X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=cebdc351b8169a09f9b0000ff707bbbd8b1a6b73;hp=3009799c3af5d96f9be3f588fb07b3531b7c7553;hb=f349143a6b680eaae1e54cb950db4c48c3ab0088;hpb=26e7673c1894d6406638526f23d8a009f227fef3 diff --git a/src/search.cpp b/src/search.cpp index 3009799c..cebdc351 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -17,11 +17,6 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - #include #include #include @@ -47,27 +42,21 @@ using std::cout; using std::endl; -//// -//// Local definitions -//// - namespace { - // Types + // Different node types, used as template parameter 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; - // Fast lookup table of sliding pieces indexed by Piece + // Lookup table to check if a Piece is a slider and its access function const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; inline bool piece_is_slider(Piece p) { return Slidings[p]; } - // ThreadsManager class is used to handle all the threads related stuff 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. + // ThreadsManager class is used to handle all the threads related stuff like init, + // starting, parking and, the most important, launching a slave thread at a split + // point. All the access to shared thread data is done through this class. class ThreadsManager { /* As long as the single ThreadsManager object is defined as a global we don't @@ -75,6 +64,7 @@ namespace { static storage duration are automatically set to zero before enter main() */ public: + Thread& operator[](int threadID) { return threads[threadID]; } void init_threads(); void exit_threads(); @@ -86,26 +76,23 @@ namespace { bool available_thread_exists(int master) const; bool thread_is_available(int slave, int master) const; bool cutoff_at_splitpoint(int threadID) const; - void wake_sleeping_thread(int threadID); void idle_loop(int threadID, SplitPoint* sp); template - void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode); - + void split(Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue, + Depth depth, Move threatMove, int moveCount, MovePicker* mp, bool pvNode); private: + Lock mpLock; Depth minimumSplitDepth; int maxThreadsPerSplitPoint; bool useSleepingThreads; int activeThreads; volatile bool allThreadsShouldExit; Thread threads[MAX_THREADS]; - Lock mpLock, sleepLock[MAX_THREADS]; - WaitCondition sleepCond[MAX_THREADS]; }; - // RootMove struct is used for moves at the root at the tree. For each root + // RootMove struct is used for moves at the root of the tree. For each root // move, we store two scores, a node count, and a PV (really a refutation // in the case of moves which fail low). Value pv_score is normally set at // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed @@ -120,8 +107,8 @@ namespace { // RootMove::operator<() is the comparison function used when // sorting the moves. A move m1 is considered to be better // than a move m2 if it has an higher pv_score, or if it has - // equal pv_score but m1 has the higher non_pv_score. In this - // way we are guaranteed that PV moves are always sorted as first. + // equal pv_score but m1 has the higher non_pv_score. In this way + // we are guaranteed that PV moves are always sorted as first. bool operator<(const RootMove& m) const { return pv_score != m.pv_score ? pv_score < m.pv_score : non_pv_score < m.non_pv_score; @@ -129,7 +116,7 @@ namespace { void extract_pv_from_tt(Position& pos); void insert_pv_in_tt(Position& pos); - std::string pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine = 0); + std::string pv_info_to_uci(Position& pos, int depth, int selDepth, Value alpha, Value beta, int pvIdx); int64_t nodes; Value pv_score; @@ -138,7 +125,7 @@ namespace { }; - // RootMoveList struct is essentially a std::vector<> of RootMove objects, + // RootMoveList struct is just a std::vector<> of RootMove objects, // with an handful of methods above the standard ones. struct RootMoveList : public std::vector { @@ -153,12 +140,21 @@ namespace { }; + // 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 use it to properly format castling moves. + // operator<<() that will read it to properly format castling moves. enum set960 {}; std::ostream& operator<< (std::ostream& os, const set960& f) { @@ -168,15 +164,6 @@ namespace { } - // Overload operator << for moves to make it easier to print moves in - // 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); - } - - /// Adjustments // Step 6. Razoring @@ -203,22 +190,18 @@ namespace { // Extensions. Configurable UCI options // Array index 0 is used at non-PV nodes, index 1 at PV nodes. - Depth CheckExtension[2], PawnPushTo7thExtension[2], PassedPawnExtension[2]; - Depth PawnEndgameExtension[2], MateThreatExtension[2]; + Depth CheckExtension[2], PawnPushTo7thExtension[2]; + Depth PassedPawnExtension[2], PawnEndgameExtension[2]; // Minimum depth for use of singular extension const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */}; - // If the TT move is at least SingularExtensionMargin better then the - // remaining ones we will extend it. - const Value SingularExtensionMargin = Value(0x20); - // Step 12. Futility pruning // Futility margin for quiescence search const Value FutilityMarginQS = Value(0x80); - // Futility lookup tables (initialized at startup) and their getter functions + // Futility lookup tables (initialized at startup) and their access functions Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber] int FutilityMoveCountArray[32]; // [depth] @@ -231,7 +214,7 @@ namespace { int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber] template - inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; } + inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / ONE_PLY, 63)][Min(mn, 63)]; } // Easy move margin. An easy move candidate must be at least this much // better than the second best move. @@ -240,16 +223,16 @@ namespace { /// Namespace variables - // Book object + // Book Book OpeningBook; // Root move list