X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=d99d5e12ec188dd2d3f5cb5f24f86f8984c96939;hb=b8930d0c267d9d01ea1f854122e663c34bf5fce2;hp=902049c351205e8f32405f999f978d8c21ef35e1;hpb=8bf9dc825420bddb6d8425352e53a97a285027ec;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index 902049c3..bf33a136 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) 2008-2013 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 @@ -17,364 +17,115 @@ along with this program. If not, see . */ +#include #include #include #include -#include #include #include -#include #include "book.h" #include "evaluate.h" -#include "history.h" -#include "misc.h" -#include "move.h" #include "movegen.h" #include "movepick.h" -#include "lock.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 { -namespace { - - // Different node types, used as template parameter - enum NodeType { NonPV, PV }; - - // Set to true to force running with one thread. Used for debugging. - const bool FakeSplit = false; - - // 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]; } - - // ThreadsManager class is used to handle all the threads related stuff like init, - // starting, parking and, the most important, launching a slave thread at a split - // point. All the access to shared thread data is done through this class. - - 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: - Thread& operator[](int threadID) { return threads[threadID]; } - 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 idle_loop(int threadID, SplitPoint* sp); - - template - void split(Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue, - Depth depth, Move threatMove, int moveCount, MovePicker* mp, bool pvNode); - private: - Lock mpLock; - Depth minimumSplitDepth; - int maxThreadsPerSplitPoint; - bool useSleepingThreads; - int activeThreads; - volatile bool allThreadsShouldExit; - Thread threads[MAX_THREADS]; - }; - - - // RootMove struct is used for moves at the root of 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 pv_score is normally set at - // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed - // according to the order in which moves are returned by MovePicker. - - struct RootMove { - - RootMove(); - RootMove(const RootMove& rm) { *this = rm; } - RootMove& operator=(const RootMove& rm); - - // 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 pv_score, or if it has - // equal pv_score but m1 has the higher non_pv_score. 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 extract_pv_from_tt(Position& pos); - void insert_pv_in_tt(Position& pos); - std::string pv_info_to_uci(Position& pos, int depth, int selDepth, Value alpha, Value beta, int pvIdx); - - int64_t nodes; - Value pv_score; - Value non_pv_score; - Move pv[PLY_MAX_PLUS_2]; - }; - - - // RootMoveList struct is just a std::vector<> of RootMove objects, - // with an handful of methods above the standard ones. - - struct RootMoveList : public std::vector { - - typedef std::vector Base; - - void init(Position& pos, Move searchMoves[]); - void sort() { insertion_sort(begin(), end()); } - void sort_multipv(int n) { insertion_sort(begin(), begin() + n); } - - int bestMoveChanges; - }; - - - // Overload operator<<() to make it easier to print moves in a coordinate - // notation compatible with UCI protocol. - std::ostream& operator<<(std::ostream& os, Move m) { - - bool chess960 = (os.iword(0) != 0); // See set960() - return os << move_to_uci(m, chess960); - } - - - // 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 read it to properly format castling moves. - enum set960 {}; - - std::ostream& operator<< (std::ostream& os, const set960& f) { + volatile SignalsType Signals; + LimitsType Limits; + std::vector RootMoves; + Position RootPos; + Color RootColor; + Time::point SearchTime; + StateStackPtr SetupStates; +} - os.iword(0) = int(f); - return os; - } +using std::string; +using Eval::evaluate; +using namespace Search; +namespace { - /// Adjustments + // Set to true to force running with one thread. Used for debugging + const bool FakeSplit = false; - // Step 6. Razoring + // This is the minimum interval in msec between two check_time() calls + const int TimerResolution = 5; - // Maximum depth for razoring - const Depth RazorDepth = 4 * ONE_PLY; + // Different node types, used as template parameter + enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; // 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], PawnPushTo7thExtension[2]; - Depth PassedPawnExtension[2], PawnEndgameExtension[2]; - - // Minimum depth for use of singular extension - const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */}; - - // Step 12. Futility pruning - - // Futility margin for quiescence search - const Value FutilityMarginQS = Value(0x80); + inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } // Futility lookup tables (initialized at startup) and their access 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 / ONE_PLY, 63)][Min(mn, 63)]; } + Value FutilityMargins[16][64]; // [depth][moveNumber] + int FutilityMoveCounts[32]; // [depth] - // Easy move margin. An easy move candidate must be at least this much - // better than the second best move. - const Value EasyMoveMargin = Value(0x200); + inline Value futility_margin(Depth d, int mn) { + return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)] + : 2 * VALUE_INFINITE; + } - /// Namespace variables - - // Book - Book OpeningBook; + // Reduction lookup tables (initialized at startup) and their access function + int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] - // Root move list - RootMoveList Rml; + template inline Depth reduction(Depth d, int mn) { - // MultiPV mode - int MultiPV, UCIMultiPV; + return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; + } - // Time management variables - int MaxNodes, MaxDepth, ExactMaxTime; - bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit; - bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow; + size_t PVSize, PVIdx; TimeManager TimeMgr; + int BestMoveChanges; + Value DrawValue[COLOR_NB]; + HistoryStats History; + GainsStats Gains; + CountermovesStats Countermoves; - // Log file - bool UseLogFile; - std::ofstream LogFile; - - // Skill level adjustment - int SkillLevel; - bool SkillLevelEnabled; - RKISS RK; - - // Multi-threads manager - 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. - bool SendSearchedNodes; - int NodesSincePoll; - int NodesBetweenPolls = 30000; - - // History table - History H; - + template + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); - /// Local functions + template + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove); - - template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); - - template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); - - template - inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { - - return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO) - : search(pos, ss, alpha, beta, depth); - } - - template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool* dangerous); - - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue); - bool connected_moves(const Position& pos, Move m1, Move m2); + void id_loop(Position& pos); 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_gains(const Position& pos, Move move, Value before, Value after); - void do_skill_level(Move* best, Move* ponder); - - int current_search_time(int set = 0); - std::string value_to_uci(Value v); - std::string speed_to_uci(int64_t nodes); - void poll(const Position& pos); - void wait_for_stop_or_ponderhit(); - -#if !defined(_MSC_VER) - void* init_thread(void* threadID); -#else - DWORD WINAPI init_thread(LPVOID threadID); -#endif - - - // MovePickerExt is an extended MovePicker used to choose at compile time - // the proper move source according to the type of node. - template struct MovePickerExt; - - // In Root nodes use RootMoveList as source. Score and sort the root moves - // before to search them. - template<> struct MovePickerExt : public MovePicker { - - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) - : MovePicker(p, ttm, d, h, ss, b), firstCall(true) { - Move move; - Value score = VALUE_ZERO; - - // Score root moves using standard ordering used in main search, the moves - // are scored according to the order in which they are returned by MovePicker. - // This is the second order score that is used to compare the moves when - // the first orders pv_score of both moves are equal. - while ((move = MovePicker::get_next_move()) != MOVE_NONE) - for (rm = Rml.begin(); rm != Rml.end(); ++rm) - if (rm->pv[0] == move) - { - rm->non_pv_score = score--; - break; - } - - Rml.sort(); - rm = Rml.begin(); - } - - Move get_next_move() { - - if (!firstCall) - ++rm; - else - firstCall = false; - - return rm != Rml.end() ? rm->pv[0] : MOVE_NONE; + bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta); + bool allows(const Position& pos, Move first, Move second); + bool refutes(const Position& pos, Move first, Move second); + string uci_pv(const Position& pos, int depth, Value alpha, Value beta); + + struct Skill { + Skill(int l) : level(l), best(MOVE_NONE) {} + ~Skill() { + if (enabled()) // Swap best PV line with the sub-optimal one + std::swap(RootMoves[0], *std::find(RootMoves.begin(), + RootMoves.end(), best ? best : pick_move())); } - RootMoveList::iterator rm; - bool firstCall; - }; - - // In SpNodes use split point's shared MovePicker object as move source - template<> struct MovePickerExt : public MovePicker { - - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) - : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {} - - Move get_next_move() { return mp->get_next_move(); } - - RootMoveList::iterator rm; // Dummy, needed to compile - MovePicker* mp; - }; - - // Default case, create and use a MovePicker object as source - template<> struct MovePickerExt : public MovePicker { - - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) - : MovePicker(p, ttm, d, h, ss, b) {} + bool enabled() const { return level < 20; } + bool time_to_pick(int depth) const { return depth == 1 + level; } + Move pick_move(); - RootMoveList::iterator rm; // Dummy, needed to compile + int level; + Move best; }; } // namespace -/// init_threads() is called during startup. It initializes various lookup tables -/// and creates and launches search threads. +/// Search::init() is called during startup to initialize various lookup tables -void init_threads() { +void Search::init() { int d; // depth (ONE_PLY == 2) int hd; // half depth (ONE_PLY == 1) @@ -385,204 +136,150 @@ void init_threads() { { 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)); - - // Create and startup threads - ThreadsMgr.init_threads(); + FutilityMoveCounts[d] = int(3.001 + 0.3 * pow(double(d), 1.8)); } -/// exit_threads() is a trampoline to access ThreadsMgr from outside of current file -void exit_threads() { ThreadsMgr.exit_threads(); } - +/// 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. -/// perft() is our utility to verify move generation. All the legal moves up to -/// given depth are generated and counted and the sum returned. +size_t Search::perft(Position& pos, Depth depth) { -int64_t perft(Position& pos, Depth depth) { - - MoveStack mlist[MOVES_MAX]; StateInfo st; - Move m; - int64_t sum = 0; - - // Generate all legal moves - MoveStack* last = generate(pos, mlist); - - // 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); - - // Loop through all legal moves + size_t cnt = 0; CheckInfo ci(pos); - for (MoveStack* cur = mlist; cur != last; cur++) + const bool leaf = depth == 2 * ONE_PLY; + + for (MoveList it(pos); *it; ++it) { - 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); + pos.do_move(*it, st, ci, pos.move_gives_check(*it, ci)); + cnt += leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); + pos.undo_move(*it); } - return sum; + 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 global -/// variables, and calls id_loop(). 