X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=b39bd53d8b8e35ce76fae02d53d6a34f158e2e58;hb=4a3b162c8cf16b2dee5f6a0899e94e018b19f483;hp=6ec744c859596415703fa8bef8e520f7eba47879;hpb=00950fec009a4f4046b8fa23eedf1b1a1c4068e6;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index 6ec744c8..851797dd 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -17,26 +17,22 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - #include #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 "san.h" #include "search.h" #include "timeman.h" #include "thread.h" @@ -45,137 +41,51 @@ using std::cout; using std::endl; - -//// -//// Local definitions -//// +using std::string; namespace { - // Types - enum NodeType { NonPV, PV }; - - // Set to true to force running with one thread. - // Used for debugging SMP code. + // Set to true to force running with one thread. Used for debugging const bool FakeSplit = false; - // ThreadsManager class is used to handle all the threads related stuff in search, - // init, starting, parking and, the most important, launching a slave thread at a - // split point are what this class does. All the access to shared thread data is - // done through this class, so that we avoid using global variables instead. - - class ThreadsManager { - /* As long as the single ThreadsManager object is defined as a global we don't - need to explicitly initialize to zero its data members because variables with - static storage duration are automatically set to zero before enter main() - */ - public: - void init_threads(); - void exit_threads(); - - int active_threads() const { return ActiveThreads; } - void set_active_threads(int newActiveThreads) { ActiveThreads = newActiveThreads; } - void incrementNodeCounter(int threadID) { threads[threadID].nodes++; } - - void resetNodeCounters(); - int64_t nodes_searched() const; - bool available_thread_exists(int master) const; - bool thread_is_available(int slave, int master) const; - bool thread_should_stop(int threadID) const; - void wake_sleeping_threads(); - void put_threads_to_sleep(); - void idle_loop(int threadID, SplitPoint* sp); - - template - void split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, Move threatMove, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode); - - private: - friend void poll(); - - int ActiveThreads; - volatile bool AllThreadsShouldExit, AllThreadsShouldSleep; - Thread threads[MAX_THREADS]; - - Lock MPLock, WaitLock; - -#if !defined(_MSC_VER) - pthread_cond_t WaitCond; -#else - HANDLE SitIdleEvent[MAX_THREADS]; -#endif - - }; - - - // RootMove struct is used for moves at the root at the tree. For each - // root move, we store a score, a node count, and a PV (really a refutation - // in the case of moves which fail low). + // Different node types, used as template parameter + enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; + // RootMove struct is used for moves at the root of the tree. For each root + // move, we store a score, a node count, and a PV (really a refutation + // in the case of moves which fail low). Score is normally set at + // -VALUE_INFINITE for all non-pv moves. struct RootMove { - RootMove() : mp_score(0), nodes(0) {} - // 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 a higher score, or if the moves - // have equal score but m1 has the higher beta cut-off count. - bool operator<(const RootMove& m) const { + // than a move m2 if it has an higher score + bool operator<(const RootMove& m) const { return score < m.score; } - return score != m.score ? score < m.score : mp_score <= m.mp_score; - } + void extract_pv_from_tt(Position& pos); + void insert_pv_in_tt(Position& pos); - Move move; - Value score; - int mp_score; int64_t nodes; - Move pv[PLY_MAX_PLUS_2]; + Value score; + Value prevScore; + std::vector pv; }; + // RootMoveList struct is mainly a std::vector of RootMove objects + struct RootMoveList : public std::vector { - // The RootMoveList class is essentially an array of RootMove objects, with - // a handful of methods for accessing the data in the individual moves. - - class RootMoveList { - - public: - RootMoveList(Position& pos, Move searchMoves[]); - - Move move(int moveNum) const { return moves[moveNum].move; } - Move move_pv(int moveNum, int i) const { return moves[moveNum].pv[i]; } - int move_count() const { return count; } - Value move_score(int moveNum) const { return moves[moveNum].score; } - int64_t move_nodes(int moveNum) const { return moves[moveNum].nodes; } - void add_move_nodes(int moveNum, int64_t nodes) { moves[moveNum].nodes += nodes; } - void set_move_score(int moveNum, Value score) { moves[moveNum].score = score; } - - void set_move_pv(int moveNum, const Move pv[]); - void score_moves(const Position& pos); - void sort(); - void sort_multipv(int n); + void init(Position& pos, Move searchMoves[]); + RootMove* find(const Move& m, int startIndex = 0); - private: - RootMove moves[MOVES_MAX]; - int count; + int bestMoveChanges; }; - // When formatting a move for std::cout we must know if we are in Chess960 - // or not. To keep using the handy operator<<() on the move the trick is to - // embed this flag in the stream itself. Function-like named enum set960 is - // used as a custom manipulator and the stream internal general-purpose array, - // accessed through ios_base::iword(), is used to pass the flag to the move's - // operator<<() that will use it to properly format castling moves. - enum set960 {}; - - std::ostream& operator<< (std::ostream& os, const set960& m) { - - os.iword(0) = int(m); - return os; - } + /// Constants - - /// Adjustments + // 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]; } // Step 6. Razoring @@ -191,7 +101,7 @@ namespace { // 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 */}; + const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY }; // At Non-PV nodes we do an internal iterative deepening search // when the static evaluation is bigger then beta - IIDMargin. @@ -199,77 +109,66 @@ namespace { // Step 11. Decide the new search depth - // Extensions. Configurable UCI options - // Array index 0 is used at non-PV nodes, index 1 at PV nodes. - Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2]; - Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2]; + // Extensions. Array index 0 is used for non-PV nodes, index 1 for PV nodes + const Depth CheckExtension[] = { ONE_PLY / 2, ONE_PLY / 1 }; + const Depth PawnEndgameExtension[] = { ONE_PLY / 1, ONE_PLY / 1 }; + const Depth PawnPushTo7thExtension[] = { ONE_PLY / 2, ONE_PLY / 2 }; + const Depth PassedPawnExtension[] = { DEPTH_ZERO, ONE_PLY / 2 }; // Minimum depth for use of singular extension - const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */}; - - // If the TT move is at least SingularExtensionMargin better then the - // remaining ones we will extend it. - const Value SingularExtensionMargin = Value(0x20); + const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY }; // Step 12. Futility pruning // Futility margin for quiescence search const Value FutilityMarginQS = Value(0x80); - // Futility lookup tables (initialized at startup) and their getter functions - Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber] - int FutilityMoveCountArray[32]; // [depth] + // Futility lookup tables (initialized at startup) and their access functions + Value FutilityMargins[16][64]; // [depth][moveNumber] + int FutilityMoveCounts[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; } + inline Value futility_margin(Depth d, int mn) { - // Step 14. Reduced search + return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)] + : 2 * VALUE_INFINITE; + } + + inline int futility_move_count(Depth d) { + + return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES; + } - // Reduction lookup tables (initialized at startup) and their getter functions - int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber] + // Step 14. Reduced search - template - inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; } + // Reduction lookup tables (initialized at startup) and their access function + int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] - // Common adjustments + template inline Depth reduction(Depth d, int mn) { - // Search depth at iteration 1 - const Depth InitialDepth = ONE_PLY; + return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; + } // Easy move margin. An easy move candidate must be at least this much // better than the second best move. const Value EasyMoveMargin = Value(0x200); - /// Global variables - - // Iteration counter - int Iteration; + /// Namespace variables - // Scores and number of times the best move changed for each iteration - Value ValueByIteration[PLY_MAX_PLUS_2]; - int BestMoveChangesByIteration[PLY_MAX_PLUS_2]; - - // Search window management - int AspirationDelta; + // Root move list + RootMoveList Rml; // MultiPV mode - int MultiPV; + int MultiPV, UCIMultiPV, MultiPVIdx; - // Time managment variables - int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime; - bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit; - bool FirstRootMove, AbortSearch, Quit, AspirationFailLow; + // Time management variables + bool StopOnPonderhit, FirstRootMove, StopRequest, QuitRequest, AspirationFailLow; TimeManager TimeMgr; + SearchLimits Limits; - // Log file - bool UseLogFile; - std::ofstream LogFile; - - // Multi-threads related variables - Depth MinimumSplitDepth; - int MaxThreadsPerSplitPoint; - ThreadsManager ThreadsMgr; + // Skill level adjustment + int SkillLevel; + bool SkillLevelEnabled; // 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. @@ -279,68 +178,126 @@ namespace { // History table History H; - /// Local functions - - Value id_loop(const Position& pos, Move searchMoves[]); - Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr); - template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); + /// Local functions - template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); + Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove); - template - void sp_search(SplitPoint* sp, int threadID); + template + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); - template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous); + template + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); + bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue); bool connected_moves(const Position& pos, Move m1, Move m2); - bool value_is_mate(Value value); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool move_is_killer(Move m, SearchStack* ss); - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); + bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply); bool connected_threat(const Position& pos, Move m, Move threat); Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); - void update_killers(Move m, SearchStack* ss); - void update_gains(const Position& pos, Move move, Value before, Value after); - - int current_search_time(); - std::string value_to_uci(Value v); - int nps(); - void poll(); - void ponderhit(); + void do_skill_level(Move* best, Move* ponder); + + int current_search_time(int set = 0); + string score_to_uci(Value v, Value alpha = -VALUE_INFINITE, Value beta = VALUE_INFINITE); + string speed_to_uci(int64_t nodes); + string pv_to_uci(const Move pv[], int pvNum, bool chess960); + string pretty_pv(Position& pos, int depth, Value score, int time, Move pv[]); + string depth_to_uci(Depth depth); + void poll(const Position& pos); void wait_for_stop_or_ponderhit(); - void init_ss_array(SearchStack* ss, int size); - void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value); - void insert_pv_in_tt(const Position& pos, Move pv[]); - void extract_pv_from_tt(const Position& pos, Move bestMove, Move pv[]); -#if !defined(_MSC_VER) - void *init_thread(void *threadID); -#else - DWORD WINAPI init_thread(LPVOID threadID); -#endif + // MovePickerExt template class extends MovePicker and allows to choose at compile + // time the proper moves source according to the type of node. In the default case + // we simply create and use a standard MovePicker object. + 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) {} + }; + + // In case of a SpNode we use split point's shared MovePicker object as moves 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(); } + MovePicker* mp; + }; + + // 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) { + + os.iword(0) = int(f); + return os; + } + + // 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 + FORCE_INLINE Depth extension(const Position& pos, Move m, bool captureOrPromotion, + bool moveIsCheck, bool* dangerous) { + assert(m != MOVE_NONE); + + Depth result = DEPTH_ZERO; + *dangerous = moveIsCheck; + + if (moveIsCheck && pos.see_sign(m) >= 0) + result += CheckExtension[PvNode]; + if (type_of(pos.