RootMoveList Rml; // MultiPV mode - int MultiPV; + int MultiPV, UCIMultiPV; - // Time managment variables + // Time management variables int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime; bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit; bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow; @@ -259,7 +242,12 @@ namespace { bool UseLogFile; std::ofstream LogFile; - // Multi-threads manager object + // Skill level adjustment + int SkillLevel; + bool SkillLevelEnabled; + RKISS RK; + + // Multi-threads manager ThreadsManager ThreadsMgr; // Node counters, used only by thread[0] but try to keep in different cache @@ -271,43 +259,41 @@ namespace { // History table History H; + /// Local functions Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove); template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); template - inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { - return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO, ply) - : search(pos, ss, alpha, beta, depth, ply); + return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO) + : search(pos, ss, alpha, beta, depth); } template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous); + Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool* dangerous); bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue); bool connected_moves(const Position& pos, Move m1, Move m2); - bool value_is_mate(Value value); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); - bool ok_to_use_TT_PV(const TTEntry* tte, Depth depth, Value alpha, 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, Move killers[]); void update_gains(const Position& pos, Move move, Value before, Value after); - void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last); + void do_skill_level(Move* best, Move* ponder); int current_search_time(); std::string value_to_uci(Value v); - int nps(const Position& pos); + std::string speed_to_uci(int64_t nodes); void poll(const Position& pos); void wait_for_stop_or_ponderhit(); @@ -322,7 +308,7 @@ namespace { // the proper move source according to the type of node. template struct MovePickerExt; - // In Root nodes use RootMoveList Rml as source. Score and sort the root moves + // In Root nodes use RootMoveList as source. Score and sort the root moves // before to search them. template<> struct MovePickerExt : public MovePicker { @@ -331,10 +317,10 @@ namespace { Move move; Value score = VALUE_ZERO; - // 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. + // Score root moves using standard ordering used in main search, the moves + // are scored according to the order in which they are returned by MovePicker. // This is the second order score that is used to compare the moves when - // the first order pv scores of both moves are equal. + // the first orders pv_score of both moves are equal. while ((move = MovePicker::get_next_move()) != MOVE_NONE) for (rm = Rml.begin(); rm != Rml.end(); ++rm) if (rm->pv[0] == move) @@ -364,9 +350,8 @@ namespace { // In SpNodes use split point's shared MovePicker object as move source template<> struct MovePickerExt : public MovePicker { - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, - SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b), - mp(ss->sp->mp) {} + 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(); } @@ -377,8 +362,8 @@ namespace { // Default case, create and use a MovePicker object as source template<> struct MovePickerExt : public MovePicker { - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, - SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {} + MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) + : MovePicker(p, ttm, d, h, ss, b) {} RootMoveList::iterator rm; // Dummy, needed to compile }; @@ -386,20 +371,10 @@ namespace { } // namespace -//// -//// Functions -//// - -/// init_threads(), exit_threads() and nodes_searched() are helpers to -/// give accessibility to some TM methods from outside of current file. - -void init_threads() { ThreadsMgr.init_threads(); } -void exit_threads() { ThreadsMgr.exit_threads(); } +/// init_threads() is called during startup. It initializes various lookup tables +/// and creates and launches search threads. - -/// init_search() is called during startup. It initializes various lookup tables - -void init_search() { +void init_threads() { int d; // depth (ONE_PLY == 2) int hd; // half depth (ONE_PLY == 1) @@ -421,49 +396,56 @@ void init_search() { // Init futility move count array for (d = 0; d < 32; d++) FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0)); + + // Create and startup threads + ThreadsMgr.init_threads(); } -/// 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. +/// exit_threads() is a trampoline to access ThreadsMgr from outside of current file +void exit_threads() { ThreadsMgr.exit_threads(); } -int64_t perft(Position& pos, Depth depth) -{ - MoveStack mlist[MOVES_MAX]; - StateInfo st; - Move m; - int64_t sum = 0; - // Generate all legal moves - MoveStack* last = generate(pos, mlist); +/// perft() is our utility to verify move generation. All the legal moves up to +/// given depth are generated and counted and the sum returned. - // 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); +int64_t perft(Position& pos, Depth depth) { - // 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; + MoveStack mlist[MOVES_MAX]; + StateInfo st; + Move m; + int64_t sum = 0; + + // Generate all legal moves + MoveStack* last = generate(pos, mlist); + + // If we are at the last ply we don't need to do and undo + // the moves, just to count them. + if (depth <= ONE_PLY) + return int(last - mlist); + + // Loop through all legal moves + 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; } /// 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 id_loop(). 