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 RootPos 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-related variables - StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false; - NodesSincePoll = 0; - current_search_time(get_system_time()); - ExactMaxTime = maxTime; - MaxDepth = maxDepth; - MaxNodes = maxNodes; - InfiniteSearch = infinite; - Pondering = 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.name()) - OpeningBook.open(Options["Book File"].value()); + RootColor = RootPos.side_to_move(); + TimeMgr.init(Limits, RootPos.game_ply(), RootColor); - Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value()); - if (bookMove != MOVE_NONE) - { - if (Pondering) - wait_for_stop_or_ponderhit(); + if (RootMoves.empty()) + { + RootMoves.push_back(MOVE_NONE); + sync_cout << "info depth 0 score " + << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << sync_endl; - cout << "bestmove " << bookMove << endl; - return !QuitRequest; - } + goto finalize; } - // Read UCI options - CheckExtension[1] = Options["Check Extension (PV nodes)"].value(); - CheckExtension[0] = Options["Check 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(); - UCIMultiPV = Options["MultiPV"].value(); - SkillLevel = Options["Skill level"].value(); - UseLogFile = Options["Use Search Log"].value(); - - read_evaluation_uci_options(pos.side_to_move()); - - if (Options["Clear Hash"].value()) + if (Options["OwnBook"] && !Limits.infinite && !Limits.mate) { - Options["Clear Hash"].set_value("false"); - TT.clear(); - } - TT.set_size(Options["Hash"].value()); + Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]); - // 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 ? Max(UCIMultiPV, 4) : UCIMultiPV); - - // Set the number of active threads - ThreadsMgr.read_uci_options(); - init_eval(ThreadsMgr.active_threads()); + if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove)) + { + std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), bookMove)); + goto finalize; + } + } - // Wake up needed threads and reset maxPly counter - for (int i = 0; i < ThreadsMgr.active_threads(); i++) + if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) { - ThreadsMgr[i].wake_up(); - ThreadsMgr[i].maxPly = 0; + int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns + cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase + DrawValue[ RootColor] = VALUE_DRAW - Value(cf); + DrawValue[~RootColor] = VALUE_DRAW + Value(cf); } - - // 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 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) + if (Options["Use Search Log"]) { - std::string name = Options["Search Log Filename"].value(); - LogFile.open(name.c_str(), std::ios::out | std::ios::app); - - LogFile << "\nSearching: " << pos.to_fen() - << "\ninfinite: " << infinite - << " ponder: " << ponder - << " time: " << myTime - << " increment: " << myIncrement - << " moves to go: " << movesToGo - << endl; + Log log(Options["Search Log Filename"]); + log << "\nSearching: " << RootPos.fen() + << "\ninfinite: " << Limits.infinite + << " ponder: " << Limits.ponder + << " time: " << Limits.time[RootColor] + << " increment: " << Limits.inc[RootColor] + << " moves to go: " << Limits.movestogo + << std::endl; } - // We're ready to start thinking. Call the iterative deepening loop function - Move ponderMove = MOVE_NONE; - Move bestMove = id_loop(pos, searchMoves, &ponderMove); + // Reset the threads, still sleeping: will be wake up at split time + for (size_t i = 0; i < Threads.size(); i++) + Threads[i]->maxPly = 0; + + Threads.sleepWhileIdle = Options["Use Sleeping Threads"]; + + // Set best timer interval to avoid lagging under time pressure. Timer is + // used to check for remaining available thinking time. + Threads.timer->msec = + Limits.use_time_management() ? std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution)) : + Limits.nodes ? 2 * TimerResolution + : 100; + + Threads.timer->notify_one(); // Wake up the recurring timer - // Print final search statistics - cout << "info" << speed_to_uci(pos.nodes_searched()) << endl; + id_loop(RootPos); // Let's start searching ! - if (UseLogFile) + Threads.timer->msec = 0; // Stop the timer + Threads.sleepWhileIdle = true; // Send idle threads to sleep + + if (Options["Use Search Log"]) { - int t = current_search_time(); + Time::point elapsed = Time::now() - SearchTime + 1; - LogFile << "Nodes: " << pos.nodes_searched() - << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0) - << "\nBest move: " << move_to_san(pos, bestMove); + Log log(Options["Search Log Filename"]); + log << "Nodes: " << RootPos.nodes_searched() + << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed + << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]); StateInfo st; - pos.do_move(bestMove, st); - LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl; - pos.undo_move(bestMove); // Return from think() with unchanged position - LogFile.close(); + RootPos.do_move(RootMoves[0].pv[0], st); + log << "\nPonder move: " << move_to_san(RootPos, RootMoves[0].pv[1]) << std::endl; + RootPos.undo_move(RootMoves[0].pv[0]); } - // This makes all the threads to go to sleep - ThreadsMgr.set_active_threads(1); - - // If we are pondering or in infinite search, we shouldn't print the - // best move before we are told to do so. - if (!StopRequest && (Pondering || InfiniteSearch)) - wait_for_stop_or_ponderhit(); +finalize: - // Could be MOVE_NONE when searching on a stalemate position - cout << "bestmove " << bestMove; + // When search is stopped this info is not printed + sync_cout << "info nodes " << RootPos.nodes_searched() + << " time " << Time::now() - SearchTime + 1 << sync_endl; - // UCI protol is not clear on allowing sending an empty ponder move, instead - // it is clear that ponder move is optional. So skip it if empty. - if (ponderMove != MOVE_NONE) - cout << " ponder " << ponderMove; - - cout << endl; + // When we reach max depth we arrive here even without Signals.stop is raised, + // but if we are pondering or in infinite search, according to UCI protocol, + // we shouldn't print the best move before the GUI sends a "stop" or "ponderhit" + // command. We simply wait here until GUI sends one of those commands (that + // raise Signals.stop). + if (!Signals.stop && (Limits.ponder || Limits.infinite)) + { + Signals.stopOnPonderhit = true; + RootPos.this_thread()->wait_for(Signals.stop); + } - return !QuitRequest; + // Best move could be MOVE_NONE when searching on a stalemate position + sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960()) + << " ponder " << move_to_uci(RootMoves[0].pv[1], RootPos.is_chess960()) + << sync_endl; } @@ -592,176 +289,187 @@ namespace { // with increasing depth until the allocated thinking time has been consumed, // user stops the search, or the maximum search depth is reached. - Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) { + void id_loop(Position& pos) { - SearchStack ss[PLY_MAX_PLUS_2]; - Value bestValues[PLY_MAX_PLUS_2]; - int bestMoveChanges[PLY_MAX_PLUS_2]; - int depth, selDepth, aspirationDelta; - Value value, alpha, beta; - Move bestMove, easyMove, skillBest, skillPonder; + Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1) + int depth, prevBestMoveChanges; + Value bestValue, alpha, beta, delta; - // Initialize stuff before a new search - memset(ss, 0, 4 * sizeof(SearchStack)); + memset(ss-1, 0, 4 * sizeof(Stack)); + depth = BestMoveChanges = 0; + bestValue = delta = -VALUE_INFINITE; + (ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains TT.new_search(); - H.clear(); - *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE; - depth = aspirationDelta = 0; - alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; - ss->currentMove = MOVE_NULL; // Hack to skip update_gains() + History.clear(); + Gains.clear(); + Countermoves.clear(); - // Moves to search are verified and copied - Rml.init(pos, searchMoves); + PVSize = Options["MultiPV"]; + Skill skill(Options["Skill Level"]); - // Handle special case of searching on a mate/stalemate position - if (Rml.size() == 0) - { - cout << "info depth 0 score " - << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW) - << endl; + // Do we have to play with skill handicap? In this case enable MultiPV search + // that we will use behind the scenes to retrieve a set of possible moves. + if (skill.enabled() && PVSize < 4) + PVSize = 4; - return MOVE_NONE; - } + PVSize = std::min(PVSize, RootMoves.size()); - // Iterative deepening loop - while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest) + // Iterative deepening loop until requested to stop or target depth reached + while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) { - Rml.bestMoveChanges = 0; - cout << set960(pos.is_chess960()) << "info depth " << depth << endl; - - // Calculate dynamic aspiration window based on previous iterations - if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN) - { - int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2]; - int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3]; - - aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24); - aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize - - alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE); - beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE); - } + // 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; - // Start with a small aspiration window and, in case of fail high/low, - // research with bigger window until not failing high/low anymore. - do { - // Search starting from ss+1 to allow calling update_gains() - value = search(pos, ss+1, alpha, beta, depth * ONE_PLY); + prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1 + BestMoveChanges = 0; - // Write PV back to transposition table in case the relevant entries - // have been overwritten during the search. - for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++) - Rml[i].insert_pv_in_tt(pos); - - // Value cannot be trusted. Break out immediately! - if (StopRequest) - break; - - assert(value >= alpha); - - // In case of failing high/low increase aspiration window and research, - // otherwise exit the fail high/low loop. - if (value >= beta) + // MultiPV loop. We perform a full root search for each PV line + for (PVIdx = 0; PVIdx < PVSize; PVIdx++) + { + // Set aspiration window default width + if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN) { - beta = Min(beta + aspirationDelta, VALUE_INFINITE); - aspirationDelta += aspirationDelta / 2; + delta = Value(16); + alpha = RootMoves[PVIdx].prevScore - delta; + beta = RootMoves[PVIdx].prevScore + delta; } - else if (value <= alpha) + else { - AspirationFailLow = true; - StopOnPonderhit = false; - - alpha = Max(alpha - aspirationDelta, -VALUE_INFINITE); - aspirationDelta += aspirationDelta / 2; + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; } - else - break; - } while (abs(value) < VALUE_KNOWN_WIN); + // 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) + { + bestValue = search(pos, ss, alpha, beta, depth * ONE_PLY, false); + + // Bring to front the best move. It is critical that sorting is + // done with a stable algorithm because all the values but the first + // and eventually the new best one are set to -VALUE_INFINITE and + // we want to keep the same order for all the moves but the new + // PV that goes to the front. Note that in case of MultiPV search + // the already searched PV lines are preserved. + std::stable_sort(RootMoves.begin() + PVIdx, RootMoves.end()); + + // Write PV back to transposition table in case the relevant + // entries have been overwritten during the search. + for (size_t i = 0; i <= PVIdx; i++) + RootMoves[i].insert_pv_in_tt(pos); + + // If search has been stopped return immediately. Sorting and + // writing PV back to TT is safe becuase RootMoves is still + // valid, although refers to previous iteration. + if (Signals.stop) + return; + + // In case of failing high/low increase aspiration window and + // research, otherwise exit the loop. + if (bestValue > alpha && bestValue < beta) + break; + + // Give some update (without cluttering the UI) before to research + if (Time::now() - SearchTime > 3000) + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; + + if (abs(bestValue) >= VALUE_KNOWN_WIN) + { + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; + } + else if (bestValue >= beta) + { + beta += delta; + delta += delta / 2; + } + else + { + Signals.failedLowAtRoot = true; + Signals.stopOnPonderhit = false; + + alpha -= delta; + delta += delta / 2; + } - // Collect info about search result - bestMove = Rml[0].pv[0]; - *ponderMove = Rml[0].pv[1]; - bestValues[depth] = value; - bestMoveChanges[depth] = Rml.bestMoveChanges; + assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); + } + + // Sort the PV lines searched so far and update the GUI + std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); - // Do we need to pick now the best and the ponder moves ? - if (SkillLevelEnabled && depth == 1 + SkillLevel) - do_skill_level(&skillBest, &skillPonder); + if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000) + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; + } - // Retrieve max searched depth among threads - selDepth = 0; - for (int i = 0; i < ThreadsMgr.active_threads(); i++) - if (ThreadsMgr[i].maxPly > selDepth) - selDepth = ThreadsMgr[i].maxPly; + // Do we need to pick now the sub-optimal best move ? + if (skill.enabled() && skill.time_to_pick(depth)) + skill.pick_move(); - // Send PV line to GUI and to log file - for (int i = 0; i < Min(UCIMultiPV, (int)Rml.size()); i++) - cout << Rml[i].pv_info_to_uci(pos, depth, selDepth, alpha, beta, i) << endl; + if (Options["Use Search Log"]) + { + RootMove& rm = RootMoves[0]; + if (skill.best != MOVE_NONE) + rm = *std::find(RootMoves.begin(), RootMoves.end(), skill.best); - if (UseLogFile) - LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl; + Log log(Options["Search Log Filename"]); + log << pretty_pv(pos, depth, rm.score, Time::now() - SearchTime, &rm.pv[0]) + << std::endl; + } - // Init easyMove after first iteration or drop if differs from the best move - if (depth == 1 && (Rml.size() == 1 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)) - easyMove = bestMove; - else if (bestMove != easyMove) - easyMove = MOVE_NONE; + // Do we have found a "mate in x"? + if ( Limits.mate + && bestValue >= VALUE_MATE_IN_MAX_PLY + && VALUE_MATE - bestValue <= 2 * Limits.mate) + Signals.stop = true; - if (UseTimeManagement && !StopRequest) + // Do we have time for the next iteration? Can we stop searching now? + if (Limits.use_time_management() && !Signals.stopOnPonderhit) { - // Time to stop? - bool noMoreTime = false; - - // Stop search early when the last two iterations returned a mate score - if ( depth >= 5 - && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100 - && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100) - noMoreTime = true; - - // Stop search early if one move seems to be much better than the - // others or if there is only a single legal move. In this latter - // case we search up to Iteration 8 anyway to get a proper score. - if ( depth >= 7 - && easyMove == bestMove - && ( Rml.size() == 1 - ||( 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))) - noMoreTime = true; - - // Add some extra time if the best move has changed during the last two iterations - if (depth > 4 && depth < 50) - TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-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) - noMoreTime = true; - - if (noMoreTime) + bool stop = false; // Local variable, not the volatile Signals.stop + + // Take in account some extra time if the best move has changed + if (depth > 4 && depth < 50 && PVSize == 1) + TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges); + + // Stop search if most of available time is already consumed. We + // probably don't have enough time to search the first move at the + // next iteration anyway. + if (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100) + stop = true; + + // Stop search early if one move seems to be much better than others + if ( depth >= 12 + && !stop + && PVSize == 1 + && bestValue > VALUE_MATED_IN_MAX_PLY + && ( RootMoves.size() == 1 + || Time::now() - SearchTime > (TimeMgr.available_time() * 20) / 100)) + { + Value rBeta = bestValue - 2 * PawnValueMg; + ss->excludedMove = RootMoves[0].pv[0]; + ss->skipNullMove = true; + Value v = search(pos, ss, rBeta - 1, rBeta, (depth - 3) * ONE_PLY, true); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; + + if (v < rBeta) + stop = true; + } + + if (stop) { - if (Pondering) - StopOnPonderhit = true; + // 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 - break; + Signals.stop = true; } } } - - // When using skills fake best and ponder moves with the sub-optimal ones - if (SkillLevelEnabled) - { - if (skillBest == MOVE_NONE) // Still unassigned ? - do_skill_level(&skillBest, &skillPonder); - - bestMove = skillBest; - *ponderMove = skillPonder; - } - - return bestMove; } @@ -772,126 +480,161 @@ 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) { + template + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { - assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); - assert(beta > alpha && beta <= VALUE_INFINITE); - assert(PvNode || alpha == beta - 1); - 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); + + assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); + assert(PvNode || (alpha == beta - 1)); + assert(depth > DEPTH_ZERO); - Move movesSearched[MOVES_MAX]; - int64_t nodes; + Move quietsSearched[64]; StateInfo st; const TTEntry *tte; + SplitPoint* splitPoint; 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 isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous, isBadCap; - int moveCount = 0, playedMoveCount = 0; - int threadID = pos.thread(); - SplitPoint* sp = NULL; - - refinedValue = bestValue = value = -VALUE_INFINITE; - oldAlpha = alpha; - isCheck = pos.is_check(); - ss->ply = (ss-1)->ply + 1; + Value bestValue, value, ttValue; + Value eval, nullValue, futilityValue; + bool inCheck, givesCheck, pvMove, singularExtensionNode; + bool captureOrPromotion, dangerous, doFullDepthSearch; + int moveCount, quietCount; - // Used to send selDepth info to GUI - if (PvNode && ThreadsMgr[threadID].maxPly < ss->ply) - ThreadsMgr[threadID].maxPly = ss->ply; + // Step 1. Initialize node + Thread* thisThread = pos.this_thread(); + moveCount = quietCount = 0; + inCheck = pos.checkers(); if (SpNode) { - sp = ss->sp; + splitPoint = ss->splitPoint; + bestMove = splitPoint->bestMove; + threatMove = splitPoint->threatMove; + bestValue = splitPoint->bestValue; tte = NULL; ttMove = excludedMove = MOVE_NONE; - threatMove = sp->threatMove; + ttValue = VALUE_NONE; + + assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0); + goto split_point_start; } - else if (Root) - bestValue = alpha; - // Step 1. Initialize node and poll. Polling can abort search - ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE; + bestValue = -VALUE_INFINITE; + ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->ply = (ss-1)->ply + 1; + ss->futilityMoveCount = 0; (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; - (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE; + (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 (( StopRequest - || ThreadsMgr.cutoff_at_splitpoint(threadID) - || pos.is_draw() - || ss->ply > PLY_MAX) && !Root) - return VALUE_DRAW; - - // Step 3. Mate