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; + } + } -//// -//// Functions -//// + if ( captureOrPromotion + && type_of(pos.piece_on(move_to(m))) != PAWN + && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) + - PieceValueMidgame[pos.piece_on(move_to(m))] == VALUE_ZERO) + && !is_special(m)) + { + result += PawnEndgameExtension[PvNode]; + *dangerous = true; + } -/// init_threads(), exit_threads() and nodes_searched() are helpers to -/// give accessibility to some TM methods from outside of current file. + return std::min(result, ONE_PLY); + } -void init_threads() { ThreadsMgr.init_threads(); } -void exit_threads() { ThreadsMgr.exit_threads(); } -int64_t nodes_searched() { return ThreadsMgr.nodes_searched(); } +} // namespace -/// init_search() is called during startup. It initializes various lookup tables +/// init_search() is called during startup to initialize various lookup tables void init_search() { @@ -351,721 +308,541 @@ void init_search() { // Init reductions array for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++) { - double pvRed = 0.33 + log(double(hd)) * log(double(mc)) / 4.5; + double pvRed = log(double(hd)) * log(double(mc)) / 3.0; double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25; - ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0); - ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0); + Reductions[1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0); + Reductions[0][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0); } // Init futility margins array for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++) - FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45); + FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45); // Init futility move count array for (d = 0; d < 32; d++) - FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0)); + FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(d, 2.0)); } -/// perft() is our utility to verify move generation is bug free. All the legal -/// moves up to given depth are generated and counted and the sum returned. +/// perft() is our utility to verify move generation. All the leaf nodes up to +/// the given depth are generated and counted and the sum returned. -int perft(Position& pos, Depth depth) -{ - MoveStack mlist[MOVES_MAX]; - StateInfo st; - Move m; - int sum = 0; +int64_t perft(Position& pos, Depth depth) { - // Generate all legal moves - MoveStack* last = generate_moves(pos, mlist); + StateInfo st; + int64_t sum = 0; - // 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); + // Generate all legal moves + MoveList ml(pos); - // Loop through all legal moves - CheckInfo ci(pos); - for (MoveStack* cur = mlist; cur != last; cur++) - { - m = cur->move; - pos.do_move(m, st, ci, pos.move_is_check(m, ci)); - sum += perft(pos, depth - ONE_PLY); - pos.undo_move(m); - } - return sum; + // 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 ml.size(); + + // Loop through all legal moves + CheckInfo ci(pos); + for ( ; !ml.end(); ++ml) + { + pos.do_move(ml.move(), st, ci, pos.move_gives_check(ml.move(), ci)); + sum += perft(pos, depth - ONE_PLY); + pos.undo_move(ml.move()); + } + return sum; } /// think() is the external interface to Stockfish's search, and is called when -/// the program receives the UCI 'go' command. It initializes various -/// search-related global variables, and calls root_search(). It returns false -/// when a quit command is received during the search. +/// 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. + +bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { -bool think(const Position& pos, bool infinite, bool ponder, int time[], int increment[], - int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) { + static Book book; // Define static to initialize the PRNG only once - // Initialize global search variables - StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false; + // Initialize global search-related variables + StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = false; NodesSincePoll = 0; - ThreadsMgr.resetNodeCounters(); - SearchStartTime = get_system_time(); - ExactMaxTime = maxTime; - MaxDepth = maxDepth; - MaxNodes = maxNodes; - InfiniteSearch = infinite; - PonderSearch = ponder; - UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch; - - // Look for a book move, only during games, not tests - if (UseTimeManagement && get_option_value_bool("OwnBook")) + current_search_time(get_system_time()); + Limits = limits; + TimeMgr.init(Limits, pos.startpos_ply_counter()); + + // Set output steram in normal or chess960 mode + cout << set960(pos.is_chess960()); + + // Set best NodesBetweenPolls interval to avoid lagging under time pressure + if (Limits.maxNodes) + NodesBetweenPolls = std::min(Limits.maxNodes, 30000); + else if (Limits.time && Limits.time < 1000) + NodesBetweenPolls = 1000; + else if (Limits.time && Limits.time < 5000) + NodesBetweenPolls = 5000; + else + NodesBetweenPolls = 30000; + + // Look for a book move + if (Options["OwnBook"].value()) { - if (get_option_value_string("Book File") != OpeningBook.file_name()) - OpeningBook.open(get_option_value_string("Book File")); + if (Options["Book File"].value() != book.name()) + book.open(Options["Book File"].value()); - Move bookMove = OpeningBook.get_move(pos, get_option_value_bool("Best Book Move")); + Move bookMove = book.probe(pos, Options["Best Book Move"].value()); if (bookMove != MOVE_NONE) { - if (PonderSearch) + if (Limits.ponder) wait_for_stop_or_ponderhit(); cout << "bestmove " << bookMove << endl; - return true; + return !QuitRequest; } } - // Read UCI option values - TT.set_size(get_option_value_int("Hash")); - if (button_was_pressed("Clear Hash")) + // Read UCI options + UCIMultiPV = Options["MultiPV"].value(); + SkillLevel = Options["Skill Level"].value(); + + read_evaluation_uci_options(pos.side_to_move()); + Threads.read_uci_options(); + + // Set a new TT size if changed + TT.set_size(Options["Hash"].value()); + + if (Options["Clear Hash"].value()) + { + Options["Clear Hash"].set_value("false"); TT.clear(); + } - CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)")); - CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)")); - SingleEvasionExtension[1] = Depth(get_option_value_int("Single Evasion Extension (PV nodes)")); - SingleEvasionExtension[0] = Depth(get_option_value_int("Single Evasion Extension (non-PV nodes)")); - PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)")); - PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)")); - PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)")); - PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)")); - PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)")); - PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)")); - MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)")); - MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)")); - - MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * ONE_PLY; - MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point"); - MultiPV = get_option_value_int("MultiPV"); - UseLogFile = get_option_value_bool("Use Search Log"); - - if (UseLogFile) - LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app); - - read_weights(pos.side_to_move()); - - // Set the number of active threads - int newActiveThreads = get_option_value_int("Threads"); - if (newActiveThreads != ThreadsMgr.active_threads()) + // Do we have to play with skill handicap? In this case enable MultiPV that + // we will use behind the scenes to retrieve a set of possible moves. + SkillLevelEnabled = (SkillLevel < 20); + MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, 4) : UCIMultiPV); + + // Wake up needed threads and reset maxPly counter + for (int i = 0; i < Threads.size(); i++) { - ThreadsMgr.set_active_threads(newActiveThreads); - init_eval(ThreadsMgr.active_threads()); + Threads[i].wake_up(); + Threads[i].maxPly = 0; } - // Wake up sleeping threads - ThreadsMgr.wake_sleeping_threads(); + // Write to log file and keep it open to be accessed during the search + if (Options["Use Search Log"].value()) + { + Log log(Options["Search Log Filename"].value()); + log << "\nSearching: " << pos.to_fen() + << "\ninfinite: " << Limits.infinite + << " ponder: " << Limits.ponder + << " time: " << Limits.time + << " increment: " << Limits.increment + << " moves to go: " << Limits.movesToGo + << endl; + } - // 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()); + // We're ready to start thinking. Call the iterative deepening loop function + Move ponderMove = MOVE_NONE; + Move bestMove = id_loop(pos, searchMoves, &ponderMove); - // Set best NodesBetweenPolls interval to avoid lagging under - // heavy time pressure. - if (MaxNodes) - NodesBetweenPolls = Min(MaxNodes, 30000); - else if (myTime && myTime < 1000) - NodesBetweenPolls = 1000; - else if (myTime && myTime < 5000) - NodesBetweenPolls = 5000; - else - NodesBetweenPolls = 30000; + // Write final search statistics and close log file + if (Options["Use Search Log"].value()) + { + int t = current_search_time(); - // Write search information to log file - if (UseLogFile) - LogFile << "Searching: " << pos.to_fen() << endl - << "infinite: " << infinite - << " ponder: " << ponder - << " time: " << myTime - << " increment: " << myIncrement - << " moves to go: " << movesToGo << endl; + Log log(Options["Search Log Filename"].value()); + log << "Nodes: " << pos.nodes_searched() + << "\nNodes/second: " << (t > 0 ? pos.nodes_searched() * 1000 / t : 0) + << "\nBest move: " << move_to_san(pos, bestMove); - // We're ready to start thinking. Call the iterative deepening loop function - id_loop(pos, searchMoves); + StateInfo st; + pos.do_move(bestMove, st); + log << "\nPonder move: " << move_to_san(pos, ponderMove) << endl; + pos.undo_move(bestMove); // Return from think() with unchanged position + } + + // This makes all the threads to go to sleep + Threads.set_size(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 && (Limits.ponder || Limits.infinite)) + wait_for_stop_or_ponderhit(); + + // Could be MOVE_NONE when searching on a stalemate position + cout << "bestmove " << bestMove; - if (UseLogFile) - LogFile.close(); + // 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; - ThreadsMgr.put_threads_to_sleep(); + cout << endl; - return !Quit; + return !QuitRequest; } namespace { - // id_loop() is the main iterative deepening loop. It calls root_search - // repeatedly with increasing depth until the allocated thinking time has - // been consumed, the user stops the search, or the maximum search depth is - // reached. + // id_loop() is the main iterative deepening loop. It calls search() repeatedly + // with increasing depth until the allocated thinking time has been consumed, + // user stops the search, or the maximum search depth is reached. - Value id_loop(const Position& pos, Move searchMoves[]) { + Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) { - Position p(pos, pos.thread()); SearchStack ss[PLY_MAX_PLUS_2]; - Move pv[PLY_MAX_PLUS_2]; - Move EasyMove = MOVE_NONE; - Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; + Value bestValues[PLY_MAX_PLUS_2]; + int bestMoveChanges[PLY_MAX_PLUS_2]; + int depth, aspirationDelta; + Value value, alpha, beta; + Move bestMove, easyMove, skillBest, skillPonder; + + // Initialize stuff before a new search + memset(ss, 0, 4 * sizeof(SearchStack)); + TT.new_search(); + H.clear(); + *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE; + depth = aspirationDelta = 0; + value = alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; + ss->currentMove = MOVE_NULL; // Hack to skip update gains - // Moves to search are verified, copied, scored and sorted - RootMoveList rml(p, searchMoves); + // Moves to search are verified and copied + Rml.init(pos, searchMoves); - // Handle special case of searching on a mate/stale position - if (rml.move_count() == 0) + // Handle special case of searching on a mate/stalemate position + if (!Rml.size()) { - if (PonderSearch) - wait_for_stop_or_ponderhit(); + cout << "info" << depth_to_uci(DEPTH_ZERO) + << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW, alpha, beta) << endl; - return pos.is_check() ? -VALUE_MATE : VALUE_DRAW; + return MOVE_NONE; } - // Print RootMoveList startup scoring to the standard output, - // so to output information also for iteration 1. - cout << set960(p.is_chess960()) // Is enough to set once at the beginning - << "info depth " << 1 - << "\ninfo depth " << 1 - << " score " << value_to_uci(rml.move_score(0)) - << " time " << current_search_time() - << " nodes " << ThreadsMgr.nodes_searched() - << " nps " << nps() - << " pv " << rml.move(0) << "\n"; - - // Initialize - TT.new_search(); - H.clear(); - init_ss_array(ss, PLY_MAX_PLUS_2); - pv[0] = pv[1] = MOVE_NONE; - ValueByIteration[1] = rml.move_score(0); - Iteration = 1; - - // Is one move significantly better than others after initial scoring ? - if ( rml.move_count() == 1 - || rml.move_score(0) > rml.move_score(1) + EasyMoveMargin) - EasyMove = rml.move(0); - - // Iterative deepening loop - while (Iteration < PLY_MAX) + // Iterative deepening loop until requested to stop or target depth reached + while (!StopRequest && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth)) { - // Initialize iteration - Iteration++; - BestMoveChangesByIteration[Iteration] = 0; - - cout << "info depth " << Iteration << endl; - - // Calculate dynamic aspiration window based on previous iterations - if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN) - { - int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2]; - int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3]; - - AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16); - AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize + // Save now last iteration's scores, before Rml moves are reordered + for (size_t i = 0; i < Rml.size(); i++) + Rml[i].prevScore = Rml[i].score; - alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE); - beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE); - } - - // Search to the current depth, rml is updated and sorted, alpha and beta could change - value = root_search(p, ss, pv, rml, &alpha, &beta); - - // Write PV to transposition table, in case the relevant entries have - // been overwritten during the search. - insert_pv_in_tt(p, pv); - - if (AbortSearch) - break; // Value cannot be trusted. Break out immediately! + Rml.bestMoveChanges = 0; - //Save info about search result - ValueByIteration[Iteration] = value; - - // Drop the easy move if differs from the new best move - if (pv[0] != EasyMove) - EasyMove = MOVE_NONE; - - if (UseTimeManagement) + // MultiPV loop. We perform a full root search for each PV line + for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, (int)Rml.size()); MultiPVIdx++) { - // Time to stop? - bool stopSearch = false; - - // Stop search early if there is only a single legal move, - // we search up to Iteration 6 anyway to get a proper score. - if (Iteration >= 6 && rml.move_count() == 1) - stopSearch = true; - - // Stop search early when the last two iterations returned a mate score - if ( Iteration >= 6 - && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100 - && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) - stopSearch = true; - - // Stop search early if one move seems to be much better than the others - int64_t nodes = ThreadsMgr.nodes_searched(); - if ( Iteration >= 8 - && EasyMove == pv[0] - && ( ( rml.move_nodes(0) > (nodes * 85) / 100 - && current_search_time() > TimeMgr.available_time() / 16) - ||( rml.move_nodes(0) > (nodes * 98) / 100 - && current_search_time() > TimeMgr.available_time() / 32))) - stopSearch = true; - - // Add some extra time if