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, bool infinite, bool ponder, int time[], int increment[], int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) { - // Initialize global search variables + // Initialize global search-related variables StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false; NodesSincePoll = 0; SearchStartTime = get_system_time(); @@ -491,14 +473,7 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ } } - // Read UCI option values - TT.set_size(Options["Hash"].value()); - if (Options["Clear Hash"].value()) - { - Options["Clear Hash"].set_value("false"); - TT.clear(); - } - + // Read UCI options CheckExtension[1] = Options["Check Extension (PV nodes)"].value(); CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value(); PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value(); @@ -507,20 +482,34 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value(); PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value(); PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value(); - MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value(); - MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value(); - MultiPV = Options["MultiPV"].value(); + UCIMultiPV = Options["MultiPV"].value(); + SkillLevel = Options["Skill level"].value(); UseLogFile = Options["Use Search Log"].value(); read_evaluation_uci_options(pos.side_to_move()); + if (Options["Clear Hash"].value()) + { + Options["Clear Hash"].set_value("false"); + TT.clear(); + } + TT.set_size(Options["Hash"].value()); + + // Do we have to play with skill handicap? In this case enable MultiPV that + // we will use behind the scenes to retrieve a set of possible moves. + SkillLevelEnabled = (SkillLevel < 20); + MultiPV = (SkillLevelEnabled ? Max(UCIMultiPV, 4) : UCIMultiPV); + // Set the number of active threads ThreadsMgr.read_uci_options(); init_eval(ThreadsMgr.active_threads()); - // Wake up needed threads - for (int i = 1; i < ThreadsMgr.active_threads(); i++) - ThreadsMgr.wake_sleeping_thread(i); + // Wake up needed threads and reset maxPly counter + for (int i = 0; i < ThreadsMgr.active_threads(); i++) + { + ThreadsMgr[i].wake_up(); + ThreadsMgr[i].maxPly = 0; + } // Set thinking time int myTime = time[pos.side_to_move()]; @@ -528,8 +517,7 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ if (UseTimeManagement) TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter()); - // Set best NodesBetweenPolls interval to avoid lagging under - // heavy time pressure. + // Set best NodesBetweenPolls interval to avoid lagging under time pressure if (MaxNodes) NodesBetweenPolls = Min(MaxNodes, 30000); else if (myTime && myTime < 1000) @@ -545,12 +533,13 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ std::string name = Options["Search Log Filename"].value(); LogFile.open(name.c_str(), std::ios::out | std::ios::app); - LogFile << "Searching: " << pos.to_fen() - << "\ninfinite: " << infinite - << " ponder: " << ponder - << " time: " << myTime - << " increment: " << myIncrement - << " moves to go: " << movesToGo << endl; + LogFile << "\nSearching: " << pos.to_fen() + << "\ninfinite: " << infinite + << " ponder: " << ponder + << " time: " << myTime + << " increment: " << myIncrement + << " moves to go: " << movesToGo + << endl; } // We're ready to start thinking. Call the iterative deepening loop function @@ -558,25 +547,20 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ Move bestMove = id_loop(pos, searchMoves, &ponderMove); // Print final search statistics - cout << "info nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " time " << current_search_time() << endl; + cout << "info" << speed_to_uci(pos.nodes_searched()) << endl; if (UseLogFile) { - LogFile << "\nNodes: " << pos.nodes_searched() - << "\nNodes/second: " << nps(pos) - << "\nBest move: " << move_to_san(pos, bestMove); + int t = current_search_time(); + + LogFile << "Nodes: " << pos.nodes_searched() + << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0) + << "\nBest move: " << move_to_san(pos, bestMove); StateInfo st; pos.do_move(bestMove, st); - LogFile << "\nPonder move: " - << move_to_san(pos, ponderMove) // Works also with MOVE_NONE - << endl; - - // Return from think() with unchanged position - pos.undo_move(bestMove); - + LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl; + pos.undo_move(bestMove); // Return from think() with unchanged position LogFile.close(); } @@ -588,8 +572,15 @@ bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[ if (!StopRequest && (Pondering || InfiniteSearch)) wait_for_stop_or_ponderhit(); - // Could be both MOVE_NONE when searching on a stalemate position - cout << "bestmove " << bestMove << " ponder " << ponderMove << endl; + // Could be MOVE_NONE when searching on a stalemate position + cout << "bestmove " << bestMove; + + // UCI protol is not clear on allowing sending an empty ponder move, instead + // it is clear that ponder move is optional. So skip it if empty. + if (ponderMove != MOVE_NONE) + cout << " ponder " << ponderMove; + + cout << endl; return !QuitRequest; } @@ -606,73 +597,58 @@ namespace { SearchStack ss[PLY_MAX_PLUS_2]; Value bestValues[PLY_MAX_PLUS_2]; int bestMoveChanges[PLY_MAX_PLUS_2]; - int iteration, researchCountFL, researchCountFH, aspirationDelta; + int depth, selDepth, aspirationDelta; Value value, alpha, beta; - Depth depth; - Move bestMove, easyMove; + Move bestMove, easyMove, skillBest, skillPonder; - // Moves to search are verified, scored and sorted - Rml.init(pos, searchMoves); - - // Initialize FIXME move before Rml.init() + // Initialize stuff before a new search + memset(ss, 0, 4 * sizeof(SearchStack)); TT.new_search(); H.clear(); - memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack)); + *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE; + depth = aspirationDelta = 0; alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; - *ponderMove = bestMove = easyMove = MOVE_NONE; - aspirationDelta = 0; - iteration = 1; ss->currentMove = MOVE_NULL; // Hack to skip update_gains() - // Handle special case of searching on a mate/stale position + // Moves to search are verified