X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=05773469c64220ca2d201c151504c5446e379f8b;hp=c98a53dac207e915bf1c691edbfca43ba73706f2;hb=14cf27e6f65787a1f9c8e4759ae0fcc218f37d2d;hpb=4ede49cd850392f28bc9da9537c111d2c3f0b297 diff --git a/src/search.cpp b/src/search.cpp index c98a53da..c774f08a 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -24,73 +24,74 @@ #include #include -#include "book.h" #include "evaluate.h" +#include "misc.h" #include "movegen.h" #include "movepick.h" -#include "notation.h" #include "search.h" #include "timeman.h" #include "thread.h" #include "tt.h" -#include "ucioption.h" +#include "uci.h" +#include "syzygy/tbprobe.h" namespace Search { volatile SignalsType Signals; LimitsType Limits; - std::vector RootMoves; + RootMoveVector RootMoves; Position RootPos; - Color RootColor; Time::point SearchTime; StateStackPtr SetupStates; } +namespace Tablebases { + + int Cardinality; + uint64_t Hits; + bool RootInTB; + bool UseRule50; + Depth ProbeDepth; + Value Score; +} + +namespace TB = Tablebases; + using std::string; using Eval::evaluate; using namespace Search; namespace { - // Set to true to force running with one thread. Used for debugging - const bool FakeSplit = false; - - // This is the minimum interval in msec between two check_time() calls - const int TimerResolution = 5; - // Different node types, used as template parameter - enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; + enum NodeType { Root, PV, NonPV }; // Dynamic razoring margin based on depth - inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } + inline Value razor_margin(Depth d) { return Value(512 + 32 * d); } // Futility lookup tables (initialized at startup) and their access functions - Value FutilityMargins[16][64]; // [depth][moveNumber] - int FutilityMoveCounts[32]; // [depth] + int FutilityMoveCounts[2][16]; // [improving][depth] - inline Value futility_margin(Depth d, int mn) { - - return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)] - : 2 * VALUE_INFINITE; + inline Value futility_margin(Depth d) { + return Value(200 * d); } // Reduction lookup tables (initialized at startup) and their access function - int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] - - template inline Depth reduction(Depth d, int mn) { + int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] - return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; + template inline Depth reduction(bool i, Depth d, int mn) { + return (Depth) Reductions[PvNode][i][std::min(int(d), 63)][std::min(mn, 63)]; } - size_t PVSize, PVIdx; + size_t PVIdx; TimeManager TimeMgr; - int BestMoveChanges; + double BestMoveChanges; Value DrawValue[COLOR_NB]; HistoryStats History; GainsStats Gains; - CountermovesStats Countermoves; + MovesStats Countermoves, Followupmoves; - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); template @@ -99,24 +100,26 @@ namespace { void id_loop(Position& pos); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta); - bool allows(const Position& pos, Move first, Move second); - bool refutes(const Position& pos, Move first, Move second); - string uci_pv(const Position& pos, int depth, Value alpha, Value beta); + 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) : level(l), best(MOVE_NONE) {} + Skill(int l, size_t rootSize) : level(l), + candidates(l < 20 ? std::min(4, (int)rootSize) : 0), + best(MOVE_NONE) {} ~Skill() { - if (enabled()) // Swap best PV line with the sub-optimal one + 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())); } - bool enabled() const { return level < 20; } - bool time_to_pick(int depth) const { return depth == 1 + level; } + 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; }; @@ -127,51 +130,62 @@ namespace { void Search::init() { - int d; // depth (ONE_PLY == 2) - int hd; // half depth (ONE_PLY == 1) - int mc; // moveCount - // Init reductions array - for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++) - { - double pvRed = log(double(hd)) * log(double(mc)) / 3.0; - double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25; - Reductions[1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0); - Reductions[0][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0); - } + 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; - // Init futility margins array - for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++) - FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45); + 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); + + Reductions[1][0][d][mc] = Reductions[1][1][d][mc]; + Reductions[0][0][d][mc] = Reductions[0][1][d][mc]; + + // Increase reduction when eval is not improving + if (Reductions[0][0][d][mc] >= 2) + Reductions[0][0][d][mc] += 1; + } // Init futility move count array - for (d = 0; d < 32; d++) - FutilityMoveCounts[d] = int(3.001 + 0.3 * pow(double(d), 1.8)); + for (int d = 0; d < 16; ++d) + { + FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8)); + FutilityMoveCounts[1][d] = int(2.9 + 1.045 * pow(d + 0.49, 1.8)); + } } /// 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. - -static size_t perft(Position& pos, Depth depth) { +template +uint64_t Search::perft(Position& pos, Depth depth) { StateInfo st; - size_t cnt = 0; + uint64_t cnt, nodes = 0; CheckInfo ci(pos); - const bool leaf = depth == 2 * ONE_PLY; + const bool leaf = (depth == 2 * ONE_PLY); for (MoveList it(pos); *it; ++it) { - pos.do_move(*it, st, ci, pos.move_gives_check(*it, ci)); - cnt += leaf ? MoveList(pos).size() : ::perft(pos, depth - ONE_PLY); - pos.undo_move(*it); + if (Root && depth <= ONE_PLY) + cnt = 1, nodes++; + else + { + pos.do_move(*it, st, ci, pos.gives_check(*it, ci)); + cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); + nodes += cnt; + pos.undo_move(*it); + } + if (Root) + sync_cout << UCI::format_move(*it, pos.is_chess960()) << ": " << cnt << sync_endl; } - return cnt; + return nodes; } -size_t Search::perft(Position& pos, Depth depth) { - return depth > ONE_PLY ? ::perft(pos, depth) : MoveList(pos).size(); -} +template uint64_t Search::perft(Position& pos, Depth 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 @@ -179,110 +193,93 @@ size_t Search::perft(Position& pos, Depth depth) { void Search::think() { - static PolyglotBook book; // Defined static to initialize the PRNG only once - - RootColor = RootPos.side_to_move(); - TimeMgr.init(Limits, RootPos.game_ply(), RootColor); + TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move()); - if (RootMoves.empty()) - { - RootMoves.push_back(MOVE_NONE); - sync_cout << "info depth 0 score " - << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) - << sync_endl; + 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); - goto finalize; - } + TB::Hits = 0; + TB::RootInTB = false; + TB::UseRule50 = Options["Syzygy50MoveRule"]; + TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; + TB::Cardinality = Options["SyzygyProbeLimit"]; - if (Options["OwnBook"] && !Limits.infinite && !Limits.mate) + // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality + if (TB::Cardinality > TB::MaxCardinality) { - Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]); - - if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove)) - { - std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), bookMove)); - goto finalize; - } + TB::Cardinality = TB::MaxCardinality; + TB::ProbeDepth = DEPTH_ZERO; } - if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) + if (RootMoves.empty()) { - int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns - cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase - DrawValue[ RootColor] = VALUE_DRAW - Value(cf); - DrawValue[~RootColor] = VALUE_DRAW + Value(cf); + RootMoves.push_back(MOVE_NONE); + sync_cout << "info depth 0 score " + << UCI::format_value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << sync_endl; } else - DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW; - - if (Options["Write Search Log"]) { - Log log(Options["Search Log Filename"]); - log << "\nSearching: " << RootPos.fen() - << "\ninfinite: " << Limits.infinite - << " ponder: " << Limits.ponder - << " time: " << Limits.time[RootColor] - << " increment: " << Limits.inc[RootColor] - << " moves to go: " << Limits.movestogo - << std::endl; - } + 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); - // Reset the threads, still sleeping: will be wake up at split time - for (size_t i = 0; i < Threads.size(); i++) - Threads[i]->maxPly = 0; + if (TB::RootInTB) + TB::Cardinality = 0; // Do not probe tablebases during the search - Threads.sleepWhileIdle = Options["Idle Threads Sleep"]; + 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); - // Set best timer interval to avoid lagging under time pressure. Timer is - // used to check for remaining available thinking time. - Threads.timer->msec = - Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) : - Limits.nodes ? 