the best move has changed during the last two iterations - if (Iteration > 5 && Iteration <= 50) - TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration], - BestMoveChangesByIteration[Iteration-1]); + // Calculate dynamic aspiration window based on previous iterations + if (depth >= 5 && abs(Rml[MultiPVIdx].prevScore) < VALUE_KNOWN_WIN) + { + int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2]; + int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3]; - // Stop search if most of MaxSearchTime is consumed at the end of the - // iteration. We probably don't have enough time to search the first - // move at the next iteration anyway. - if (current_search_time() > (TimeMgr.available_time() * 80) / 128) - stopSearch = true; + aspirationDelta = std::min(std::max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24); + aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize - if (stopSearch) + alpha = std::max(Rml[MultiPVIdx].prevScore - aspirationDelta, -VALUE_INFINITE); + beta = std::min(Rml[MultiPVIdx].prevScore + aspirationDelta, VALUE_INFINITE); + } + else { - if (PonderSearch) - StopOnPonderhit = true; - else - break; + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; } - } - - if (MaxDepth && Iteration >= MaxDepth) - break; - } - - // If we are pondering or in infinite search, we shouldn't print the - // best move before we are told to do so. - if (!AbortSearch && (PonderSearch || InfiniteSearch)) - wait_for_stop_or_ponderhit(); - else - // Print final search statistics - cout << "info nodes " << ThreadsMgr.nodes_searched() - << " nps " << nps() - << " time " << current_search_time() << endl; - - // Print the best move and the ponder move to the standard output - if (pv[0] == MOVE_NONE) - { - pv[0] = rml.move(0); - pv[1] = MOVE_NONE; - } - - assert(pv[0] != MOVE_NONE); - cout << "bestmove " << pv[0]; - - if (pv[1] != MOVE_NONE) - cout << " ponder " << pv[1]; - - cout << endl; - - if (UseLogFile) - { - if (dbg_show_mean) - dbg_print_mean(LogFile); - - if (dbg_show_hit_rate) - dbg_print_hit_rate(LogFile); - - LogFile << "\nNodes: " << ThreadsMgr.nodes_searched() - << "\nNodes/second: " << nps() - << "\nBest move: " << move_to_san(p, pv[0]); - - StateInfo st; - p.do_move(pv[0], st); - LogFile << "\nPonder move: " - << move_to_san(p, pv[1]) // Works also with MOVE_NONE - << endl; - } - return rml.move_score(0); - } - - - // root_search() is the function which searches the root node. It is - // similar to search_pv except that it uses a different move ordering - // scheme, prints some information to the standard output and handles - // the fail low/high loops. - - Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) { - - StateInfo st; - CheckInfo ci(pos); - int64_t nodes; - Move move; - Depth depth, ext, newDepth; - Value value, evalMargin, alpha, beta; - bool isCheck, moveIsCheck, captureOrPromotion, dangerous; - int researchCountFH, researchCountFL; - - researchCountFH = researchCountFL = 0; - alpha = *alphaPtr; - beta = *betaPtr; - isCheck = pos.is_check(); - depth = (Iteration - 2) * ONE_PLY + InitialDepth; - - // Step 1. Initialize node (polling is omitted at root) - ss->currentMove = ss->bestMove = MOVE_NONE; - - // Step 2. Check for aborted search (omitted at root) - // Step 3. Mate distance pruning (omitted at root) - // Step 4. Transposition table lookup (omitted at root) - - // Step 5. Evaluate the position statically - // At root we do this only to get reference value for child nodes - ss->eval = isCheck ? VALUE_NONE : evaluate(pos, evalMargin); - - // Step 6. Razoring (omitted at root) - // Step 7. Static null move pruning (omitted at root) - // Step 8. Null move search with verification search (omitted at root) - // Step 9. Internal iterative deepening (omitted at root) - - // Step extra. Fail low loop - // We start with small aspiration window and in case of fail low, we research - // with bigger window until we are not failing low anymore. - while (1) - { - // Sort the moves before to (re)search - rml.score_moves(pos); - rml.sort(); - - // Step 10. Loop through all moves in the root move list - for (int i = 0; i < rml.move_count() && !AbortSearch; i++) - { - // This is used by time management - FirstRootMove = (i == 0); - - // Save the current node count before the move is searched - nodes = ThreadsMgr.nodes_searched(); - - // Pick the next root move, and print the move and the move number to - // the standard output. - move = ss->currentMove = rml.move(i); - - if (current_search_time() >= 1000) - cout << "info currmove " << move - << " currmovenumber " << i + 1 << endl; - - moveIsCheck = pos.move_is_check(move); - captureOrPromotion = pos.move_is_capture_or_promotion(move); + // 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 starts from ss+1 to allow referencing (ss-1). This is + // needed by update gains and ss copy when splitting at Root. + value = search(pos, ss+1, alpha, beta, depth * ONE_PLY); + + // Bring to front the best move. It is critical that sorting is + // done with a stable algorithm because all the values but the first + // and eventually the new best one are set to -VALUE_INFINITE and + // we want to keep the same order for all the moves but the new + // PV that goes to the front. Note that in case of MultiPV search + // the already searched PV lines are preserved. + sort(Rml.begin() + MultiPVIdx, Rml.end()); + + // In case we have found an exact score and we are going to leave + // the fail high/low loop then reorder the PV moves, otherwise + // leave the last PV move in its position so to be searched again. + // Of course this is needed only in MultiPV search. + if (MultiPVIdx && value > alpha && value < beta) + sort(Rml.begin(), Rml.begin() + MultiPVIdx); + + // Write PV back to transposition table in case the relevant entries + // have been overwritten during the search. + for (int i = 0; i <= MultiPVIdx; i++) + Rml[i].insert_pv_in_tt(pos); + + // If search has been stopped exit the aspiration window loop, + // note that sorting and writing PV back to TT is safe becuase + // Rml is still valid, although refers to the previous iteration. + if (StopRequest) + break; - // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous); - newDepth = depth + ext; + // Send full PV info to GUI if we are going to leave the loop or + // if we have a fail high/low and we are deep in the search. UCI + // protocol requires to send all the PV lines also if are still + // to be searched and so refer to the previous search's score. + if ((value > alpha && value < beta) || current_search_time() > 2000) + for (int i = 0; i < std::min(UCIMultiPV, (int)Rml.size()); i++) + { + bool updated = (i <= MultiPVIdx); - // Step 12. Futility pruning (omitted at root) + if (depth == 1 && !updated) + continue; - // Step extra. Fail high loop - // If move fails high, we research with bigger window until we are not failing - // high anymore. - value = - VALUE_INFINITE; + Depth d = (updated ? depth : depth - 1) * ONE_PLY; + Value s = (updated ? Rml[i].score : Rml[i].prevScore); - while (1) - { - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); + cout << "info" + << depth_to_uci(d) + << (i == MultiPVIdx ? score_to_uci(s, alpha, beta) : score_to_uci(s)) + << speed_to_uci(pos.nodes_searched()) + << pv_to_uci(&Rml[i].pv[0], i + 1, pos.is_chess960()) + << endl; + } - // Step extra. pv search - // We do pv search for first moves (i < MultiPV) - // and for fail high research (value > alpha) - if (i < MultiPV || value > alpha) + // In case of failing high/low increase aspiration window and + // research, otherwise exit the fail high/low loop. + if (value >= beta) { - // Aspiration window is disabled in multi-pv case - if (MultiPV > 1) - alpha = -VALUE_INFINITE; - - // Full depth PV search, done on first move or after a fail high - value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); + beta = std::min(beta + aspirationDelta, VALUE_INFINITE); + aspirationDelta += aspirationDelta / 2; } - else + else if (value <= alpha) { - // Step 14. Reduced search - // if the move fails high will be re-searched at full depth - bool doFullDepthSearch = true; - - if ( depth >= 3 * ONE_PLY - && !dangerous - && !captureOrPromotion - && !move_is_castle(move)) - { - ss->reduction = reduction(depth, i - MultiPV + 2); - if (ss->reduction) - { - assert(newDepth-ss->reduction >= ONE_PLY); - - // Reduced depth non-pv search using alpha as upperbound - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); - doFullDepthSearch = (value > alpha); - } - - // The move failed high, but if reduction is very big we could - // face a false positive, retry with a less aggressive reduction, - // if the move fails high again then go with full depth search. - if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY) - { - assert(newDepth - ONE_PLY >= ONE_PLY); - - ss->reduction = ONE_PLY; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); - doFullDepthSearch = (value > alpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction - } - - // Step 15. Full depth search - if (doFullDepthSearch) - { - // Full depth non-pv search using alpha as upperbound - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, 1); + AspirationFailLow = true; + StopOnPonderhit = false; - // If we are above alpha then research at same depth but as PV - // to get a correct score or eventually a fail high above beta. - if (value > alpha) - value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); - } + alpha = std::max(alpha - aspirationDelta, -VALUE_INFINITE); + aspirationDelta += aspirationDelta / 2; } - - // Step 16. Undo move - pos.undo_move(move); - - // Can we exit fail high loop ? - if (AbortSearch || value < beta) + else break; - // We are failing high and going to do a research. It's important to update - // the score before research in case we run out of time while researching. - rml.set_move_score(i, value); - ss->bestMove = move; - extract_pv_from_tt(pos, move, pv); - rml.set_move_pv(i, pv); - - // Print information to the standard output - print_pv_info(pos, pv, alpha, beta, value); - - // Prepare for a research after a fail high, each time with a wider window - *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE); - researchCountFH++; - - } // End of fail high loop - - // Finished searching the move. If AbortSearch is true, the search - // was aborted because the user interrupted the search or because we - // ran out of time. In this case, the return value of the search cannot - // be trusted, and we break out of the loop without updating the best - // move and/or PV. - if (AbortSearch) - break; + } while (abs(value) < VALUE_KNOWN_WIN); + } - // Remember searched nodes counts for this move - rml.add_move_nodes(i, ThreadsMgr.nodes_searched() - nodes); + // Collect info about search result + bestMove = Rml[0].pv[0]; + *ponderMove = Rml[0].pv[1]; + bestValues[depth] = value; + bestMoveChanges[depth] = Rml.bestMoveChanges; - assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE); - assert(value < beta); + // Skills: Do we need to pick now the best and the ponder moves ? + if (SkillLevelEnabled && depth == 1 + SkillLevel) + do_skill_level(&skillBest, &skillPonder); - // Step 17. Check for new best move - if (value <= alpha && i >= MultiPV) - rml.set_move_score(i, -VALUE_INFINITE); - else - { - // PV move or new best move! + if (Options["Use Search Log"].value()) + { + Log log(Options["Search Log Filename"].value()); + log << pretty_pv(pos, depth, value, current_search_time(), &Rml[0].pv[0]) << endl; + } - // Update PV - rml.set_move_score(i, value); - ss->bestMove = move; - extract_pv_from_tt(pos, move, pv); - rml.set_move_pv(i, pv); + // Init easyMove at first iteration or drop it if differs from the best move + if (depth == 1 && (Rml.size() == 1 || Rml[0].score > Rml[1].score + EasyMoveMargin)) + easyMove = bestMove; + else if (bestMove != easyMove) + easyMove = MOVE_NONE; - if (MultiPV == 1) - { - // We record how often the best move has been changed in each - // iteration. This information is used for time managment: When - // the best move changes frequently, we allocate some more time. - if (i > 0) - BestMoveChangesByIteration[Iteration]++; - - // Print information to the standard output - print_pv_info(pos, pv, alpha, beta, value); - - // Raise alpha to setup proper non-pv search upper bound - if (value > alpha) - alpha = value; - } - else // MultiPV > 1 - { - rml.sort_multipv(i); - for (int j = 0; j < Min(MultiPV, rml.move_count()); j++) - { - cout << "info multipv " << j + 1 - << " score " << value_to_uci(rml.move_score(j)) - << " depth " << (j <= i ? Iteration : Iteration - 1) - << " time " << current_search_time() - << " nodes " << ThreadsMgr.nodes_searched() - << " nps " << nps() - << " pv "; - - for (int k = 0; rml.move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++) - cout << rml.move_pv(j, k) << " "; - - cout << endl; - } - alpha = rml.move_score(Min(i, MultiPV - 1)); - } - } // PV move or new best move + // Check for some early stop condition + if (!StopRequest && Limits.useTimeManagement()) + { + // Easy move: Stop search early if one move seems to be much better + // than the others or if there is only a single legal move. Also in + // the latter case search to some depth 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))) + StopRequest = true; - assert(alpha >= *alphaPtr); + // Take in account some extra time if the best move has changed + if (depth > 4 && depth < 50) + TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth - 1]); - AspirationFailLow = (alpha == *alphaPtr); + // 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 (current_search_time() > (TimeMgr.available_time() * 62) / 100) + StopRequest = true; - if (AspirationFailLow && StopOnPonderhit) - StopOnPonderhit = false; + // If we are allowed to ponder do not stop the search now but keep pondering + if (StopRequest && Limits.ponder) + { + StopRequest = false; + StopOnPonderhit = true; + } } + } - // Can we exit fail low loop ? - if (AbortSearch || !AspirationFailLow) - break; - - // Prepare for a research after a fail low, each time with a wider window - *alphaPtr = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE); - researchCountFL++; - - } // Fail low loop + // When using skills overwrite best and