X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=204e5fc8b7440cf941c893fe3a4deafc68285d3c;hb=e40b06a0503b44bae5508a371d961914828214b6;hp=fdad3e51d50f9183c378f1aa1ded6205aa52d426;hpb=30c14fdc9532fc94217eba708653a188a9b24504;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index fdad3e51..204e5fc8 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) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2012 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 @@ -17,342 +17,106 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include #include #include -#include #include #include -#include #include "book.h" #include "evaluate.h" #include "history.h" -#include "misc.h" #include "movegen.h" #include "movepick.h" -#include "lock.h" -#include "san.h" +#include "notation.h" #include "search.h" #include "timeman.h" #include "thread.h" #include "tt.h" #include "ucioption.h" -using std::cout; -using std::endl; +namespace Search { -//// -//// Local definitions -//// + volatile SignalsType Signals; + LimitsType Limits; + std::vector RootMoves; + Position RootPosition; + Color RootColor; + Time::point SearchTime; + StateStackPtr SetupStates; +} -namespace { +using std::string; +using Eval::evaluate; +using namespace Search; - // Types - enum NodeType { NonPV, PV }; +namespace { - // Set to true to force running with one thread. - // Used for debugging SMP code. + // Set to true to force running with one thread. Used for debugging const bool FakeSplit = false; - // Fast lookup table of sliding pieces indexed by Piece - const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; - inline bool piece_is_slider(Piece p) { return Slidings[p]; } - - // ThreadsManager class is used to handle all the threads related stuff in search, - // init, starting, parking and, the most important, launching a slave thread at a - // split point are what this class does. All the access to shared thread data is - // done through this class, so that we avoid using global variables instead. - - class ThreadsManager { - /* As long as the single ThreadsManager object is defined as a global we don't - need to explicitly initialize to zero its data members because variables with - static storage duration are automatically set to zero before enter main() - */ - public: - void init_threads(); - void exit_threads(); - - int min_split_depth() const { return minimumSplitDepth; } - int active_threads() const { return activeThreads; } - void set_active_threads(int cnt) { activeThreads = cnt; } - - void read_uci_options(); - bool available_thread_exists(int master) const; - bool thread_is_available(int slave, int master) const; - bool cutoff_at_splitpoint(int threadID) const; - void wake_sleeping_thread(int threadID); - void idle_loop(int threadID, SplitPoint* sp); - - template - void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode); - - private: - Depth minimumSplitDepth; - int maxThreadsPerSplitPoint; - bool useSleepingThreads; - int activeThreads; - volatile bool allThreadsShouldExit; - Thread threads[MAX_THREADS]; - Lock mpLock, sleepLock[MAX_THREADS]; - WaitCondition sleepCond[MAX_THREADS]; - }; - - - // RootMove struct is used for moves at the root at the tree. For each root - // move, we store two scores, a node count, and a PV (really a refutation - // in the case of moves which fail low). Value pvScore is normally set at - // -VALUE_INFINITE for all non-pv moves, while nonPvScore is computed - // according to the order in which moves are returned by MovePicker. - - struct RootMove { - - RootMove() : nodes(0) { pv_score = non_pv_score = -VALUE_INFINITE; move = pv[0] = MOVE_NONE; } - RootMove(const RootMove& rm) { *this = rm; } - RootMove& operator=(const RootMove& rm); // Skip costly full pv[] copy - - // RootMove::operator<() is the comparison function used when - // sorting the moves. A move m1 is considered to be better - // than a move m2 if it has an higher pvScore, or if it has - // equal pvScore but m1 has the higher nonPvScore. In this way - // we are guaranteed that PV moves are always sorted as first. - bool operator<(const RootMove& m) const { - return pv_score != m.pv_score ? pv_score < m.pv_score : non_pv_score <= m.non_pv_score; - } - void set_pv(const Move newPv[]); - - int64_t nodes; - Value pv_score, non_pv_score; - Move move, pv[PLY_MAX_PLUS_2]; - }; + // This is the minimum interval in msec between two check_time() calls + const int TimerResolution = 5; - RootMove& RootMove::operator=(const RootMove& rm) { + // Different node types, used as template parameter + enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; - pv_score = rm.pv_score; non_pv_score = rm.non_pv_score; - nodes = rm.nodes; move = rm.move; - set_pv(rm.pv); - return *this; - } + // Lookup table to check if a Piece is a slider and its access function + const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; + inline bool piece_is_slider(Piece p) { return Slidings[p]; } - void RootMove::set_pv(const Move newPv[]) { + // Dynamic razoring margin based on depth + inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } - int i = -1; + // Futility lookup tables (initialized at startup) and their access functions + Value FutilityMargins[16][64]; // [depth][moveNumber] + int FutilityMoveCounts[32]; // [depth] - while (newPv[++i] != MOVE_NONE) - pv[i] = newPv[i]; + inline Value futility_margin(Depth d, int mn) { - pv[i] = MOVE_NONE; + return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)] + : 2 * VALUE_INFINITE; } + // Reduction lookup tables (initialized at startup) and their access function + int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] - // The RootMoveList struct is essentially a std::vector<> of RootMove objects, - // with an handful of methods above the standard ones. - - struct RootMoveList : public std::vector { - - typedef std::vector Base; + template inline Depth reduction(Depth d, int mn) { - RootMoveList(Position& pos, Move searchMoves[]); - void sort() { sort_multipv((int)size() - 1); } // Sort all items - - void set_non_pv_scores(const Position& pos); - void sort_multipv(int n); - }; - - - // When formatting a move for std::cout we must know if we are in Chess960 - // or not. To keep using the handy operator<<() on the move the trick is to - // embed this flag in the stream itself. Function-like named enum set960 is - // used as a custom manipulator and the stream internal general-purpose array, - // accessed through ios_base::iword(), is used to pass the flag to the move's - // operator<<() that will use it to properly format castling moves. - enum set960 {}; - - std::ostream& operator<< (std::ostream& os, const set960& m) { - - os.iword(0) = int(m); - return os; + return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; } - - /// Adjustments - - // Step 6. Razoring - - // Maximum depth for razoring - const Depth RazorDepth = 4 * ONE_PLY; - - // Dynamic razoring margin based on depth - inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); } - - // Maximum depth for use of dynamic threat detection when null move fails low - const Depth ThreatDepth = 5 * ONE_PLY; - - // Step 9. Internal iterative deepening - - // Minimum depth for use of internal iterative deepening - const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */}; - - // At Non-PV nodes we do an internal iterative deepening search - // when the static evaluation is bigger then beta - IIDMargin. - const Value IIDMargin = Value(0x100); - - // Step 11. Decide the new search depth - - // Extensions. Configurable UCI options - // Array index 0 is used at non-PV nodes, index 1 at PV nodes. - Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2]; - Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2]; - - // Minimum depth for use of singular extension - const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */}; - - // If the TT move is at least SingularExtensionMargin better then the - // remaining ones we will extend it. - const Value SingularExtensionMargin = Value(0x20); - - // Step 12. Futility pruning - - // Futility margin for quiescence search - const Value FutilityMarginQS = Value(0x80); - - // Futility lookup tables (initialized at startup) and their getter functions - Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber] - int FutilityMoveCountArray[32]; // [depth] - - inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; } - inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; } - - // Step 14. Reduced search - - // Reduction lookup tables (initialized at startup) and their getter functions - int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber] - - template - inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; } - - // Common adjustments - - // Search depth at iteration 1 - const Depth InitialDepth = ONE_PLY; - - // Easy move margin. An easy move candidate must be at least this much - // better than the second best move. - const Value EasyMoveMargin = Value(0x200); - - - /// Namespace variables - - // Book object - Book OpeningBook; - - // Iteration counter - int Iteration; - - // Scores and number of times the best move changed for each iteration - Value ValueByIteration[PLY_MAX_PLUS_2]; - int BestMoveChangesByIteration[PLY_MAX_PLUS_2]; - - // Search window management - int AspirationDelta; - - // MultiPV mode - int MultiPV; - - // Time managment variables - int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime; - bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit; - bool FirstRootMove, AbortSearch, Quit, AspirationFailLow; + size_t MultiPV, UCIMultiPV, PVIdx; TimeManager TimeMgr; - - // Log file - bool UseLogFile; - std::ofstream LogFile; - - // Multi-threads manager object - ThreadsManager ThreadsMgr; - - // Node counters, used only by thread[0] but try to keep in different cache - // lines (64 bytes each) from the heavy multi-thread read accessed variables. - int NodesSincePoll; - int NodesBetweenPolls = 30000; - - // History table + int BestMoveChanges; + int SkillLevel; + bool SkillLevelEnabled, Chess960; + Value DrawValue[COLOR_NB]; History H; - /// Local functions + template + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - Value id_loop(Position& pos, Move searchMoves[]); - Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr); + template + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); - - template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); - - template - inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { - - return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO, ply) - : search(pos, ss, alpha, beta, depth, ply); - } - - template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous); - - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue); + void id_loop(Position& pos); + bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta); bool connected_moves(const Position& pos, Move m1, Move m2); - bool value_is_mate(Value value); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); bool connected_threat(const Position& pos, Move m, Move threat); - Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); - void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); - void update_killers(Move m, SearchStack* ss); - void update_gains(const Position& pos, Move move, Value before, Value after); - - int current_search_time(); - std::string value_to_uci(Value v); - int nps(const Position& pos); - void poll(const Position& pos); - void ponderhit(); - void wait_for_stop_or_ponderhit(); - void init_ss_array(SearchStack* ss, int size); - void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value); - void insert_pv_in_tt(const Position& pos, Move pv[]); - void extract_pv_from_tt(const Position& pos, Move bestMove, Move pv[]); - -#if !defined(_MSC_VER) - void* init_thread(void* threadID); -#else - DWORD WINAPI init_thread(LPVOID threadID); -#endif - -} + Value refine_eval(const TTEntry* tte, Value ttValue, Value defaultEval); + Move do_skill_level(); + string uci_pv(const Position& pos, int depth, Value alpha, Value beta); - -//// -//// Functions -//// - -/// init_threads(), exit_threads() and nodes_searched() are helpers to -/// give accessibility to some TM methods from outside of current file. - -void init_threads() { ThreadsMgr.init_threads(); } -void exit_threads() { ThreadsMgr.exit_threads(); } +} // namespace -/// init_search() is called during startup. It initializes various lookup tables +/// Search::init() is called during startup to initialize various lookup tables -void init_search() { +void Search::init() { int d; // depth (ONE_PLY == 2) int hd; // half depth (ONE_PLY == 1) @@ -363,601 +127,336 @@ void init_search() { { double pvRed = log(double(hd)) * log(double(mc)) / 3.0; double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25; - ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0); - ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0); + 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); } // Init futility margins array for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++) - FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45); + FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45); // Init futility move count array for (d = 0; d < 32; d++) - FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0)); + FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(double(d), 2.0)); } -/// perft() is our utility to verify move generation is bug free. All the legal -/// moves up to given depth are generated and counted and the sum returned. +/// 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. -int perft(Position& pos, Depth depth) -{ - MoveStack mlist[MOVES_MAX]; - StateInfo st; - Move m; - int sum = 0; +size_t Search::perft(Position& pos, Depth depth) { - // Generate all legal moves - MoveStack* last = generate_moves(pos, mlist); + // At the last ply just return the number of legal moves (leaf nodes) + if (depth == ONE_PLY) + return MoveList(pos).size(); - // If we are at the last ply we don't need to do and undo - // the moves, just to count them. - if (depth <= ONE_PLY) - return int(last - mlist); + StateInfo st; + size_t cnt = 0; + CheckInfo ci(pos); - // Loop through all legal moves - CheckInfo ci(pos); - for (MoveStack* cur = mlist; cur != last; cur++) - { - m = cur->move; - pos.do_move(m, st, ci, pos.move_is_check(m, ci)); - sum += perft(pos, depth - ONE_PLY); - pos.undo_move(m); - } - return sum; + for (MoveList ml(pos); !ml.end(); ++ml) + { + pos.do_move(ml.move(), st, ci, pos.move_gives_check(ml.move(), ci)); + cnt += perft(pos, depth - ONE_PLY); + pos.undo_move(ml.move()); + } + + return cnt; } -/// think() is the external interface to Stockfish's search, and is called when -/// the program receives the UCI 'go' command. It initializes various -/// search-related global variables, and calls root_search(). It returns false -/// when a quit command is received during the search. +/// 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 RootPosition and at the end prints the "bestmove" to output. -bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[], - int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) { +void Search::think() { - // Initialize global search variables - StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false; - NodesSincePoll = 0; - SearchStartTime = get_system_time(); - ExactMaxTime = maxTime; - MaxDepth = maxDepth; - MaxNodes = maxNodes; - InfiniteSearch = infinite; - PonderSearch = ponder; - UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch; + static PolyglotBook book; // Defined static to initialize the PRNG only once - // Look for a book move, only during games, not tests - if (UseTimeManagement && Options["OwnBook"].value()) - { - if (Options["Book File"].value() != OpeningBook.file_name()) - OpeningBook.open(Options["Book File"].value()); + Position& pos = RootPosition; + Chess960 = pos.is_chess960(); + RootColor = pos.side_to_move(); + TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move()); + TT.new_search(); + H.clear(); - Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value()); - if (bookMove != MOVE_NONE) - { - if (PonderSearch) - wait_for_stop_or_ponderhit(); + if (RootMoves.empty()) + { + sync_cout << "info depth 0 score " + << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; - cout << "bestmove " << bookMove << endl; - return true; - } + RootMoves.push_back(MOVE_NONE); + goto finalize; } - // Read UCI option values - TT.set_size(Options["Hash"].value()); - if (Options["Clear Hash"].value()) + if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) { - Options["Clear Hash"].set_value("false"); - TT.clear(); + int cf = Options["Contempt Factor"] * PawnValueMg / 100; // In centipawns + cf = cf * MaterialTable::game_phase(pos) / PHASE_MIDGAME; // Scale down with phase + DrawValue[ RootColor] = VALUE_DRAW - Value(cf); + DrawValue[~RootColor] = VALUE_DRAW + Value(cf); } - - CheckExtension[1] = Options["Check Extension (PV nodes)"].value(); - CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value(); - SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value(); - SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value(); - PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value(); - PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value(); - PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value(); - PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value(); - PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value(); - PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value(); - MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value(); - MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value(); - MultiPV = Options["MultiPV"].value(); - UseLogFile = Options["Use Search Log"].value(); - - if (UseLogFile) - LogFile.open(Options["Search Log Filename"].value().c_str(), std::ios::out | std::ios::app); - - read_weights(pos.side_to_move()); - - // Set the number of active threads - ThreadsMgr.read_uci_options(); - init_eval(ThreadsMgr.active_threads()); - - // Wake up needed threads - for (int i = 1; i < ThreadsMgr.active_threads(); i++) - ThreadsMgr.wake_sleeping_thread(i); - - // Set thinking time - int myTime = time[pos.side_to_move()]; - int myIncrement = increment[pos.side_to_move()]; - if (UseTimeManagement) - TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter()); - - // Set best NodesBetweenPolls interval to avoid lagging under - // heavy time pressure. - if (MaxNodes) - NodesBetweenPolls = Min(MaxNodes, 30000); - else if (myTime && myTime < 1000) - NodesBetweenPolls = 1000; - else if (myTime && myTime < 5000) - NodesBetweenPolls = 5000; else - NodesBetweenPolls = 30000; + DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW; - // Write search information to log file - if (UseLogFile) - LogFile << "Searching: " << pos.to_fen() << endl - << "infinite: " << infinite - << " ponder: " << ponder - << " time: " << myTime - << " increment: " << myIncrement - << " moves to go: " << movesToGo << endl; + if (Options["OwnBook"] && !Limits.infinite) + { + Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]); - // We're ready to start thinking. Call the iterative deepening loop function - id_loop(pos, searchMoves); + if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove)) + { + std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), bookMove)); + goto finalize; + } + } - if (UseLogFile) - LogFile.close(); + UCIMultiPV = Options["MultiPV"]; + SkillLevel = Options["Skill Level"]; - // This makes all the threads to go to sleep - ThreadsMgr.set_active_threads(1); + // Do we have to play with skill handicap? In this case enable MultiPV that + // we will use behind the scenes to retrieve a set of possible moves. + SkillLevelEnabled = (SkillLevel < 20); + MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV); - return !Quit; -} + if (Options["Use Search Log"]) + { + Log log(Options["Search Log Filename"]); + log << "\nSearching: " << pos.to_fen() + << "\ninfinite: " << Limits.infinite + << " ponder: " << Limits.ponder + << " time: " << Limits.time[pos.side_to_move()] + << " increment: " << Limits.inc[pos.side_to_move()] + << " moves to go: " << Limits.movestogo + << std::endl; + } + Threads.wake_up(); -namespace { + // Set best timer interval to avoid lagging under time pressure. Timer is + // used to check for remaining available thinking time. + if (Limits.use_time_management()) + Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution))); + else if (Limits.nodes) + Threads.set_timer(2 * TimerResolution); + else + Threads.set_timer(100); - // id_loop() is the main iterative deepening loop. It calls root_search - // repeatedly with increasing depth until the allocated thinking time has - // been consumed, the user stops the search, or the maximum search depth is - // reached. + // We're ready to start searching. Call the iterative deepening loop function + id_loop(pos); - Value id_loop(Position& pos, Move searchMoves[]) { + Threads.set_timer(0); // Stop timer + Threads.sleep(); - SearchStack ss[PLY_MAX_PLUS_2]; - Move pv[PLY_MAX_PLUS_2]; - Move EasyMove = MOVE_NONE; - Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; + if (Options["Use Search Log"]) + { + Time::point elapsed = Time::now() - SearchTime + 1; - // Moves to search are verified, copied, scored and sorted - RootMoveList rml(pos, searchMoves); + Log log(Options["Search Log Filename"]); + log << "Nodes: " << pos.nodes_searched() + << "\nNodes/second: " << pos.nodes_searched() * 1000 / elapsed + << "\nBest move: " << move_to_san(pos, RootMoves[0].pv[0]); - // Handle special case of searching on a mate/stale position - if (rml.size() == 0) - { - if (PonderSearch) - wait_for_stop_or_ponderhit(); + StateInfo st; + pos.do_move(RootMoves[0].pv[0], st); + log << "\nPonder move: " << move_to_san(pos, RootMoves[0].pv[1]) << std::endl; + pos.undo_move(RootMoves[0].pv[0]); + } - return pos.is_check() ? -VALUE_MATE : VALUE_DRAW; - } +finalize: - // Print RootMoveList startup scoring to the standard output, - // so to output information also for iteration 1. - cout << set960(pos.is_chess960()) // Is enough to set once at the beginning - << "info depth " << 1 - << "\ninfo depth " << 1 - << " score " << value_to_uci(rml[0].pv_score) - << " time " << current_search_time() - << " nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " pv " << rml[0].move << "\n"; - - // Initialize - TT.new_search(); - H.clear(); - init_ss_array(ss, PLY_MAX_PLUS_2); - pv[0] = pv[1] = MOVE_NONE; - ValueByIteration[1] = rml[0].pv_score; - Iteration = 1; - - // Is one move significantly better than others after initial scoring ? - if ( rml.size() == 1 - || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin) - EasyMove = rml[0].move; - - // Iterative deepening loop - while (Iteration < PLY_MAX) - { - // Initialize iteration - Iteration++; - BestMoveChangesByIteration[Iteration] = 0; + // When we reach max depth we arrive here even without Signals.stop is raised, + // but if we are pondering or in infinite search, we shouldn't print the best + // move before we are told to do so. + if (!Signals.stop && (Limits.ponder || Limits.infinite)) + pos.this_thread()->wait_for_stop_or_ponderhit(); - cout << "info depth " << Iteration << endl; + // Best move could be MOVE_NONE when searching on a stalemate position + sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], Chess960) + << " ponder " << move_to_uci(RootMoves[0].pv[1], Chess960) << sync_endl; +} - // Calculate dynamic aspiration window based on previous iterations - if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN) - { - int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2]; - int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3]; - AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16); - AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize +namespace { - alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE); - beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE); - } + // 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. - // Search to the current depth, rml is updated and sorted, alpha and beta could change - value = root_search(pos, ss, pv, rml, &alpha, &beta); + void id_loop(Position& pos) { - // Write PV to transposition table, in case the relevant entries have - // been overwritten during the search. - insert_pv_in_tt(pos, pv); + Stack ss[MAX_PLY_PLUS_2]; + int depth, prevBestMoveChanges; + Value bestValue, alpha, beta, delta; + bool bestMoveNeverChanged = true; + Move skillBest = MOVE_NONE; - if (AbortSearch) - break; // Value cannot be trusted. Break out immediately! + memset(ss, 0, 4 * sizeof(Stack)); + depth = BestMoveChanges = 0; + bestValue = delta = -VALUE_INFINITE; + ss->currentMove = MOVE_NULL; // Hack to skip update gains - //Save info about search result - ValueByIteration[Iteration] = value; + // Iterative deepening loop until requested to stop or target depth reached + while (!Signals.stop && ++depth <= MAX_PLY && (!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; - // Drop the easy move if differs from the new best move - if (pv[0] != EasyMove) - EasyMove = MOVE_NONE; + prevBestMoveChanges = BestMoveChanges; + BestMoveChanges = 0; - if (UseTimeManagement) + // MultiPV loop. We perform a full root search for each PV line + for (PVIdx = 0; PVIdx < std::min(MultiPV, RootMoves.size()); PVIdx++) { - // Time to stop? - bool stopSearch = false; - - // Stop search early if there is only a single legal move, - // we search up to Iteration 6 anyway to get a proper score. - if (Iteration >= 6 && rml.size() == 1) - stopSearch = true; - - // Stop search early when the last two iterations returned a mate score - if ( Iteration >= 6 - && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100 - && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) - stopSearch = true; - - // Stop search early if one move seems to be much better than the others - if ( Iteration >= 8 - && EasyMove == pv[0] - && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100 - && current_search_time() > TimeMgr.available_time() / 16) - ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100 - && current_search_time() > TimeMgr.available_time() / 32))) - stopSearch = true; - - // Add some extra time if the best move has changed during the last two iterations - if (Iteration > 5 && Iteration <= 50) - TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration], - BestMoveChangesByIteration[Iteration-1]); - - // Stop search if most of MaxSearchTime is consumed at the end of the - // iteration. We probably don't have enough time to search the first - // move at the next iteration anyway. - if (current_search_time() > (TimeMgr.available_time() * 80) / 128) - stopSearch = true; - - if (stopSearch) + // Set aspiration window default width + if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN) { - if (PonderSearch) - StopOnPonderhit = true; - else - break; + delta = Value(16); + alpha = RootMoves[PVIdx].prevScore - delta; + beta = RootMoves[PVIdx].prevScore + delta; + } + else + { + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; } - } - - if (MaxDepth && Iteration >= MaxDepth) - break; - } - - // If we are pondering or in infinite search, we shouldn't print the - // best move before we are told to do so. - if (!AbortSearch && (PonderSearch || InfiniteSearch)) - wait_for_stop_or_ponderhit(); - else - // Print final search statistics - cout << "info nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " time " << current_search_time() << endl; - - // Print the best move and the ponder move to the standard output - if (pv[0] == MOVE_NONE || MultiPV > 1) - { - pv[0] = rml[0].move; - pv[1] = MOVE_NONE; - } - - assert(pv[0] != MOVE_NONE); - - cout << "bestmove " << pv[0]; - - if (pv[1] != MOVE_NONE) - cout << " ponder " << pv[1]; - - cout << endl; - - if (UseLogFile) - { - if (dbg_show_mean) - dbg_print_mean(LogFile); - - if (dbg_show_hit_rate) - dbg_print_hit_rate(LogFile); - - LogFile << "\nNodes: " << pos.nodes_searched() - << "\nNodes/second: " << nps(pos) - << "\nBest move: " << move_to_san(pos, pv[0]); - - StateInfo st; - pos.do_move(pv[0], st); - LogFile << "\nPonder move: " - << move_to_san(pos, pv[1]) // Works also with MOVE_NONE - << endl; - } - return rml[0].pv_score; - } - - - // root_search() is the function which searches the root node. It is - // similar to search_pv except that it uses a different move ordering - // scheme, prints some information to the standard output and handles - // the fail low/high loops. - - Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) { - - StateInfo st; - CheckInfo ci(pos); - int64_t nodes; - Move move; - Depth depth, ext, newDepth; - Value value, alpha, beta; - bool isCheck, moveIsCheck, captureOrPromotion, dangerous; - int researchCountFH, researchCountFL; - - researchCountFH = researchCountFL = 0; - alpha = *alphaPtr; - beta = *betaPtr; - isCheck = pos.is_check(); - depth = (Iteration - 2) * ONE_PLY + InitialDepth; - - // Step 1. Initialize node (polling is omitted at root) - ss->currentMove = ss->bestMove = MOVE_NONE; - - // Step 2. Check for aborted search (omitted at root) - // Step 3. Mate distance pruning (omitted at root) - // Step 4. Transposition table lookup (omitted at root) - - // Step 5. Evaluate the position statically - // At root we do this only to get reference value for child nodes - ss->evalMargin = VALUE_NONE; - ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin); - - // Step 6. Razoring (omitted at root) - // Step 7. Static null move pruning (omitted at root) - // Step 8. Null move search with verification search (omitted at root) - // Step 9. Internal iterative deepening (omitted at root) - - // Step extra. Fail low loop - // We start with small aspiration window and in case of fail low, we research - // with bigger window until we are not failing low anymore. - while (1) - { - // Sort the moves before to (re)search - rml.set_non_pv_scores(pos); - rml.sort(); - - // Step 10. Loop through all moves in the root move list - for (int i = 0; i < (int)rml.size() && !AbortSearch; i++) - { - // This is used by time management - FirstRootMove = (i == 0); - - // Save the current node count before the move is searched - nodes = pos.nodes_searched(); - - // Pick the next root move, and print the move and the move number to - // the standard output. - move = ss->currentMove = rml[i].move; - - if (current_search_time() >= 1000) - cout << "info currmove " << move - << " currmovenumber " << i + 1 << endl; - - moveIsCheck = pos.move_is_check(move); - captureOrPromotion = pos.move_is_capture_or_promotion(move); - - // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous); - newDepth = depth + ext; - - // Step 12. Futility pruning (omitted at root) - - // Step extra. Fail high loop - // If move fails high, we research with bigger window until we are not failing - // high anymore. - value = -VALUE_INFINITE; - while (1) + // Start with a small aspiration window and, in case of fail high/low, + // research with bigger window until not failing high/low anymore. + while (true) { - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); + // Search starts from ss+1 to allow referencing (ss-1). This is + // needed by update gains and ss copy when splitting at Root. + bestValue = search(pos, ss+1, alpha, beta, depth * ONE_PLY); + + // 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. + sort(RootMoves.begin() + PVIdx, RootMoves.end()); + + // In case we have found an exact score and we are going to leave + // the fail high/low loop then reorder the PV moves, otherwise + // leave the last PV move in its position so to be searched again. + // Of course this is needed only in MultiPV search. + if (PVIdx && bestValue > alpha && bestValue < beta) + sort(RootMoves.begin(), RootMoves.begin() + PVIdx); + + // 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 exit the aspiration window loop. + // Sorting and writing PV back to TT is safe becuase RootMoves + // is still valid, although refers to previous iteration. + if (Signals.stop) + break; - // Step extra. pv search - // We do pv search for first moves (i < MultiPV) - // and for fail high research (value > alpha) - if (i < MultiPV || value > alpha) - { - // Aspiration window is disabled in multi-pv case - if (MultiPV > 1) - alpha = -VALUE_INFINITE; + // Send full PV info to GUI if we are going to leave the loop or + // if we have a fail high/low and we are deep in the search. + if ((bestValue > alpha && bestValue < beta) || Time::now() - SearchTime > 2000) + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; - // Full depth PV search, done on first move or after a fail high - value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); - } - else + // In case of failing high/low increase aspiration window and + // research, otherwise exit the fail high/low loop. + if (bestValue >= beta) { - // Step 14. Reduced search - // if the move fails high will be re-searched at full depth - bool doFullDepthSearch = true; - - if ( depth >= 3 * ONE_PLY - && !dangerous - && !captureOrPromotion - && !move_is_castle(move)) - { - ss->reduction = reduction(depth, i - MultiPV + 2); - if (ss->reduction) - { - assert(newDepth-ss->reduction >= ONE_PLY); - - // Reduced depth non-pv search using alpha as upperbound - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); - doFullDepthSearch = (value > alpha); - } - - // The move failed high, but if reduction is very big we could - // face a false positive, retry with a less aggressive reduction, - // if the move fails high again then go with full depth search. - if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY) - { - assert(newDepth - ONE_PLY >= ONE_PLY); - - ss->reduction = ONE_PLY; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); - doFullDepthSearch = (value > alpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction - } - - // Step 15. Full depth search - if (doFullDepthSearch) - { - // Full depth non-pv search using alpha as upperbound - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, 1); - - // If we are above alpha then research at same depth but as PV - // to get a correct score or eventually a fail high above beta. - if (value > alpha) - value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); - } + beta += delta; + delta += delta / 2; } + else if (bestValue <= alpha) + { + Signals.failedLowAtRoot = true; + Signals.stopOnPonderhit = false; - // Step 16. Undo move - pos.undo_move(move); - - // Can we exit fail high loop ? - if (AbortSearch || value < beta) + alpha -= delta; + delta += delta / 2; + } + else break; - // We are failing high and going to do a research. It's important to update - // the score before research in case we run out of time while researching. - rml[i].pv_score = value; - ss->bestMove = move; - extract_pv_from_tt(pos, move, pv); - rml[i].set_pv(pv); - - // Print information to the standard output - print_pv_info(pos, pv, alpha, beta, value); - - // Prepare for a research after a fail high, each time with a wider window - *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE); - researchCountFH++; - - } // End of fail high loop - - // Finished searching the move. If AbortSearch 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 break out of the loop without updating the best - // move and/or PV. - if (AbortSearch) - break; - - // Remember searched nodes counts for this move - rml[i].nodes += pos.nodes_searched() - nodes; - - assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE); - assert(value < beta); - - // Step 17. Check for new best move - if (value <= alpha && i >= MultiPV) - rml[i].pv_score = -VALUE_INFINITE; - else - { - // PV move or new best move! - - // Update PV - rml[i].pv_score = value; - ss->bestMove = move; - extract_pv_from_tt(pos, move, pv); - rml[i].set_pv(pv); - - if (MultiPV == 1) + // Search with full window in case we have a win/mate score + if (abs(bestValue) >= VALUE_KNOWN_WIN) { - // We record how often the best move has been changed in each - // iteration. This information is used for time managment: When - // the best move changes frequently, we allocate some more time. - if (i > 0) - BestMoveChangesByIteration[Iteration]++; - - // Print information to the standard output - print_pv_info(pos, pv, alpha, beta, value); - - // Raise alpha to setup proper non-pv search upper bound - if (value > alpha) - alpha = value; + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; } - else // MultiPV > 1 - { - rml.sort_multipv(i); - for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++) - { - cout << "info multipv " << j + 1 - << " score " << value_to_uci(rml[j].pv_score) - << " depth " << (j <= i ? Iteration : Iteration - 1) - << " time " << current_search_time() - << " nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " pv "; - - for (int k = 0; rml[j].pv[k] != MOVE_NONE && k < PLY_MAX; k++) - cout << rml[j].pv[k] << " "; - - cout << endl; - } - alpha = rml[Min(i, MultiPV - 1)].pv_score; - } - } // PV move or new best move - assert(alpha >= *alphaPtr); + assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); + } + } - AspirationFailLow = (alpha == *alphaPtr); + // Skills: Do we need to pick now the best move ? + if (SkillLevelEnabled && depth == 1 + SkillLevel) + skillBest = do_skill_level(); - if (AspirationFailLow && StopOnPonderhit) - StopOnPonderhit = false; + if (!Signals.stop && Options["Use Search Log"]) + { + Log log(Options["Search Log Filename"]); + log << pretty_pv(pos, depth, bestValue, Time::now() - SearchTime, &RootMoves[0].pv[0]) + << std::endl; } - // Can we exit fail low loop ? - if (AbortSearch || !AspirationFailLow) - break; + // Filter out startup noise when monitoring best move stability + if (depth > 2 && BestMoveChanges) + bestMoveNeverChanged = false; - // Prepare for a research after a fail low, each time with a wider window - *alphaPtr = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE); - researchCountFL++; + // Do we have time for the next iteration? Can we stop searching now? + if (!Signals.stop && !Signals.stopOnPonderhit && Limits.use_time_management()) + { + 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) + 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 + && ( (bestMoveNeverChanged && pos.captured_piece_type()) + || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100)) + { + Value rBeta = bestValue - 2 * PawnValueMg; + (ss+1)->excludedMove = RootMoves[0].pv[0]; + (ss+1)->skipNullMove = true; + Value v = search(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY); + (ss+1)->skipNullMove = false; + (ss+1)->excludedMove = MOVE_NONE; + + if (v < rBeta) + stop = true; + } - } // Fail low loop + if (stop) + { + // If we are allowed to ponder do not stop the search now but + // keep pondering until GUI sends "ponderhit" or "stop". + if (Limits.ponder) + Signals.stopOnPonderhit = true; + else + Signals.stop = true; + } + } + } - // Sort the moves before to return - rml.sort(); + // When using skills swap best PV line with the sub-optimal one + if (SkillLevelEnabled) + { + if (skillBest == MOVE_NONE) // Still unassigned ? + skillBest = do_skill_level(); - return alpha; + std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), skillBest)); + } } @@ -968,123 +467,155 @@ namespace { // 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 - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + template + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { - assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); - assert(beta > alpha && beta <= VALUE_INFINITE); - assert(PvNode || alpha == beta - 1); - assert(ply > 0 && ply < PLY_MAX); - assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); + 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); - Move movesSearched[MOVES_MAX]; + assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); + assert(PvNode || (alpha == beta - 1)); + assert(depth > DEPTH_ZERO); + + Move movesSearched[64]; StateInfo st; const TTEntry *tte; + SplitPoint* sp; Key posKey; - Move ttMove, move, excludedMove, threatMove; + Move ttMove, move, excludedMove, bestMove, threatMove; Depth ext, newDepth; - ValueType vt; - Value bestValue, value, oldAlpha; - Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific - bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous; - bool mateThreat = false; - int moveCount = 0; - int threadID = pos.thread(); - SplitPoint* sp = NULL; - refinedValue = bestValue = value = -VALUE_INFINITE; - oldAlpha = alpha; - isCheck = pos.is_check(); + Value bestValue, value, ttValue; + Value refinedValue, nullValue, futilityValue; + bool inCheck, givesCheck, pvMove, singularExtensionNode; + bool captureOrPromotion, dangerous, doFullDepthSearch; + int moveCount, playedMoveCount; + + // Step 1. Initialize node + Thread* thisThread = pos.this_thread(); + moveCount = playedMoveCount = 0; + inCheck = pos.in_check(); if (SpNode) { sp = ss->sp; + bestMove = sp->bestMove; + threatMove = sp->threatMove; + bestValue = sp->bestValue; tte = NULL; ttMove = excludedMove = MOVE_NONE; - threatMove = sp->threatMove; - mateThreat = sp->mateThreat; + ttValue = VALUE_NONE; + + assert(sp->bestValue > -VALUE_INFINITE && sp->moveCount > 0); + goto split_point_start; } - else {} // Hack to fix icc's "statement is unreachable" warning - // Step 1. Initialize node and poll. Polling can abort search - ss->currentMove = ss->bestMove = threatMove = MOVE_NONE; - (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE; + bestValue = -VALUE_INFINITE; + ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->ply = (ss-1)->ply + 1; + (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) + thisThread->maxPly = ss->ply; - if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls) + if (!RootNode) { - NodesSincePoll = 0; - poll(pos); + // 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()]; + + // 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. + alpha = std::max(mated_in(ss->ply), alpha); + beta = std::min(mate_in(ss->ply+1), beta); + if (alpha >= beta) + return alpha; } - // Step 2. Check for aborted search and immediate draw - if ( AbortSearch - || ThreadsMgr.cutoff_at_splitpoint(threadID) - || pos.is_draw() - || ply >= PLY_MAX - 1) - return VALUE_DRAW; - - // Step 3. Mate distance pruning - alpha = Max(value_mated_in(ply), alpha); - beta = Min(value_mate_in(ply+1), beta); - if (alpha >= beta) - return alpha; - // 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 exists. + // TT value, so we use a different position key in case of an excluded move. excludedMove = ss->excludedMove; - posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); - - tte = TT.retrieve(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; - - // At PV nodes, we don't use the TT for pruning, but only for move ordering. - // This is to avoid problems in the following areas: - // - // * Repetition draw detection - // * Fifty move rule detection - // * Searching for a mate - // * Printing of full PV line - if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) + 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->depth() >= depth + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { + assert(ttValue != VALUE_NONE); // Due to depth > DEPTH_NONE + TT.refresh(tte); - ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ply); + ss->currentMove = ttMove; // Can be MOVE_NONE + + if ( ttValue >= beta + && ttMove + && !pos.is_capture_or_promotion(ttMove) + && ttMove != ss->killers[0]) + { + ss->killers[1] = ss->killers[0]; + ss->killers[0] = ttMove; + } + return ttValue; } - // Step 5. Evaluate the position statically and - // update gain statistics of parent move. - if (isCheck) - ss->eval = ss->evalMargin = VALUE_NONE; + // Step 5. Evaluate the position statically and update parent's gain statistics + if (inCheck) + ss->eval = ss->evalMargin = refinedValue = VALUE_NONE; + else if (tte) { assert(tte->static_value() != VALUE_NONE); ss->eval = tte->static_value(); ss->evalMargin = tte->static_value_margin(); - refinedValue = refine_eval(tte, ss->eval, ply); + refinedValue = refine_eval(tte, ttValue, ss->eval); } else { refinedValue = ss->eval = evaluate(pos, ss->evalMargin); - TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin); + TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, + ss->eval, ss->evalMargin); } - // Save gain for the parent non-capture move - update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); + // Update gain for the parent non-capture move given the static position + // evaluation before and after the move. + if ( (move = (ss-1)->currentMove) != MOVE_NULL + && (ss-1)->eval != VALUE_NONE + && ss->eval != VALUE_NONE + && !pos.captured_piece_type() + && type_of(move) == NORMAL) + { + Square to = to_sq(move); + H.update_gain(pos.piece_on(to), to, -(ss-1)->eval - ss->eval); + } // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode - && depth < RazorDepth - && !isCheck - && refinedValue < beta - razor_margin(depth) + && depth < 4 * ONE_PLY + && !inCheck + && refinedValue + razor_margin(depth) < beta && ttMove == MOVE_NONE - && !value_is_mate(beta) - && !pos.has_pawn_on_7th(pos.side_to_move())) + && 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, ply); + 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. @@ -1096,41 +627,42 @@ namespace { // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode && !ss->skipNullMove - && depth < RazorDepth - && !isCheck - && refinedValue >= beta + futility_margin(depth, 0) - && !value_is_mate(beta) + && depth < 4 * ONE_PLY + && !inCheck + && refinedValue - FutilityMargins[depth][0] >= beta + && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) - return refinedValue - futility_margin(depth, 0); + return refinedValue - FutilityMargins[depth][0]; // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode && !ss->skipNullMove && depth > ONE_PLY - && !isCheck + && !inCheck && refinedValue >= beta - && !value_is_mate(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 - int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0); + Depth R = 3 * ONE_PLY + depth / 4; // Null move dynamic reduction based on value - if (refinedValue - beta > PawnValueMidgame) - R++; + if (refinedValue - PawnValueMg > beta) + R += ONE_PLY; - pos.do_null_move(st); + pos.do_null_move(st); (ss+1)->skipNullMove = true; - nullValue = -search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1); + nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, depth-R); (ss+1)->skipNullMove = false; - pos.undo_null_move(); + pos.do_null_move(st); if (nullValue >= beta) { // Do not return unproven mate scores - if (nullValue >= value_mate_in(PLY_MAX)) + if (nullValue >= VALUE_MATE_IN_MAX_PLY) nullValue = beta; if (depth < 6 * ONE_PLY) @@ -1138,7 +670,7 @@ namespace { // Do verification search at high depths ss->skipNullMove = true; - Value v = search(pos, ss, alpha, beta, depth-R*ONE_PLY, ply); + Value v = search(pos, ss, alpha, beta, depth-R); ss->skipNullMove = false; if (v >= beta) @@ -1152,11 +684,9 @@ namespace { // 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). - if (nullValue == value_mated_in(ply + 2)) - mateThreat = true; + threatMove = (ss+1)->currentMove; - threatMove = (ss+1)->bestMove; - if ( depth < ThreatDepth + if ( depth < 5 * ONE_PLY && (ss-1)->reduction && threatMove != MOVE_NONE && connected_moves(pos, (ss-1)->currentMove, threatMove)) @@ -1164,115 +694,166 @@ namespace { } } - // Step 9. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] - && ttMove == MOVE_NONE - && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) + // Step 9. ProbCut (is omitted in PV nodes) + // 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 + && !inCheck + && !ss->skipNullMove + && excludedMove == MOVE_NONE + && abs(beta) < VALUE_MATE_IN_MAX_PLY) + { + Value rbeta = beta + 200; + Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY; + + assert(rdepth >= ONE_PLY); + assert((ss-1)->currentMove != MOVE_NONE); + assert((ss-1)->currentMove != MOVE_NULL); + + MovePicker mp(pos, ttMove, H, pos.captured_piece_type()); + CheckInfo ci(pos); + + while ((move = mp.next_move()) != MOVE_NONE) + if (pos.pl_move_is_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); + 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 || (!inCheck && ss->eval + Value(256) >= beta))) { Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2); ss->skipNullMove = true; - search(pos, ss, alpha, beta, d, ply); + search(pos, ss, alpha, beta, d); ss->skipNullMove = false; - ttMove = ss->bestMove; - tte = TT.retrieve(posKey); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; } - // Expensive mate threat detection (only for PV nodes) - if (PvNode) - mateThreat = pos.has_mate_threat(); - split_point_start: // At split points actual search starts from here - // Initialize a MovePicker object for the current position - // FIXME currently MovePicker() c'tor is needless called also in SplitPoint - MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta)); - MovePicker& mp = SpNode ? *sp->mp : mpBase; + MovePicker mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta); CheckInfo ci(pos); - ss->bestMove = MOVE_NONE; - singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1; - futilityBase = ss->eval + ss->evalMargin; - singularExtensionNode = !SpNode - && depth >= SingularExtensionDepth[PvNode] - && tte - && tte->move() - && !excludedMove // Do not allow recursive singular extension search - && (tte->type() & VALUE_TYPE_LOWER) - && tte->depth() >= depth - 3 * ONE_PLY; - if (SpNode) + value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc + singularExtensionNode = !RootNode + && !SpNode + && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY) + && ttMove != MOVE_NONE + && !excludedMove // Recursive singular search is not allowed + && (tte->type() & BOUND_LOWER) + && tte->depth() >= depth - 3 * ONE_PLY; + + // 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) { - lock_grab(&(sp->lock)); - bestValue = sp->bestValue; - } + assert(is_ok(move)); - // Step 10. Loop through moves - // Loop through all legal moves until no moves remain or a beta cutoff occurs - while ( bestValue < beta - && (move = mp.get_next_move()) != MOVE_NONE - && !ThreadsMgr.cutoff_at_splitpoint(threadID)) - { - assert(move_is_ok(move)); + if (move == excludedMove) + 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 + // 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)) + continue; + moveCount = ++sp->moveCount; - lock_release(&(sp->lock)); + sp->mutex.unlock(); } - else if (move == excludedMove) - continue; else - movesSearched[moveCount++] = move; + moveCount++; - moveIsCheck = pos.move_is_check(move, ci); - captureOrPromotion = pos.move_is_capture_or_promotion(move); + if (RootNode) + { + Signals.firstRootMove = (moveCount == 1); - // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous); + if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000) + sync_cout << "info depth " << depth / ONE_PLY + << " currmove " << move_to_uci(move, Chess960) + << " currmovenumber " << moveCount + PVIdx << sync_endl; + } - // 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 then ttValue minus a margin then we extend ttMove. - if ( singularExtensionNode - && move == tte->move() - && ext < ONE_PLY) + 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 + || ( captureOrPromotion // Entering a pawn endgame? + && type_of(pos.piece_on(to_sq(move))) != PAWN + && type_of(move) == NORMAL + && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) + - PieceValue[MG][pos.piece_on(to_sq(move))] == VALUE_ZERO)); + + // Step 12. Extend checks and, in PV nodes, also dangerous moves + if (PvNode && dangerous) + ext = ONE_PLY; + + else if (givesCheck && pos.see_sign(move) >= 0) + ext = ONE_PLY / 2; + + // 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. + if ( singularExtensionNode + && !ext + && move == ttMove + && pos.pl_move_is_legal(move, ci.pinned) + && abs(ttValue) < VALUE_KNOWN_WIN) { - Value ttValue = value_from_tt(tte->value(), ply); + assert(ttValue != VALUE_NONE); - if (abs(ttValue) < VALUE_KNOWN_WIN) - { - Value b = ttValue - SingularExtensionMargin; - ss->excludedMove = move; - ss->skipNullMove = true; - Value v = search(pos, ss, b - 1, b, depth / 2, ply); - ss->skipNullMove = false; - ss->excludedMove = MOVE_NONE; - ss->bestMove = MOVE_NONE; - if (v < b) - ext = ONE_PLY; - } + Value rBeta = ttValue - int(depth); + ss->excludedMove = move; + ss->skipNullMove = true; + value = search(pos, ss, rBeta - 1, rBeta, depth / 2); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; + + if (value < rBeta) + ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY; } // Update current move (this must be done after singular extension search) - ss->currentMove = move; newDepth = depth - ONE_PLY + ext; - // Step 12. Futility pruning (is omitted in PV nodes) + // Step 13. Futility pruning (is omitted in PV nodes) if ( !PvNode && !captureOrPromotion - && !isCheck + && !inCheck && !dangerous && move != ttMove - && !move_is_castle(move)) + && (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE + && alpha > VALUE_MATED_IN_MAX_PLY))) { // Move count based pruning - if ( moveCount >= futility_move_count(depth) - && !