distance pruning - alpha = Max(value_mated_in(ss->ply), alpha); - beta = Min(value_mate_in(ss->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. excludedMove = ss->excludedMove; - posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); - - tte = TT.retrieve(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; + 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. - if ( !Root + // 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 - && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT - : ok_to_use_TT(tte, depth, beta, ss->ply))) + && tte->depth() >= depth + && ttValue != VALUE_NONE // Only in case of TT access race + && ( PvNode ? tte->bound() == BOUND_EXACT + : ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { TT.refresh(tte); - ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ss->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 parent's gain statistics - if (isCheck) - ss->eval = ss->evalMargin = VALUE_NONE; + if (inCheck) + ss->staticEval = ss->evalMargin = eval = 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, ss->ply); + // Never assume anything on values stored in TT + if ( (ss->staticEval = eval = tte->eval_value()) == VALUE_NONE + ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE) + eval = ss->staticEval = evaluate(pos, ss->evalMargin); + + // Can ttValue be used as a better position evaluation? + if (ttValue != VALUE_NONE) + if ( ((tte->bound() & BOUND_LOWER) && ttValue > eval) + || ((tte->bound() & BOUND_UPPER) && ttValue < eval)) + eval = ttValue; } else { - refinedValue = ss->eval = evaluate(pos, ss->evalMargin); - TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin); + eval = ss->staticEval = evaluate(pos, ss->evalMargin); + TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, + ss->staticEval, 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 ( !pos.captured_piece_type() + && ss->staticEval != VALUE_NONE + && (ss-1)->staticEval != VALUE_NONE + && (move = (ss-1)->currentMove) != MOVE_NULL + && type_of(move) == NORMAL) + { + Square to = to_sq(move); + Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval); + } // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode - && depth < RazorDepth - && !isCheck - && refinedValue + razor_margin(depth) < beta + && depth < 4 * ONE_PLY + && !inCheck + && eval + razor_margin(depth) < beta && ttMove == MOVE_NONE - && abs(beta) < VALUE_MATE_IN_PLY_MAX - && !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); + 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. @@ -903,49 +646,51 @@ namespace { // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode && !ss->skipNullMove - && depth < RazorDepth - && !isCheck - && refinedValue - futility_margin(depth, 0) >= beta - && abs(beta) < VALUE_MATE_IN_PLY_MAX + && depth < 4 * ONE_PLY + && !inCheck + && eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta + && abs(beta) < VALUE_MATE_IN_MAX_PLY + && abs(eval) < VALUE_KNOWN_WIN && pos.non_pawn_material(pos.side_to_move())) - return refinedValue - futility_margin(depth, 0); + return eval - futility_margin(depth, (ss-1)->futilityMoveCount); // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode && !ss->skipNullMove && depth > ONE_PLY - && !isCheck - && refinedValue >= beta - && abs(beta) < VALUE_MATE_IN_PLY_MAX + && !inCheck + && eval >= beta + && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; // Null move dynamic reduction based on depth - 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 - PawnValueMidgame > beta) - R++; + if (eval - PawnValueMg > beta) + R += ONE_PLY; pos.do_null_move(st); (ss+1)->skipNullMove = true; - nullValue = -search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY); + nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, depth-R, !cutNode); (ss+1)->skipNullMove = false; pos.undo_null_move(); 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) + if (depth < 12 * ONE_PLY) return nullValue; // Do verification search at high depths ss->skipNullMove = true; - Value v = search(pos, ss, alpha, beta, depth-R*ONE_PLY); + Value v = search(pos, ss, alpha, beta, depth-R, false); ss->skipNullMove = false; if (v >= beta) @@ -959,143 +704,178 @@ 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). - threatMove = (ss+1)->bestMove; + threatMove = (ss+1)->currentMove; - if ( depth < ThreatDepth + if ( depth < 5 * ONE_PLY && (ss-1)->reduction && threatMove != MOVE_NONE - && connected_moves(pos, (ss-1)->currentMove, threatMove)) - return beta - 1; + && allows(pos, (ss-1)->currentMove, threatMove)) + return alpha; } } - // Step 9. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] + // 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 + && 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, History, 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, !cutNode); + pos.undo_move(move); + if (value >= rbeta) + return value; + } + } + + // Step 10. Internal iterative deepening + if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) && ttMove == MOVE_NONE - && (PvNode || (!isCheck && ss->eval + IIDMargin >= beta))) + && (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta))) { - Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2); + Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); ss->skipNullMove = true; - search(pos, ss, alpha, beta, d); + search(pos, ss, alpha, beta, d, true); ss->skipNullMove = false; - ttMove = ss->bestMove; - tte = TT.retrieve(posKey); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; } split_point_start: // At split points actual search starts from here - // Initialize a MovePicker object for the current position - MovePickerExt mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta)); + Square prevMoveSq = to_sq((ss-1)->currentMove); + Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first, + Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second }; + + MovePicker mp(pos, ttMove, depth, History, countermoves, ss, PvNode ? -VALUE_INFINITE : beta); CheckInfo ci(pos); - ss->bestMove = MOVE_NONE; - futilityBase = ss->eval + ss->evalMargin; - singularExtensionNode = !Root + value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc + singularExtensionNode = !RootNode && !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) + && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY) + && ttMove != MOVE_NONE + && !excludedMove // Recursive singular search is not allowed + && (tte->bound() & 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) { - moveCount = ++sp->moveCount; - lock_release(&(sp->lock)); + // Shared counter cannot be decremented later if move turns out to be illegal + if (!pos.pl_move_is_legal(move, ci.pinned)) + continue; + + moveCount = ++splitPoint->moveCount; + splitPoint->mutex.unlock(); } - else if (move == excludedMove) - continue; else moveCount++; - if (Root) + if (RootNode) { - // This is used by time management - FirstRootMove = (moveCount == 1); - - // Save the current node count before the move is searched - nodes = pos.nodes_searched(); + Signals.firstRootMove = (moveCount == 1); - // If it's time to send nodes info, do it here where we have the - // correct accumulated node counts searched by each thread. - if (SendSearchedNodes) - { - SendSearchedNodes = false; - cout << "info" << speed_to_uci(pos.nodes_searched()) << endl; - } - - if (current_search_time() > 2000) - cout << "info currmove " << move - << " currmovenumber " << moveCount << endl; + if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000) + sync_cout << "info depth " << depth / ONE_PLY + << " currmove " << move_to_uci(move, pos.is_chess960()) + << " currmovenumber " << moveCount + PVIdx << sync_endl; } - // At Root and at first iteration do a PV search on all the moves to score root moves - isPvMove = (PvNode && moveCount <= (Root ? depth <= ONE_PLY ? 1000 : MultiPV : 1)); - moveIsCheck = pos.move_is_check(move, ci); - captureOrPromotion = pos.move_is_capture_or_promotion(move); - - // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, &dangerous); + 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 - && move == tte->move() - && ext < ONE_PLY) + if ( singularExtensionNode + && move == ttMove + && !ext + && pos.pl_move_is_legal(move, ci.pinned) + && abs(ttValue) < VALUE_KNOWN_WIN) { - Value ttValue = value_from_tt(tte->value(), ss->ply); + assert(ttValue != VALUE_NONE); - if (abs(ttValue) < VALUE_KNOWN_WIN) - { - Value rBeta = ttValue - int(depth); - ss->excludedMove = move; - ss->skipNullMove = true; - Value v = search(pos, ss, rBeta - 1, rBeta, depth / 2); - ss->skipNullMove = false; - ss->excludedMove = MOVE_NONE; - ss->bestMove = MOVE_NONE; - if (v < rBeta) - ext = ONE_PLY; - } + Value rBeta = ttValue - int(depth); + ss->excludedMove = move; + ss->skipNullMove = true; + value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; + + if (value < rBeta) + ext = 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)) + /* && move != ttMove Already implicit in the next condition */ + && bestValue > 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 || !refutes(pos, move, threatMove))) { if (SpNode) - lock_grab(&(sp->lock)); + splitPoint->mutex.lock(); continue; } @@ -1103,325 +883,321 @@ 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->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount) + + Gains[pos.piece_moved(move)][to_sq(move)]; - if (futilityValueScaled < beta) + if (futilityValue < beta) { + bestValue = std::max(bestValue, futilityValue); + if (SpNode) { - lock_grab(&(sp->lock)); - if (futilityValueScaled > sp->bestValue) - sp->bestValue = bestValue = futilityValueScaled; + splitPoint->mutex.lock(); + if (bestValue > splitPoint->bestValue) + splitPoint->bestValue = bestValue; } - else if (futilityValueScaled > bestValue) - bestValue = futilityValueScaled; - continue; } // Prune moves with negative SEE at low depths - if ( predictedDepth < 2 * ONE_PLY - && bestValue > VALUE_MATED_IN_PLY_MAX + if ( predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < 0) { if (SpNode) - lock_grab(&(sp->lock)); + splitPoint->mutex.lock(); continue; } - } - // Bad capture detection. Will be used by prob-cut search - isBadCap = depth >= 3 * ONE_PLY - && depth < 8 * ONE_PLY - && captureOrPromotion - && move != ttMove - && !dangerous - && !move_is_promotion(move) - && abs(alpha) < VALUE_MATE_IN_PLY_MAX - && pos.see_sign(move) < 0; - - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); - - if (!SpNode && !captureOrPromotion) - movesSearched[playedMoveCount++] = move; - - // Step