2 * TimerResolution - : 100; + // Only probe during search if winning + if (TB::Score <= VALUE_DRAW) + TB::Cardinality = 0; + } - Threads.timer->notify_one(); // Wake up the recurring timer + if (TB::RootInTB) + { + TB::Hits = RootMoves.size(); - id_loop(RootPos); // Let's start searching ! + 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; + } + } - Threads.timer->msec = 0; // Stop the timer - Threads.sleepWhileIdle = true; // Send idle threads to sleep + for (size_t i = 0; i < Threads.size(); ++i) + Threads[i]->maxPly = 0; - if (Options["Write Search Log"]) - { - Time::point elapsed = Time::now() - SearchTime + 1; + Threads.timer->run = true; + Threads.timer->notify_one(); // Wake up the recurring timer - Log log(Options["Search Log Filename"]); - log << "Nodes: " << RootPos.nodes_searched() - << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed - << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]); + id_loop(RootPos); // Let's start searching ! - StateInfo st; - RootPos.do_move(RootMoves[0].pv[0], st); - log << "\nPonder move: " << move_to_san(RootPos, RootMoves[0].pv[1]) << std::endl; - RootPos.undo_move(RootMoves[0].pv[0]); + Threads.timer->run = false; } -finalize: - - // When search is stopped this info is not printed - sync_cout << "info nodes " << RootPos.nodes_searched() - << " time " << Time::now() - SearchTime + 1 << sync_endl; - - // When we reach max depth we arrive here even without Signals.stop is raised, - // but if we are pondering or in infinite search, according to UCI protocol, - // we shouldn't print the best move before the GUI sends a "stop" or "ponderhit" - // command. We simply wait here until GUI sends one of those commands (that - // raise Signals.stop). + // 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 + // GUI sends a "stop" or "ponderhit" command. We therefore simply wait here + // until the GUI sends one of those commands (which also raises Signals.stop). if (!Signals.stop && (Limits.ponder || Limits.infinite)) { Signals.stopOnPonderhit = true; RootPos.this_thread()->wait_for(Signals.stop); } - // Best move could be MOVE_NONE when searching on a stalemate position - sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960()) - << " ponder " << move_to_uci(RootMoves[0].pv[1], RootPos.is_chess960()) - << sync_endl; + sync_cout << "bestmove " << UCI::format_move(RootMoves[0].pv[0], RootPos.is_chess960()); + + if (RootMoves[0].pv.size() > 1) + std::cout << " ponder " << UCI::format_move(RootMoves[0].pv[1], RootPos.is_chess960()); + + std::cout << sync_endl; } @@ -294,14 +291,14 @@ namespace { void id_loop(Position& pos) { - Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1) - int depth, prevBestMoveChanges; + 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-1, 0, 4 * sizeof(Stack)); - (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains + std::memset(ss-2, 0, 5 * sizeof(Stack)); - depth = BestMoveChanges = 0; + depth = DEPTH_ZERO; + BestMoveChanges = 0; bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -309,82 +306,84 @@ namespace { History.clear(); Gains.clear(); Countermoves.clear(); + Followupmoves.clear(); - PVSize = Options["MultiPV"]; - Skill skill(Options["Skill Level"]); + size_t multiPV = Options["MultiPV"]; + Skill skill(Options["Skill Level"], RootMoves.size()); // 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. - if (skill.enabled() && PVSize < 4) - PVSize = 4; - - PVSize = std::min(PVSize, RootMoves.size()); + multiPV = std::max(multiPV, skill.candidates_size()); // Iterative deepening loop until requested to stop or target depth reached - while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) + while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) { - // Save last iteration's scores before first PV line is searched and all - // the move scores but the (new) PV are set to -VALUE_INFINITE. - for (size_t i = 0; i < RootMoves.size(); i++) - RootMoves[i].prevScore = RootMoves[i].score; + // Age out PV variability metric + BestMoveChanges *= 0.5; - prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1 - BestMoveChanges = 0; + // 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; // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < PVSize; PVIdx++) + for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx) { // Reset aspiration window starting size - if (depth >= 5) + if (depth >= 5 * ONE_PLY) { delta = Value(16); - alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE); - beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE); + alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); + beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); } - // Start with a small aspiration window and, in case of fail high/low, - // research with bigger window until not failing high/low anymore. + // 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 * ONE_PLY, false); - - // Bring to front the best move. 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 but the new - // PV that goes to the front. Note that in case of MultiPV search - // the already searched PV lines are preserved. + 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++) + for (size_t i = 0; i <= PVIdx; ++i) RootMoves[i].insert_pv_in_tt(pos); - // If search has been stopped return immediately. Sorting and - // writing PV back to TT is safe becuase RootMoves is still - // valid, although refers to previous iteration. + // 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) - return; + break; // When failing high/low give some update (without cluttering - // the UI) before to research. + // the UI) before a re-search. if ( (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 - // research, otherwise exit the loop. + // 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; @@ -396,69 +395,39 @@ namespace { // Sort the PV lines searched so far and update the GUI std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); - if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000) + if (Signals.stop) + sync_cout << "info nodes " << RootPos.nodes_searched() + << " time " << Time::now() - SearchTime << sync_endl; + + else if ( PVIdx + 1 == std::min(multiPV, RootMoves.size()) + || Time::now() - SearchTime > 3000) sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; } - // Do we need to pick now the sub-optimal best move ? - if (skill.enabled() && skill.time_to_pick(depth)) + // 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(); - if (Options["Write Search Log"]) - { - RootMove& rm = RootMoves[0]; - if (skill.best != MOVE_NONE) - rm = *std::find(RootMoves.begin(), RootMoves.end(), skill.best); - - Log log(Options["Search Log Filename"]); - log << pretty_pv(pos, depth, rm.score, Time::now() - SearchTime, &rm.pv[0]) - << std::endl; - } - - // Do we have found a "mate in x"? + // 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() && !Signals.stopOnPonderhit) + if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit) { - bool stop = false; // Local variable, not the volatile Signals.stop - - // Take in account some extra time if the best move has changed - if (depth > 4 && depth < 50 && PVSize == 1) - TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges); - - // Stop search if most of available time is already consumed. We - // probably don't have enough time to search the first move at the - // next iteration anyway. - if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100) - stop = true; - - // Stop search early if one move seems to be much better than others - if ( depth >= 12 - && !stop - && PVSize == 1 - && bestValue > VALUE_MATED_IN_MAX_PLY - && ( RootMoves.size() == 1 - || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100)) - { - Value rBeta = bestValue - 2 * PawnValueMg; - ss->excludedMove = RootMoves[0].pv[0]; - ss->skipNullMove = true; - Value v = search(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true); - ss->skipNullMove = false; - ss->excludedMove = MOVE_NONE; - - if (v < rBeta) - stop = true; - } - - if (stop) + // 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 GUI sends "ponderhit" or "stop". + // keep pondering until the GUI sends "ponderhit" or "stop". if (Limits.ponder) Signals.stopOnPonderhit = true; else @@ -472,31 +441,30 @@ namespace { // 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, 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. + // 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. - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { - const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot); - const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot); - const bool RootNode = (NT == Root || NT == SplitPointRoot); + const bool RootNode = NT == Root; + const bool PvNode = NT == PV || NT == Root; - assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); + assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(depth > DEPTH_ZERO); - Move quietsSearched[64]; + Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; - const TTEntry *tte; + TTEntry* tte; + bool ttHit; SplitPoint* splitPoint; Key posKey; - Move ttMove, move, excludedMove, bestMove, threatMove; - Depth ext, newDepth; - Value bestValue, value, ttValue; - Value eval, nullValue, futilityValue; - bool inCheck, givesCheck, pvMove, singularExtensionNode; + Move ttMove, move, excludedMove, bestMove; + Depth extension, newDepth, predictedDepth; + Value bestValue, value, ttValue, eval, nullValue, futilityValue; + bool inCheck, givesCheck, singularExtensionNode, improving; bool captureOrPromotion, dangerous, doFullDepthSearch; int moveCount, quietCount; @@ -508,9 +476,9 @@ namespace { { splitPoint = ss->splitPoint; bestMove = splitPoint->bestMove; - threatMove = splitPoint->threatMove; bestValue = splitPoint->bestValue; tte = NULL; + ttHit = false; ttMove = excludedMove = MOVE_NONE; ttValue = VALUE_NONE; @@ -521,11 +489,7 @@ namespace { moveCount = quietCount = 0; bestValue = -VALUE_INFINITE; - ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; - ss->futilityMoveCount = 0; - (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; - (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; // Used to send selDepth info to GUI if (PvNode && thisThread->maxPly < ss->ply) @@ -534,145 +498,166 @@ namespace { if (!RootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) - return DrawValue[pos.side_to_move()]; + if (Signals.stop || 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 // a shorter mate was found upward in the tree then there is no need to search - // further, we will never beat current alpha. Same logic but with reversed signs - // applies also in the opposite condition of being mated instead of giving mate, - // in this case return a fail-high score. + // because we will never beat the current alpha. Same logic but with reversed + // signs applies also in the opposite condition of being mated instead of giving + // mate. In this case return a fail-high score. alpha = std::max(mated_in(ss->ply), alpha); beta = std::min(mate_in(ss->ply+1), beta); if (alpha >= beta) return alpha; } + 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+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. excludedMove = ss->excludedMove; posKey = excludedMove ? pos.exclusion_key() : pos.key(); - tte = TT.probe(posKey); - ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE; - ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - - // At PV nodes we check for exact scores, while at non-PV nodes we check for - // a fail high/low. Biggest advantage at probing at PV nodes is to have a - // smooth experience in analysis mode. We don't probe at Root nodes otherwise - // we should also update RootMoveList to avoid bogus output. - if ( !RootNode - && tte + 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; + + // At non-PV nodes we check for a fail high/low. We don't probe at PV nodes + if ( !PvNode + && ttHit && tte->depth() >= depth && ttValue != VALUE_NONE // Only in case of TT access race - && ( PvNode ? tte->bound() == BOUND_EXACT - : ttValue >= beta ? (tte->bound() & BOUND_LOWER) - : (tte->bound() & BOUND_UPPER))) + && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { - TT.refresh(tte); ss->currentMove = ttMove; // Can be MOVE_NONE - if ( ttValue >= beta - && ttMove - && !pos.is_capture_or_promotion(ttMove) - && ttMove != ss->killers[0]) + // 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); + + return ttValue; + } + + // Step 4a. Tablebase probe + 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) { - ss->killers[1] = ss->killers[0]; - ss->killers[0] = ttMove; + int found, v = Tablebases::probe_wdl(pos, &found); + + if (found) + { + TB::Hits++; + + int drawScore = TB::UseRule50 ? 1 : 0; + + value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply + : VALUE_DRAW + 2 * v * drawScore; + + tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT, + std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY), + MOVE_NONE, VALUE_NONE, TT.get_generation()); + + return value; + } } - return ttValue; } // Step 5. Evaluate the position statically and update parent's gain statistics if (inCheck) { - ss->staticEval = ss->evalMargin = eval = VALUE_NONE; + ss->staticEval = eval = VALUE_NONE; goto moves_loop; } - else if (tte) + else if (ttHit) { // Never assume anything on values stored in TT - if ( (ss->staticEval = eval = tte->eval_value()) == VALUE_NONE - ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE) - eval = ss->staticEval = evaluate(pos, ss->evalMargin); + if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE) + eval = ss->staticEval = evaluate(pos); // Can ttValue be used as a better position evaluation? if (ttValue != VALUE_NONE) - if ( ((tte->bound() & BOUND_LOWER) && ttValue > eval) - || ((tte->bound() & BOUND_UPPER) && ttValue < eval)) + if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)) eval = ttValue; } else { - eval = ss->staticEval = evaluate(pos, ss->evalMargin); - TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, - ss->staticEval, ss->evalMargin); + eval = ss->staticEval = + (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.get_generation()); } - // Update gain for the parent non-capture move given the static position - // evaluation before and after the move. + 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 (is omitted in PV nodes) + // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && eval + razor_margin(depth) < beta + && eval + razor_margin(depth) <= alpha && ttMove == MOVE_NONE - && abs(beta) < VALUE_MATE_IN_MAX_PLY && !pos.pawn_on_7th(pos.side_to_move())) { - Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); - if (v < rbeta) - // Logically we should return (v + razor_margin(depth)), but - // surprisingly this did slightly weaker in tests. + 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 v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); + if (v <= ralpha) return v; } - // Step 7. Static null move pruning (is omitted in PV nodes) - // We're betting that the opponent doesn't have a move that will reduce - // the score by more than futility_margin(depth) if we do a null move. + // Step 7. Futility pruning: child node (skipped when in check) if ( !PvNode - && !ss->skipNullMove - && depth < 4 * ONE_PLY - && eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta - && abs(beta) < VALUE_MATE_IN_MAX_PLY - && abs(eval) < VALUE_KNOWN_WIN + && depth < 7 * ONE_PLY + && eval - futility_margin(depth) >= beta + && eval < VALUE_KNOWN_WIN // Do not return unproven wins && pos.non_pawn_material(pos.side_to_move())) - return eval - futility_margin(depth, (ss-1)->futilityMoveCount); + return eval - futility_margin(depth); // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode - && !ss->skipNullMove - && depth > ONE_PLY + && depth >= 2 * ONE_PLY && eval >= beta - && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; - // Null move dynamic reduction based on depth - Depth R = 3 * ONE_PLY + depth / 4; + assert(eval - beta >= 0); - // Null move dynamic reduction based on value - if (eval - PawnValueMg > beta) - R += ONE_PLY; + // Null move dynamic reduction based on depth