ponder moves with the sub-optimal ones + if (SkillLevelEnabled) + { + if (skillBest == MOVE_NONE) // Still unassigned ? + do_skill_level(&skillBest, &skillPonder); - // Sort the moves before to return - rml.sort(); + bestMove = skillBest; + *ponderMove = skillPonder; + } - return alpha; + return bestMove; } - // search<>() is the main search function for both PV and non-PV nodes + // search<>() is the main search function for both PV and non-PV nodes and for + // normal and SplitPoint nodes. When called just after a split point the search + // is simpler because we have already probed the hash table, done a null move + // search, and searched the first move before splitting, we don't have to repeat + // all this work again. We also don't need to store anything to the hash table + // here: This is taken care of after we return from the split point. - template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + template + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { + + 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 <= VALUE_INFINITE); assert(beta > alpha && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); - assert(ply > 0 && ply < PLY_MAX); - assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); + assert(pos.thread() >= 0 && pos.thread() < Threads.size()); - Move movesSearched[MOVES_MAX]; + Move movesSearched[MAX_MOVES]; + int64_t nodes; StateInfo st; const TTEntry *tte; Key posKey; Move ttMove, move, excludedMove, threatMove; Depth ext, newDepth; - Value bestValue, value, evalMargin, oldAlpha; - Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific - bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous; - bool mateThreat = false; - int moveCount = 0; - int threadID = pos.thread(); + ValueType vt; + Value bestValue, value, oldAlpha; + Value refinedValue, nullValue, futilityBase, futilityValue; + bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous; + int moveCount = 0, playedMoveCount = 0; + Thread& thread = Threads[pos.thread()]; + SplitPoint* sp = NULL; + refinedValue = bestValue = value = -VALUE_INFINITE; oldAlpha = alpha; + inCheck = pos.in_check(); + ss->ply = (ss-1)->ply + 1; + + // Used to send selDepth info to GUI + if (PvNode && thread.maxPly < ss->ply) + thread.maxPly = ss->ply; // Step 1. Initialize node and poll. Polling can abort search - ThreadsMgr.incrementNodeCounter(threadID); - ss->currentMove = ss->bestMove = threatMove = MOVE_NONE; - (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE; + if (!SpNode) + { + ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE; + (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; + (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + } + else + { + sp = ss->sp; + tte = NULL; + ttMove = excludedMove = MOVE_NONE; + threatMove = sp->threatMove; + goto split_point_start; + } - if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls) + if (pos.thread() == 0 && ++NodesSincePoll > NodesBetweenPolls) { NodesSincePoll = 0; - poll(); + poll(pos); } // Step 2. Check for aborted search and immediate draw - if (AbortSearch || ThreadsMgr.thread_should_stop(threadID)) - return VALUE_DRAW; - - if (pos.is_draw() || ply >= PLY_MAX - 1) + if (( StopRequest + || pos.is_draw() + || ss->ply > PLY_MAX) && !RootNode) return VALUE_DRAW; // Step 3. Mate distance pruning - alpha = Max(value_mated_in(ply), alpha); - beta = Min(value_mate_in(ply+1), beta); - if (alpha >= beta) - return alpha; + if (!RootNode) + { + alpha = std::max(value_mated_in(ss->ply), alpha); + beta = std::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 exists. + // TT value, so we use a different position key in case of an excluded move. excludedMove = ss->excludedMove; posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); - - tte = TT.retrieve(posKey); - ttMove = (tte ? tte->move() : MOVE_NONE); - - // At PV nodes, we don't use the TT for pruning, but only for move ordering. - // This is to avoid problems in the following areas: - // - // * Repetition draw detection - // * Fifty move rule detection - // * Searching for a mate - // * Printing of full PV line - - if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) + tte = TT.probe(posKey); + ttMove = RootNode ? Rml[MultiPVIdx].pv[0] : tte ? tte->move() : MOVE_NONE; + + // At PV nodes we check for exact scores, while at non-PV nodes we check for + // a fail high/low. Biggest advantage at probing at PV nodes is to have a + // smooth experience in analysis mode. We don't probe at Root nodes otherwise + // we should also update RootMoveList to avoid bogus output. + if (!RootNode && tte && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT + : can_return_tt(tte, depth, beta, ss->ply))) { - // Refresh tte entry to avoid aging - TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove, tte->static_value(), tte->static_value_margin()); - - ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ply); + TT.refresh(tte); + ss->bestMove = move = ttMove; // Can be MOVE_NONE + value = value_from_tt(tte->value(), ss->ply); + + if ( value >= beta + && move + && !pos.is_capture_or_promotion(move) + && move != ss->killers[0]) + { + ss->killers[1] = ss->killers[0]; + ss->killers[0] = move; + } + return value; } - // Step 5. Evaluate the position statically and - // update gain statistics of parent move. - isCheck = pos.is_check(); - if (isCheck) - ss->eval = evalMargin = VALUE_NONE; + // Step 5. Evaluate the position statically and update parent's gain statistics + if (inCheck) + ss->eval = ss->evalMargin = VALUE_NONE; else if (tte) { assert(tte->static_value() != VALUE_NONE); ss->eval = tte->static_value(); - evalMargin = tte->static_value_margin(); - refinedValue = refine_eval(tte, ss->eval, ply); + ss->evalMargin = tte->static_value_margin(); + refinedValue = refine_eval(tte, ss->eval, ss->ply); } else { - refinedValue = ss->eval = evaluate(pos, evalMargin); - TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin); + refinedValue = ss->eval = evaluate(pos, ss->evalMargin); + TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin); } - // Save gain for the parent non-capture move - update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); + // Update gain for the parent non-capture move given the static position + // evaluation before and after the move. + if ( (move = (ss-1)->currentMove) != MOVE_NULL + && (ss-1)->eval != VALUE_NONE + && ss->eval != VALUE_NONE + && pos.captured_piece_type() == PIECE_TYPE_NONE + && !is_special(move)) + { + Square to = move_to(move); + H.update_gain(pos.piece_on(to), to, -(ss-1)->eval - ss->eval); + } // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode && depth < RazorDepth - && !isCheck - && refinedValue < beta - razor_margin(depth) + && !inCheck + && refinedValue + razor_margin(depth) < beta && ttMove == MOVE_NONE - && (ss-1)->currentMove != MOVE_NULL - && !value_is_mate(beta) + && abs(beta) < VALUE_MATE_IN_PLY_MAX && !pos.has_pawn_on_7th(pos.side_to_move())) { Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply); + Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -1078,9 +855,9 @@ namespace { if ( !PvNode && !ss->skipNullMove && depth < RazorDepth - && !isCheck - && refinedValue >= beta + futility_margin(depth, 0) - && !value_is_mate(beta) + && !inCheck + && refinedValue - futility_margin(depth, 0) >= beta + && abs(beta) < VALUE_MATE_IN_PLY_MAX && pos.non_pawn_material(pos.side_to_move())) return refinedValue - futility_margin(depth, 0); @@ -1088,9 +865,9 @@ namespace { if ( !PvNode && !ss->skipNullMove && depth > ONE_PLY - && !isCheck + && !inCheck && refinedValue >= beta - && !value_is_mate(beta) + && abs(beta) < VALUE_MATE_IN_PLY_MAX && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; @@ -1099,21 +876,20 @@ namespace { int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0); // Null move dynamic reduction based on value - if (refinedValue - beta > PawnValueMidgame) + if (refinedValue - PawnValueMidgame > beta) R++; - pos.do_null_move(st); + pos.do_null_move(st); (ss+1)->skipNullMove = true; - - nullValue = depth-R*ONE_PLY < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO, ply+1) - : - search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1); + nullValue = depth-R*ONE_PLY < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY); (ss+1)->skipNullMove = false; - pos.undo_null_move(); + pos.do_null_move(st); if (nullValue >= beta) { // Do not return unproven mate scores - if (nullValue >= value_mate_in(PLY_MAX)) + if (nullValue >= VALUE_MATE_IN_PLY_MAX) nullValue = beta; if (depth < 6 * ONE_PLY) @@ -1121,7 +897,7 @@ namespace { // Do verification search at high depths ss->skipNullMove = true; - Value v = search(pos, ss, alpha, beta, depth-R*ONE_PLY, ply); + Value v = search(pos, ss, alpha, beta, depth-R*ONE_PLY); ss->skipNullMove = false; if (v >= beta) @@ -1135,239 +911,386 @@ namespace { // move which was reduced. If a connection is found, return a fail // low score (which will cause the reduced move to fail high in the // parent node, which will trigger a re-search with full depth). - if (nullValue == value_mated_in(ply + 2)) - mateThreat = true; - threatMove = (ss+1)->bestMove; + if ( depth < ThreatDepth && (ss-1)->reduction + && threatMove != MOVE_NONE && connected_moves(pos, (ss-1)->currentMove, threatMove)) return beta - 1; } } - // Step 9. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] - && ttMove == MOVE_NONE - && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) + // Step 9. ProbCut (is omitted in PV nodes) + // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type]) + // and a reduced search returns a value much above beta, we can (almost) safely + // prune the previous move. + if ( !PvNode + && depth >= RazorDepth + ONE_PLY + && !inCheck + && !ss->skipNullMove + && excludedMove == MOVE_NONE + && abs(beta) < VALUE_MATE_IN_PLY_MAX) + { + Value rbeta = beta + 200; + Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY; + + assert(rdepth >= ONE_PLY); + + MovePicker mp(pos, ttMove, H, pos.captured_piece_type()); + CheckInfo ci(pos); + + while ((move = mp.get_next_move()) != MOVE_NONE) + if (pos.pl_move_is_legal(move, ci.pinned)) + { + pos.do_move(move, st, ci, pos.move_gives_check(move, ci)); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth); + pos.undo_move(move); + if (value >= rbeta) + return value; + } + } + + // Step 10. Internal iterative deepening + if ( depth >= IIDDepth[PvNode] + && ttMove == MOVE_NONE + && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta))) { Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2); ss->skipNullMove = true; - search(pos, ss, alpha, beta, d, ply); + search(pos, ss, alpha, beta, d); ss->skipNullMove = false; - ttMove = ss->bestMove; - tte = TT.retrieve(posKey); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; } - // Expensive mate threat detection (only for PV nodes) - if (PvNode) - mateThreat = pos.has_mate_threat(); +split_point_start: // At split points actual search starts from here // Initialize a MovePicker object for the current position - MovePicker mp = MovePicker(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta)); + MovePickerExt mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta); CheckInfo ci(pos); ss->bestMove = MOVE_NONE; - singleEvasion = isCheck && mp.number_of_evasions() == 1; - futilityBase = ss->eval + evalMargin; - singularExtensionNode = depth >= SingularExtensionDepth[PvNode] - && tte - && tte->move() + futilityBase = ss->eval + ss->evalMargin; + singularExtensionNode = !RootNode + && !SpNode + && depth >= SingularExtensionDepth[PvNode] + && ttMove != MOVE_NONE && !excludedMove // Do not allow recursive singular extension search && (tte->type() & VALUE_TYPE_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; + if (SpNode) + { + lock_grab(&(sp->lock)); + bestValue = sp->bestValue; + } - // Step 10. Loop through moves - // Loop through all legal moves until no moves remain or a beta cutoff occurs + // Step 11. Loop through moves + // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs while ( bestValue < beta && (move = mp.get_next_move()) != MOVE_NONE - && !ThreadsMgr.thread_should_stop(threadID)) + && !thread.cutoff_occurred()) { - assert(move_is_ok(move)); + assert(is_ok(move)); if (move == excludedMove) continue; - moveIsCheck = pos.move_is_check(move, ci); - captureOrPromotion = pos.move_is_capture_or_promotion(move); + // 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 && !Rml.find(move, MultiPVIdx)) + continue; + + // At PV and SpNode nodes we want all moves to be legal since the beginning + if ((PvNode || SpNode) && !pos.pl_move_is_legal(move, ci.pinned)) + continue; + + if (SpNode) + { + moveCount = ++sp->moveCount; + lock_release(&(sp->lock)); + } + else + moveCount++; + + 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(); + + // For long searches send current move info to GUI + if (pos.thread() == 0 && current_search_time() > 2000) + cout << "info" << depth_to_uci(depth) + << " currmove " << move + << " currmovenumber " << moveCount + MultiPVIdx << endl; + } + + // At Root and at first iteration do a PV search on all the moves to score root moves + isPvMove = (PvNode && moveCount <= (RootNode && depth <= ONE_PLY ? MAX_MOVES : 1)); + givesCheck = pos.move_gives_check(move, ci); + captureOrPromotion = pos.is_capture_or_promotion(move); - // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous); + // Step 12. Decide the new search depth + ext = extension(pos, move, captureOrPromotion, givesCheck, &dangerous); - // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s), - // and just one fails high on (alpha, beta), then that move is singular and should be extended. - // To verify this we do a reduced search on all the other moves but the ttMove, if result is - // lower then ttValue minus a margin then we extend ttMove. + // 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() + && move == ttMove + && pos.pl_move_is_legal(move, ci.pinned) && ext < ONE_PLY) { - Value ttValue = value_from_tt(tte->value(), ply); + Value ttValue = value_from_tt(tte->value(), ss->ply); if (abs(ttValue) < VALUE_KNOWN_WIN) { - Value b = ttValue - SingularExtensionMargin; + Value rBeta = ttValue - int(depth); ss->excludedMove = move; ss->skipNullMove = true; - Value v = search(pos, ss, b - 1, b, depth / 2, ply); + Value v = search(pos, ss, rBeta - 1, rBeta, depth / 2); ss->skipNullMove = false; ss->excludedMove = MOVE_NONE; ss->bestMove = MOVE_NONE; - if (v < b) + if (v < rBeta) ext = ONE_PLY; } } - newDepth = depth - ONE_PLY + ext; - // Update current move (this must be done after singular extension search) - movesSearched[moveCount++] = 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)) + && !is_castle(move)) { // Move count based pruning if ( moveCount >= futility_move_count(depth) - && !