(threatMove && connected_threat(pos, move, threatMove)) - && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy + if ( depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[depth] + && (!threatMove || !connected_threat(pos, move, threatMove))) { if (SpNode) - lock_grab(&(sp->lock)); + sp->mutex.lock(); continue; } @@ -1280,241 +861,274 @@ split_point_start: // At split points actual search starts from here // 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); - futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount) - + H.gain(pos.piece_on(move_from(move)), move_to(move)); + Depth predictedDepth = newDepth - reduction(depth, moveCount); + futilityValue = ss->eval + ss->evalMargin + futility_margin(predictedDepth, moveCount) + + H.gain(pos.piece_moved(move), to_sq(move)); - if (futilityValueScaled < beta) + if (futilityValue < beta) { if (SpNode) - { - lock_grab(&(sp->lock)); - if (futilityValueScaled > sp->bestValue) - sp->bestValue = bestValue = futilityValueScaled; - } - else if (futilityValueScaled > bestValue) - bestValue = futilityValueScaled; + sp->mutex.lock(); continue; } // Prune moves with negative SEE at low depths if ( predictedDepth < 2 * ONE_PLY - && bestValue > value_mated_in(PLY_MAX) && pos.see_sign(move) < 0) { if (SpNode) - lock_grab(&(sp->lock)); + sp->mutex.lock(); continue; } } - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); - - // Step extra. pv search (only in PV nodes) - // The first move in list is the expected PV - if (PvNode && moveCount == 1) - value = -search(pos, ss+1, -beta, -alpha, newDepth, ply+1); - else + // Check for legality only before to do the move + if (!pos.pl_move_is_legal(move, ci.pinned)) { - // Step 14. Reduced depth search - // If the move fails high will be re-searched at full depth. - bool doFullDepthSearch = true; - - if ( depth >= 3 * ONE_PLY - && !captureOrPromotion - && !dangerous - && !move_is_castle(move) - && ss->killers[0] != move - && ss->killers[1] != move) - { - ss->reduction = reduction(depth, moveCount); + moveCount--; + continue; + } - if (ss->reduction) - { - alpha = SpNode ? sp->alpha : alpha; - Depth d = newDepth - ss->reduction; - value = -search(pos, ss+1, -(alpha+1), -alpha, d, ply+1); + pvMove = PvNode ? moveCount == 1 : false; + ss->currentMove = move; + if (!SpNode && !captureOrPromotion && playedMoveCount < 64) + movesSearched[playedMoveCount++] = move; - doFullDepthSearch = (value > alpha); - } + // Step 14. Make the move + pos.do_move(move, st, ci, givesCheck); - // The move failed high, but if reduction is very big we could - // face a false positive, retry with a less aggressive reduction, - // if the move fails high again then go with full depth search. - if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY) - { - assert(newDepth - ONE_PLY >= ONE_PLY); + // Step 15. Reduced depth search (LMR). If the move fails high will be + // re-searched at full depth. + if ( depth > 3 * ONE_PLY + && !pvMove + && !captureOrPromotion + && !dangerous + && ss->killers[0] != move + && ss->killers[1] != move) + { + ss->reduction = reduction(depth, moveCount); + Depth d = std::max(newDepth - ss->reduction, ONE_PLY); + alpha = SpNode ? sp->alpha : alpha; - ss->reduction = ONE_PLY; - alpha = SpNode ? sp->alpha : alpha; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1); - doFullDepthSearch = (value > alpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction - } + value = -search(pos, ss+1, -(alpha+1), -alpha, d); - // Step 15. Full depth search - if (doFullDepthSearch) - { - alpha = SpNode ? sp->alpha : alpha; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1); - - // Step extra. pv search (only in PV nodes) - // Search only for possible new PV nodes, if instead value >= beta then - // parent node fails low with value <= alpha and tries another move. - if (PvNode && value > alpha && value < beta) - value = -search(pos, ss+1, -beta, -alpha, newDepth, ply+1); - } + doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); + ss->reduction = DEPTH_ZERO; + } + else + doFullDepthSearch = !pvMove; + + // Step 16. Full depth search, when LMR is skipped or fails high + if (doFullDepthSearch) + { + alpha = SpNode ? sp->alpha : alpha; + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); } - // Step 16. Undo move + // 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 ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, newDepth); + + // Step 17. Undo move pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 17. Check for new best move + // Step 18. Check for new best move if (SpNode) { - lock_grab(&(sp->lock)); + sp->mutex.lock(); bestValue = sp->bestValue; alpha = sp->alpha; } - if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID))) - { - bestValue = value; + // 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. + if (Signals.stop || thisThread->cutoff_occurred()) + return bestValue; - if (SpNode) - sp->bestValue = value; + if (RootNode) + { + RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); - if (value > alpha) + // PV move or new best move ? + if (pvMove || value > alpha) { - if (PvNode && value < beta) // We want always alpha < beta - { - alpha = value; - - if (SpNode) - sp->alpha = value; - } - else if (SpNode) - sp->betaCutoff = true; + rm.score = value; + rm.extract_pv_from_tt(pos); + + // 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 && MultiPV == 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. + rm.score = -VALUE_INFINITE; + } - if (value == value_mate_in(ply + 1)) - ss->mateKiller = move; + if (value > bestValue) + { + bestValue = value; + if (SpNode) sp->bestValue = value; - ss->bestMove = move; + if (value > alpha) + { + bestMove = move; + if (SpNode) sp->bestMove = move; - if (SpNode) - sp->parentSstack->bestMove = move; + if (PvNode && value < beta) + { + alpha = value; // Update alpha here! Always alpha < beta + if (SpNode) sp->alpha = value; + } + else // Fail high + { + if (SpNode) sp->cutoff = true; + break; + } } } - // Step 18. Check for split + // Step 19. Check for splitting the search if ( !SpNode - && depth >= ThreadsMgr.min_split_depth() - && ThreadsMgr.active_threads() > 1 - && bestValue < beta - && ThreadsMgr.available_thread_exists(threadID) - && !AbortSearch - && !ThreadsMgr.cutoff_at_splitpoint(threadID) - && Iteration <= 99) - ThreadsMgr.split(pos, ss, ply, &alpha, beta, &bestValue, depth, - threatMove, mateThreat, moveCount, &mp, PvNode); + && depth >= Threads.min_split_depth() + && bestValue < beta + && Threads.available_slave_exists(thisThread)) + { + bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove, + depth, threatMove, moveCount, mp, NT); + break; + } } - // Step 19. Check for mate and stalemate - // All legal moves have been searched and if there are - // no legal moves, it must be mate or stalemate. - // If one move was excluded return fail low score. - if (!SpNode && !moveCount) - return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW; - - // Step 20. Update tables - // If the search is not aborted, update the transposition table, - // history counters, and killer moves. - if (!SpNode && !AbortSearch && !ThreadsMgr.cutoff_at_splitpoint(threadID)) + if (SpNode) + return bestValue; + + // 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. + 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) { - move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove; - vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER - : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT; + assert(!playedMoveCount); - TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin); - - // Update killers and history only for non capture moves that fails high - if ( bestValue >= beta - && !pos.move_is_capture_or_promotion(move)) - { - update_history(pos, move, depth, movesSearched, moveCount); - update_killers(move, ss); - } + bestValue = alpha; } - if (SpNode) + if (bestValue >= beta) // Failed high { - // Here we have the lock still grabbed - sp->slaves[threadID] = 0; - sp->nodes += pos.nodes_searched(); - lock_release(&(sp->lock)); + TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, + bestMove, ss->eval, ss->evalMargin); + + if (!pos.is_capture_or_promotion(bestMove) && !inCheck) + { + if (bestMove != ss->killers[0]) + { + ss->killers[1] = ss->killers[0]; + ss->killers[0] = bestMove; + } + + // Increase history value of the cut-off move + Value bonus = Value(int(depth) * int(depth)); + H.add(pos.piece_moved(bestMove), to_sq(bestMove), bonus); + + // Decrease history of all the other played non-capture moves + for (int i = 0; i < playedMoveCount - 1; i++) + { + Move m = movesSearched[i]; + H.add(pos.piece_moved(m), to_sq(m), -bonus); + } + } } + else // Failed low or PV search + TT.store(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->eval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); return bestValue; } + // qsearch() is the quiescence search function, which is called by the main // search function when the remaining depth is zero (or, to be more precise, // less than ONE_PLY). - template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + template + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { - assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); - assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); - assert(PvNode || alpha == beta - 1); - assert(depth <= 0); - assert(ply > 0 && ply < PLY_MAX); - assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); + const bool PvNode = (NT == PV); + + assert(NT == PV || NT == NonPV); + assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); + assert(PvNode || (alpha == beta - 1)); + assert(depth <= DEPTH_ZERO); StateInfo st; - Move ttMove, move; - Value bestValue, value, evalMargin, futilityValue, futilityBase; - bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable; const TTEntry* tte; + Key posKey; + Move ttMove, move, bestMove; + Value bestValue, value, ttValue, futilityValue, futilityBase; + bool inCheck, givesCheck, enoughMaterial, evasionPrunable; Depth ttDepth; - Value oldAlpha = alpha; - ss->bestMove = ss->currentMove = MOVE_NONE; + inCheck = pos.in_check(); + ss->currentMove = bestMove = MOVE_NONE; + ss->ply = (ss-1)->ply + 1; // Check for an instant draw or maximum ply reached - if (pos.is_draw() || ply >= PLY_MAX - 1) - return VALUE_DRAW; - - // 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. - isCheck = pos.is_check(); - ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS); + if (pos.is_draw() || ss->ply > MAX_PLY) + return DrawValue[pos.side_to_move()]; // Transposition table lookup. At PV nodes, we don't use the TT for // pruning, but only for move ordering. - tte = TT.retrieve(pos.get_key()); - ttMove = (tte ? tte->move() : MOVE_NONE); + posKey = pos.key(); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; + ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE; - if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, 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 + : DEPTH_QS_NO_CHECKS; + if ( tte && tte->depth() >= ttDepth + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { - ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ply); + assert(ttValue != VALUE_NONE); // Due to ttDepth > DEPTH_NONE + + ss->currentMove = ttMove; // Can be MOVE_NONE + return ttValue; } // Evaluate the position statically - if (isCheck) + if (inCheck) { + ss->eval = ss->evalMargin = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; - ss->eval = evalMargin = VALUE_NONE; enoughMaterial = false; } else @@ -1523,19 +1137,18 @@ split_point_start: // At split points actual search starts from here { assert(tte->static_value() != VALUE_NONE); - evalMargin = tte->static_value_margin(); ss->eval = bestValue = tte->static_value(); + ss->evalMargin = tte->static_value_margin(); } else - ss->eval = bestValue = evaluate(pos, evalMargin); - - update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); + ss->eval = bestValue = evaluate(pos, ss->evalMargin); // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { if (!tte) - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin); + TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, + DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin); return bestValue; } @@ -1543,106 +1156,121 @@ split_point_start: // At split points actual search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - // Futility pruning parameters, not needed when in check - futilityBase = ss->eval + evalMargin + FutilityMarginQS; - enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; + futilityBase = ss->eval + ss->evalMargin + Value(128); + enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg; } // Initialize a MovePicker object for the current position, and prepare // 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, H); + MovePicker mp(pos, ttMove, depth, H, to_sq((ss-1)->currentMove)); CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs - while ( alpha < beta - && (move = mp.get_next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) { - assert(move_is_ok(move)); + assert(is_ok(move)); - moveIsCheck = pos.move_is_check(move, ci); + givesCheck = pos.move_gives_check(move, ci); // Futility pruning if ( !PvNode - && !isCheck - && !moveIsCheck + && !inCheck + && !givesCheck && move != ttMove && enoughMaterial - && !move_is_promotion(move) - && !pos.move_is_passed_pawn_push(move)) + && type_of(move) != PROMOTION + && !pos.is_passed_pawn_push(move)) { futilityValue = futilityBase - + pos.endgame_value_of_piece_on(move_to(move)) - + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO); + + PieceValue[EG][pos.piece_on(to_sq(move))] + + (type_of(move) == ENPASSANT ? PawnValueEg : VALUE_ZERO); - if (futilityValue < alpha) + if (futilityValue < beta) { if (futilityValue > bestValue) bestValue = futilityValue; + continue; } + + // Prune moves with negative or equal SEE + if ( futilityBase < beta + && depth < DEPTH_ZERO + && pos.see(move) <= 0) + continue; } // Detect non-capture evasions that are candidate to be pruned - evasionPrunable = isCheck - && bestValue > value_mated_in(PLY_MAX) - && !pos.move_is_capture(move) + evasionPrunable = !PvNode + && inCheck + && bestValue > VALUE_MATED_IN_MAX_PLY + && !pos.is_capture(move) && !pos.can_castle(pos.side_to_move()); // Don't search moves with negative SEE values if ( !PvNode - && (!isCheck || evasionPrunable) + && (!inCheck || evasionPrunable) && move != ttMove - && !move_is_promotion(move) + && type_of(move) != PROMOTION && pos.see_sign(move) < 0) continue; // Don't search useless checks if ( !PvNode - && !isCheck - && moveIsCheck + && !inCheck + && givesCheck && move != ttMove - && !pos.move_is_capture_or_promotion(move) - && ss->eval + PawnValueMidgame / 4 < beta - && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue)) - { - if (ss->eval + PawnValueMidgame / 4 > bestValue) - bestValue = ss->eval + PawnValueMidgame / 4; + && !pos.is_capture_or_promotion(move) + && ss->eval + PawnValueMg / 4 < beta + && !check_is_dangerous(pos, move, futilityBase, beta)) + continue; + // Check for legality only before to do the move + if (!pos.pl_move_is_legal(move, ci.pinned)) continue; - } - // Update