extra. pv search (only in PV nodes) - // The first move in list is the expected PV - if (isPvMove) - { - // Aspiration window is disabled in multi-pv case - if (Root && MultiPV > 1) - alpha = -VALUE_INFINITE; - - value = -search(pos, ss+1, -beta, -alpha, newDepth); + // We have not pruned the move that will be searched, but remember how + // far in the move list we are to be more aggressive in the child node. + ss->futilityMoveCount = moveCount; } else + ss->futilityMoveCount = 0; + + // Check for legality only before to do the move + if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned)) { - // Step 14. Reduced depth search - // If the move fails high will be re-searched at full depth. - bool doFullDepthSearch = true; - alpha = SpNode ? sp->alpha : alpha; - - if ( depth >= 3 * ONE_PLY - && !captureOrPromotion - && !dangerous - && !move_is_castle(move) - && ss->killers[0] != move - && ss->killers[1] != move) - { - ss->reduction = reduction(depth, moveCount); - if (ss->reduction) - { - alpha = SpNode ? sp->alpha : alpha; - Depth d = newDepth - ss->reduction; - value = -search(pos, ss+1, -(alpha+1), -alpha, d); + moveCount--; + continue; + } - doFullDepthSearch = (value > alpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction - } + pvMove = PvNode && moveCount == 1; + ss->currentMove = move; + if (!SpNode && !captureOrPromotion && quietCount < 64) + quietsSearched[quietCount++] = move; - // Probcut search for bad captures. If a reduced search returns a value - // very below beta then we can (almost) safely prune the bad capture. - if (isBadCap) - { - ss->reduction = 3 * ONE_PLY; - Value rAlpha = alpha - 300; - Depth d = newDepth - ss->reduction; - value = -search(pos, ss+1, -(rAlpha+1), -rAlpha, d); - doFullDepthSearch = (value > rAlpha); - ss->reduction = DEPTH_ZERO; // Restore original reduction - } + // Step 14. Make the move + pos.do_move(move, st, ci, givesCheck); - // Step 15. Full depth search - if (doFullDepthSearch) - { - alpha = SpNode ? sp->alpha : alpha; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth); - - // 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 && (Root || value < beta)) - value = -search(pos, ss+1, -beta, -alpha, newDepth); - } - } + // 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 + && move != ttMove + && move != ss->killers[0] + && move != ss->killers[1]) + { + ss->reduction = reduction(depth, moveCount); - // Step 16. Undo move - pos.undo_move(move); + if (!PvNode && cutNode) + ss->reduction += ONE_PLY; - assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); + if (move == countermoves[0] || move == countermoves[1]) + ss->reduction = std::max(DEPTH_ZERO, ss->reduction-ONE_PLY); - // Step 17. Check for new best move - if (SpNode) - { - lock_grab(&(sp->lock)); - bestValue = sp->bestValue; - alpha = sp->alpha; + Depth d = std::max(newDepth - ss->reduction, ONE_PLY); + if (SpNode) + alpha = splitPoint->alpha; + + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + + doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); + ss->reduction = DEPTH_ZERO; } + else + doFullDepthSearch = !pvMove; - if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID))) + // Step 16. Full depth search, when LMR is skipped or fails high + if (doFullDepthSearch) { - bestValue = value; - if (SpNode) - sp->bestValue = value; - - if (!Root && value > alpha) - { - if (PvNode && value < beta) // We want always alpha < beta - { - alpha = value; + alpha = splitPoint->alpha; - if (SpNode) - sp->alpha = value; - } - else if (SpNode) - sp->betaCutoff = true; + value = newDepth < ONE_PLY ? + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); + } - if (value == value_mate_in(ss->ply + 1)) - ss->mateKiller = 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 ? + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, newDepth, false); + // Step 17. Undo move + pos.undo_move(move); - ss->bestMove = move; + assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - if (SpNode) - sp->ss->bestMove = move; - } + // Step 18. Check for new best move + if (SpNode) + { + splitPoint->mutex.lock(); + bestValue = splitPoint->bestValue; + alpha = splitPoint->alpha; } - if (Root) - { - // Finished searching the move. If StopRequest 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 (StopRequest) - break; + // 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 value; // To avoid returning VALUE_INFINITE - // Remember searched nodes counts for this move - mp.rm->nodes += pos.nodes_searched() - nodes; + if (RootNode) + { + RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); // PV move or new best move ? - if (isPvMove || value > alpha) + if (pvMove || value > alpha) { - // Update PV - ss->bestMove = move; - mp.rm->pv_score = value; - mp.rm->extract_pv_from_tt(pos); + 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 (!isPvMove && MultiPV == 1) - Rml.bestMoveChanges++; - - Rml.sort_multipv(moveCount); - - // Update alpha. In multi-pv we don't use aspiration window, so - // set alpha equal to minimum score among the PV lines. - if (MultiPV > 1) - alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount? - else if (value > alpha) - alpha = value; + if (!pvMove) + BestMoveChanges++; } else - mp.rm->pv_score = -VALUE_INFINITE; - - } // Root - - // Step 18. Check for split - if ( !Root - && !SpNode - && depth >= ThreadsMgr.min_split_depth() - && ThreadsMgr.active_threads() > 1 - && bestValue < beta - && ThreadsMgr.available_thread_exists(threadID) - && !StopRequest - && !ThreadsMgr.cutoff_at_splitpoint(threadID)) - ThreadsMgr.split(pos, ss, &alpha, beta, &bestValue, depth, - threatMove, moveCount, &mp, PvNode); - } + // 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; + } - // 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(ss->ply) : VALUE_DRAW; - - // Step 20. Update tables - // If the search is not aborted, update the transposition table, - // history counters, and killer moves. - if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID)) - { - move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove; - vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER - : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT; + if (value > bestValue) + { + bestValue = SpNode ? splitPoint->bestValue = value : value; - TT.store(posKey, value_to_tt(bestValue, ss->ply), vt, depth, move, ss->eval, ss->evalMargin); + if (value > alpha) + { + bestMove = SpNode ? splitPoint->bestMove = move : move; - // Update killers and history only for non capture moves that fails high - if ( bestValue >= beta - && !pos.move_is_capture_or_promotion(move)) - { - if (move != ss->killers[0]) - { - ss->killers[1] = ss->killers[0]; - ss->killers[0] = move; - } - update_history(pos, move, depth, movesSearched, playedMoveCount); - } - } + if (PvNode && value < beta) // Update alpha! Always alpha < beta + alpha = SpNode ? splitPoint->alpha = value : value; + else + { + assert(value >= beta); // Fail high - if (SpNode) - { - // Here we have the lock still grabbed - sp->slaves[threadID] = 0; - sp->nodes += pos.nodes_searched(); - lock_release(&(sp->lock)); - } + if (SpNode) + splitPoint->cutoff = true; + + break; + } + } + } + + // Step 19. Check for splitting the search + if ( !SpNode + && depth >= Threads.minimumSplitDepth + && Threads.available_slave(thisThread) + && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD) + { + assert(bestValue < beta); + + thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove, + depth, threatMove, moveCount, &mp, NT, cutNode); + if (bestValue >= beta) + break; + } + } + + 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) + bestValue = alpha; + + TT.store(posKey, value_to_tt(bestValue, ss->ply), + bestValue >= beta ? BOUND_LOWER : + PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->staticEval, ss->evalMargin); + + // Quiet best move: update killers, history and countermoves + if ( bestValue >= beta + && !pos.is_capture_or_promotion(bestMove) + && !inCheck) + { + if (ss->killers[0] != bestMove) + { + ss->killers[1] = ss->killers[0]; + ss->killers[0] = bestMove; + } + + // Increase history value of the cut-off move and decrease all the other + // played non-capture moves. + Value bonus = Value(int(depth) * int(depth)); + History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus); + for (int i = 0; i < quietCount - 1; i++) + { + Move m = quietsSearched[i]; + History.update(pos.piece_moved(m), to_sq(m), -bonus); + } + + if (is_ok((ss-1)->currentMove)) + Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove); + } 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) { + template + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { + + const bool PvNode = (NT == PV); - assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); - assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); - assert(PvNode || alpha == beta - 1); - assert(depth <= 0); - assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); + assert(NT == PV || NT == NonPV); + assert(InCheck == !!pos.checkers()); + assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); + assert(PvNode || (alpha == beta - 1)); + assert(depth <= DEPTH_ZERO); 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, oldAlpha; + bool givesCheck, enoughMaterial, evasionPrunable; Depth ttDepth; - Value oldAlpha = alpha; - ss->bestMove = ss->currentMove = MOVE_NONE; + // To flag BOUND_EXACT a node with eval above alpha and no available moves + if (PvNode) + oldAlpha = alpha; + + ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; // Check for an instant draw or maximum ply reached - if (ss->ply > PLY_MAX || pos.is_draw()) - return VALUE_DRAW; + if (pos.is_draw() || ss->ply > MAX_PLY) + return DrawValue[pos.side_to_move()]; // 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); - - // 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); + ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS + : DEPTH_QS_NO_CHECKS; - if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ss->ply)) + // Transposition table lookup + posKey = pos.key(); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; + ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE; + + if ( tte + && tte->depth() >= ttDepth + && ttValue != VALUE_NONE // Only in case of TT access race + && ( PvNode ? tte->bound() == BOUND_EXACT + : ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { - ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ss->ply); + ss->currentMove = ttMove; // Can be MOVE_NONE + return