and value + Depth R = (3 + depth / 4 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; pos.do_null_move(st); - (ss+1)->skipNullMove = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, depth-R, !cutNode); - (ss+1)->skipNullMove = false; + (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); + (ss+1)->skipEarlyPruning = false; pos.undo_null_move(); if (nullValue >= beta) @@ -681,46 +666,30 @@ namespace { if (nullValue >= VALUE_MATE_IN_MAX_PLY) nullValue = beta; - if (depth < 12 * ONE_PLY) + if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN) return nullValue; // Do verification search at high depths - ss->skipNullMove = true; - Value v = search(pos, ss, alpha, beta, depth-R, false); - ss->skipNullMove = false; + 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); + ss->skipEarlyPruning = false; if (v >= beta) return nullValue; } - else - { - // The null move failed low, which means that we may be faced with - // some kind of threat. If the previous move was reduced, check if - // the move that refuted the null move was somehow connected to the - // move which was reduced. If a connection is found, return a fail - // low score (which will cause the reduced move to fail high in the - // parent node, which will trigger a re-search with full depth). - threatMove = (ss+1)->currentMove; - - if ( depth < 5 * ONE_PLY - && (ss-1)->reduction - && threatMove != MOVE_NONE - && allows(pos, (ss-1)->currentMove, threatMove)) - return alpha; - } } - // Step 9. ProbCut (is omitted in PV nodes) + // 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 ( !PvNode && depth >= 5 * ONE_PLY - && !ss->skipNullMove && abs(beta) < VALUE_MATE_IN_MAX_PLY) { - Value rbeta = beta + 200; - Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY; + Value rbeta = std::min(beta + 200, VALUE_INFINITE); + Depth rdepth = depth - 4 * ONE_PLY; assert(rdepth >= ONE_PLY); assert((ss-1)->currentMove != MOVE_NONE); @@ -730,30 +699,29 @@ namespace { CheckInfo ci(pos); while ((move = mp.next_move()) != MOVE_NONE) - if (pos.pl_move_is_legal(move, ci.pinned)) + if (pos.legal(move, ci.pinned)) { ss->currentMove = move; - pos.do_move(move, st, ci, pos.move_gives_check(move, ci)); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + pos.do_move(move, st, ci, pos.gives_check(move, ci)); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); pos.undo_move(move); if (value >= rbeta) return value; } } - // Step 10. Internal iterative deepening - if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) - && ttMove == MOVE_NONE - && (PvNode || ss->staticEval + Value(256) >= beta)) + // Step 10. Internal iterative deepening (skipped when in check) + if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) + && !ttMove + && (PvNode || ss->staticEval + 256 >= beta)) { - Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); + Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2); + ss->skipEarlyPruning = true; + search(pos, ss, alpha, beta, d / 2, true); + ss->skipEarlyPruning = false; - ss->skipNullMove = true; - search(pos, ss, alpha, beta, d, true); - ss->skipNullMove = false; - - tte = TT.probe(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; + tte = TT.probe(posKey, ttHit); + ttMove = ttHit ? tte->move() : MOVE_NONE; } moves_loop: // When in check and at SpNode search starts from here @@ -762,13 +730,23 @@ moves_loop: // When in check and at SpNode search starts from here Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first, Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second }; - MovePicker mp(pos, ttMove, depth, History, countermoves, ss, PvNode ? -VALUE_INFINITE : beta); + 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); CheckInfo ci(pos); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc + improving = ss->staticEval >= (ss-2)->staticEval + || ss->staticEval == VALUE_NONE + ||(ss-2)->staticEval == VALUE_NONE; + singularExtensionNode = !RootNode && !SpNode - && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY) + && depth >= 8 * ONE_PLY && ttMove != MOVE_NONE + /* && ttValue != VALUE_NONE Already implicit in the next condition */ + && abs(ttValue) < VALUE_KNOWN_WIN && !excludedMove // Recursive singular search is not allowed && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; @@ -783,86 +761,85 @@ moves_loop: // When in check and at SpNode search starts from here continue; // 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 + // 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)) continue; if (SpNode) { - // Shared counter cannot be decremented later if move turns out to be illegal - if (!pos.pl_move_is_legal(move, ci.pinned)) + // 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++; + ++moveCount; if (RootNode) { Signals.firstRootMove = (moveCount == 1); - if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000) + if (thisThread == Threads.main() && Time::now() - SearchTime > 3000) sync_cout << "info depth " << depth / ONE_PLY - << " currmove " << move_to_uci(move, pos.is_chess960()) + << " currmove " << UCI::format_move(move, pos.is_chess960()) << " currmovenumber " << moveCount + PVIdx << sync_endl; } - ext = DEPTH_ZERO; - captureOrPromotion = pos.is_capture_or_promotion(move); - givesCheck = pos.move_gives_check(move, ci); - dangerous = givesCheck - || pos.is_passed_pawn_push(move) - || type_of(move) == CASTLE; + if (PvNode) + (ss+1)->pv = NULL; + + extension = DEPTH_ZERO; + captureOrPromotion = pos.capture_or_promotion(move); - // Step 12. Extend checks and, in PV nodes, also dangerous moves - if (PvNode && dangerous) - ext = ONE_PLY; + givesCheck = type_of(move) == NORMAL && !ci.dcCandidates + ? ci.checkSq[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); - else if (givesCheck && pos.see_sign(move) >= 0) - ext = ONE_PLY / 2; + // Step 12. Extend checks + if (givesCheck && pos.see_sign(move) >= VALUE_ZERO) + extension = ONE_PLY; // Singular extension search. If all moves but one fail low on a search of // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move // is singular and should be extended. To verify this we do a reduced search - // on all the other moves but the ttMove, if result is lower than ttValue minus - // a margin then we extend ttMove. + // on all the other moves but the ttMove and if the result is lower than + // ttValue minus a margin then we extend the ttMove. if ( singularExtensionNode && move == ttMove - && !ext - && pos.pl_move_is_legal(move, ci.pinned) - && abs(ttValue) < VALUE_KNOWN_WIN) + && !extension + && pos.legal(move, ci.pinned)) { - assert(ttValue != VALUE_NONE); - - Value rBeta = ttValue - int(depth); + Value rBeta = ttValue - 2 * depth / ONE_PLY; ss->excludedMove = move; - ss->skipNullMove = true; - value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); - ss->skipNullMove = false; + ss->skipEarlyPruning = true; + value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); + ss->skipEarlyPruning = false; ss->excludedMove = MOVE_NONE; if (value < rBeta) - ext = ONE_PLY; + extension = ONE_PLY; } - // Update current move (this must be done after singular extension search) - newDepth = depth - ONE_PLY + ext; + // Update the current move (this must be done after singular extension search) + newDepth = depth - ONE_PLY + extension; - // Step 13. Futility pruning (is omitted in PV nodes) + // Step 13. Pruning at shallow depth (exclude PV nodes) if ( !PvNode && !captureOrPromotion && !inCheck && !dangerous - /* && move != ttMove Already implicit in the next condition */ && bestValue > VALUE_MATED_IN_MAX_PLY) { // Move count based pruning if ( depth < 16 * ONE_PLY - && moveCount >= FutilityMoveCounts[depth] - && (!threatMove || !refutes(pos, move, threatMove))) + && moveCount >= FutilityMoveCounts[improving][depth]) { if (SpNode) splitPoint->mutex.lock(); @@ -870,51 +847,48 @@ moves_loop: // When in check and at SpNode search starts from here continue; } - // Value based pruning - // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth, - // but fixing this made program slightly weaker. - Depth predictedDepth = newDepth - reduction(depth, moveCount); - futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount) - + Gains[pos.piece_moved(move)][to_sq(move)]; + predictedDepth = newDepth - reduction(improving, depth, moveCount); - if (futilityValue < beta) + // Futility pruning: parent node + if (predictedDepth < 7 * ONE_PLY) { - bestValue = std::max(bestValue, futilityValue); + futilityValue = ss->staticEval + futility_margin(predictedDepth) + + 128 + Gains[pos.moved_piece(move)][to_sq(move)]; - if (SpNode) + if (futilityValue <= alpha) { - splitPoint->mutex.lock(); - if (bestValue > splitPoint->bestValue) - splitPoint->bestValue = bestValue; + bestValue = std::max(bestValue, futilityValue); + + if (SpNode) + { + splitPoint->mutex.lock(); + if (bestValue > splitPoint->bestValue) + splitPoint->bestValue = bestValue; + } + continue; } - continue; } // Prune moves with negative SEE at low depths - if ( predictedDepth < 4 * ONE_PLY - && pos.see_sign(move) < 0) + if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO) { if (SpNode) splitPoint->mutex.lock(); continue; } - - // We have not pruned the move that will be searched, but remember how - // far in the move list we are to be more aggressive in the child node. - ss->futilityMoveCount = moveCount; } - else - ss->futilityMoveCount = 0; - // Check for legality only before to do the move - if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned)) + // Speculative prefetch as early as possible + prefetch((char*)TT.first_entry(pos.key_after(move))); + + // Check for legality just before making the move + if (!RootNode && !SpNode && !pos.legal(move, ci.pinned)) { moveCount--; continue; } - pvMove = PvNode && moveCount == 1; ss->currentMove = move; if (!SpNode && !captureOrPromotion && quietCount < 64) quietsSearched[quietCount++] = move; @@ -922,35 +896,48 @@ moves_loop: // When in check and at SpNode search starts from here // Step 14. Make the move pos.do_move(move, st, ci, givesCheck); - // Step 15. Reduced depth search (LMR). If the move fails high will be + // Step 15. Reduced depth search (LMR). If the move fails high it will be // re-searched at full depth. - if ( depth > 3 * ONE_PLY - && !pvMove + if ( depth >= 3 * ONE_PLY + && moveCount > 1 && !captureOrPromotion - && !dangerous - && move != ttMove && move != ss->killers[0] && move != ss->killers[1]) { - ss->reduction = reduction(depth, moveCount); + ss->reduction = reduction(improving, depth, moveCount); - if (!PvNode && cutNode) + if ( (!PvNode && cutNode) + || History[pos.piece_on(to_sq(move))][to_sq(move)] < 0) ss->reduction += ONE_PLY; if (move == countermoves[0] || move == countermoves[1]) - ss->reduction = std::max(DEPTH_ZERO, ss->reduction-ONE_PLY); + ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); + + // Decrease reduction for moves that escape a capture + if ( ss->reduction + && type_of(move) == NORMAL + && type_of(pos.piece_on(to_sq(move))) != PAWN + && pos.see(make_move(to_sq(move), from_sq(move))) < 0) + ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); Depth d = std::max(newDepth - ss->reduction, ONE_PLY); if (SpNode) alpha = splitPoint->alpha; - value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + + // 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); + } doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); ss->reduction = DEPTH_ZERO; } else - doFullDepthSearch = !pvMove; + doFullDepthSearch = !PvNode || moveCount > 1; // Step 16. Full depth search, when LMR is skipped or fails high if (doFullDepthSearch) @@ -958,20 +945,26 @@ moves_loop: // When in check and at SpNode search starts from here 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); + 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); + } + + // 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)))) + { + (ss+1)->pv = pv; + (ss+1)->pv[0] = MOVE_NONE; + + 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); } - // Only for PV nodes 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 to fail low with value <= alpha and to try another move. - if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta)))) - 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); // Step 17. Undo move pos.undo_move(move); @@ -985,33 +978,37 @@ moves_loop: // When in check and at SpNode search starts from here alpha = splitPoint->alpha; } - // Finished searching the move. If Signals.stop is true, the search - // was aborted because the user interrupted the search or because we - // ran out of time. In this case, the return value of the search cannot - // be trusted, and we don't update the best move and/or PV. + // 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 + // updating best move, PV and TT. if (Signals.stop || thisThread->cutoff_occurred()) - return value; // To avoid returning VALUE_INFINITE + return VALUE_ZERO; if (RootNode) { RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); // PV move or new best move ? - if (pvMove || value > alpha) + if (moveCount == 1 || value > alpha) { rm.score = value; - rm.extract_pv_from_tt(pos); + rm.pv.resize(1); + + assert((ss+1)->pv); + + for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m) + rm.pv.push_back(*m); // 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 (!pvMove) - BestMoveChanges++; + if (moveCount > 1) + ++BestMoveChanges; } else - // All other moves but the PV are set to the lowest value, this - // is not a problem when sorting becuase sort is stable and move - // position in the list is preserved, just the PV is pushed up. + // All other moves but the PV are set to the lowest value: this is + // not a problem when sorting because the sort is stable and the + // move position in the list is preserved - just the PV is pushed up. rm.score = -VALUE_INFINITE; } @@ -1023,6 +1020,9 @@ moves_loop: // When in check and at SpNode search starts from here { bestMove = SpNode ? splitPoint->bestMove = move : move; + if (PvNode && !RootNode) // Update pv even in fail-high case + update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv); + if (PvNode && value < beta) // Update alpha! Always alpha < beta alpha = SpNode ? splitPoint->alpha = value : value; else @@ -1039,14 +1039,20 @@ moves_loop: // When in check and at SpNode search starts from here // Step 19. Check for splitting the search if ( !SpNode + && Threads.size() >= 2 && depth >= Threads.minimumSplitDepth - && Threads.available_slave(thisThread) + && ( !thisThread->activeSplitPoint + || !thisThread->activeSplitPoint->allSlavesSearching) && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD) { - assert(bestValue < beta); + 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; - thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove, - depth, threatMove, moveCount, &mp, NT, cutNode); if (bestValue >= beta) break; } @@ -1055,50 +1061,30 @@ moves_loop: // When in check and at SpNode search starts from here 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. + /* + if (Signals.stop || thisThread->cutoff_occurred()) + return VALUE_DRAW; + */ + // 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. Note that we can have a false positive in - // case of Signals.stop or thread.cutoff_occurred() are set, but this is - // harmless because return value is discarded anyhow in the parent nodes. - // If we are in a singular extension search then return a fail low score. - // A split node has at least one move, the one tried before to be splitted. + // must be mate or stalemate. If we are in a singular extension search then + // return a fail low score. if (!moveCount) - return excludedMove ? alpha - : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; - - // If we have pruned all the moves without searching return a fail-low score - if (bestValue == -VALUE_INFINITE) - bestValue = alpha; - - TT.store(posKey, value_to_tt(bestValue, ss->ply), - bestValue >= beta ? BOUND_LOWER : - PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval, ss->evalMargin); - - // Quiet best move: update killers, history and countermoves - if ( bestValue >= beta - && !pos.is_capture_or_promotion(bestMove) - && !inCheck) - { - if (ss->killers[0] != bestMove) - { - ss->killers[1] = ss->killers[0]; - ss->killers[0] = bestMove; - } + bestValue = excludedMove ? alpha + : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; - // Increase history value of the cut-off move and decrease all the other - // played non-capture moves. - Value bonus = Value(int(depth) * int(depth)); - History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus); - for (int i = 0; i < quietCount - 1; i++) - { - Move m = quietsSearched[i]; - History.update(pos.piece_moved(m), to_sq(m), -bonus); - } + // 