(threatMove && connected_threat(pos, move, threatMove)) - && bestValue > value_mated_in(PLY_MAX)) + && (!threatMove || !connected_threat(pos, move, threatMove)) + && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy + { + if (SpNode) + lock_grab(&(sp->lock)); + continue; + } // Value based pruning // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth, // but fixing this made program slightly weaker. - Depth predictedDepth = newDepth - reduction(depth, moveCount); - futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount) - + H.gain(pos.piece_on(move_from(move)), move_to(move)); + Depth predictedDepth = newDepth - reduction(depth, moveCount); + futilityValue = futilityBase + futility_margin(predictedDepth, moveCount) + + H.gain(pos.piece_on(move_from(move)), move_to(move)); + + if (futilityValue < beta) + { + if (SpNode) + { + lock_grab(&(sp->lock)); + if (futilityValue > sp->bestValue) + sp->bestValue = bestValue = futilityValue; + } + else if (futilityValue > bestValue) + bestValue = futilityValue; + + continue; + } - if (futilityValueScaled < beta) + // Prune moves with negative SEE at low depths + if ( predictedDepth < 2 * ONE_PLY + && bestValue > VALUE_MATED_IN_PLY_MAX + && pos.see_sign(move) < 0) { - if (futilityValueScaled > bestValue) - bestValue = futilityValueScaled; + if (SpNode) + lock_grab(&(sp->lock)); + continue; } } - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); + // Check for legality only before to do the move + if (!pos.pl_move_is_legal(move, ci.pinned)) + { + moveCount--; + continue; + } + + ss->currentMove = move; + if (!SpNode && !captureOrPromotion) + movesSearched[playedMoveCount++] = move; + + // Step 14. Make the move + pos.do_move(move, st, ci, givesCheck); // Step extra. pv search (only in PV nodes) // The first move in list is the expected PV - if (PvNode && moveCount == 1) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO, ply+1) - : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); + if (isPvMove) + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, newDepth); else { - // Step 14. Reduced depth search + // Step 15. Reduced depth search // If the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; - if ( depth >= 3 * ONE_PLY + if ( depth > 3 * ONE_PLY && !captureOrPromotion && !dangerous - && !move_is_castle(move) - && !move_is_killer(move, ss)) + && !is_castle(move) + && ss->killers[0] != move + && ss->killers[1] != move + && (ss->reduction = reduction(depth, moveCount)) != DEPTH_ZERO) { - ss->reduction = reduction(depth, moveCount); - if (ss->reduction) - { - Depth d = newDepth - ss->reduction; - value = d < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO, ply+1) - : - search(pos, ss+1, -(alpha+1), -alpha, d, ply+1); - - doFullDepthSearch = (value > alpha); - } + Depth d = newDepth - ss->reduction; + alpha = SpNode ? sp->alpha : alpha; - // The move failed high, but if reduction is very big we could - // face a false positive, retry with a less aggressive reduction, - // if the move fails high again then go with full depth search. - if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY) - { - assert(newDepth - ONE_PLY >= ONE_PLY); + value = d < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, d); - ss->reduction = ONE_PLY; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1); - doFullDepthSearch = (value > alpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction + ss->reduction = DEPTH_ZERO; + doFullDepthSearch = (value > alpha); } - // Step 15. Full depth search + // Step 16. Full depth search if (doFullDepthSearch) { - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO, ply+1) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1); + alpha = SpNode ? sp->alpha : alpha; + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); // Step extra. pv search (only in PV nodes) // Search only for possible new PV nodes, if instead value >= beta then // parent node fails low with value <= alpha and tries another move. - if (PvNode && value > alpha && value < beta) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO, ply+1) - : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); + if (PvNode && value > alpha && (RootNode || value < beta)) + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, newDepth); } } - // Step 16. Undo move + // Step 17. Undo move pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 17. Check for new best move + // Step 18. Check for new best move + if (SpNode) + { + lock_grab(&(sp->lock)); + bestValue = sp->bestValue; + alpha = sp->alpha; + } + + // 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 don't update the best move and/or PV. + if (RootNode && !StopRequest) + { + // Remember searched nodes counts for this move + RootMove* rm = Rml.find(move); + rm->nodes += pos.nodes_searched() - nodes; + + // PV move or new best move ? + if (isPvMove || value > alpha) + { + // Update PV + 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++; + } + else + // All other moves but the PV are set to the lowest value, this + // is not a problem when sorting becuase sort is stable and move + // position in the list is preserved, just the PV is pushed up. + rm->score = -VALUE_INFINITE; + + } // RootNode + if (value > bestValue) { bestValue = value; - if (value > alpha) - { - if (PvNode && value < beta) // We want always alpha < beta - alpha = value; + ss->bestMove = move; - if (value == value_mate_in(ply + 1)) - ss->mateKiller = move; + if ( PvNode + && value > alpha + && value < beta) // We want always alpha < beta + alpha = value; - ss->bestMove = move; + if (SpNode && !thread.cutoff_occurred()) + { + sp->bestValue = value; + sp->ss->bestMove = move; + sp->alpha = alpha; + sp->is_betaCutoff = (value >= beta); } } - // Step 18. Check for split - if ( depth >= MinimumSplitDepth - && ThreadsMgr.active_threads() > 1 + // Step 19. Check for split + if ( !SpNode + && depth >= Threads.min_split_depth() && bestValue < beta - && ThreadsMgr.available_thread_exists(threadID) - && !AbortSearch - && !ThreadsMgr.thread_should_stop(threadID) - && Iteration <= 99) - ThreadsMgr.split(pos, ss, ply, &alpha, beta, &bestValue, depth, - threatMove, mateThreat, &moveCount, &mp, PvNode); + && Threads.available_slave_exists(pos.thread()) + && !StopRequest + && !thread.cutoff_occurred()) + bestValue = Threads.split(pos, ss, alpha, beta, bestValue, depth, + threatMove, moveCount, &mp, NT); } - // 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 (!moveCount) - return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW; + // Step 20. Check for mate and stalemate + // All legal moves have been searched and if there are no legal moves, it + // must be mate or stalemate. Note that we can have a false positive in + // case of StopRequest 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. + if (!SpNode && !moveCount) + return excludedMove ? oldAlpha : inCheck ? value_mated_in(ss->ply) : VALUE_DRAW; - // Step 20. Update tables + // Step 21. Update tables // If the search is not aborted, update the transposition table, // history counters, and killer moves. - if (AbortSearch || ThreadsMgr.thread_should_stop(threadID)) - return bestValue; + if (!SpNode && !StopRequest && !thread.cutoff_occurred()) + { + move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove; + vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER + : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT; - ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); - move = (bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove); - TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), vt, depth, move, ss->eval, ss->evalMargin); - // Update killers and history only for non capture moves that fails high - if ( bestValue >= beta - && !pos.move_is_capture_or_promotion(move)) + // Update killers and history only for non capture moves that fails high + if ( bestValue >= beta + && !pos.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 (SpNode) { - update_history(pos, move, depth, movesSearched, moveCount); - update_killers(move, ss); + // Here we have the lock still grabbed + sp->is_slave[pos.thread()] = false; + sp->nodes += pos.nodes_searched(); + lock_release(&(sp->lock)); } assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1375,54 +1298,61 @@ namespace { return bestValue; } - // qsearch() is the quiescence search function, which is called by the main // search function when the remaining depth is zero (or, to be more precise, // less than ONE_PLY). - template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + template + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { + + const bool PvNode = (NT == PV); + assert(NT == PV || NT == NonPV); assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); assert(depth <= 0); - assert(ply > 0 && ply < PLY_MAX); - assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); + assert(pos.thread() >= 0 && pos.thread() < Threads.size()); StateInfo st; Move ttMove, move; Value bestValue, value, evalMargin, futilityValue, futilityBase; - bool isCheck, deepChecks, enoughMaterial, moveIsCheck, evasionPrunable; + bool inCheck, enoughMaterial, givesCheck, evasionPrunable; const TTEntry* tte; + Depth ttDepth; + ValueType vt; Value oldAlpha = alpha; - ThreadsMgr.incrementNodeCounter(pos.thread()); ss->bestMove = ss->currentMove = MOVE_NONE; + ss->ply = (ss-1)->ply + 1; // Check for an instant draw or maximum ply reached - if (pos.is_draw() || ply >= PLY_MAX - 1) + if (pos.is_draw() || ss->ply > PLY_MAX) return VALUE_DRAW; + // Decide whether or not to include checks, this fixes also the type of + // TT entry depth that we are going to use. Note that in qsearch we use + // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. + inCheck = pos.in_check(); + ttDepth = (inCheck || 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()); + tte = TT.probe(pos.get_key()); ttMove = (tte ? tte->move() : MOVE_NONE); - if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) + if (!PvNode && tte && can_return_tt(tte, ttDepth, beta, ss->ply)) { ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ply); + return value_from_tt(tte->value(), ss->ply); } - isCheck = pos.is_check(); - // Evaluate the position statically - if (isCheck) + if (inCheck) { bestValue = futilityBase = -VALUE_INFINITE; ss->eval = evalMargin = VALUE_NONE; - deepChecks = enoughMaterial = false; + enoughMaterial = false; } else { @@ -1436,13 +1366,11 @@ namespace { else ss->eval = bestValue = evaluate(pos, evalMargin); - update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); - // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { if (!tte) - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin); + TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin); return bestValue; } @@ -1450,9 +1378,6 @@ namespace { if (PvNode && bestValue > alpha) alpha = bestValue; - // If we are near beta then try to get a cutoff pushing checks a bit further - deepChecks = (depth == -ONE_PLY && bestValue >= beta - PawnValueMidgame / 8); - // Futility pruning parameters, not needed when in check futilityBase = ss->eval + evalMargin + FutilityMarginQS; enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; @@ -1460,60 +1385,87 @@ namespace { // 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 == 0 or depth == -ONE_PLY - // and we are near beta) will be generated. - MovePicker mp = MovePicker(pos, ttMove, deepChecks ? DEPTH_ZERO : depth, H); + // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will + // be generated. + MovePicker mp(pos, ttMove, depth, H, move_to((ss-1)->currentMove)); CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs - while ( alpha < beta + while ( bestValue < beta && (move = mp.get_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)) + && !is_promotion(move) + && !pos.is_passed_pawn_push(move)) { futilityValue = futilityBase - + pos.endgame_value_of_piece_on(move_to(move)) - + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO); + + PieceValueEndgame[pos.piece_on(move_to(move))] + + (is_enpassant(move) ? PawnValueEndgame : VALUE_ZERO); - if (futilityValue < alpha) + if (futilityValue < beta) { if (futilityValue > bestValue) bestValue = futilityValue; + continue; } + + // Prune moves with negative or equal SEE + if ( futilityBase < beta + && depth < DEPTH_ZERO + && pos.see(move) <= 0) + continue; } // Detect non-capture evasions that are candidate to be pruned - evasionPrunable = isCheck - && bestValue > value_mated_in(PLY_MAX) - && !pos.move_is_capture(move) + evasionPrunable = !PvNode + && inCheck + && bestValue > VALUE_MATED_IN_PLY_MAX + && !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) + && !is_promotion(move) && pos.see_sign(move) < 0) continue; + // Don't search useless checks + if ( !PvNode + && !inCheck + && givesCheck + && move != ttMove + && !pos.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; + + continue; + } + + // Check for legality only before to do the move + if (!pos.pl_move_is_legal(move, ci.pinned)) + continue; + // Update current move ss->currentMove = move; // Make and search the move - pos.do_move(move, st, ci, moveIsCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1); + pos.do_move(move, st, ci, givesCheck); + value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1522,23 +1474,26 @@ namespace { if (value > bestValue) { bestValue = value; - if (value > alpha) - { + ss->bestMove = move; + + if ( PvNode + && value > alpha + && value < beta) // We want always alpha < beta alpha = value; - ss->bestMove = move; - } } } // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (isCheck && bestValue == -VALUE_INFINITE) - return value_mated_in(ply); + if (inCheck && bestValue == -VALUE_INFINITE) + return value_mated_in(ss->ply); // Update transposition table - Depth d = (depth == DEPTH_ZERO ? DEPTH_ZERO : DEPTH_ZERO - ONE_PLY); - ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); - TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, d, ss->bestMove, ss->eval, evalMargin); + move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove; + 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, move, ss->eval, evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1546,170 +1501,60 @@ namespace { } - // sp_search() is used to search from a split point. This function is called - // by each thread working at the split point. It is similar to the normal - // search() function, but simpler. Because we have already probed the hash - // table, done a null move search, and searched the first move before - // splitting, we don't have to repeat all this work in sp_search(). 