ttValue; } // Evaluate the position statically - if (isCheck) + if (InCheck) { + ss->staticEval = ss->evalMargin = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; - ss->eval = evalMargin = VALUE_NONE; enoughMaterial = false; } else { if (tte) { - assert(tte->static_value() != VALUE_NONE); - - evalMargin = tte->static_value_margin(); - ss->eval = bestValue = tte->static_value(); + // Never assume anything on values stored in TT + if ( (ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE + ||(ss->evalMargin = tte->eval_margin()) == VALUE_NONE) + ss->staticEval = bestValue = evaluate(pos, ss->evalMargin); } else - ss->eval = bestValue = evaluate(pos, evalMargin); - - update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); + ss->staticEval = 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, ss->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->staticEval, ss->evalMargin); return bestValue; } @@ -1429,112 +1205,123 @@ 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->staticEval + 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, History, 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; + bestValue = std::max(bestValue, futilityValue); continue; } - // Prune moves with negative or equal SEE + // Prune moves with negative or equal SEE and also moves with positive + // SEE where capturing piece loses a tempo and SEE < beta - futilityBase. if ( futilityBase < beta - && depth < DEPTH_ZERO - && pos.see(move) <= 0) + && pos.see(move, beta - futilityBase) <= 0) + { + bestValue = std::max(bestValue, futilityBase); 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->staticEval + 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); + pos.do_move(move, st, ci, givesCheck); + value = givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY) + : -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->staticEval, 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(ss->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, ss->ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove, ss->staticEval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1542,1036 +1329,482 @@ split_point_start: // At split points actual search starts from here } - // check_is_dangerous() tests if a checking move can be pruned in qsearch(). - // 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) - { - Bitboard b, occ, oldAtt, newAtt, kingAtt; - Square from, to, ksq, victimSq; - Piece pc; - Color them; - Value futilityValue, bv = *bestValue; - - from = move_from(move); - to = move_to(move); - them = opposite_color(pos.side_to_move()); - ksq = pos.king_square(them); - kingAtt = pos.attacks_from(ksq); - pc = pos.piece_on(from); - - occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << 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); - - if (!(b && (b & (b - 1)))) - return true; - - // Rule 2. Queen contact check is very dangerous - if ( type_of_piece(pc) == QUEEN - && bit_is_set(kingAtt, to)) - return true; - - // Rule 3. Creating new double threats with checks - b = pos.pieces_of_color(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) - 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; - } - - - // connected_moves() tests whether two moves are 'connected' in the sense - // that the first move somehow made the second move possible (for instance - // if the moving piece is the same in both moves). The first move is assumed - // to be the move that was made to reach the current position, while the - // second move is assumed to be a move from the current position. - - bool connected_moves(const Position& pos, Move m1, Move m2) { - - Square f1, t1, f2, t2; - Piece p; - - assert(m1 && move_is_ok(m1)); - assert(m2 && move_is_ok(m2)); - - // Case 1: The moving piece is the same in both moves - f2 = move_from(m2); - t1 = move_to(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); - 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)) - 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)) - 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); - - if (bit_is_set(dcCandidates, f2)) - return true; - } - return false; - } - - // 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; + assert(v != VALUE_NONE); - if (v <= VALUE_MATED_IN_PLY_MAX) - return v - ply; - - 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; + return v == VALUE_NONE ? VALUE_NONE + : v >= VALUE_MATE_IN_MAX_PLY ? v - ply + : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : 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* dangerous) { - - assert(m != MOVE_NONE); - - Depth result = DEPTH_ZERO; - *dangerous = moveIsCheck; + // check_is_dangerous() tests if a checking move can be pruned in qsearch() - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; + bool check_is_dangerous(const Position& pos, Move move, Value futilityBase, Value beta) + { + Piece pc = pos.piece_moved(move); + Square from = from_sq(move); + Square to = to_sq(move); + Color them = ~pos.side_to_move(); + Square ksq = pos.king_square(them); + Bitboard enemies = pos.pieces(them); + Bitboard kingAtt = pos.attacks_from(ksq); + Bitboard occ = pos.pieces() ^ from ^ ksq; + Bitboard oldAtt = pos.attacks_from(pc, from, occ); + Bitboard newAtt = pos.attacks_from(pc, to, occ); + + // Checks which give opponent's king at most one escape square are dangerous + if (!more_than_one(kingAtt & ~(enemies | newAtt | to))) + return true; - 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; - } - } + // Queen contact check is very dangerous + if (type_of(pc) == QUEEN && (kingAtt & to)) + return 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)) + // Creating new double threats with checks is dangerous + Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt; + while (b) { - result += PawnEndgameExtension[PvNode]; - *dangerous = true; + // Note that here we generate illegal "double move"! + if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta) + return true; } - return Min(result, ONE_PLY); + return false; } - // connected_threat() tests whether it is safe to forward prune a move or if - // is somehow connected to the threat move returned by null search. - - bool connected_threat(const Position& pos, Move m, Move threat) { + // allows() tests whether the 'first' move at previous ply somehow makes the + // 'second' move possible, for instance if the moving piece is the same in + // both moves. Normally the second move is the threat (the best move returned + // from a null search that fails low). - 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)); + bool allows(const Position& pos, Move first, Move second) { - Square mfrom, mto, tfrom, tto; + assert(is_ok(first)); + assert(is_ok(second)); + assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move()); + assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move()); - mfrom = move_from(m); - mto = move_to(m); - tfrom = move_from(threat); - tto = move_to(threat); + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); - // Case 1: Don't prune moves which move the threatened piece - if (mfrom == tto) + // The piece is the same or second's destination was vacated by the first move + if (m1to == m2from || m2to == m1from) return true; - // Case 2: If the threatened piece has value less than or equal to the - // value of the threatening piece, don't prune moves 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) - && pos.move_attacks_square(m, tto)) - return true; + // Second one moves through the square vacated by first one + if (between_bb(m2from, m2to) & m1from) + 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) + // Second's destination is defended by the first move's piece + Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from); + if (m1att & m2to) return true; - 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. - - Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) { - - assert(tte); - - Value v = value_from_tt(tte->value(), ply); - - if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval) - || ((tte->type() & VALUE_TYPE_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; - Value bonus = Value(int(depth) * int(depth)); - - H.update(pos.piece_on(move_from(move)), move_to(move), bonus); - - for (int i = 0; i < moveCount - 1; i++) + // Second move gives a discovered check through the first's checking piece + if (m1att & pos.king_square(pos.side_to_move())) { - m = movesSearched[i]; - - assert(m != move); - - H.update(pos.piece_on(move_from(m)), move_to(m), -bonus); + assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from); + return true; } - } - - - // 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.update_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(int set) { - - static int searchStartTime; - - if (set) - searchStartTime = set; - - return get_system_time() - searchStartTime; - } - - - // value_to_uci() converts a value to a string suitable for use with the UCI - // protocol specifications: - // - // cp The score from the engine's point of view in centipawns. - // mate Mate in y moves, not plies. If the engine is getting mated - // use negative values for y. - - 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 centipawns - else - s << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2; - return s.str(); + return false; } - // speed_to_uci() returns a string with time stats of current search suitable - // to be sent to UCI gui. - - std::string speed_to_uci(int64_t nodes) { + // refutes() tests whether a 'first' move is able to defend against a 'second' + // opponent's move. In this case will not be pruned. Normally the second move + // is the threat (the best move returned from a null search that fails low). - std::stringstream s; - int t = current_search_time(); + bool refutes(const Position& pos, Move first, Move second) { - s << " nodes " << nodes - << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0) - << " time " << t; + assert(is_ok(first)); + assert(is_ok(second)); - return s.str(); - } + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); + // Don't prune moves of the threatened piece + if (m1from == m2to) + return true; - // 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 (input_available()) + // If the threatened piece has value less than or equal to the value of the + // threat piece, don't prune moves which defend it. + if ( pos.is_capture(second) + && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)] + || type_of(pos.piece_on(m2from)) == KING)) { - // We are line