current move ss->currentMove = move; // Make and search the move - pos.do_move(move, st, ci, moveIsCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1); + pos.do_move(move, st, ci, givesCheck); + value = -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // New best move? + // Check for new best move if (value > bestValue) { bestValue = value; + if (value > alpha) { - alpha = value; - ss->bestMove = move; + if (PvNode && value < beta) // Update alpha here! Always alpha < beta + { + alpha = value; + bestMove = move; + } + else // Fail high + { + TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, + ttDepth, move, ss->eval, ss->evalMargin); + + return value; + } } } } // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (isCheck && bestValue == -VALUE_INFINITE) - return value_mated_in(ply); + if (inCheck && bestValue == -VALUE_INFINITE) + return mated_in(ss->ply); // Plies to mate from the root - // Update transposition table - ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); - TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove, ss->eval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1654,55 +1282,43 @@ split_point_start: // At split points actual search starts from here // bestValue is updated only when returning false because in that case move // will be pruned. - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue) + bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta) { Bitboard b, occ, oldAtt, newAtt, kingAtt; - Square from, to, ksq, victimSq; + Square from, to, ksq; Piece pc; Color them; - Value futilityValue, bv = *bestValue; - from = move_from(move); - to = move_to(move); - them = opposite_color(pos.side_to_move()); + from = from_sq(move); + to = to_sq(move); + them = ~pos.side_to_move(); ksq = pos.king_square(them); kingAtt = pos.attacks_from(ksq); - pc = pos.piece_on(from); + pc = pos.piece_moved(move); - occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq); + occ = pos.pieces() ^ from ^ ksq; oldAtt = pos.attacks_from(pc, from, occ); newAtt = pos.attacks_from(pc, to, occ); // Rule 1. Checks which give opponent's king at most one escape square are dangerous - b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to); + b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to); - if (!(b && (b & (b - 1)))) + if (!more_than_one(b)) return true; // Rule 2. Queen contact check is very dangerous - if ( type_of_piece(pc) == QUEEN - && bit_is_set(kingAtt, to)) + if (type_of(pc) == QUEEN && (kingAtt & to)) return true; // Rule 3. Creating new double threats with checks - b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq); - + b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq); while (b) { - victimSq = pop_1st_bit(&b); - futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq); - // Note that here we generate illegal "double move"! - if ( futilityValue >= beta - && pos.see_sign(make_move(from, victimSq)) >= 0) + if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta) return true; - - if (futilityValue > bv) - bv = futilityValue; } - // Update bestValue only if check is not dangerous (because we will prune the move) - *bestValue = bv; return false; } @@ -1716,1040 +1332,448 @@ split_point_start: // At split points actual search starts from here bool connected_moves(const Position& pos, Move m1, Move m2) { Square f1, t1, f2, t2; - Piece p; + Piece p1, p2; + Square ksq; - assert(m1 && move_is_ok(m1)); - assert(m2 && move_is_ok(m2)); + assert(is_ok(m1)); + assert(is_ok(m2)); // Case 1: The moving piece is the same in both moves - f2 = move_from(m2); - t1 = move_to(m1); + f2 = from_sq(m2); + t1 = to_sq(m1); if (f2 == t1) return true; // Case 2: The destination square for m2 was vacated by m1 - t2 = move_to(m2); - f1 = move_from(m1); + t2 = to_sq(m2); + f1 = from_sq(m1); if (t2 == f1) return true; // Case 3: Moving through the vacated square - if ( piece_is_slider(pos.piece_on(f2)) - && bit_is_set(squares_between(f2, t2), f1)) + p2 = pos.piece_on(f2); + if (piece_is_slider(p2) && (between_bb(f2, t2) & f1)) return true; // Case 4: The destination square for m2 is defended by the moving piece in m1 - p = pos.piece_on(t1); - if (bit_is_set(pos.attacks_from(p, t1), t2)) + p1 = pos.piece_on(t1); + if (pos.attacks_from(p1, t1) & t2) return true; // Case 5: Discovered check, checking piece is the piece moved in m1 - if ( piece_is_slider(p) - && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2) - && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2)) - { - // discovered_check_candidates() works also if the Position's side to - // move is the opposite of the checking piece. - Color them = opposite_color(pos.side_to_move()); - Bitboard dcCandidates = pos.discovered_check_candidates(them); + ksq = pos.king_square(pos.side_to_move()); + if ( piece_is_slider(p1) + && (between_bb(t1, ksq) & f2) + && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq)) + return true; - if (bit_is_set(dcCandidates, f2)) - return true; - } return false; } - // value_is_mate() checks if the given value is a mate one eventually - // compensated for the ply. - - bool value_is_mate(Value value) { - - assert(abs(value) <= VALUE_INFINITE); - - return value <= value_mated_in(PLY_MAX) - || value >= value_mate_in(PLY_MAX); - } - - // value_to_tt() adjusts a mate score from "plies to mate from the root" to - // "plies to mate from the current ply". Non-mate scores are unchanged. + // "plies to mate from the current position". Non-mate scores are unchanged. // The function is called before storing a value to the transposition table. Value value_to_tt(Value v, int ply) { - if (v >= value_mate_in(PLY_MAX)) - return v + ply; - - if (v <= value_mated_in(PLY_MAX)) - return v - ply; + assert(v != VALUE_NONE); - return v; + return v >= VALUE_MATE_IN_MAX_PLY ? v + ply + : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; } - // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from - // the transposition table to a mate score corrected for the current ply. + // 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 current position) to "plies to mate/be mated from the root". Value value_from_tt(Value v, int ply) { - if (v >= value_mate_in(PLY_MAX)) - return v - ply; - - if (v <= value_mated_in(PLY_MAX)) - return v + ply; - - return v; - } - - - // extension() decides whether a move should be searched with normal depth, - // or with extended depth. Certain classes of moves (checking moves, in - // particular) are searched with bigger depth than ordinary moves and in - // any case are marked as 'dangerous'. Note that also if a move is not - // extended, as example because the corresponding UCI option is set to zero, - // the move is marked as 'dangerous' so, at least, we avoid to prune it. - template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, - bool singleEvasion, bool mateThreat, bool* dangerous) { - - assert(m != MOVE_NONE); - - Depth result = DEPTH_ZERO; - *dangerous = moveIsCheck | singleEvasion | mateThreat; - - if (*dangerous) - { - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; - - if (singleEvasion) - result += SingleEvasionExtension[PvNode]; - - if (mateThreat) - result += MateThreatExtension[PvNode]; - } - - if (pos.type_of_piece_on(move_from(m)) == PAWN) - { - Color c = pos.side_to_move(); - if (relative_rank(c, move_to(m)) == RANK_7) - { - result += PawnPushTo7thExtension[PvNode]; - *dangerous = true; - } - if (pos.pawn_is_passed(c, move_to(m))) - { - result += PassedPawnExtension[PvNode]; - *dangerous = true; - } - } - - if ( captureOrPromotion - && pos.type_of_piece_on(move_to(m)) != PAWN - && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) - - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO) - && !move_is_promotion(m) - && !move_is_ep(m)) - { - result += PawnEndgameExtension[PvNode]; - *dangerous = true; - } - - if ( PvNode - && captureOrPromotion - && pos.type_of_piece_on(move_to(m)) != PAWN - && pos.see_sign(m) >= 0) - { - result += ONE_PLY / 2; - *dangerous = true; - } - - return Min(result, ONE_PLY); + return v == VALUE_NONE ? VALUE_NONE + : v >= VALUE_MATE_IN_MAX_PLY ? v - ply + : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v; } // connected_threat() tests whether it is safe to forward prune a move or if - // is somehow coonected to the threat move returned by null search. + // is somehow connected to the threat move returned by null search. bool connected_threat(const Position& pos, Move m, Move threat) { - assert(move_is_ok(m)); - assert(threat && move_is_ok(threat)); - assert(!pos.move_is_check(m)); - assert(!pos.move_is_capture_or_promotion(m)); - assert(!pos.move_is_passed_pawn_push(m)); + assert(is_ok(m)); + assert(is_ok(threat)); + assert(!pos.is_capture_or_promotion(m)); + assert(!pos.is_passed_pawn_push(m)); Square mfrom, mto, tfrom, tto; - mfrom = move_from(m); - mto = move_to(m); - tfrom = move_from(threat); - tto = move_to(threat); + mfrom = from_sq(m); + mto = to_sq(m); + tfrom = from_sq(threat); + tto = to_sq(threat); // Case 1: Don't prune moves which move the threatened piece if (mfrom == tto) return true; // Case 2: If the threatened piece has value less than or equal to the - // value of the threatening piece, don't prune move which defend it. - if ( pos.move_is_capture(threat) - && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) - || pos.type_of_piece_on(tfrom) == KING) + // value of the threatening piece, don't prune moves which defend it. + if ( pos.is_capture(threat) + && ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)] + || type_of(pos.piece_on(tfrom)) == KING) && pos.move_attacks_square(m, tto)) return true; // Case 3: If the moving piece in the threatened move is a slider, don't // prune safe moves which block its ray. - if ( piece_is_slider(pos.piece_on(tfrom)) - && bit_is_set(squares_between(tfrom, tto), mto) - && pos.see_sign(m) >= 0) + if ( piece_is_slider(pos.piece_on(tfrom)) + && (between_bb(tfrom, tto) & mto) + && pos.see_sign(m) >= 0) return true; return false; } - // ok_to_use_TT() returns true if a transposition table score - // can be used at a given point in search. - - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) { - - Value v = value_from_tt(tte->value(), ply); - - return ( tte->depth() >= depth - || v >= Max(value_mate_in(PLY_MAX), beta) - || v < Min(value_mated_in(PLY_MAX), beta)) - - && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta) - || ((tte->type() & VALUE_TYPE_UPPER) && v < beta)); - } - - - // refine_eval() returns the transposition table score if - // possible otherwise falls back on static position evaluation. + // refine_eval() returns the transposition table score if possible, otherwise + // falls back on static position evaluation. Note that we never return VALUE_NONE + // even if v == VALUE_NONE. - Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) { + Value refine_eval(const TTEntry* tte, Value v, Value defaultEval) { assert(tte); + assert(v != VALUE_NONE || !tte->type()); - Value v = value_from_tt(tte->value(), ply); - - if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval) - || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval)) + if ( ((tte->type() & BOUND_LOWER) && v >= defaultEval) + || ((tte->type() & BOUND_UPPER) && v < defaultEval)) return v; return defaultEval; } - // update_history() registers a good move that produced a beta-cutoff - // in history and marks as failures all the other moves of that ply. - - void update_history(const Position& pos, Move move, Depth depth, - Move movesSearched[], int moveCount) { - Move m; - - H.success(pos.piece_on(move_from(move)), move_to(move), depth); - - for (int i = 0; i < moveCount - 1; i++) - { - m = movesSearched[i]; - - assert(m != move); - - if (!pos.move_is_capture_or_promotion(m)) - H.failure(pos.piece_on(move_from(m)), move_to(m), depth); - } - } - - - // update_killers() add a good move that produced a beta-cutoff - // among the killer moves of that ply. - - void update_killers(Move m, SearchStack* ss) { - - if (m == ss->killers[0]) - return; - - ss->killers[1] = ss->killers[0]; - ss->killers[0] = m; - } - - - // update_gains() updates the gains table of a non-capture move given - // the static position evaluation before and after the move. - - void update_gains(const Position& pos, Move m, Value before, Value after) { - - if ( m != MOVE_NULL - && before != VALUE_NONE - && after != VALUE_NONE - && pos.captured_piece_type() == PIECE_TYPE_NONE - && !move_is_special(m)) - H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after)); - } - - - // current_search_time() returns the number of milliseconds which have passed - // since the beginning of the current search. - - int current_search_time() { - - return get_system_time() - SearchStartTime; - } - - - // value_to_uci() converts a value to a string suitable for use with the UCI protocol - - std::string value_to_uci(Value v) { - - std::stringstream s; - - if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY) - s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to pawn = 100 - else - s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 ); - - return s.str(); - } - - // nps() computes the current nodes/second count. - - int nps(const Position& pos) { - - int t = current_search_time(); - return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0); - } - - - // poll() performs two different functions: It polls for user input, and it - // looks at the time consumed so far and decides if it's time to abort the - // search. - - void poll(const Position& pos) { - - static int lastInfoTime; - int t = current_search_time(); - - // Poll for input - if (data_available()) - { - // We are line oriented, don't read single