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 - void sp_search(SplitPoint* sp, int threadID) { + // 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. - assert(threadID >= 0 && threadID < ThreadsMgr.active_threads()); - assert(ThreadsMgr.active_threads() > 1); - - StateInfo st; - Move move; - Depth ext, newDepth; - Value value; - Value futilityValueScaled; // NonPV specific - bool isCheck, moveIsCheck, captureOrPromotion, dangerous; - int moveCount; - value = -VALUE_INFINITE; + 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 = flip(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(them) & ~newAtt & ~(1ULL << to); + + if (!(b && (b & (b - 1)))) + return true; - Position pos(*sp->pos, threadID); - CheckInfo ci(pos); - SearchStack* ss = sp->sstack[threadID] + 1; - isCheck = pos.is_check(); + // Rule 2. Queen contact check is very dangerous + if ( type_of(pc) == QUEEN + && bit_is_set(kingAtt, to)) + return true; - // Step 10. Loop through moves - // Loop through all legal moves until no moves remain or a beta cutoff occurs - lock_grab(&(sp->lock)); + // Rule 3. Creating new double threats with checks + b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq); - while ( sp->bestValue < sp->beta - && (move = sp->mp->get_next_move()) != MOVE_NONE - && !ThreadsMgr.thread_should_stop(threadID)) + while (b) { - moveCount = ++sp->moveCount; - lock_release(&(sp->lock)); - - assert(move_is_ok(move)); - - 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, false, sp->mateThreat, &dangerous); - newDepth = sp->depth - ONE_PLY + ext; - - // Update current move - ss->currentMove = move; - - // Step 12. Futility pruning (is omitted in PV nodes) - if ( !PvNode - && !captureOrPromotion - && !isCheck - && !dangerous - && !move_is_castle(move)) - { - // Move count based pruning - if ( moveCount >= futility_move_count(sp->depth) - && !(sp->threatMove && connected_threat(pos, move, sp->threatMove)) - && sp->bestValue > value_mated_in(PLY_MAX)) - { - lock_grab(&(sp->lock)); - continue; - } - - // Value based pruning - Depth predictedDepth = newDepth - reduction(sp->depth, moveCount); - futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount) - + H.gain(pos.piece_on(move_from(move)), move_to(move)); - - if (futilityValueScaled < sp->beta) - { - lock_grab(&(sp->lock)); - - if (futilityValueScaled > sp->bestValue) - sp->bestValue = futilityValueScaled; - continue; - } - } - - // Step 13. Make the move - pos.do_move(move, st, ci, moveIsCheck); - - // Step 14. Reduced search - // If the move fails high will be re-searched at full depth. - bool doFullDepthSearch = true; - - if ( !captureOrPromotion - && !dangerous - && !move_is_castle(move) - && !move_is_killer(move, ss)) - { - ss->reduction = reduction(sp->depth, moveCount); - if (ss->reduction) - { - Value localAlpha = sp->alpha; - Depth d = newDepth - ss->reduction; - value = d < ONE_PLY ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, sp->ply+1) - : - search(pos, ss+1, -(localAlpha+1), -localAlpha, d, sp->ply+1); - - doFullDepthSearch = (value > localAlpha); - } - - // The move failed high, but if reduction is very big we could - // face a false positive, retry with a less aggressive reduction, - // if the move fails high again then go with full depth search. - if (doFullDepthSearch && ss->reduction > 2 * ONE_PLY) - { - assert(newDepth - ONE_PLY >= ONE_PLY); - - ss->reduction = ONE_PLY; - Value localAlpha = sp->alpha; - value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, sp->ply+1); - doFullDepthSearch = (value > localAlpha); - } - ss->reduction = DEPTH_ZERO; // Restore original reduction - } - - // Step 15. Full depth search - if (doFullDepthSearch) - { - Value localAlpha = sp->alpha; - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, DEPTH_ZERO, sp->ply+1) - : - search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1); - - // Step extra. pv search (only in PV nodes) - // Search only for possible new PV nodes, if instead value >= beta then - // parent node fails low with value <= alpha and tries another move. - if (PvNode && value > localAlpha && value < sp->beta) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -sp->beta, -sp->alpha, DEPTH_ZERO, sp->ply+1) - : - search(pos, ss+1, -sp->beta, -sp->alpha, newDepth, sp->ply+1); - } - - // Step 16. Undo move - pos.undo_move(move); + victimSq = pop_1st_bit(&b); + futilityValue = futilityBase + PieceValueEndgame[pos.piece_on(victimSq)]; - assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - - // Step 17. Check for new best move - lock_grab(&(sp->lock)); - - if (value > sp->bestValue && !ThreadsMgr.thread_should_stop(threadID)) - { - sp->bestValue = value; - if (value > sp->alpha) - { - if (!PvNode || value >= sp->beta) - sp->stopRequest = true; - - if (PvNode && value < sp->beta) // We want always sp->alpha < sp->beta - sp->alpha = value; + // Note that here we generate illegal "double move"! + if ( futilityValue >= beta + && pos.see_sign(make_move(from, victimSq)) >= 0) + return true; - sp->parentSstack->bestMove = ss->bestMove = move; - } - } + if (futilityValue > bv) + bv = futilityValue; } - /* Here we have the lock still grabbed */ - - sp->slaves[threadID] = 0; - - lock_release(&(sp->lock)); + // Update bestValue only if check is not dangerous (because we will prune the move) + *bestValue = bv; + return false; } @@ -1722,13 +1567,11 @@ namespace { bool connected_moves(const Position& pos, Move m1, Move m2) { Square f1, t1, f2, t2; - Piece p; + Piece p1, p2; + Square ksq; - assert(move_is_ok(m1)); - assert(move_is_ok(m2)); - - if (m2 == MOVE_NONE) - return false; + assert(is_ok(m1)); + assert(is_ok(m2)); // Case 1: The moving piece is the same in both moves f2 = move_from(m2); @@ -1743,54 +1586,40 @@ namespace { return true; // Case 3: Moving through the vacated square - if ( piece_is_slider(pos.piece_on(f2)) + p2 = pos.piece_on(f2); + if ( piece_is_slider(p2) && 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)) + p1 = pos.piece_on(t1); + if (bit_is_set(pos.attacks_from(p1, t1), t2)) return true; // Case 5: Discovered check, checking piece is the piece moved in m1 - if ( piece_is_slider(p) - && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2) - && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2)) + ksq = pos.king_square(pos.side_to_move()); + if ( piece_is_slider(p1) + && bit_is_set(squares_between(t1, ksq), f2)) { - // 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)) + Bitboard occ = pos.occupied_squares(); + clear_bit(&occ, f2); + if (bit_is_set(pos.attacks_from(p1, t1, occ), ksq)) return true; } return false; } - // value_is_mate() checks if the given value is a mate one eventually - // compensated for the ply. - - bool value_is_mate(Value value) { - - assert(abs(value) <= VALUE_INFINITE); - - return value <= value_mated_in(PLY_MAX) - || value >= value_mate_in(PLY_MAX); - } - - // value_to_tt() adjusts a mate score from "plies to mate from the root" to // "plies to mate from the current ply". Non-mate scores are unchanged. // 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)) + if (v >= VALUE_MATE_IN_PLY_MAX) return v + ply; - if (v <= value_mated_in(PLY_MAX)) + if (v <= VALUE_MATED_IN_PLY_MAX) return v - ply; return v; @@ -1802,103 +1631,25 @@ namespace { Value value_from_tt(Value v, int ply) { - if (v >= value_mate_in(PLY_MAX)) + if (v >= VALUE_MATE_IN_PLY_MAX) return v - ply; - if (v <= value_mated_in(PLY_MAX)) + if (v <= VALUE_MATED_IN_PLY_MAX) return v + ply; return v; } - // move_is_killer() checks if the given move is among the killer moves - - bool move_is_killer(Move m, SearchStack* ss) { - - if (ss->killers[0] == m || ss->killers[1] == m) - return true; - - return false; - } - - - // extension() decides whether a move should be searched with normal depth, - // or with extended depth. Certain classes of moves (checking moves, in - // particular) are searched with bigger depth than ordinary moves and in - // any case are marked as 'dangerous'. Note that also if a move is not - // extended, as example because the corresponding UCI option is set to zero, - // the move is marked as 'dangerous' so, at least, we avoid to prune it. - template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, - bool singleEvasion, bool mateThreat, bool* dangerous) { - - assert(m != MOVE_NONE); - - Depth result = DEPTH_ZERO; - *dangerous = moveIsCheck | singleEvasion | mateThreat; - - if (*dangerous) - { - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; - - if (singleEvasion) - result += SingleEvasionExtension[PvNode]; - - if (mateThreat) - result += MateThreatExtension[PvNode]; - } - - if (pos.type_of_piece_on(move_from(m)) == PAWN) - { - Color c = pos.side_to_move(); - if (relative_rank(c, move_to(m)) == RANK_7) - { - result += PawnPushTo7thExtension[PvNode]; - *dangerous = true; - } - if (pos.pawn_is_passed(c, move_to(m))) - { - result += PassedPawnExtension[PvNode]; - *dangerous = true; - } - } - - if ( captureOrPromotion - && pos.type_of_piece_on(move_to(m)) != PAWN - && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) - - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO) - && !move_is_promotion(m) - && !move_is_ep(m)) - { - result += PawnEndgameExtension[PvNode]; - *dangerous = true; - } - - if ( PvNode - && captureOrPromotion - && pos.type_of_piece_on(move_to(m)) != PAWN - && pos.see_sign(m) >= 0) - { - result += ONE_PLY / 2; - *dangerous = true; - } - - return Min(result, ONE_PLY); - } - - // connected_threat() tests whether it is safe to forward prune a move or if - // is somehow coonected to the threat move returned by null search. + // is somehow connected to the threat move returned by null search. bool connected_threat(const Position& pos, Move m, Move threat) { - assert(move_is_ok(m)); - assert(threat && move_is_ok(threat)); - assert(!pos.move_is_check(m)); - assert(!pos.move_is_capture_or_promotion(m)); - assert(!pos.move_is_passed_pawn_push(m)); + assert(is_ok(m)); + assert(is_ok(threat)); + assert(!pos.is_capture_or_promotion(m)); + assert(!pos.is_passed_pawn_push(m)); Square mfrom, mto, tfrom, tto; @@ -1912,10 +1663,10 @@ namespace { return true; // Case 2: If the threatened piece has value less than or equal to the - // value of the threatening piece, don't prune move which defend it. - if ( pos.move_is_capture(threat) - && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) - || pos.type_of_piece_on(tfrom) == KING) + // value of the threatening piece, don't prune moves which defend it. + if ( pos.is_capture(threat) + && ( PieceValueMidgame[pos.piece_on(tfrom)] >= PieceValueMidgame[pos.piece_on(tto)] + || type_of(pos.piece_on(tfrom)) == KING) && pos.move_attacks_square(m, tto)) return true; @@ -1930,16 +1681,16 @@ namespace { } - // ok_to_use_TT() returns true if a transposition table score - // can be used at a given point in search. + // can_return_tt() returns true if a transposition table score + // can be used to cut-off at a given point in search. - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) { + bool can_return_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)) + || v >= std::max(VALUE_MATE_IN_PLY_MAX, beta) + || v < std::min(VALUE_MATED_IN_PLY_MAX, beta)) && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta) || ((tte->type() & VALUE_TYPE_UPPER) && v < beta)); @@ -1968,10 +1719,10 @@ namespace { void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount) { - Move m; + Value bonus = Value(int(depth) * int(depth)); - H.success(pos.piece_on(move_from(move)), move_to(move), depth); + H.update(pos.piece_on(move_from(move)), move_to(move), bonus); for (int i = 0; i < moveCount - 1; i++) { @@ -1979,103 +1730,218 @@ namespace { assert(m != move); - if (!pos.move_is_capture_or_promotion(m)) - H.failure(pos.piece_on(move_from(m)), move_to(m), depth); + H.update(pos.piece_on(move_from(m)), move_to(m), -bonus); } } - // update_killers() add a good move that produced a beta-cutoff - // among the killer moves of that ply. + // current_search_time() returns the number of milliseconds which have passed + // since the beginning of the current search. - void update_killers(Move m, SearchStack* ss) { + int current_search_time(int set) { - if (m == ss->killers[0]) - return; + static int searchStartTime; + + if (set) + searchStartTime = set; - ss->killers[1] = ss->killers[0]; - ss->killers[0] = m; + return get_system_time() - searchStartTime; } - // update_gains() updates the gains table of a non-capture move given - // the static position evaluation before and after the move. + // score_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. - void update_gains(const Position& pos, Move m, Value before, Value after) { + string score_to_uci(Value v, Value alpha, Value beta) { - if ( m != MOVE_NULL - && before != VALUE_NONE - && after != VALUE_NONE - && pos.captured_piece_type() == PIECE_TYPE_NONE - && !move_is_special(m)) - H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after)); + std::stringstream s; + + if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY) + s << " score cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns + else + s << " score mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2; + + s << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); + + return s.str(); } - // current_search_time() returns the number of milliseconds which have passed - // since the beginning of the current search. + // speed_to_uci() returns a string with time stats of current search suitable + // to