oriented, don't read single chars - std::string command; - - if (!std::getline(std::cin, command) || command == "quit") - { - // Quit the program as soon as possible - Pondering = false; - QuitRequest = StopRequest = true; - return; - } - else if (command == "stop") - { - // Stop calculating as soon as possible, but still send the "bestmove" - // and possibly the "ponder" token when finishing the search. - Pondering = false; - StopRequest = true; - } - else if (command == "ponderhit") - { - // The opponent has played the expected move. GUI sends "ponderhit" if - // we were told to ponder on the same move the opponent has played. We - // should continue searching but switching from pondering to normal search. - Pondering = false; - - if (StopOnPonderhit) - StopRequest = true; - } - } - - // 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; + // Update occupancy as if the piece and the threat are moving + Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from; + Piece pc = pos.piece_on(m1from); - else if (t - lastInfoTime >= 1000) - { - lastInfoTime = t; + // The moved piece attacks the square 'tto' ? + if (pos.attacks_from(pc, m1to, occ) & m2to) + return true; - dbg_print_mean(); - dbg_print_hit_rate(); + // Scan for possible X-ray attackers behind the moved piece + Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, ROOK)) + | (attacks_bb(m2to, occ) & pos.pieces(color_of(pc), QUEEN, BISHOP)); - // Send info on searched nodes as soon as we return to root - SendSearchedNodes = true; + // Verify attackers are triggered by our move and not already existing + if (xray && (xray ^ (xray & pos.attacks_from(m2to)))) + return true; } - // Should we stop the search? - if (Pondering) - return; - - bool stillAtFirstMove = FirstRootMove - && !AspirationFailLow - && t > TimeMgr.available_time(); - - bool noMoreTime = t > TimeMgr.maximum_time() - || stillAtFirstMove; - - if ( (UseTimeManagement && noMoreTime) - || (ExactMaxTime && t >= ExactMaxTime) - || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME - StopRequest = true; - } - - - // 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. - - void wait_for_stop_or_ponderhit() { - - std::string command; - - // Wait for a command from stdin - while ( std::getline(std::cin, command) - && command != "ponderhit" && command != "stop" && command != "quit") {}; - - if (command != "ponderhit" && command != "stop") - QuitRequest = true; // Must be "quit" or getline() returned false - } - - - // 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) - - void* init_thread(void* threadID) { - - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return NULL; - } - -#else - - DWORD WINAPI init_thread(LPVOID threadID) { + // Don't prune safe moves which block the threat path + if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0) + return true; - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return 0; + return false; } -#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(); - } + // When playing with strength handicap choose best move among the MultiPV set + // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. - // 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. + Move Skill::pick_move() { - void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) { + static RKISS rk; - assert(threadID >= 0 && threadID < MAX_THREADS); + // PRNG sequence should be not deterministic + for (int i = Time::now() % 50; i > 0; i--) + rk.rand(); - int i; - bool allFinished; + // RootMoves are already sorted by score in descending order + int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg); + int weakness = 120 - 2 * level; + int max_s = -VALUE_INFINITE; + 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 < PVSize; 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 Thread::wake_up() - lock_grab(&threads[threadID].sleepLock); - - // 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(&threads[threadID].sleepLock); - break; - } - - // Do sleep here after retesting sleep conditions - if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE) - cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock); - - lock_release(&threads[threadID].sleepLock); - } - - // If this thread has been assigned work, launch a search - if (threads[threadID].state == THREAD_WORKISWAITING) - { - assert(!allThreadsShouldExit); - - threads[threadID].state = THREAD_SEARCHING; - - // Copy split point position and search stack and call search() - // with SplitPoint template parameter set to true. - SearchStack ss[PLY_MAX_PLUS_2]; - SplitPoint* tsp = threads[threadID].splitPoint; - Position pos(*tsp->pos, threadID); - - memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack)); - (ss+1)->sp = tsp; - - if (tsp->pvNode) - search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); - else - search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); + int s = RootMoves[i].score; - 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) - threads[tsp->master].wake_up(); - } + // Don't allow crazy blunders even at very low skills + if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg) + break; - // 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); + // This is our magic formula + s += ( weakness * int(RootMoves[0].score - s) + + variance * (rk.rand() % weakness)) / 128; - if (allFinished) + if (s > max_s) { - // 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; + max_s = s; + best = RootMoves[i].pv[0]; } } + return best; } - // init_threads() is called during startup. Initializes locks and condition - // variables and launches all threads sending them immediately to sleep. - - void ThreadsManager::init_threads() { - - int i, arg[MAX_THREADS]; - bool ok; + // 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. - // This flag is needed to properly end the threads when program exits - allThreadsShouldExit = false; + string uci_pv(const Position& pos, int depth, Value alpha, Value beta) { - // Threads will sent to sleep as soon as created, only main thread is kept alive - activeThreads = 1; - - lock_init(&mpLock); - - for (i = 0; i < MAX_THREADS; i++) - { - // Initialize thread and split point locks - lock_init(&threads[i].sleepLock); - cond_init(&threads[i].sleepCond); - - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_init(&(threads[i].splitPoints[j].lock)); + std::stringstream s; + Time::point elapsed = Time::now() - SearchTime + 1; + size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size()); + int selDepth = 0; - // All threads but first should be set to THREAD_INITIALIZING - threads[i].state = (i == 0 ? THREAD_SEARCHING : THREAD_INITIALIZING); - } + for (size_t i = 0; i < Threads.size(); i++) + if (Threads[i]->maxPly > selDepth) + selDepth = Threads[i]->maxPly; - // Create and startup the threads - for (i = 1; i < MAX_THREADS; i++) + for (size_t i = 0; i < uciPVSize; 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) {} - } - } + bool updated = (i <= PVIdx); + if (depth == 1 && !updated) + continue; - // exit_threads() is called when the program exits. It makes all the - // helper threads exit cleanly. - - void ThreadsManager::exit_threads() { - - // Force the woken up threads to exit idle_loop() and hence terminate - allThreadsShouldExit = true; + int d = updated ? depth : depth - 1; + Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore; - for (int i = 0; i < MAX_THREADS; i++) - { - // Wake up all the threads and waits for termination - if (i != 0) - { - threads[i].wake_up(); - while (threads[i].state != THREAD_TERMINATED) {} - } + if (s.rdbuf()->in_avail()) // Not at first line + s << "\n"; - // Now we can safely destroy the locks and wait conditions - lock_destroy(&threads[i].sleepLock); - cond_destroy(&threads[i].sleepCond); + s << "info depth " << d + << " seldepth " << selDepth + << " score " << (i == PVIdx ? score_to_uci(v, alpha, beta) : score_to_uci(v)) + << " nodes " << pos.nodes_searched() + << " nps " << pos.nodes_searched() * 1000 / elapsed + << " time " << elapsed + << " multipv " << i + 1 + << " pv"; - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_destroy(&(threads[i].splitPoints[j].lock)); + for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++) + s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960()); } - lock_destroy(&mpLock); + return s.str(); } +} // namespace - // 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. - - 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; - } +/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table. +/// We consider also failing high nodes and not only BOUND_EXACT nodes so to +/// allow to always have a ponder move even when we fail high at root, and a +/// long PV to print that is important for position analysis. +void RootMove::extract_pv_from_tt(Position& pos) { - // 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). + StateInfo state[MAX_PLY_PLUS_2], *st = state; + const TTEntry* tte; + int ply = 0; + Move m = pv[0]; - bool ThreadsManager::thread_is_available(int slave, int master) const { + pv.clear(); - assert(slave >= 0 && slave < activeThreads); - assert(master >= 0 && master < activeThreads); - assert(activeThreads > 1); + do { + pv.push_back(m); - if (threads[slave].state != THREAD_AVAILABLE || slave == master) - return false; + assert(MoveList(pos).contains(pv[ply])); - // Make a local copy to be sure doesn't change under our feet - int localActiveSplitPoints = threads[slave].activeSplitPoints; + pos.do_move(pv[ply++], *st++); + tte = TT.probe(pos.key()); - // No active split points means that the thread is available as - // a slave for any other thread. - if (localActiveSplitPoints == 0 || activeThreads == 2) - return true; + } while ( tte + && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change + && pos.pl_move_is_legal(m, pos.pinned_pieces()) + && ply < MAX_PLY + && (!pos.is_draw() || ply < 2)); - // 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; - - return false; - } + pv.push_back(MOVE_NONE); // Must be zero-terminating + while (ply) pos.undo_move(pv[--ply]); +} - // available_thread_exists() tries to find an idle thread which is available as - // a slave for the thread with threadID "master". - bool ThreadsManager::available_thread_exists(int master) const { +/// 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. - assert(master >= 0 && master < activeThreads); - assert(activeThreads > 1); +void RootMove::insert_pv_in_tt(Position& pos) { - for (int i = 0; i < activeThreads; i++) - if (thread_is_available(i, master)) - return