lock(); - - int64_t nodes = RootPos.nodes_searched(); + for (size_t i = pv.size(); i > 0; ) + pos.undo_move(pv[--i]); +} - // Loop across all split points and sum accumulated SplitPoint nodes plus - // all the currently active positions nodes. - for (size_t i = 0; i < Threads.size(); ++i) - for (int j = 0; j < Threads[i]->splitPointsSize; ++j) - { - SplitPoint& sp = Threads[i]->splitPoints[j]; - sp.mutex.lock(); +/// 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, +/// otherwise in case of 'ponder on' we have nothing to think on. - nodes += sp.nodes; +bool RootMove::extract_ponder_from_tt(Position& pos) +{ + StateInfo st; + bool ttHit; - for (size_t idx = 0; idx < Threads.size(); ++idx) - if (sp.slavesMask.test(idx) && Threads[idx]->activePosition) - nodes += Threads[idx]->activePosition->nodes_searched(); + assert(pv.size() == 1); - sp.mutex.unlock(); - } + pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos))); + TTEntry* tte = TT.probe(pos.key(), ttHit); + pos.undo_move(pv[0]); - Threads.mutex.unlock(); + if (ttHit) + { + Move m = tte->move(); // Local copy to be SMP safe + if (MoveList(pos).contains(m)) + return pv.push_back(m), true; + } - if (nodes >= Limits.nodes) - Signals.stop = true; - } + return false; }