be sent to UCI gui. + + string speed_to_uci(int64_t nodes) { + + std::stringstream s; + int t = current_search_time(); - int current_search_time() { + s << " nodes " << nodes + << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0) + << " time " << t; - return get_system_time() - SearchStartTime; + return s.str(); } + // pv_to_uci() returns a string with information on the current PV line + // formatted according to UCI specification. + + string pv_to_uci(const Move pv[], int pvNum, bool chess960) { - // value_to_uci() converts a value to a string suitable for use with the UCI protocol + std::stringstream s; + + s << " multipv " << pvNum << " pv " << set960(chess960); - std::string value_to_uci(Value v) { + for ( ; *pv != MOVE_NONE; pv++) + s << *pv << " "; + + return s.str(); + } + + // depth_to_uci() returns a string with information on the current depth and + // seldepth formatted according to UCI specification. + + string depth_to_uci(Depth depth) { std::stringstream s; - if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY) - s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to pawn = 100 - else - s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 ); + // Retrieve max searched depth among threads + int selDepth = 0; + for (int i = 0; i < Threads.size(); i++) + if (Threads[i].maxPly > selDepth) + selDepth = Threads[i].maxPly; + + s << " depth " << depth / ONE_PLY << " seldepth " << selDepth; return s.str(); } - // nps() computes the current nodes/second count. + string time_to_string(int millisecs) { - int nps() { + const int MSecMinute = 1000 * 60; + const int MSecHour = 1000 * 60 * 60; - int t = current_search_time(); - return (t > 0 ? int((ThreadsMgr.nodes_searched() * 1000) / t) : 0); + int hours = millisecs / MSecHour; + int minutes = (millisecs % MSecHour) / MSecMinute; + int seconds = ((millisecs % MSecHour) % MSecMinute) / 1000; + + std::stringstream s; + + if (hours) + s << hours << ':'; + + s << std::setfill('0') << std::setw(2) << minutes << ':' << std::setw(2) << seconds; + return s.str(); } + string score_to_string(Value v) { + + std::stringstream s; + + if (v >= VALUE_MATE_IN_PLY_MAX) + s << "#" << (VALUE_MATE - v + 1) / 2; + else if (v <= VALUE_MATED_IN_PLY_MAX) + s << "-#" << (VALUE_MATE + v) / 2; + else + s << std::setprecision(2) << std::fixed << std::showpos << float(v) / PawnValueMidgame; + + return s.str(); + } + + // pretty_pv() creates a human-readable string from a position and a PV. + // It is used to write search information to the log file (which is created + // when the UCI parameter "Use Search Log" is "true"). + + string pretty_pv(Position& pos, int depth, Value value, int time, Move pv[]) { + + const int64_t K = 1000; + const int64_t M = 1000000; + const int startColumn = 28; + const size_t maxLength = 80 - startColumn; + + StateInfo state[PLY_MAX_PLUS_2], *st = state; + Move* m = pv; + string san; + std::stringstream s; + size_t length = 0; + + // First print depth, score, time and searched nodes... + s << set960(pos.is_chess960()) + << std::setw(2) << depth + << std::setw(8) << score_to_string(value) + << std::setw(8) << time_to_string(time); + + if (pos.nodes_searched() < M) + s << std::setw(8) << pos.nodes_searched() / 1 << " "; + else if (pos.nodes_searched() < K * M) + s << std::setw(7) << pos.nodes_searched() / K << "K "; + else + s << std::setw(7) << pos.nodes_searched() / M << "M "; + + // ...then print the full PV line in short algebraic notation + while (*m != MOVE_NONE) + { + san = move_to_san(pos, *m); + length += san.length() + 1; + + if (length > maxLength) + { + length = san.length() + 1; + s << "\n" + string(startColumn, ' '); + } + s << san << ' '; + + pos.do_move(*m++, *st++); + } + + // Restore original position before to leave + while (m != pv) pos.undo_move(*--m); + + return s.str(); + } // 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() { + void poll(const Position& pos) { static int lastInfoTime; int t = current_search_time(); // Poll for input - if (Bioskey()) + if (input_available()) { // We are line oriented, don't read single chars - std::string command; - - if (!std::getline(std::cin, command)) - command = "quit"; + string command; - if (command == "quit") + if (!std::getline(std::cin, command) || command == "quit") { - AbortSearch = true; - PonderSearch = false; - Quit = true; + // Quit the program as soon as possible + Limits.ponder = false; + QuitRequest = StopRequest = true; return; } else if (command == "stop") { - AbortSearch = true; - PonderSearch = false; + // Stop calculating as soon as possible, but still send the "bestmove" + // and possibly the "ponder" token when finishing the search. + Limits.ponder = false; + StopRequest = true; } else if (command == "ponderhit") - 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. + Limits.ponder = false; + + if (StopOnPonderhit) + StopRequest = true; + } } // Print search information @@ -2091,18 +1957,12 @@ namespace { { lastInfoTime = t; - if (dbg_show_mean) - dbg_print_mean(); - - if (dbg_show_hit_rate) - dbg_print_hit_rate(); - - cout << "info nodes " << ThreadsMgr.nodes_searched() << " nps " << nps() - << " time " << t << endl; + dbg_print_mean(); + dbg_print_hit_rate(); } // Should we stop the search? - if (PonderSearch) + if (Limits.ponder) return; bool stillAtFirstMove = FirstRootMove @@ -2112,48 +1972,10 @@ namespace { bool noMoreTime = t > TimeMgr.maximum_time() || stillAtFirstMove; - if ( (Iteration >= 3 && UseTimeManagement && noMoreTime) - || (ExactMaxTime && t >= ExactMaxTime) - || (Iteration >= 3 && MaxNodes && ThreadsMgr.nodes_searched() >= MaxNodes)) - AbortSearch = true; - } - - - // ponderhit() is called when the program is pondering (i.e. thinking while - // it's the opponent's turn to move) in order to let the engine know that - // it correctly predicted the opponent's move. - - void ponderhit() { - - int t = current_search_time(); - PonderSearch = false; - - bool stillAtFirstMove = FirstRootMove - && !AspirationFailLow - && t > TimeMgr.available_time(); - - bool noMoreTime = t > TimeMgr.maximum_time() - || stillAtFirstMove; - - if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit)) - AbortSearch = true; - } - - - // init_ss_array() does a fast reset of the first entries of a SearchStack - // array and of all the excludedMove and skipNullMove entries. - - void init_ss_array(SearchStack* ss, int size) { - - for (int i = 0; i < size; i++, ss++) - { - ss->excludedMove = MOVE_NONE; - ss->skipNullMove = false; - ss->reduction = DEPTH_ZERO; - - if (i < 3) - ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE; - } + if ( (Limits.useTimeManagement() && noMoreTime) + || (Limits.maxTime && t >= Limits.maxTime) + || (Limits.maxNodes && pos.nodes_searched() >= Limits.maxNodes)) // FIXME + StopRequest = true; } @@ -2162,638 +1984,267 @@ namespace { // the UCI protocol: When pondering, the engine is not allowed to give a // "bestmove" before the GUI sends it a "stop" or "ponderhit" command. // We simply wait here until one of these commands is sent, and return, - // after which the bestmove and pondermove will be printed (in id_loop()). + // after which the bestmove and pondermove will be printed. void wait_for_stop_or_ponderhit() { - std::string command; + string command; - while (true) - { - if (!std::getline(std::cin, command)) - command = "quit"; + // Wait for a command from stdin + while ( std::getline(std::cin, command) + && command != "ponderhit" && command != "stop" && command != "quit") {}; - if (command == "quit") - { - Quit = true; - break; - } - else if (command == "ponderhit" || command == "stop") - break; - } + if (command != "ponderhit" && command != "stop") + QuitRequest = true; // Must be "quit" or getline() returned false } - // print_pv_info() prints to standard output and eventually to log file information on - // the current PV line. It is called at each iteration or after a new pv is found. + // 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) { - void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value) { + assert(MultiPV > 1); - cout << "info depth " << Iteration - << " score " << value_to_uci(value) - << (value >= beta ? " lowerbound" : value <= alpha ? " upperbound" : "") - << " time " << current_search_time() - << " nodes " << ThreadsMgr.nodes_searched() - << " nps " << nps() - << " pv "; + static RKISS rk; - for (Move* m = pv; *m != MOVE_NONE; m++) - cout << *m << " "; + // Rml list is already sorted by score in descending order + int s; + int max_s = -VALUE_INFINITE; + int size = std::min(MultiPV, (int)Rml.size()); + int max = Rml[0].score; + int var = std::min(max - Rml[size - 1].score, int(PawnValueMidgame)); + int wk = 120 - 2 * SkillLevel; - cout << endl; + // PRNG sequence should be non deterministic + for (int i = abs(get_system_time() % 50); i > 0; i--) + rk.rand(); - if (UseLogFile) + // 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++) { - ValueType t = value >= beta ? VALUE_TYPE_LOWER : - value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT; - - LogFile << pretty_pv(pos, current_search_time(), Iteration, - ThreadsMgr.nodes_searched(), value, t, pv) << endl; - } - } - - - // insert_pv_in_tt() is called at the end of a search iteration, and inserts - // the PV back into the TT. This makes sure the old PV moves are searched - // first, even if the old TT entries have been overwritten. + s = Rml[i].score; - void insert_pv_in_tt(const Position& pos, Move pv[]) { + // Don't allow crazy blunders even at very low skills + if (i > 0 && Rml[i-1].score > s + EasyMoveMargin) + break; - StateInfo st; - TTEntry* tte; - Position p(pos, pos.thread()); - Value v, m = VALUE_NONE; + // This is our magical formula + s += ((max - s) * wk + var * (rk.rand() % wk)) / 128; - for (int i = 0; pv[i] != MOVE_NONE; i++) - { - tte = TT.retrieve(p.get_key()); - if (!tte || tte->move() != pv[i]) + if (s > max_s) { - v = (p.is_check() ? VALUE_NONE : evaluate(p, m)); - TT.store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[i], v, m); + max_s = s; + *best = Rml[i].pv[0]; + *ponder = Rml[i].pv[1]; } - p.do_move(pv[i], st); } } - // extract_pv_from_tt() builds a PV by adding moves from the transposition table. - // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This - // allow to always have a ponder move even when we fail high at root and also a - // long PV to print that is important for position analysis. + /// RootMove and RootMoveList method's definitions - void extract_pv_from_tt(const Position& pos, Move bestMove, Move pv[]) { + void RootMoveList::init(Position& pos, Move searchMoves[]) { - StateInfo st; - TTEntry* tte; - Position p(pos, pos.thread()); - int ply = 0; + Move* sm; + bestMoveChanges = 0; + clear(); - assert(bestMove != MOVE_NONE); + // Generate all legal moves and add them to RootMoveList + for (MoveList ml(pos); !ml.end(); ++ml) + { + // If we have a searchMoves[] list then verify the move + // is in the list before to add it. + for (sm = searchMoves; *sm && *sm != ml.move(); sm++) {} - pv[ply] = bestMove; - p.do_move(pv[ply++], st); + if (sm != searchMoves && *sm != ml.move()) + continue; - while ( (tte = TT.retrieve(p.get_key())) != NULL - && tte->move() != MOVE_NONE - && move_is_legal(p, tte->move()) - && ply < PLY_MAX - && (!p.is_draw() || ply < 2)) - { - pv[ply] = tte->move(); - p.do_move(pv[ply++], st); + RootMove rm; + rm.pv.push_back(ml.move()); + rm.pv.push_back(MOVE_NONE); + rm.score = rm.prevScore = -VALUE_INFINITE; + rm.nodes = 0; + push_back(rm); } - pv[ply] = MOVE_NONE; } + RootMove* RootMoveList::find(const Move& m, int startIndex) { - // 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) + for (size_t i = startIndex; i < size(); i++) + if ((*this)[i].pv[0] == m) + return &(*this)[i]; - void* init_thread(void *threadID) { - - ThreadsMgr.idle_loop(*(int*)threadID, NULL); return NULL; } -#else - - DWORD WINAPI init_thread(LPVOID threadID) { - - ThreadsMgr.idle_loop(*(int*)threadID, NULL); - return 0; - } - -#endif - - - /// The ThreadsManager class - - // resetNodeCounters(), resetBetaCounters(), searched_nodes() and - // get_beta_counters() are getters/setters for the per thread - // counters used to sort the moves at root. - - void ThreadsManager::resetNodeCounters() { - - for (int i = 0; i < MAX_THREADS; i++) - threads[i].nodes = 0ULL; - } - - int64_t ThreadsManager::nodes_searched() const { - - int64_t result = 0ULL; - for (int i = 0; i < ActiveThreads; i++) - result += threads[i].nodes; - - return result; - } - - - // idle_loop() is where the threads are parked when they have no work to do. - // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint - // object for which the current thread is the master. - - void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) { - - assert(threadID >= 0 && threadID < MAX_THREADS); - - while (true) - { - // 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 (AllThreadsShouldSleep || threadID >= ActiveThreads) - { - assert(!sp); - assert(threadID != 0); - threads[threadID].state = THREAD_SLEEPING; - -#if !defined(_MSC_VER) - lock_grab(&WaitLock); - if (AllThreadsShouldSleep || threadID >= ActiveThreads) - pthread_cond_wait(&WaitCond, &WaitLock); - lock_release(&WaitLock); -#else - WaitForSingleObject(SitIdleEvent[threadID], INFINITE); -#endif - } - - // If thread has just woken up, mark it as available - if (threads[threadID].state == THREAD_SLEEPING) - threads[threadID].state = THREAD_AVAILABLE; - - // If this thread has been assigned work, launch a search - if (threads[threadID].state == THREAD_WORKISWAITING) - { - assert(!AllThreadsShouldExit && !AllThreadsShouldSleep); - - threads[threadID].state = THREAD_SEARCHING; - - if (threads[threadID].splitPoint->pvNode) - sp_search(threads[threadID].splitPoint, threadID); - else - sp_search(threads[threadID].splitPoint, threadID); - - assert(threads[threadID].state == THREAD_SEARCHING); - - threads[threadID].state = THREAD_AVAILABLE; - } - - // 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. - int i = 0; - for ( ; sp && i < ActiveThreads && !sp->slaves[i]; i++) {} - - if (i == ActiveThreads) - { - // 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; - } - } - } - - - // init_threads() is called during startup. It launches all helper threads, - // and initializes