true; + StateInfo state[MAX_PLY_PLUS_2], *st = state; + const TTEntry* tte; + int ply = 0; - return false; - } + do { + tte = TT.probe(pos.key()); + if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries + TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], VALUE_NONE, VALUE_NONE); - // 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, Value* alpha, const Value beta, - Value* bestValue, Depth depth, Move threatMove, - int moveCount, MovePicker* mp, bool pvNode) { - assert(pos.is_ok()); - 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); + assert(MoveList(pos).contains(pv[ply])); - int i, master = pos.thread(); - Thread& masterThread = threads[master]; + pos.do_move(pv[ply++], *st++); - lock_grab(&mpLock); + } while (pv[ply] != MOVE_NONE); - // 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; - } + while (ply) pos.undo_move(pv[--ply]); +} - // 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.depth = depth; - splitPoint.threatMove = threatMove; - 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.ss = 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++; - } - assert(Fake || workersCnt > 1); +/// Thread::idle_loop() is where the thread is parked when it has no work to do - // We can release the lock because slave threads are already booked and master is not available - lock_release(&mpLock); +void Thread::idle_loop() { - // Tell the threads that they have work to do. This will make them leave - // their idle loop. - for (i = 0; i < activeThreads; i++) - if (i == master || splitPoint.slaves[i]) - { - assert(i == master || threads[i].state == THREAD_BOOKED); + // Pointer 'this_sp' is not null only if we are called from split(), and not + // at the thread creation. So it means we are the split point's master. + SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL; - threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop() + assert(!this_sp || (this_sp->masterThread == this && searching)); - if (useSleepingThreads && i != master) - threads[i].wake_up(); - } + while (true) + { + // If we are not searching, wait for a condition to be signaled instead of + // wasting CPU time polling for work. + while ((!searching && Threads.sleepWhileIdle) || exit) + { + if (exit) + { + assert(!this_sp); + return; + } - // 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); + // Grab the lock to avoid races with Thread::notify_one() + 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); + // If we are master and all slaves have finished then exit idle_loop + if (this_sp && !this_sp->slavesMask) + { + mutex.unlock(); + break; + } - *alpha = splitPoint.alpha; - *bestValue = splitPoint.bestValue; - masterThread.activeSplitPoints--; - masterThread.splitPoint = splitPoint.parent; - pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes); + // Do sleep after retesting sleep conditions under lock protection, in + // particular we need to avoid a deadlock in case a master thread has, + // in the meanwhile, allocated us and sent the notify_one() call before + // we had the chance to grab the lock. + if (!searching && !exit) + sleepCondition.wait(mutex); - lock_release(&mpLock); - } + mutex.unlock(); + } + // If this thread has been assigned work, launch a search + if (searching) + { + assert(!exit); - /// RootMove and RootMoveList method's definitions + Threads.mutex.lock(); - RootMove::RootMove() { + assert(searching); + SplitPoint* sp = activeSplitPoint; - nodes = 0; - pv_score = non_pv_score = -VALUE_INFINITE; - pv[0] = MOVE_NONE; - } + Threads.mutex.unlock(); - RootMove& RootMove::operator=(const RootMove& rm) { + Stack stack[MAX_PLY_PLUS_2], *ss = stack+1; // To allow referencing (ss-1) + Position pos(*sp->pos, this); - const Move* src = rm.pv; - Move* dst = pv; + memcpy(ss-1, sp->ss-1, 4 * sizeof(Stack)); + ss->splitPoint = sp; - // Avoid a costly full rm.pv[] copy - do *dst++ = *src; while (*src++ != MOVE_NONE); + sp->mutex.lock(); - nodes = rm.nodes; - pv_score = rm.pv_score; - non_pv_score = rm.non_pv_score; - return *this; - } + assert(activePosition == NULL); - // 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. + activePosition = &pos; - void RootMove::extract_pv_from_tt(Position& pos) { + switch (sp->nodeType) { + case Root: + search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); + break; + case PV: + search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); + break; + case NonPV: + search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); + break; + default: + assert(false); + } - StateInfo state[PLY_MAX_PLUS_2], *st = state; - TTEntry* tte; - int ply = 1; + assert(searching); - assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0])); + searching = false; + activePosition = NULL; + sp->slavesMask &= ~(1ULL << idx); + sp->nodes += pos.nodes_searched(); - pos.do_move(pv[0], *st++); + // Wake up master thread so to allow it to return from the idle loop + // in case we are the last slave of the split point. + if ( Threads.sleepWhileIdle + && this != sp->masterThread + && !sp->slavesMask) + { + assert(!sp->masterThread->searching); + sp->masterThread->notify_one(); + } - while ( (tte = TT.retrieve(pos.get_key())) != NULL - && tte->move() != MOVE_NONE - && pos.move_is_legal(tte->move()) - && ply < PLY_MAX - && (!pos.is_draw() || ply < 2)) - { - pv[ply] = tte->move(); - pos.do_move(pv[ply++], *st++); - } - pv[ply] = MOVE_NONE; + // 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(); + } - do pos.undo_move(pv[--ply]); while (ply); + // If this thread is the master of a split point and all slaves have finished + // their work at this split point, return from the idle loop. + if (this_sp && !this_sp->slavesMask) + { + this_sp->mutex.lock(); + bool finished = !this_sp->slavesMask; // Retest under lock protection + this_sp->mutex.unlock(); + if (finished) + return; + } } +} - // insert_pv_in_tt() is called at the end of a search iteration, and inserts - // the PV back into the TT. This makes sure the old PV moves are searched - // first, even if the old TT entries have been overwritten. - - void RootMove::insert_pv_in_tt(Position& pos) { - - StateInfo state[PLY_MAX_PLUS_2], *st = state; - TTEntry* tte; - Key k; - Value v, m = VALUE_NONE; - int ply = 0; - - assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0])); - do { - k = pos.get_key(); - tte = TT.retrieve(k); +/// 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. - // Don't overwrite existing correct entries - if (!tte || tte->move() != pv[ply]) - { - v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m)); - TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m); - } - pos.do_move(pv[ply], *st++); +void check_time() { - } while (pv[++ply] != MOVE_NONE); + static Time::point lastInfoTime = Time::now(); + int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning - do pos.undo_move(pv[--ply]); while (ply); + if (Time::now() - lastInfoTime >= 1000) + { + lastInfoTime = Time::now(); + dbg_print(); } - // pv_info_to_uci() returns a string with information on the current PV line - // formatted according to UCI specification. - - std::string RootMove::pv_info_to_uci(Position& pos, int depth, int selDepth, Value alpha, - Value beta, int pvIdx) { - std::stringstream s; - - s << "info depth " << depth - << " seldepth " << selDepth - << " multipv " << pvIdx + 1 - << " score " << value_to_uci(pv_score) - << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "") - << speed_to_uci(pos.nodes_searched()) - << " pv "; - - for (Move* m = pv; *m != MOVE_NONE; m++) - s << *m << " "; - - return s.str(); - } + if (Limits.ponder) + return; + if (Limits.nodes) + { + Threads.mutex.lock(); - void RootMoveList::init(Position& pos, Move searchMoves[]) { + nodes = RootPos.nodes_searched(); - MoveStack mlist[MOVES_MAX]; - Move* sm; + // Loop across all split points and sum accumulated SplitPoint nodes plus + // all the currently active positions nodes. + for (size_t i = 0; i < Threads.size(); i++) + for (int j = 0; j < Threads[i]->splitPointsSize; j++) + { + SplitPoint& sp = Threads[i]->splitPoints[j]; - clear(); - bestMoveChanges = 0; + sp.mutex.lock(); - // Generate all legal moves and add them to RootMoveList - MoveStack* last = generate(pos, mlist); - for (MoveStack* cur = mlist; cur != last; cur++) - { - // If we have a searchMoves[] list then verify cur->move - // is in the list before to add it. - for (sm = searchMoves; *sm && *sm != cur->move; sm++) {} + nodes += sp.nodes; + Bitboard sm = sp.slavesMask; + while (sm) + { + Position* pos = Threads[pop_lsb(&sm)]->activePosition; + if (pos) + nodes += pos->nodes_searched(); + } - if (searchMoves[0] && *sm != cur->move) - continue; + sp.mutex.unlock(); + } - RootMove rm; - rm.pv[0] = cur->move; - rm.pv[1] = MOVE_NONE; - rm.pv_score = -VALUE_INFINITE; - push_back(rm); - } + Threads.mutex.unlock(); } + Time::point elapsed = Time::now() - SearchTime; + bool stillAtFirstMove = Signals.firstRootMove + && !Signals.failedLowAtRoot + && elapsed > TimeMgr.available_time(); - // When playing with strength handicap choose best move among the MultiPV set - // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen. - void do_skill_level(Move* best, Move* ponder) { - - assert(MultiPV > 1); - - // Rml list is already sorted by pv_score in descending order - int s; - int max_s = -VALUE_INFINITE; - int size = Min(MultiPV, (int)Rml.size()); - int max = Rml[0].pv_score; - int var = Min(max - Rml[size - 1].pv_score, PawnValueMidgame); - int wk = 120 - 2 * SkillLevel; - - // PRNG sequence should be non deterministic - for (int i = abs(get_system_time() % 50); i > 0; i--) - RK.rand(); - - // Choose best move. For each move's score we add two terms both dependent - // on wk, one deterministic and bigger for weaker moves, and one random, - // then we choose the move with the resulting highest score. - for (int i = 0; i < size; i++) - { - s = Rml[i].pv_score; - - // Don't allow crazy blunders even at very low skills - if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin) - break; + bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution + || stillAtFirstMove; - // This is our magical formula - s += ((max - s) * wk + var * (RK.rand() % wk)) / 128; - - if (s > max_s) - { - max_s = s; - *best = Rml[i].pv[0]; - *ponder = Rml[i].pv[1]; - } - } - } - -} // namespace + if ( (Limits.use_time_management() && noMoreTime) + || (Limits.movetime && elapsed >= Limits.movetime) + || (Limits.nodes && nodes >= Limits.nodes)) + Signals.stop = true; +}