chars - std::string command; - - if (!std::getline(std::cin, command)) - command = "quit"; - - if (command == "quit") - { - AbortSearch = true; - PonderSearch = false; - Quit = true; - return; - } - else if (command == "stop") - { - AbortSearch = true; - PonderSearch = false; - } - else if (command == "ponderhit") - ponderhit(); - } - - // Print search information - if (t < 1000) - lastInfoTime = 0; - - else if (lastInfoTime > t) - // HACK: Must be a new search where we searched less than - // NodesBetweenPolls nodes during the first second of search. - lastInfoTime = 0; - - else if (t - lastInfoTime >= 1000) - { - lastInfoTime = t; - - if (dbg_show_mean) - dbg_print_mean(); - - if (dbg_show_hit_rate) - dbg_print_hit_rate(); - - cout << "info nodes " << pos.nodes_searched() << " nps " << nps(pos) - << " time " << t << endl; - } - - // Should we stop the search? - if (PonderSearch) - return; - - bool stillAtFirstMove = FirstRootMove - && !AspirationFailLow - && t > TimeMgr.available_time(); - - bool noMoreTime = t > TimeMgr.maximum_time() - || stillAtFirstMove; - - if ( (Iteration >= 3 && UseTimeManagement && noMoreTime) - || (ExactMaxTime && t >= ExactMaxTime) - || (Iteration >= 3 && MaxNodes && pos.nodes_searched() >= MaxNodes)) - AbortSearch = true; - } - - - // ponderhit() is called when the program is pondering (i.e. thinking while - // it's the opponent's turn to move) in order to let the engine know that - // it correctly predicted the opponent's move. - - void ponderhit() { - - int t = current_search_time(); - PonderSearch = false; - - bool stillAtFirstMove = FirstRootMove - && !AspirationFailLow - && t > TimeMgr.available_time(); - - bool noMoreTime = t > TimeMgr.maximum_time() - || stillAtFirstMove; - - if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit)) - AbortSearch = true; - } - - - // init_ss_array() does a fast reset of the first entries of a SearchStack - // array and of all the excludedMove and skipNullMove entries. - - void init_ss_array(SearchStack* ss, int size) { + // When playing with strength handicap choose best move among the MultiPV set + // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen. - for (int i = 0; i < size; i++, ss++) - { - ss->excludedMove = MOVE_NONE; - ss->skipNullMove = false; - ss->reduction = DEPTH_ZERO; - ss->sp = NULL; - - if (i < 3) - ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE; - } - } + Move do_skill_level() { + assert(MultiPV > 1); - // wait_for_stop_or_ponderhit() is called when the maximum depth is reached - // while the program is pondering. The point is to work around a wrinkle in - // the UCI protocol: When pondering, the engine is not allowed to give a - // "bestmove" before the GUI sends it a "stop" or "ponderhit" command. - // We simply wait here until one of these commands is sent, and return, - // after which the bestmove and pondermove will be printed (in id_loop()). + static RKISS rk; - void wait_for_stop_or_ponderhit() { + // PRNG sequence should be not deterministic + for (int i = Time::now() % 50; i > 0; i--) + rk.rand(); - std::string command; + // RootMoves are already sorted by score in descending order + size_t size = std::min(MultiPV, RootMoves.size()); + int variance = std::min(RootMoves[0].score - RootMoves[size - 1].score, PawnValueMg); + int weakness = 120 - 2 * SkillLevel; + int max_s = -VALUE_INFINITE; + Move best = MOVE_NONE; - while (true) + // 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, + // then we choose the move with the resulting highest score. + for (size_t i = 0; i < size; i++) { - if (!std::getline(std::cin, command)) - command = "quit"; + int s = RootMoves[i].score; - if (command == "quit") - { - Quit = true; - break; - } - else if (command == "ponderhit" || command == "stop") + // Don't allow crazy blunders even at very low skills + if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg) break; - } - } - - - // print_pv_info() prints to standard output and eventually to log file information on - // the current PV line. It is called at each iteration or after a new pv is found. - - void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value) { - - cout << "info depth " << Iteration - << " score " << value_to_uci(value) - << (value >= beta ? " lowerbound" : value <= alpha ? " upperbound" : "") - << " time " << current_search_time() - << " nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " pv "; - - for (Move* m = pv; *m != MOVE_NONE; m++) - cout << *m << " "; - - cout << endl; - if (UseLogFile) - { - ValueType t = value >= beta ? VALUE_TYPE_LOWER : - value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT; - - LogFile << pretty_pv(pos, current_search_time(), Iteration, value, t, pv) << endl; - } - } - - - // 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. + // This is our magic formula + s += ( weakness * int(RootMoves[0].score - s) + + variance * (rk.rand() % weakness)) / 128; - void insert_pv_in_tt(const Position& pos, Move pv[]) { - - StateInfo st; - TTEntry* tte; - Position p(pos, pos.thread()); - Value v, m = VALUE_NONE; - - for (int i = 0; pv[i] != MOVE_NONE; i++) - { - tte = TT.retrieve(p.get_key()); - if (!tte || tte->move() != pv[i]) + if (s > max_s) { - v = (p.is_check() ? VALUE_NONE : evaluate(p, m)); - TT.store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[i], v, m); + max_s = s; + best = RootMoves[i].pv[0]; } - p.do_move(pv[i], st); - } - } - - - // extract_pv_from_tt() builds a PV by adding moves from the transposition table. - // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This - // allow to always have a ponder move even when we fail high at root and also a - // long PV to print that is important for position analysis. - - void extract_pv_from_tt(const Position& pos, Move bestMove, Move pv[]) { - - StateInfo st; - TTEntry* tte; - Position p(pos, pos.thread()); - int ply = 0; - - assert(bestMove != MOVE_NONE); - - pv[ply] = bestMove; - p.do_move(pv[ply++], st); - - while ( (tte = TT.retrieve(p.get_key())) != NULL - && tte->move() != MOVE_NONE - && move_is_legal(p, tte->move()) - && ply < PLY_MAX - && (!p.is_draw() || ply < 2)) - { - pv[ply] = tte->move(); - p.do_move(pv[ply++], st); } - pv[ply] = MOVE_NONE; + return best; } - // init_thread() is the function which is called when a new thread is - // launched. It simply calls the idle_loop() function with the supplied - // threadID. There are two versions of this function; one for POSIX - // threads and one for Windows threads. - -#if !defined(_MSC_VER) + // 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. - void* init_thread(void* threadID) { + string uci_pv(const Position& pos, int depth, Value alpha, Value beta) { - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return NULL; - } - -#else - - DWORD WINAPI init_thread(LPVOID threadID) { - - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return 0; - } - -#endif - - - /// The ThreadsManager class - - - // read_uci_options() updates number of active threads and other internal - // parameters according to the UCI options values. It is called before - // to start a new search. - - void ThreadsManager::read_uci_options() { - - maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value(); - minimumSplitDepth = Options["Minimum Split Depth"].value() * ONE_PLY; - useSleepingThreads = Options["Use Sleeping Threads"].value(); - activeThreads = Options["Threads"].value(); - } - - - // idle_loop() is where the threads are parked when they have no work to do. - // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint - // object for which the current thread is the master. - - void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) { - - assert(threadID >= 0 && threadID < MAX_THREADS); + std::stringstream s; + Time::point elaspsed = Time::now() - SearchTime + 1; + int selDepth = 0; - int i; - bool allFinished = false; + for (size_t i = 0; i < Threads.size(); i++) + if (Threads[i].maxPly > selDepth) + selDepth = Threads[i].maxPly; - while (true) + for (size_t i = 0; i < std::min(UCIMultiPV, RootMoves.size()); i++) { - // Slave threads can exit as soon as AllThreadsShouldExit raises, - // master should exit as last one. - if (allThreadsShouldExit) - { - assert(!sp); - threads[threadID].state = THREAD_TERMINATED; - return; - } - - // If we are not thinking, wait for a condition to be signaled - // instead of wasting CPU time polling for work. - while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING - || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE)) - { - assert(!sp || useSleepingThreads); - assert(threadID != 0 || useSleepingThreads); - - if (threads[threadID].state == THREAD_INITIALIZING) - threads[threadID].state = THREAD_AVAILABLE; - - // Grab the lock to avoid races with wake_sleeping_thread() - lock_grab(&sleepLock[threadID]); - - // If we are master and all slaves have finished do not go to sleep - for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {} - allFinished = (i == activeThreads); - - if (allFinished || allThreadsShouldExit) - { - lock_release(&sleepLock[threadID]); - break; - } - - // Do sleep here after retesting sleep conditions - if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE) - cond_wait(&sleepCond[threadID], &sleepLock[threadID]); - - lock_release(&sleepLock[threadID]); - } - - // If this thread has been assigned work, launch a search - if (threads[threadID].state == THREAD_WORKISWAITING) - { - assert(!allThreadsShouldExit); - - threads[threadID].state = THREAD_SEARCHING; - - // Here we call search() with SplitPoint template parameter set to true - SplitPoint* tsp = threads[threadID].splitPoint; - Position pos(*tsp->pos, threadID); - SearchStack* ss = tsp->sstack[threadID] + 1; - ss->sp = tsp; - - if (tsp->pvNode) - search(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply); - else - search(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply); - - assert(threads[threadID].state == THREAD_SEARCHING); - - threads[threadID].state = THREAD_AVAILABLE; - - // 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 (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE) - wake_sleeping_thread(tsp->master); - } - - // 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. - for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {} - allFinished = (i == activeThreads); - - if (allFinished) - { - // Because sp->slaves[] is reset under lock protection, - // be sure sp->lock has been released before to return. - lock_grab(&(sp->lock)); - lock_release(&(sp->lock)); - - // In helpful master concept a master can help only a sub-tree, and - // because here is all finished is not possible master is booked. - assert(threads[threadID].state == THREAD_AVAILABLE); - - threads[threadID].state = THREAD_SEARCHING; - return; - } - } - } + bool updated = (i <= PVIdx); + if (depth == 1 && !updated) + continue; - // init_threads() is called during startup. It launches all helper threads, - // and initializes the split point stack and the global locks and condition - // objects. - - void ThreadsManager::init_threads() { + int d = (updated ? depth : depth - 1); + Value v = (updated ? RootMoves[i].score : RootMoves[i].prevScore); - int i, arg[MAX_THREADS]; - bool ok; + if (s.rdbuf()->in_avail()) + s << "\n"; - // Initialize global locks - lock_init(&mpLock); + 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 / elaspsed + << " time " << elaspsed + << " multipv " << i + 1 + << " pv"; - for (i = 0; i < MAX_THREADS; i++) - { - lock_init(&sleepLock[i]); - cond_init(&sleepCond[i]); + for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++) + s << " " << move_to_uci(RootMoves[i].pv[j], Chess960); } - // Initialize splitPoints[] locks - for (i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_init(&(threads[i].splitPoints[j].lock)); - - // Will be set just before program exits to properly end the threads - allThreadsShouldExit = false; - - // Threads will be put all threads to sleep as soon as created - activeThreads = 1; - - // All threads except the main thread should be initialized to THREAD_INITIALIZING - threads[0].state = THREAD_SEARCHING; - for (i = 1; i < MAX_THREADS; i++) - threads[i].state = THREAD_INITIALIZING; - - // Launch the helper threads - for (i = 1; i < MAX_THREADS; i++) - { - arg[i] = i; - -#if !defined(_MSC_VER) - pthread_t pthread[1]; - ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0); - pthread_detach(pthread[0]); -#else - ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL); -#endif - if (!ok) - { - cout << "Failed to create thread number " << i << endl; - exit(EXIT_FAILURE); - } - - // Wait until the thread has finished launching and is gone to sleep - while (threads[i].state == THREAD_INITIALIZING) {} - } + return s.str(); } +} // namespace - // exit_threads() is called when the program exits. It makes all the - // helper threads exit cleanly. - - void ThreadsManager::exit_threads() { - - allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop() - - // Wake up all the threads and waits for termination - for (int i = 1; i < MAX_THREADS; i++) - { - wake_sleeping_thread(i); - while (threads[i].state != THREAD_TERMINATED) {} - } - // Now we can safely destroy the locks - for (int i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_destroy(&(threads[i].splitPoints[j].lock)); +/// 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. - lock_destroy(&mpLock); +void RootMove::extract_pv_from_tt(Position& pos) { - // Now we can safely destroy the wait conditions - for (int i = 0; i < MAX_THREADS; i++) - { - lock_destroy(&sleepLock[i]); - cond_destroy(&sleepCond[i]); - } - } + StateInfo state[MAX_PLY_PLUS_2], *st = state; + TTEntry* tte; + int ply = 1; + Move m = pv[0]; + assert(m != MOVE_NONE && pos.is_pseudo_legal(m)); - // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in - // the thread's currently active split point, or in some ancestor of - // the current split point. + pv.clear(); + pv.push_back(m); + pos.do_move(m, *st++); - bool ThreadsManager::cutoff_at_splitpoint(int threadID) const { - - assert(threadID >= 0 && threadID < activeThreads); - - SplitPoint* sp = threads[threadID].splitPoint; - - for ( ; sp && !sp->betaCutoff; sp = sp->parent) {} - return sp != NULL; + while ( (tte = TT.probe(pos.key())) != NULL + && (m = tte->move()) != MOVE_NONE // Local copy, TT entry could change + && pos.is_pseudo_legal(m) + && pos.pl_move_is_legal(m, pos.pinned_pieces()) + && ply < MAX_PLY + && (!pos.is_draw() || ply < 2)) + { + pv.push_back(m); + pos.do_move(m, *st++); + ply++; } + pv.push_back(MOVE_NONE); + do pos.undo_move(pv[--ply]); while (ply); +} - // thread_is_available() checks whether the thread with threadID "slave" is - // available to help the thread with threadID "master" at a split point. An - // obvious requirement is that "slave" must be idle. With more than two - // threads, this is not by itself sufficient: If "slave" is the master of - // some active split point, it is only available as a slave to the other - // threads which are busy searching the split point at the top of "slave"'s - // split point stack (the "helpful master concept" in YBWC terminology). - - bool ThreadsManager::thread_is_available(int slave, int master) const { - assert(slave >= 0 && slave < activeThreads); - assert(master >= 0 && master < activeThreads); - assert(activeThreads > 1); +/// 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. - if (threads[slave].state != THREAD_AVAILABLE || slave == master) - return false; +void RootMove::insert_pv_in_tt(Position& pos) { - // Make a local copy to be sure doesn't change under our feet - int localActiveSplitPoints = threads[slave].activeSplitPoints; + StateInfo state[MAX_PLY_PLUS_2], *st = state; + TTEntry* tte; + Key k; + Value v, m = VALUE_NONE; + int ply = 0; - // No active split points means that the thread is available as - // a slave for any other thread. - if (localActiveSplitPoints == 0 || activeThreads == 2) - return true; + assert(pv[ply] != MOVE_NONE && pos.is_pseudo_legal(pv[ply])); - // Apply the "helpful master" concept if possible. Use localActiveSplitPoints - // that is known to be > 0, instead of threads[slave].activeSplitPoints that - // could have been set to 0 by another thread leading to an out of bound access. - if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master]) - return true; + do { + k = pos.key(); + tte = TT.probe(k); - return false; - } + // Don't overwrite existing correct entries + if (!tte || tte->move() != pv[ply]) + { + v = (pos.in_check() ? VALUE_NONE : evaluate(pos, m)); + TT.store(k, VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m); + } + pos.do_move(pv[ply], *st++); + } while (pv[++ply] != MOVE_NONE); - // available_thread_exists() tries to find an idle thread which is available as - // a slave for the thread with threadID "master". + do pos.undo_move(pv[--ply]); while (ply); +} - bool ThreadsManager::available_thread_exists(int master) const { - assert(master >= 0 && master < activeThreads); - assert(activeThreads > 1); +/// Thread::idle_loop() is where the thread is parked when it has no work to do - for (int i = 0; i < activeThreads; i++) - if (thread_is_available(i, master)) - return true; +void Thread::idle_loop() { - return false; - } + // Pointer 'sp_master', if non-NULL, points to the active SplitPoint + // object for which the thread is the master. + const SplitPoint* sp_master = splitPointsCnt ? curSplitPoint : NULL; + assert(!sp_master || (sp_master->master == this && is_searching)); - // split() does the actual work of distributing the work at a node between - // several available threads. If it does not succeed in splitting the - // node (because no idle threads are available, or because we have no unused - // split point objects), the function immediately returns. If splitting is - // possible, a SplitPoint object is initialized with all the data that must be - // copied to the helper threads and we tell our helper threads that they have - // been assigned work. This will cause them to instantly leave their idle loops and - // call search().When all threads have returned from search() then split() returns. - - template - void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha, - const Value beta, Value* bestValue, Depth depth, Move threatMove, - bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) { - assert(pos.is_ok()); - assert(ply > 0 && ply < PLY_MAX); - assert(*bestValue >= -VALUE_INFINITE); - assert(*bestValue <= *alpha); - assert(*alpha < beta); - assert(beta <= VALUE_INFINITE); - assert(depth > DEPTH_ZERO); - assert(pos.thread() >= 0 && pos.thread() < activeThreads); - assert(activeThreads > 1); + // 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. + while (!sp_master || sp_master->slavesMask) + { + // If we are not searching, wait for a condition to be signaled + // instead of wasting CPU time polling for work. + while ( do_sleep + || do_exit + || (!is_searching && Threads.use_sleeping_threads())) + { + if (do_exit) + { + assert(!sp_master); + return; + } - int i, master = pos.thread(); - Thread& masterThread = threads[master]; + // Grab the lock to avoid races with Thread::wake_up() + mutex.lock(); - lock_grab(&mpLock); + // If we are master and all slaves have finished don't go to sleep + if (sp_master && !sp_master->slavesMask) + { + mutex.unlock(); + break; + } - // If no other thread is available to help us, or if we have too many - // active split points, don't split. - if ( !available_thread_exists(master) - || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS) - { - lock_release(&mpLock); - return; - } + // 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 wake_up() call before we + // had the chance to grab the lock. + if (do_sleep || !is_searching) + sleepCondition.wait(mutex); - // Pick the next available split point object from the split point stack - SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++]; - - // Initialize the split point object - splitPoint.parent = masterThread.splitPoint; - splitPoint.master = master; - splitPoint.betaCutoff = false; - splitPoint.ply = ply; - splitPoint.depth = depth; - splitPoint.threatMove = threatMove; - splitPoint.mateThreat = mateThreat; - splitPoint.alpha = *alpha; - splitPoint.beta = beta; - splitPoint.pvNode = pvNode; - splitPoint.bestValue = *bestValue; - splitPoint.mp = mp; - splitPoint.moveCount = moveCount; - splitPoint.pos = &pos; - splitPoint.nodes = 0; - splitPoint.parentSstack = ss; - for (i = 0; i < activeThreads; i++) - splitPoint.slaves[i] = 0; - - masterThread.splitPoint = &splitPoint; - - // If we are here it means we are not available - assert(masterThread.state != THREAD_AVAILABLE); - - int workersCnt = 1; // At least the master is included - - // Allocate available threads setting state to THREAD_BOOKED - for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++) - if (thread_is_available(i, master)) - { - threads[i].state = THREAD_BOOKED; - threads[i].splitPoint = &splitPoint; - splitPoint.slaves[i] = 1; - workersCnt++; - } + mutex.unlock(); + } - assert(Fake || workersCnt > 1); + // If this thread has been assigned work, launch a search + if (is_searching) + { + assert(!do_sleep && !do_exit); - // We can release the lock because slave threads are already booked and master is not available - lock_release(&mpLock); + Threads.mutex.lock(); - // Tell the threads that they have work to do. This will make them leave - // their idle loop. But before copy search stack tail for each thread. - for (i = 0; i < activeThreads; i++) - if (i == master || splitPoint.slaves[i]) - { - memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack)); + assert(is_searching); + SplitPoint* sp = curSplitPoint; - assert(i == master || threads[i].state == THREAD_BOOKED); + Threads.mutex.unlock(); - threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop() + Stack ss[MAX_PLY_PLUS_2]; + Position pos(*sp->pos, this); - if (useSleepingThreads && i != master) - wake_sleeping_thread(i); - } + memcpy(ss, sp->ss - 1, 4 * sizeof(Stack)); + (ss+1)->sp = sp; - // Everything is set up. The master thread enters the idle loop, from - // which it will instantly launch a search, because its state is - // THREAD_WORKISWAITING. We send the split point as a second parameter to the - // idle loop, which means that the main thread will return from the idle - // loop when all threads have finished their work at this split point. - idle_loop(master, &splitPoint); + sp->mutex.lock(); - // We have returned from the idle loop, which means that all threads are - // finished. Update alpha and bestValue, and return. - lock_grab(&mpLock); + assert(sp->activePositions[idx] == NULL); - *alpha = splitPoint.alpha; - *bestValue = splitPoint.bestValue; - masterThread.activeSplitPoints--; - masterThread.splitPoint = splitPoint.parent; - pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes); + sp->activePositions[idx] = &pos; - lock_release(&mpLock); - } + if (sp->nodeType == Root) + search(pos, ss+1, sp->alpha, sp->beta, sp->depth); + else if (sp->nodeType == PV) + search(pos, ss+1, sp->alpha, sp->beta, sp->depth); + else if (sp->nodeType == NonPV) + search(pos, ss+1, sp->alpha, sp->beta, sp->depth); + else + assert(false); + assert(is_searching); - // wake_sleeping_thread() wakes up the thread with the given threadID - // when it is time to start a new search. + is_searching = false; + sp->activePositions[idx] = NULL; + sp->slavesMask &= ~(1ULL << idx); + sp->nodes += pos.nodes_searched(); - void ThreadsManager::wake_sleeping_thread(int threadID) { + // 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.use_sleeping_threads() + && this != sp->master + && !sp->slavesMask) + { + assert(!sp->master->is_searching); + sp->master->wake_up(); + } - lock_grab(&sleepLock[threadID]); - cond_signal(&sleepCond[threadID]); - lock_release(&sleepLock[threadID]); + // 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. + sp->mutex.unlock(); + } } +} - /// The RootMoveList class - - // RootMoveList c'tor - - RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) { - - SearchStack ss[PLY_MAX_PLUS_2]; - MoveStack mlist[MOVES_MAX]; - StateInfo st; - bool includeAllMoves = (searchMoves[0] == MOVE_NONE); +/// 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. - // Initialize search stack - init_ss_array(ss, PLY_MAX_PLUS_2); - ss[0].eval = ss[0].evalMargin = VALUE_NONE; +void check_time() { - // Generate all legal moves - MoveStack* last = generate_moves(pos, mlist); + static Time::point lastInfoTime = Time::now(); + int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning - // Add each move to the moves[] array - for (MoveStack* cur = mlist; cur != last; cur++) - { - bool includeMove = includeAllMoves; + if (Time::now() - lastInfoTime >= 1000) + { + lastInfoTime = Time::now(); + dbg_print(); + } - for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++) - includeMove = (searchMoves[k] == cur->move); + if (Limits.ponder) + return; - if (!includeMove) - continue; + if (Limits.nodes) + { + Threads.mutex.lock(); - // Find a quick score for the move and add to the list - RootMove rm; - rm.move = ss[0].currentMove = rm.pv[0] = cur->move; - rm.pv[1] = MOVE_NONE; - pos.do_move(cur->move, st); - rm.pv_score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1); - pos.undo_move(cur->move); - push_back(rm); - } - sort(); - } + nodes = RootPosition.nodes_searched(); - // Score root moves using the standard way used in main search, the moves - // are scored according to the order in which are returned by MovePicker. - // This is the second order score that is used to compare the moves when - // the first order pv scores of both moves are equal. + // Loop across all split points and sum accumulated SplitPoint nodes plus + // all the currently active slaves positions. + for (size_t i = 0; i < Threads.size(); i++) + for (int j = 0; j < Threads[i].splitPointsCnt; j++) + { + SplitPoint& sp = Threads[i].splitPoints[j]; - void RootMoveList::set_non_pv_scores(const Position& pos) - { - Move move; - Value score = VALUE_ZERO; - MovePicker mp(pos, MOVE_NONE, ONE_PLY, H); + sp.mutex.lock(); - while ((move = mp.get_next_move()) != MOVE_NONE) - for (Base::iterator it = begin(); it != end(); ++it) - if (it->move == move) + nodes += sp.nodes; + Bitboard sm = sp.slavesMask; + while (sm) { - it->non_pv_score = score--; - break; + Position* pos = sp.activePositions[pop_lsb(&sm)]; + nodes += pos ? pos->nodes_searched() : 0; } - } - - // RootMoveList::sort_multipv() sorts the first few moves in the root move - // list by their scores and depths. It is used to order the different PVs - // correctly in MultiPV mode. - void RootMoveList::sort_multipv(int n) { + sp.mutex.unlock(); + } - int i,j; + Threads.mutex.unlock(); + } - for (i = 1; i <= n; i++) - { - const RootMove& rm = this->at(i); - for (j = i; j > 0 && this->at(j - 1) < rm; j--) - (*this)[j] = this->at(j - 1); + Time::point elapsed = Time::now() - SearchTime; + bool stillAtFirstMove = Signals.firstRootMove + && !Signals.failedLowAtRoot + && elapsed > TimeMgr.available_time(); - (*this)[j] = rm; - } - } + bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution + || stillAtFirstMove; -} // namespace + if ( (Limits.use_time_management() && noMoreTime) + || (Limits.movetime && elapsed >= Limits.movetime) + || (Limits.nodes && nodes >= Limits.nodes)) + Signals.stop = true; +}