the split point stack and the global locks and condition - // objects. - - void ThreadsManager::init_threads() { - - volatile int i; - bool ok; - -#if !defined(_MSC_VER) - pthread_t pthread[1]; -#endif - - // Initialize global locks - lock_init(&MPLock); - lock_init(&WaitLock); - -#if !defined(_MSC_VER) - pthread_cond_init(&WaitCond, NULL); -#else - for (i = 0; i < MAX_THREADS; i++) - SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0); -#endif + // 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. - // Initialize splitPoints[] locks - for (i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_init(&(threads[i].splitPoints[j].lock)); + void RootMove::extract_pv_from_tt(Position& pos) { - // Will be set just before program exits to properly end the threads - AllThreadsShouldExit = false; + StateInfo state[PLY_MAX_PLUS_2], *st = state; + TTEntry* tte; + int ply = 1; + Move m = pv[0]; - // Threads will be put to sleep as soon as created - AllThreadsShouldSleep = true; + assert(m != MOVE_NONE && pos.is_pseudo_legal(m)); - // All threads except the main thread should be initialized to THREAD_AVAILABLE - ActiveThreads = 1; - threads[0].state = THREAD_SEARCHING; - for (i = 1; i < MAX_THREADS; i++) - threads[i].state = THREAD_AVAILABLE; + pv.clear(); + pv.push_back(m); + pos.do_move(m, *st++); - // Launch the helper threads - for (i = 1; i < MAX_THREADS; i++) + while ( (tte = TT.probe(pos.get_key())) != NULL + && tte->move() != MOVE_NONE + && pos.is_pseudo_legal(tte->move()) + && pos.pl_move_is_legal(tte->move(), pos.pinned_pieces()) + && ply < PLY_MAX + && (!pos.is_draw() || ply < 2)) { - -#if !defined(_MSC_VER) - ok = (pthread_create(pthread, NULL, init_thread, (void*)(&i)) == 0); -#else - ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, NULL) != NULL); -#endif - - if (!ok) - { - cout << "Failed to create thread number " << i << endl; - Application::exit_with_failure(); - } - - // Wait until the thread has finished launching and is gone to sleep - while (threads[i].state != THREAD_SLEEPING) {} + pv.push_back(tte->move()); + pos.do_move(tte->move(), *st++); + ply++; } - } - - - // exit_threads() is called when the program exits. It makes all the - // helper threads exit cleanly. - - void ThreadsManager::exit_threads() { - - ActiveThreads = MAX_THREADS; // Wake up all the threads - AllThreadsShouldExit = true; // Let the woken up threads to exit idle_loop() - AllThreadsShouldSleep = true; // Avoid an assert in wake_sleeping_threads() - wake_sleeping_threads(); + pv.push_back(MOVE_NONE); - // Wait for thread termination - for (int i = 1; i < MAX_THREADS; i++) - while (threads[i].state != THREAD_TERMINATED) {} - - // Now we can safely destroy the locks - for (int i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) - lock_destroy(&(threads[i].splitPoints[j].lock)); - - lock_destroy(&WaitLock); - lock_destroy(&MPLock); + do pos.undo_move(pv[--ply]); while (ply); } + // 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. - // thread_should_stop() checks whether the thread should stop its search. - // This can happen if a beta cutoff has occurred in the thread's currently - // active split point, or in some ancestor of the current split point. - - bool ThreadsManager::thread_should_stop(int threadID) const { - - assert(threadID >= 0 && threadID < ActiveThreads); - - SplitPoint* sp = threads[threadID].splitPoint; - - for ( ; sp && !sp->stopRequest; sp = sp->parent) {} - return sp != NULL; - } - - - // thread_is_available() checks whether the thread with threadID "slave" is - // available to help the thread with threadID "master" at a split point. An - // obvious requirement is that "slave" must be idle. With more than two - // threads, this is not by itself sufficient: If "slave" is the master of - // some active split point, it is only available as a slave to the other - // threads which are busy searching the split point at the top of "slave"'s - // split point stack (the "helpful master concept" in YBWC terminology). - - bool ThreadsManager::thread_is_available(int slave, int master) const { - - assert(slave >= 0 && slave < ActiveThreads); - assert(master >= 0 && master < ActiveThreads); - assert(ActiveThreads > 1); - - if (threads[slave].state != THREAD_AVAILABLE || slave == master) - return false; - - // Make a local copy to be sure doesn't change under our feet - int localActiveSplitPoints = threads[slave].activeSplitPoints; - - // No active split points means that the thread is available as - // a slave for any other thread. - if (localActiveSplitPoints == 0 || ActiveThreads == 2) - return true; - - // 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; - } - - - // 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 { - - assert(master >= 0 && master < ActiveThreads); - assert(ActiveThreads > 1); - - for (int i = 0; i < ActiveThreads; i++) - if (thread_is_available(i, master)) - return true; - - return false; - } - - - // 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 sp_search(). When all threads have returned from sp_search() then - // split() returns. - - template - void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha, - const Value beta, Value* bestValue, Depth depth, Move threatMove, - bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode) { - assert(p.is_ok()); - assert(ply > 0 && ply < PLY_MAX); - assert(*bestValue >= -VALUE_INFINITE); - assert(*bestValue <= *alpha); - assert(*alpha < beta); - assert(beta <= VALUE_INFINITE); - assert(depth > DEPTH_ZERO); - assert(p.thread() >= 0 && p.thread() < ActiveThreads); - assert(ActiveThreads > 1); - - int i, master = p.thread(); - Thread& masterThread = threads[master]; - - lock_grab(&MPLock); - - // 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; - } + void RootMove::insert_pv_in_tt(Position& pos) { - // 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.stopRequest = false; - splitPoint.ply = ply; - splitPoint.depth = depth; - splitPoint.threatMove = threatMove; - splitPoint.mateThreat = mateThreat; - splitPoint.alpha = *alpha; - splitPoint.beta = beta; - splitPoint.pvNode = pvNode; - splitPoint.bestValue = *bestValue; - splitPoint.mp = mp; - splitPoint.moveCount = *moveCount; - splitPoint.pos = &p; - splitPoint.parentSstack = ss; - for (i = 0; i < ActiveThreads; i++) - splitPoint.slaves[i] = 0; - - masterThread.splitPoint = &splitPoint; - - // If we are here it means we are not available - assert(masterThread.state != THREAD_AVAILABLE); - - int workersCnt = 1; // At least the master is included - - // Allocate available threads setting state to THREAD_BOOKED - for (i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++) - if (thread_is_available(i, master)) - { - threads[i].state = THREAD_BOOKED; - threads[i].splitPoint = &splitPoint; - splitPoint.slaves[i] = 1; - workersCnt++; - } + StateInfo state[PLY_MAX_PLUS_2], *st = state; + TTEntry* tte; + Key k; + Value v, m = VALUE_NONE; + int ply = 0; - assert(Fake || workersCnt > 1); + assert(pv[0] != MOVE_NONE && pos.is_pseudo_legal(pv[0])); - // We can release the lock because slave threads are already booked and master is not available - lock_release(&MPLock); + do { + k = pos.get_key(); + tte = TT.probe(k); - // Tell the threads that they have work to do. This will make them leave - // their idle loop. But before copy search stack tail for each thread. - for (i = 0; i < ActiveThreads; i++) - if (i == master || splitPoint.slaves[i]) + // Don't overwrite existing correct entries + if (!tte || tte->move() != pv[ply]) { - memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack)); - - assert(i == master || threads[i].state == THREAD_BOOKED); - - threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop() + v = (pos.in_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++); - // 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); - - // We have returned from the idle loop, which means that all threads are - // finished. Update alpha and bestValue, and return. - lock_grab(&MPLock); - - *alpha = splitPoint.alpha; - *bestValue = splitPoint.bestValue; - masterThread.activeSplitPoints--; - masterThread.splitPoint = splitPoint.parent; - - lock_release(&MPLock); - } - - - // wake_sleeping_threads() wakes up all sleeping threads when it is time - // to start a new search from the root. - - void ThreadsManager::wake_sleeping_threads() { - - assert(AllThreadsShouldSleep); - assert(ActiveThreads > 0); - - AllThreadsShouldSleep = false; - - if (ActiveThreads == 1) - return; - -#if !defined(_MSC_VER) - pthread_mutex_lock(&WaitLock); - pthread_cond_broadcast(&WaitCond); - pthread_mutex_unlock(&WaitLock); -#else - for (int i = 1; i < MAX_THREADS; i++) - SetEvent(SitIdleEvent[i]); -#endif - - } - + } while (pv[++ply] != MOVE_NONE); - // put_threads_to_sleep() makes all the threads go to sleep just before - // to leave think(), at the end of the search. Threads should have already - // finished the job and should be idle. - - void ThreadsManager::put_threads_to_sleep() { - - assert(!AllThreadsShouldSleep); - - // This makes the threads to go to sleep - AllThreadsShouldSleep = true; + do pos.undo_move(pv[--ply]); while (ply); } +} // namespace - /// The RootMoveList class - - // RootMoveList c'tor - RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) { +// Little helper used by idle_loop() to check that all the slave threads of a +// split point have finished searching. - SearchStack ss[PLY_MAX_PLUS_2]; - MoveStack mlist[MOVES_MAX]; - StateInfo st; - bool includeAllMoves = (searchMoves[0] == MOVE_NONE); +static bool all_slaves_finished(SplitPoint* sp) { - // Initialize search stack - init_ss_array(ss, PLY_MAX_PLUS_2); - ss[0].eval = VALUE_NONE; - count = 0; + for (int i = 0; i < Threads.size(); i++) + if (sp->is_slave[i]) + return false; - // Generate all legal moves - MoveStack* last = generate_moves(pos, mlist); + return true; +} - // Add each move to the moves[] array - for (MoveStack* cur = mlist; cur != last; cur++) - { - bool includeMove = includeAllMoves; - for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++) - includeMove = (searchMoves[k] == cur->move); +// Thread::idle_loop() is where the thread is parked when it has no work to do. +// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object +// for which the thread is the master. - if (!includeMove) - continue; +void Thread::idle_loop(SplitPoint* sp) { - // Find a quick score for the move - moves[count].move = ss[0].currentMove = moves[count].pv[0] = cur->move; - moves[count].pv[1] = MOVE_NONE; - pos.do_move(cur->move, st); - moves[count].score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1); - pos.undo_move(cur->move); - count++; - } - sort(); - } - - // Score root moves using the standard way used in main search, the moves - // are scored according to the order in which are returned by MovePicker. - - void RootMoveList::score_moves(const Position& pos) + while (true) { - Move move; - int score = 1000; - MovePicker mp = MovePicker(pos, MOVE_NONE, ONE_PLY, H); - - while ((move = mp.get_next_move()) != MOVE_NONE) - for (int i = 0; i < count; i++) - if (moves[i].move == move) - { - moves[i].mp_score = score--; - break; - } - } - - // RootMoveList simple methods definitions - - void RootMoveList::set_move_pv(int moveNum, const Move pv[]) { - - int j; - - for (j = 0; pv[j] != MOVE_NONE; j++) - moves[moveNum].pv[j] = pv[j]; - - moves[moveNum].pv[j] = MOVE_NONE; - } - - - // RootMoveList::sort() sorts the root move list at the beginning of a new - // iteration. - - void RootMoveList::sort() { + // If we are not searching, wait for a condition to be signaled + // instead of wasting CPU time polling for work. + while ( do_sleep + || do_terminate + || (Threads.use_sleeping_threads() && !is_searching)) + { + assert((!sp && threadID) || Threads.use_sleeping_threads()); - sort_multipv(count - 1); // Sort all items - } + // Slave thread should exit as soon as do_terminate flag raises + if (do_terminate) + { + assert(!sp); + return; + } + // Grab the lock to avoid races with Thread::wake_up() + lock_grab(&sleepLock); - // RootMoveList::sort_multipv() sorts the first few moves in the root move - // list by their scores and depths. It is used to order the different PVs - // correctly in MultiPV mode. + // If we are master and all slaves have finished don't go to sleep + if (sp && all_slaves_finished(sp)) + { + lock_release(&sleepLock); + break; + } - void RootMoveList::sort_multipv(int n) { + // Do sleep after retesting sleep conditions under lock protection, in + // particular we need to avoid a deadlock in case a master thread has, + // in the meanwhile, allocated us and sent the wake_up() call before we + // had the chance to grab the lock. + if (do_sleep || !is_searching) + cond_wait(&sleepCond, &sleepLock); - int i,j; + lock_release(&sleepLock); + } - for (i = 1; i <= n; i++) - { - RootMove rm = moves[i]; - for (j = i; j > 0 && moves[j - 1] < rm; j--) - moves[j] = moves[j - 1]; + // If this thread has been assigned work, launch a search + if (is_searching) + { + assert(!do_terminate); + + // Copy split point position and search stack and call search() + SearchStack ss[PLY_MAX_PLUS_2]; + SplitPoint* tsp = splitPoint; + Position pos(*tsp->pos, threadID); + + memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack)); + (ss+1)->sp = tsp; + + if (tsp->nodeType == Root) + search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); + else if (tsp->nodeType == PV) + search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); + else if (tsp->nodeType == NonPV) + search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); + else + assert(false); + + assert(is_searching); + + is_searching = false; + + // Wake up master thread so to allow it to return from the idle loop in + // case we are the last slave of the split point. + if ( Threads.use_sleeping_threads() + && threadID != tsp->master + && !Threads[tsp->master].is_searching) + Threads[tsp->master].wake_up(); + } - moves[j] = rm; - } + // 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 (sp && all_slaves_finished(sp)) + { + // Because sp->is_slave[] is reset under lock protection, + // be sure sp->lock has been released before to return. + lock_grab(&(sp->lock)); + lock_release(&(sp->lock)); + return; + } } - -} // namespace +}