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); - if (is_ok((ss-1)->currentMove)) - Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove); - } + tte->save(posKey, value_to_tt(bestValue, ss->ply), + bestValue >= beta ? BOUND_LOWER : + PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->staticEval, TT.get_generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1113,7 +1099,7 @@ moves_loop: // When in check and at SpNode search starts from here template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { - const bool PvNode = (NT == PV); + const bool PvNode = NT == PV; assert(NT == PV || NT == NonPV); assert(InCheck == !!pos.checkers()); @@ -1121,26 +1107,33 @@ moves_loop: // When in check and at SpNode search starts from here assert(PvNode || (alpha == beta - 1)); assert(depth <= DEPTH_ZERO); + Move pv[MAX_PLY+1]; StateInfo st; - const TTEntry* tte; + TTEntry* tte; + bool ttHit; Key posKey; Move ttMove, move, bestMove; Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; bool givesCheck, evasionPrunable; Depth ttDepth; - // To flag BOUND_EXACT a node with eval above alpha and no available moves if (PvNode) - oldAlpha = alpha; + { + oldAlpha = alpha; // To flag BOUND_EXACT when eval above alpha and no available moves + (ss+1)->pv = pv; + ss->pv[0] = MOVE_NONE; + } ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; - // Check for an instant draw or maximum ply reached - if (pos.is_draw() || ss->ply > MAX_PLY) - return DrawValue[pos.side_to_move()]; + // 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()]; - // Decide whether or not to include checks, this fixes also the type of + assert(0 <= ss->ply && ss->ply < MAX_PLY); + + // Decide whether or not to include checks: this fixes also the type of // TT entry depth that we are going to use. Note that in qsearch we use // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS @@ -1148,16 +1141,16 @@ moves_loop: // When in check and at SpNode search starts from here // Transposition table lookup posKey = pos.key(); - tte = TT.probe(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; - ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE; + tte = TT.probe(posKey, ttHit); + ttMove = ttHit ? tte->move() : MOVE_NONE; + ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - if ( tte + if ( !PvNode + && ttHit && tte->depth() >= ttDepth && ttValue != VALUE_NONE // Only in case of TT access race - && ( PvNode ? tte->bound() == BOUND_EXACT - : ttValue >= beta ? (tte->bound() & BOUND_LOWER) - : (tte->bound() & BOUND_UPPER))) + && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; @@ -1166,27 +1159,32 @@ moves_loop: // When in check and at SpNode search starts from here // Evaluate the position statically if (InCheck) { - ss->staticEval = ss->evalMargin = VALUE_NONE; + ss->staticEval = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; } else { - if (tte) + if (ttHit) { // Never assume anything on values stored in TT - if ( (ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE - ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE) - ss->staticEval = bestValue = evaluate(pos, ss->evalMargin); + if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE) + ss->staticEval = bestValue = evaluate(pos); + + // Can ttValue be used as a better position evaluation? + if (ttValue != VALUE_NONE) + if (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER)) + bestValue = ttValue; } else - ss->staticEval = bestValue = evaluate(pos, ss->evalMargin); + ss->staticEval = bestValue = + (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) { - if (!tte) - TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, - DEPTH_NONE, MOVE_NONE, ss->staticEval, ss->evalMargin); + if (!ttHit) + tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, + DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.get_generation()); return bestValue; } @@ -1194,7 +1192,7 @@ moves_loop: // When in check and at SpNode search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = ss->staticEval + ss->evalMargin + Value(128); + futilityBase = bestValue + 128; } // Initialize a MovePicker object for the current position, and prepare @@ -1209,19 +1207,20 @@ moves_loop: // When in check and at SpNode search starts from here { assert(is_ok(move)); - givesCheck = pos.move_gives_check(move, ci); + givesCheck = type_of(move) == NORMAL && !ci.dcCandidates + ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) + : pos.gives_check(move, ci); // Futility pruning if ( !PvNode && !InCheck && !givesCheck - && move != ttMove - && type_of(move) != PROMOTION - && !pos.is_passed_pawn_push(move)) + && futilityBase > -VALUE_KNOWN_WIN + && !pos.advanced_pawn_push(move)) { - futilityValue = futilityBase - + PieceValue[EG][pos.piece_on(to_sq(move))] - + (type_of(move) == ENPASSANT ? PawnValueEg : VALUE_ZERO); + assert(type_of(move) != ENPASSANT); // Due to !pos.advanced_pawn_push + + futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))]; if (futilityValue < beta) { @@ -1229,42 +1228,31 @@ moves_loop: // When in check and at SpNode search starts from here continue; } - // Prune moves with negative or equal SEE and also moves with positive - // SEE where capturing piece loses a tempo and SEE < beta - futilityBase. - if ( futilityBase < beta - && pos.see(move, beta - futilityBase) <= 0) + if (futilityBase < beta && pos.see(move) <= VALUE_ZERO) { bestValue = std::max(bestValue, futilityBase); continue; } } - // Detect non-capture evasions that are candidate to be pruned + // Detect non-capture evasions that are candidates to be pruned evasionPrunable = InCheck && bestValue > VALUE_MATED_IN_MAX_PLY - && !pos.is_capture(move) + && !pos.capture(move) && !pos.can_castle(pos.side_to_move()); // Don't search moves with negative SEE values if ( !PvNode && (!InCheck || evasionPrunable) - && move != ttMove && type_of(move) != PROMOTION - && pos.see_sign(move) < 0) + && pos.see_sign(move) < VALUE_ZERO) continue; - // Don't search useless checks - if ( !PvNode - && !InCheck - && givesCheck - && move != ttMove - && !pos.is_capture_or_promotion(move) - && ss->staticEval + PawnValueMg / 4 < beta - && !check_is_dangerous(pos, move, futilityBase, beta)) - continue; + // Speculative prefetch as early as possible + prefetch((char*)TT.first_entry(pos.key_after(move))); - // Check for legality only before to do the move - if (!pos.pl_move_is_legal(move, ci.pinned)) + // Check for legality just before making the move + if (!pos.legal(move, ci.pinned)) continue; ss->currentMove = move; @@ -1284,6 +1272,9 @@ moves_loop: // When in check and at SpNode search starts from here if (value > alpha) { + 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 { alpha = value; @@ -1291,8 +1282,8 @@ moves_loop: // When in check and at SpNode search starts from here } else // Fail high { - TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, - ttDepth, move, ss->staticEval, ss->evalMargin); + tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, + ttDepth, move, ss->staticEval, TT.get_generation()); return value; } @@ -1305,9 +1296,9 @@ moves_loop: // When in check and at SpNode search starts from here if (InCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root - TT.store(posKey, value_to_tt(bestValue, ss->ply), - PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, - ttDepth, bestMove, ss->staticEval, ss->evalMargin); + tte->save(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove, ss->staticEval, TT.get_generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1317,7 +1308,7 @@ moves_loop: // When in check and at SpNode search starts from here // value_to_tt() adjusts a mate score from "plies to mate from the root" to // "plies to mate from the current position". Non-mate scores are unchanged. - // The function is called before storing a value to the transposition table. + // The function is called before storing a value in the transposition table. Value value_to_tt(Value v, int ply) { @@ -1329,7 +1320,7 @@ moves_loop: // When in check and at SpNode search starts from here // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score - // from the transposition table (where refers to the plies to mate/be mated + // from the transposition table (which refers to the plies to mate/be mated // from current position) to "plies to mate/be mated from the root". Value value_from_tt(Value v, int ply) { @@ -1340,167 +1331,82 @@ moves_loop: // When in check and at SpNode search starts from here } - // check_is_dangerous() tests if a checking move can be pruned in qsearch() + // update_pv() adds current move and appends child pv[] - bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta) - { - Piece pc = pos.piece_moved(move); - Square from = from_sq(move); - Square to = to_sq(move); - Color them = ~pos.side_to_move(); - Square ksq = pos.king_square(them); - Bitboard enemies = pos.pieces(them); - Bitboard kingAtt = pos.attacks_from(ksq); - Bitboard occ = pos.pieces() ^ from ^ ksq; - Bitboard oldAtt = pos.attacks_from(pc, from, occ); - Bitboard newAtt = pos.attacks_from(pc, to, occ); - - // Checks which give opponent's king at most one escape square are dangerous - if (!more_than_one(kingAtt & ~(enemies | newAtt | to))) - return true; - - // Queen contact check is very dangerous - if (type_of(pc) == QUEEN && (kingAtt & to)) - return true; - - // Creating new double threats with checks is dangerous - Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt; - while (b) - { - // Note that here we generate illegal "double move"! - if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta) - return true; - } + void update_pv(Move* pv, Move move, Move* childPv) { - return false; + for (*pv++ = move; childPv && *childPv != MOVE_NONE; ) + *pv++ = *childPv++; + *pv = MOVE_NONE; } + // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high + // of a quiet move. - // allows() tests whether the 'first' move at previous ply somehow makes the - // 'second' move possible, for instance if the moving piece is the same in - // both moves. Normally the second move is the threat (the best move returned - // from a null search that fails low). - - bool allows(const Position& pos, Move first, Move second) { + void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) { - assert(is_ok(first)); - assert(is_ok(second)); - assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move()); - assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move()); - - Square m1from = from_sq(first); - Square m2from = from_sq(second); - Square m1to = to_sq(first); - Square m2to = to_sq(second); - - // The piece is the same or second's destination was vacated by the first move - if (m1to == m2from || m2to == m1from) - return true; - - // Second one moves through the square vacated by first one - if (between_bb(m2from, m2to) & m1from) - return true; - - // Second's destination is defended by the first move's piece - Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from); - if (m1att & m2to) - return true; - - // Second move gives a discovered check through the first's checking piece - if (m1att & pos.king_square(pos.side_to_move())) + if (ss->killers[0] != move) { - assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from); - return true; + ss->killers[1] = ss->killers[0]; + ss->killers[0] = move; } - return false; - } - - - // refutes() tests whether a 'first' move is able to defend against a 'second' - // opponent's move. In this case will not be pruned. Normally the second move - // is the threat (the best move returned from a null search that fails low). - - bool refutes(const Position& pos, Move first, Move second) { - - assert(is_ok(first)); - assert(is_ok(second)); - - Square m1from = from_sq(first); - Square m2from = from_sq(second); - Square m1to = to_sq(first); - Square m2to = to_sq(second); - - // Don't prune moves of the threatened piece - if (m1from == m2to) - return true; - - // If the threatened piece has value less than or equal to the value of the - // threat piece, don't prune moves which defend it. - if ( pos.is_capture(second) - && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)] - || type_of(pos.piece_on(m2from)) == KING)) + // 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) { - // Update occupancy as if the piece and the threat are moving - Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from; - Piece pc = pos.piece_on(m1from); - - // The moved piece attacks the square 'tto' ? - if (pos.attacks_from(pc, m1to, occ) & m2to) - return true; - - // Scan for possible X-ray attackers behind the moved piece - Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, ROOK)) - | (attacks_bb(m2to, occ) & pos.pieces(color_of(pc), QUEEN, BISHOP)); - - // Verify attackers are triggered by our move and not already existing - if (xray && (xray ^ (xray & pos.attacks_from(m2to)))) - return true; + Move m = quiets[i]; + History.update(pos.moved_piece(m), to_sq(m), -bonus); } - // Don't prune safe moves which block the threat path - if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0) - return true; + if (is_ok((ss-1)->currentMove)) + { + Square prevMoveSq = to_sq((ss-1)->currentMove); + Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move); + } - return false; + if (is_ok((ss-2)->currentMove) && (ss-1)->currentMove == (ss-1)->ttMove) + { + Square prevOwnMoveSq = to_sq((ss-2)->currentMove); + Followupmoves.update(pos.piece_on(prevOwnMoveSq), prevOwnMoveSq, move); + } } - // When playing with strength handicap choose best move among the MultiPV set - // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. + // 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. Move Skill::pick_move() { - static RKISS rk; - - // PRNG sequence should be not deterministic - for (int i = Time::now() % 50; i > 0; i--) - rk.rand(); + // PRNG sequence should be non-deterministic, so we seed it with the time at init + static PRNG rng(Time::now()); // RootMoves are already sorted by score in descending order - int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg); + int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg); int weakness = 120 - 2 * level; - int max_s = -VALUE_INFINITE; + 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, + // weakness. One deterministic and bigger for weaker moves, and one random, // then we choose the move with the resulting highest score. - for (size_t i = 0; i < PVSize; i++) + for (size_t i = 0; i < candidates; ++i) { - int s = RootMoves[i].score; + int score = RootMoves[i].score; // Don't allow crazy blunders even at very low skills - if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg) + if (i > 0 && RootMoves[i - 1].score > score + 2 * PawnValueMg) break; // This is our magic formula - s += ( weakness * int(RootMoves[0].score - s) - + variance * (rk.rand() % weakness)) / 128; + score += ( weakness * int(RootMoves[0].score - score) + + variance * (rng.rand() % weakness)) / 128; - if (s > max_s) + if (score > maxScore) { - max_s = s; + maxScore = score; best = RootMoves[i].pv[0]; } } @@ -1508,110 +1414,80 @@ moves_loop: // When in check and at SpNode search starts from here } - // uci_pv() formats PV information according to UCI protocol. UCI requires - // to send all the PV lines also if are still to be searched and so refer to - // the previous search score. + // 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. - string uci_pv(const Position& pos, int depth, Value alpha, Value beta) { + string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta) { - std::stringstream s; + std::stringstream ss; Time::point elapsed = Time::now() - SearchTime + 1; size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size()); int selDepth = 0; - for (size_t i = 0; i < Threads.size(); i++) + for (size_t i = 0; i < Threads.size(); ++i) if (Threads[i]->maxPly > selDepth) selDepth = Threads[i]->maxPly; - for (size_t i = 0; i < uciPVSize; i++) + for (size_t i = 0; i < uciPVSize; ++i) { bool updated = (i <= PVIdx); - if (depth == 1 && !updated) + if (depth == ONE_PLY && !updated) continue; - int d = updated ? depth : depth - 1; - Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore; + 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 (s.rdbuf()->in_avail()) // Not at first line - s << "\n"; + if (ss.rdbuf()->in_avail()) // Not at first line + ss << "\n"; - s << "info depth " << d - << " seldepth " << selDepth - << " score " << (i == PVIdx ? score_to_uci(v, alpha, beta) : score_to_uci(v)) - << " nodes " << pos.nodes_searched() - << " nps " << pos.nodes_searched() * 1000 / elapsed - << " time " << elapsed - << " multipv " << i + 1 - << " pv"; + ss << "info depth " << d / ONE_PLY + << " seldepth " << selDepth + << " multipv " << i + 1 + << " score " << ((!tb && i == PVIdx) ? UCI::format_value(v, alpha, beta) : UCI::format_value(v)) + << " nodes " << pos.nodes_searched() + << " nps " << pos.nodes_searched() * 1000 / elapsed + << " tbhits " << TB::Hits + << " time " << elapsed + << " pv"; - for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++) - s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960()); + for (size_t j = 0; j < RootMoves[i].pv.size(); ++j) + ss << " " << UCI::format_move(RootMoves[i].pv[j], pos.is_chess960()); } - return s.str(); + return ss.str(); } } // namespace -/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table. -/// We consider also failing high nodes and not only BOUND_EXACT nodes so to -/// allow to always have a ponder move even when we fail high at root, and a -/// long PV to print that is important for position analysis. - -void RootMove::extract_pv_from_tt(Position& pos) { - - StateInfo state[MAX_PLY_PLUS_2], *st = state; - const TTEntry* tte; - int ply = 0; - Move m = pv[0]; - - pv.clear(); - - do { - pv.push_back(m); - - assert(MoveList(pos).contains(pv[ply])); - - pos.do_move(pv[ply++], *st++); - tte = TT.probe(pos.key()); - - } while ( tte - && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change - && pos.pl_move_is_legal(m, pos.pinned_pieces()) - && ply < MAX_PLY - && (!pos.is_draw() || ply < 2)); - - pv.push_back(MOVE_NONE); // Must be zero-terminating - - while (ply) pos.undo_move(pv[--ply]); -} - - /// 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_PLUS_2], *st = state; - const TTEntry* tte; - int ply = 0; - - do { - tte = TT.probe(pos.key()); + StateInfo state[MAX_PLY], *st = state; + size_t idx = 0; - if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries - TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE, VALUE_NONE); + for ( ; idx < pv.size(); ++idx) + { + bool ttHit; + TTEntry* tte = TT.probe(pos.key(), ttHit); - assert(MoveList(pos).contains(pv[ply])); + 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.get_generation()); - pos.do_move(pv[ply++], *st++); + assert(MoveList(pos).contains(pv[idx])); - } while (pv[ply] != MOVE_NONE); + pos.do_move(pv[idx], *st++); + } - while (ply) pos.undo_move(pv[--ply]); + while (idx) pos.undo_move(pv[--idx]); } @@ -1620,60 +1496,27 @@ void RootMove::insert_pv_in_tt(Position& pos) { void Thread::idle_loop() { // Pointer 'this_sp' is not null only if we are called from split(), and not - // at the thread creation. So it means we are the split point's master. + // at the thread creation. This means we are the split point's master. SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL; assert(!this_sp || (this_sp->masterThread == this && searching)); - while (true) + while (!exit) { - // If we are not searching, wait for a condition to be signaled instead of - // wasting CPU time polling for work. - while ((!searching && Threads.sleepWhileIdle) || exit) - { - if (exit) - { - assert(!this_sp); - return; - } - - // Grab the lock to avoid races with Thread::notify_one() - mutex.lock(); - - // If we are master and all slaves have finished then exit idle_loop - if (this_sp && !this_sp->slavesMask) - { - mutex.unlock(); - break; - } - - // Do sleep after retesting sleep conditions under lock protection, in - // particular we need to avoid a deadlock in case a master thread has, - // in the meanwhile, allocated us and sent the notify_one() call before - // we had the chance to grab the lock. - if (!searching && !exit) - sleepCondition.wait(mutex); - - mutex.unlock(); - } - // If this thread has been assigned work, launch a search - if (searching) + while (searching) { - assert(!exit); - Threads.mutex.lock(); - assert(searching); assert(activeSplitPoint); SplitPoint* sp = activeSplitPoint; Threads.mutex.unlock(); - Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1) + Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) Position pos(*sp->pos, this); - std::memcpy(ss-1, sp->ss-1, 4 * sizeof(Stack)); + std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack)); ss->splitPoint = sp; sp->mutex.lock(); @@ -1682,66 +1525,101 @@ void Thread::idle_loop() { activePosition = &pos; - switch (sp->nodeType) { - case Root: - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - break; - case PV: - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - break; - case NonPV: - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - break; - default: + 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); - } assert(searching); searching = false; activePosition = NULL; - sp->slavesMask &= ~(1ULL << idx); + sp->slavesMask.reset(idx); + sp->allSlavesSearching = false; sp->nodes += pos.nodes_searched(); - // Wake up master thread so to allow it to return from the idle loop - // in case we are the last slave of the split point. - if ( Threads.sleepWhileIdle - && this != sp->masterThread - && !sp->slavesMask) + // 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(); } - // After releasing the lock we cannot access anymore any SplitPoint - // related data in a safe way becuase it could have been released under - // our feet by the sp master. Also accessing other Thread objects is - // unsafe because if we are exiting there is a chance are already freed. + // 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(); + + // 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; + + 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 this thread is the master of a split point and all slaves have finished - // their work at this split point, return from the idle loop. - if (this_sp && !this_sp->slavesMask) + // Grab the lock to avoid races with Thread::notify_one() + mutex.lock(); + + // If we are master and all slaves have finished then exit idle_loop + if (this_sp && this_sp->slavesMask.none()) { - this_sp->mutex.lock(); - bool finished = !this_sp->slavesMask; // Retest under lock protection - this_sp->mutex.unlock(); - if (finished) - return; + assert(!searching); + mutex.unlock(); + break; } + + // 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); + + mutex.unlock(); } } /// check_time() is called by the timer thread when the timer triggers. It is -/// used to print debug info and, more important, to detect when we are out of -/// available time and so stop the search. +/// used to print debug info and, more importantly, to detect when we are out of +/// available time and thus stop the search. void check_time() { static Time::point lastInfoTime = Time::now(); - int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning + Time::point elapsed = Time::now() - SearchTime; if (Time::now() - lastInfoTime >= 1000) { @@ -1749,49 +1627,50 @@ void check_time() { dbg_print(); } + // An engine may not stop pondering until told so by the GUI if (Limits.ponder) return; - if (Limits.nodes) + if (Limits.use_time_management()) + { + bool stillAtFirstMove = Signals.firstRootMove + && !Signals.failedLowAtRoot + && elapsed > TimeMgr.available_time() * 75 / 100; + + if ( stillAtFirstMove + || elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution) + Signals.stop = true; + } + else if (Limits.movetime && elapsed >= Limits.movetime) + Signals.stop = true; + + else if (Limits.nodes) { Threads.mutex.lock(); - nodes = RootPos.nodes_searched(); + int64_t nodes = RootPos.nodes_searched(); // 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++) + 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(); nodes += sp.nodes; - Bitboard sm = sp.slavesMask; - while (sm) - { - Position* pos = Threads[pop_lsb(&sm)]->activePosition; - if (pos) - nodes += pos->nodes_searched(); - } + + for (size_t idx = 0; idx < Threads.size(); ++idx) + if (sp.slavesMask.test(idx) && Threads[idx]->activePosition) + nodes += Threads[idx]->activePosition->nodes_searched(); sp.mutex.unlock(); } Threads.mutex.unlock(); - } - - Time::point elapsed = Time::now() - SearchTime; - bool stillAtFirstMove = Signals.firstRootMove - && !Signals.failedLowAtRoot - && elapsed > TimeMgr.available_time(); - bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution - || stillAtFirstMove; - - if ( (Limits.use_time_management() && noMoreTime) - || (Limits.movetime && elapsed >= Limits.movetime) - || (Limits.nodes && nodes >= Limits.nodes)) - Signals.stop = true; + if (nodes >= Limits.nodes) + Signals.stop = true; + } }