and copied + Rml.init(pos, searchMoves); + + // Handle special case of searching on a mate/stalemate position if (Rml.size() == 0) { - cout << "info depth " << iteration << " score " + cout << "info depth 0 score " << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW) << endl; return MOVE_NONE; } - // Send initial scoring (iteration 1) - cout << set960(pos.is_chess960()) // Is enough to set once at the beginning - << "info depth " << iteration - << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl; - - // Is one move significantly better than others after initial scoring ? - if ( Rml.size() == 1 - || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin) - easyMove = Rml[0].pv[0]; - // Iterative deepening loop - while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest) + while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest) { - cout << "info depth " << iteration << endl; - - Rml.bestMoveChanges = researchCountFL = researchCountFH = 0; - depth = (iteration - 1) * ONE_PLY; + Rml.bestMoveChanges = 0; + cout << set960(pos.is_chess960()) << "info depth " << depth << endl; // Calculate dynamic aspiration window based on previous iterations - if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN) + if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN) { - int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2]; - int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3]; + int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2]; + int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3]; - aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16); + aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24); aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize - alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE); - beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE); + alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE); + beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE); } // Start with a small aspiration window and, in case of fail high/low, // research with bigger window until not failing high/low anymore. - while (true) - { + do { // Search starting from ss+1 to allow calling update_gains() - value = search(pos, ss+1, alpha, beta, depth, 0); + value = search(pos, ss+1, alpha, beta, depth * ONE_PLY); - // Write PV lines to transposition table, in case the relevant entries + // Write PV back to transposition table in case the relevant entries // have been overwritten during the search. for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++) Rml[i].insert_pv_in_tt(pos); @@ -687,28 +663,49 @@ namespace { // otherwise exit the fail high/low loop. if (value >= beta) { - beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE); - researchCountFH++; + beta = Min(beta + aspirationDelta, VALUE_INFINITE); + aspirationDelta += aspirationDelta / 2; } else if (value <= alpha) { AspirationFailLow = true; StopOnPonderhit = false; - alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE); - researchCountFL++; + alpha = Max(alpha - aspirationDelta, -VALUE_INFINITE); + aspirationDelta += aspirationDelta / 2; } else break; - } + + } while (abs(value) < VALUE_KNOWN_WIN); // Collect info about search result bestMove = Rml[0].pv[0]; - bestValues[iteration] = value; - bestMoveChanges[iteration] = Rml.bestMoveChanges; - - // Drop the easy move if differs from the new best move - if (bestMove != easyMove) + *ponderMove = Rml[0].pv[1]; + bestValues[depth] = value; + bestMoveChanges[depth] = Rml.bestMoveChanges; + + // Do we need to pick now the best and the ponder moves ? + if (SkillLevelEnabled && depth == 1 + SkillLevel) + do_skill_level(&skillBest, &skillPonder); + + // Retrieve max searched depth among threads + selDepth = 0; + for (int i = 0; i < ThreadsMgr.active_threads(); i++) + if (ThreadsMgr[i].maxPly > selDepth) + selDepth = ThreadsMgr[i].maxPly; + + // Send PV line to GUI and to log file + for (int i = 0; i < Min(UCIMultiPV, (int)Rml.size()); i++) + cout << Rml[i].pv_info_to_uci(pos, depth, selDepth, alpha, beta, i) << endl; + + if (UseLogFile) + LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl; + + // Init easyMove after first iteration or drop if differs from the best move + if (depth == 1 && (Rml.size() == 1 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)) + easyMove = bestMove; + else if (bestMove != easyMove) easyMove = MOVE_NONE; if (UseTimeManagement && !StopRequest) @@ -717,15 +714,15 @@ namespace { bool noMoreTime = false; // Stop search early when the last two iterations returned a mate score - if ( iteration >= 6 - && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100 - && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100) + if ( depth >= 5 + && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100 + && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100) noMoreTime = true; // Stop search early if one move seems to be much better than the // others or if there is only a single legal move. In this latter // case we search up to Iteration 8 anyway to get a proper score. - if ( iteration >= 8 + if ( depth >= 7 && easyMove == bestMove && ( Rml.size() == 1 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100 @@ -735,8 +732,8 @@ namespace { noMoreTime = true; // Add some extra time if the best move has changed during the last two iterations - if (iteration > 5 && iteration <= 50) - TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]); + if (depth > 4 && depth < 50) + TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]); // Stop search if most of MaxSearchTime is consumed at the end of the // iteration. We probably don't have enough time to search the first @@ -754,7 +751,16 @@ namespace { } } - *ponderMove = Rml[0].pv[1]; + // When using skills fake best and ponder moves with the sub-optimal ones + if (SkillLevelEnabled) + { + if (skillBest == MOVE_NONE) // Still unassigned ? + do_skill_level(&skillBest, &skillPonder); + + bestMove = skillBest; + *ponderMove = skillPonder; + } + return bestMove; } @@ -767,12 +773,11 @@ namespace { // 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) { + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta > alpha && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); - assert((Root || ply > 0) && ply < PLY_MAX); assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); Move movesSearched[MOVES_MAX]; @@ -785,8 +790,7 @@ namespace { ValueType vt; Value bestValue, value, oldAlpha; Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific - bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous; - bool mateThreat = false; + bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous, isBadCap; int moveCount = 0, playedMoveCount = 0; int threadID = pos.thread(); SplitPoint* sp = NULL; @@ -794,6 +798,11 @@ namespace { refinedValue = bestValue = value = -VALUE_INFINITE; oldAlpha = alpha; isCheck = pos.is_check(); + ss->ply = (ss-1)->ply + 1; + + // Used to send selDepth info to GUI + if (PvNode && ThreadsMgr[threadID].maxPly < ss->ply) + ThreadsMgr[threadID].maxPly = ss->ply; if (SpNode) { @@ -801,14 +810,14 @@ namespace { tte = NULL; ttMove = excludedMove = MOVE_NONE; threatMove = sp->threatMove; - mateThreat = sp->mateThreat; goto split_point_start; } else if (Root) bestValue = alpha; // Step 1. Initialize node and poll. Polling can abort search - ss->currentMove = ss->bestMove = threatMove = MOVE_NONE; + 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] = (ss+2)->mateKiller = MOVE_NONE; if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls) @@ -821,36 +830,38 @@ namespace { if (( StopRequest || ThreadsMgr.cutoff_at_splitpoint(threadID) || pos.is_draw() - || ply >= PLY_MAX - 1) && !Root) + || ss->ply > PLY_MAX) && !Root) return VALUE_DRAW; // Step 3. Mate distance pruning - alpha = Max(value_mated_in(ply), alpha); - beta = Min(value_mate_in(ply+1), beta); + alpha = Max(value_mated_in(ss->ply), alpha); + beta = Min(value_mate_in(ss->ply+1), beta); if (alpha >= beta) return alpha; // Step 4. Transposition table lookup // We don't want the score of a partial search to overwrite a previous full search - // TT value, so we use a different position key in case of an excluded move 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 check for exact scores within (alha, beta) range, while - // at non-PV nodes we check for and return a fail high/low. Biggest advantage - // at probing at PV nodes is to have a smooth experience in analysis mode. - if (!Root && tte && (PvNode ? ok_to_use_TT_PV(tte, depth, alpha, beta, ply) : ok_to_use_TT(tte, depth, beta, ply))) + // At PV nodes we check for exact scores, while at non-PV nodes we check for + // a fail high/low. Biggest advantage at probing at PV nodes is to have a + // smooth experience in analysis mode. + if ( !Root + && tte + && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT + : ok_to_use_TT(tte, depth, beta, ss->ply))) { TT.refresh(tte); ss->bestMove = ttMove; // Can be MOVE_NONE - return value_from_tt(tte->value(), ply); + return value_from_tt(tte->value(), ss->ply); } - // Step 5. Evaluate the position statically and - // update gain statistics of parent move. + // Step 5. Evaluate the position statically and update parent's gain statistics if (isCheck) ss->eval = ss->evalMargin = VALUE_NONE; else if (tte) @@ -859,7 +870,7 @@ namespace { ss->eval = tte->static_value(); ss->evalMargin = tte->static_value_margin(); - refinedValue = refine_eval(tte, ss->eval, ply); + refinedValue = refine_eval(tte, ss->eval, ss->ply); } else { @@ -874,13 +885,13 @@ namespace { if ( !PvNode && depth < RazorDepth && !isCheck - && refinedValue < beta - razor_margin(depth) + && refinedValue + razor_margin(depth) < beta && ttMove == MOVE_NONE - && !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. @@ -894,8 +905,8 @@ namespace { && !ss->skipNullMove && depth < RazorDepth && !isCheck - && refinedValue >= beta + futility_margin(depth, 0) - && !value_is_mate(beta) + && 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); @@ -905,7 +916,7 @@ namespace { && depth > ONE_PLY && !isCheck && 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; @@ -914,19 +925,19 @@ 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); (ss+1)->skipNullMove = true; - nullValue = -search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1); + nullValue = -search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY); (ss+1)->skipNullMove = false; pos.undo_null_move(); if (nullValue >= beta) { // Do not return unproven mate scores - if (nullValue >= value_mate_in(PLY_MAX)) + if (nullValue >= VALUE_MATE_IN_PLY_MAX) nullValue = beta; if (depth < 6 * ONE_PLY) @@ -934,7 +945,7 @@ 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) @@ -948,10 +959,8 @@ 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 @@ -963,22 +972,18 @@ namespace { // Step 9. Internal iterative deepening if ( depth >= IIDDepth[PvNode] && ttMove == MOVE_NONE - && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) + && (PvNode || (!isCheck && 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); } - // 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 @@ -1031,50 +1036,50 @@ split_point_start: // At split points actual search starts from here if (SendSearchedNodes) { SendSearchedNodes = false; - cout << "info nodes " << nodes - << " nps " << nps(pos) - << " time " << current_search_time() << endl; + cout << "info" << speed_to_uci(pos.nodes_searched()) << endl; } - if (current_search_time() >= 1000) + if (current_search_time() > 2000) cout << "info currmove " << move << " currmovenumber " << moveCount << endl; } - isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1)); + // At Root and at first iteration do a PV search on all the moves to score root moves + isPvMove = (PvNode && moveCount <= (Root ? depth <= ONE_PLY ? 1000 : MultiPV : 1)); moveIsCheck = pos.move_is_check(move, ci); captureOrPromotion = pos.move_is_capture_or_promotion(move); // Step 11. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous); + ext = extension(pos, move, captureOrPromotion, moveIsCheck, &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() && 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; } } // Update current move (this must be done after singular extension search) ss->currentMove = move; - newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext; + newDepth = depth - ONE_PLY + ext; // Step 12. Futility pruning (is omitted in PV nodes) if ( !PvNode @@ -1086,8 +1091,8 @@ split_point_start: // At split points actual search starts from here { // Move count based pruning if ( moveCount >= futility_move_count(depth) - && !(threatMove && connected_threat(pos, move, threatMove)) - && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy + && (!threatMove || !connected_threat(pos, move, threatMove)) + && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy { if (SpNode) lock_grab(&(sp->lock)); @@ -1118,7 +1123,7 @@ split_point_start: // At split points actual search starts from here // Prune moves with negative SEE at low depths if ( predictedDepth < 2 * ONE_PLY - && bestValue > value_mated_in(PLY_MAX) + && bestValue > VALUE_MATED_IN_PLY_MAX && pos.see_sign(move) < 0) { if (SpNode) @@ -1128,6 +1133,16 @@ split_point_start: // At split points actual search starts from here } } + // Bad capture detection. Will be used by prob-cut search + isBadCap = depth >= 3 * ONE_PLY + && depth < 8 * ONE_PLY + && captureOrPromotion + && move != ttMove + && !dangerous + && !move_is_promotion(move) + && abs(alpha) < VALUE_MATE_IN_PLY_MAX + && pos.see_sign(move) < 0; + // Step 13. Make the move pos.do_move(move, st, ci, moveIsCheck); @@ -1142,13 +1157,14 @@ split_point_start: // At split points actual search starts from here if (Root && MultiPV > 1) alpha = -VALUE_INFINITE; - value = -search(pos, ss+1, -beta, -alpha, newDepth, ply+1); + value = -search(pos, ss+1, -beta, -alpha, newDepth); } else { // Step 14. Reduced depth search // If the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; + alpha = SpNode ? sp->alpha : alpha; if ( depth >= 3 * ONE_PLY && !captureOrPromotion @@ -1157,30 +1173,41 @@ split_point_start: // At split points actual search starts from here && ss->killers[0] != move && ss->killers[1] != move) { - ss->reduction = Root ? reduction(depth, moveCount - MultiPV + 1) - : reduction(depth, moveCount); + ss->reduction = reduction(depth, moveCount); if (ss->reduction) { alpha = SpNode ? sp->alpha : alpha; Depth d = newDepth - ss->reduction; - value = -search(pos, ss+1, -(alpha+1), -alpha, d, ply+1); + value = -search(pos, ss+1, -(alpha+1), -alpha, d); doFullDepthSearch = (value > alpha); } ss->reduction = DEPTH_ZERO; // Restore original reduction } + // Probcut search for bad captures. If a reduced search returns a value + // very below beta then we can (almost) safely prune the bad capture. + if (isBadCap) + { + ss->reduction = 3 * ONE_PLY; + Value rAlpha = alpha - 300; + Depth d = newDepth - ss->reduction; + value = -search(pos, ss+1, -(rAlpha+1), -rAlpha, d); + doFullDepthSearch = (value > rAlpha); + ss->reduction = DEPTH_ZERO; // Restore original reduction + } + // Step 15. Full depth search if (doFullDepthSearch) { alpha = SpNode ? sp->alpha : alpha; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth); // Step extra. pv search (only in PV nodes) // Search only for possible new PV nodes, if instead value >= beta then // parent node fails low with value <= alpha and tries another move. if (PvNode && value > alpha && (Root || value < beta)) - value = -search(pos, ss+1, -beta, -alpha, newDepth, ply+1); + value = -search(pos, ss+1, -beta, -alpha, newDepth); } } @@ -1197,14 +1224,14 @@ split_point_start: // At split points actual search starts from here alpha = sp->alpha; } - if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID))) + if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID))) { bestValue = value; if (SpNode) sp->bestValue = value; - if (value > alpha) + if (!Root && value > alpha) { if (PvNode && value < beta) // We want always alpha < beta { @@ -1216,22 +1243,18 @@ split_point_start: // At split points actual search starts from here else if (SpNode) sp->betaCutoff = true; - if (value == value_mate_in(ply + 1)) + if (value == value_mate_in(ss->ply + 1)) ss->mateKiller = move; ss->bestMove = move; if (SpNode) - sp->parentSstack->bestMove = move; + sp->ss->bestMove = move; } } if (Root) { - // To avoid to exit with bestValue == -VALUE_INFINITE - if (value > bestValue) - bestValue = value; - // 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 @@ -1243,40 +1266,33 @@ split_point_start: // At split points actual search starts from here // Remember searched nodes counts for this move mp.rm->nodes += pos.nodes_searched() - nodes; - // Step 17. Check for new best move - if (!isPvMove && value <= alpha) - mp.rm->pv_score = -VALUE_INFINITE; - else + // PV move or new best move ? + if (isPvMove || value > alpha) { - // PV move or new best move! - // Update PV ss->bestMove = move; mp.rm->pv_score = value; mp.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 managment: When + // 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++; - // Inform GUI that PV has changed, in case of multi-pv UCI protocol - // requires we send all the PV lines properly sorted. Rml.sort_multipv(moveCount); - for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++) - cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl; - // Update alpha. In multi-pv we don't use aspiration window, so // set alpha equal to minimum score among the PV lines. if (MultiPV > 1) alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount? else if (value > alpha) alpha = value; + } + else + mp.rm->pv_score = -VALUE_INFINITE; - } // PV move or new best move - } + } // Root // Step 18. Check for split if ( !Root @@ -1287,8 +1303,8 @@ split_point_start: // At split points actual search starts from here && ThreadsMgr.available_thread_exists(threadID) && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID)) - ThreadsMgr.split(pos, ss, ply, &alpha, beta, &bestValue, depth, - threatMove, mateThreat, moveCount, &mp, PvNode); + ThreadsMgr.split(pos, ss, &alpha, beta, &bestValue, depth, + threatMove, moveCount, &mp, PvNode); } // Step 19. Check for mate and stalemate @@ -1296,7 +1312,7 @@ split_point_start: // At split points actual search starts from here // no legal moves, it must be mate or stalemate. // If one move was excluded return fail low score. if (!SpNode && !moveCount) - return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW; + return excludedMove ? oldAlpha : isCheck ? value_mated_in(ss->ply) : VALUE_DRAW; // Step 20. Update tables // If the search is not aborted, update the transposition table, @@ -1307,14 +1323,18 @@ split_point_start: // At split points actual search starts from here vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT; - TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->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)) { + if (move != ss->killers[0]) + { + ss->killers[1] = ss->killers[0]; + ss->killers[0] = move; + } update_history(pos, move, depth, movesSearched, playedMoveCount); - update_killers(move, ss->killers); } } @@ -1336,13 +1356,12 @@ split_point_start: // At split points actual search starts from here // less than ONE_PLY). template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); assert(depth <= 0); - assert(ply > 0 && ply < PLY_MAX); assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads()); StateInfo st; @@ -1354,9 +1373,10 @@ split_point_start: // At split points actual search starts from here Value oldAlpha = alpha; 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 (ss->ply > PLY_MAX || pos.is_draw()) return VALUE_DRAW; // Decide whether or not to include checks, this fixes also the type of @@ -1370,10 +1390,10 @@ split_point_start: // At split points actual search starts from here tte = TT.retrieve(pos.get_key()); ttMove = (tte ? tte->move() : MOVE_NONE); - if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply)) + if (!PvNode && tte && ok_to_use_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); } // Evaluate the position statically @@ -1401,7 +1421,7 @@ split_point_start: // At split points actual search starts from here 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; } @@ -1448,11 +1468,17 @@ split_point_start: // At split points actual search starts from here 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) + && bestValue > VALUE_MATED_IN_PLY_MAX && !pos.move_is_capture(move) && !pos.can_castle(pos.side_to_move()); @@ -1484,7 +1510,7 @@ split_point_start: // At split points actual search starts from here // Make and search the move pos.do_move(move, st, ci, moveIsCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1); + value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1504,11 +1530,11 @@ split_point_start: // At split points actual search starts from here // 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); + return value_mated_in(ss->ply); // Update transposition table ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); - TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin); + TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1516,26 +1542,6 @@ split_point_start: // At split points actual search starts from here } - // qsearch_scoring() scores each move of a list using a qsearch() evaluation, - // it is used in RootMoveList to get an initial scoring. - void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) { - - SearchStack ss[PLY_MAX_PLUS_2]; - StateInfo st; - - memset(ss, 0, 4 * sizeof(SearchStack)); - ss[0].eval = ss[0].evalMargin = VALUE_NONE; - - for (MoveStack* cur = mlist; cur != last; cur++) - { - ss[0].currentMove = cur->move; - pos.do_move(cur->move, st); - cur->score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1); - pos.undo_move(cur->move); - } - } - - // 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. @@ -1646,28 +1652,16 @@ split_point_start: // At split points actual search starts from here } - // 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; @@ -1679,10 +1673,10 @@ split_point_start: // At split points actual search starts from here 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; @@ -1697,21 +1691,15 @@ split_point_start: // At split points actual search starts from here // 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 mateThreat, bool* dangerous) { + bool moveIsCheck, bool* dangerous) { assert(m != MOVE_NONE); Depth result = DEPTH_ZERO; - *dangerous = moveIsCheck | mateThreat; + *dangerous = moveIsCheck; - if (*dangerous) - { - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; - - if (mateThreat) - result += MateThreatExtension[PvNode]; - } + if (moveIsCheck && pos.see_sign(m) >= 0) + result += CheckExtension[PvNode]; if (pos.type_of_piece_on(move_from(m)) == PAWN) { @@ -1739,21 +1727,12 @@ split_point_start: // At split points actual search starts from here *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) { @@ -1775,7 +1754,7 @@ split_point_start: // At split points actual search starts from here 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. + // value of the threatening piece, don't prune moves which defend it. if ( pos.move_is_capture(threat) && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) || pos.type_of_piece_on(tfrom) == KING) @@ -1794,30 +1773,20 @@ split_point_start: // At split points actual search starts from here // ok_to_use_TT() returns true if a transposition table score - // can be used at a given point in search. There are two versions - // one to be used in non-PV nodes and one in PV nodes where we look - // for an exact score that falls between (alha, beta) boundaries. + // can be used at a given point in search. bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) { Value v = value_from_tt(tte->value(), ply); return ( tte->depth() >= depth - || v >= Max(value_mate_in(PLY_MAX), beta) - || v < Min(value_mated_in(PLY_MAX), beta)) + || v >= Max(VALUE_MATE_IN_PLY_MAX, beta) + || v < Min(VALUE_MATED_IN_PLY_MAX, beta)) && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta) || ((tte->type() & VALUE_TYPE_UPPER) && v < beta)); } - bool ok_to_use_TT_PV(const TTEntry* tte, Depth depth, Value alpha, Value beta, int ply) { - - Value v = value_from_tt(tte->value(), ply); - - return tte->depth() >= depth - && tte->type() == VALUE_TYPE_EXACT; - } - // refine_eval() returns the transposition table score if // possible otherwise falls back on static position evaluation. @@ -1857,19 +1826,6 @@ split_point_start: // At split points actual search starts from here } - // update_killers() add a good move that produced a beta-cutoff - // among the killer moves of that ply. - - void update_killers(Move m, Move killers[]) { - - if (m != killers[0]) - { - killers[1] = killers[0]; - killers[0] = m; - } - } - - // update_gains() updates the gains table of a non-capture move given // the static position evaluation before and after the move. @@ -1884,6 +1840,15 @@ split_point_start: // At split points actual search starts from here } + // current_search_time() returns the number of milliseconds which have passed + // since the beginning of the current search. + + int current_search_time() { + + return get_system_time() - SearchStartTime; + } + + // value_to_uci() converts a value to a string suitable for use with the UCI // protocol specifications: // @@ -1898,27 +1863,25 @@ split_point_start: // At split points actual search starts from here if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY) s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns else - s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 ); + s << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2; return s.str(); } - // current_search_time() returns the number of milliseconds which have passed - // since the beginning of the current search. - - int current_search_time() { - - return get_system_time() - SearchStartTime; - } + // speed_to_uci() returns a string with time stats of current search suitable + // to be sent to UCI gui. + std::string speed_to_uci(int64_t nodes) { - // nps() computes the current nodes/second count + std::stringstream s; + int t = current_search_time(); - int nps(const Position& pos) { + s << " nodes " << nodes + << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0) + << " time " << t; - int t = current_search_time(); - return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0); + return s.str(); } @@ -1937,10 +1900,7 @@ split_point_start: // At split points actual search starts from here // We are line oriented, don't read single chars std::string command; - if (!std::getline(std::cin, command)) - command = "quit"; - - if (command == "quit") + if (!std::getline(std::cin, command) || command == "quit") { // Quit the program as soon as possible Pondering = false; @@ -1979,11 +1939,8 @@ split_point_start: // At split points actual search starts from here { lastInfoTime = t; - if (dbg_show_mean) - dbg_print_mean(); - - if (dbg_show_hit_rate) - dbg_print_hit_rate(); + dbg_print_mean(); + dbg_print_hit_rate(); // Send info on searched nodes as soon as we return to root SendSearchedNodes = true; @@ -2018,20 +1975,12 @@ split_point_start: // At split points actual search starts from here std::string command; - while (true) - { - // Wait for a command from stdin - 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") - { - QuitRequest = true; - break; - } - else if (command == "ponderhit" || command == "stop") - break; - } + if (command != "ponderhit" && command != "stop") + QuitRequest = true; // Must be "quit" or getline() returned false } @@ -2099,7 +2048,8 @@ split_point_start: // At split points actual search starts from here // If we are not thinking, wait for a condition to be signaled // instead of wasting CPU time polling for work. - while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING + while ( threadID >= activeThreads + || threads[threadID].state == THREAD_INITIALIZING || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE)) { assert(!sp || useSleepingThreads); @@ -2109,7 +2059,7 @@ split_point_start: // At split points actual search starts from here threads[threadID].state = THREAD_AVAILABLE; // Grab the lock to avoid races with wake_sleeping_thread() - lock_grab(&sleepLock[threadID]); + lock_grab(&threads[threadID].sleepLock); // If we are master and all slaves have finished do not go to sleep for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {} @@ -2117,15 +2067,15 @@ split_point_start: // At split points actual search starts from here if (allFinished || allThreadsShouldExit) { - lock_release(&sleepLock[threadID]); + lock_release(&threads[threadID].sleepLock); break; } // Do sleep here after retesting sleep conditions if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE) - cond_wait(&sleepCond[threadID], &sleepLock[threadID]); + cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock); - lock_release(&sleepLock[threadID]); + lock_release(&threads[threadID].sleepLock); } // If this thread has been assigned work, launch a search @@ -2135,16 +2085,19 @@ split_point_start: // At split points actual search starts from here threads[threadID].state = THREAD_SEARCHING; - // Here we call search() with SplitPoint template parameter set to true + // Copy split point position and search stack and call search() + // with SplitPoint template parameter set to true. + SearchStack ss[PLY_MAX_PLUS_2]; SplitPoint* tsp = threads[threadID].splitPoint; Position pos(*tsp->pos, threadID); - SearchStack* ss = tsp->sstack[threadID] + 1; - ss->sp = tsp; + + memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack)); + (ss+1)->sp = tsp; if (tsp->pvNode) - search(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply); + search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); else - search(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply); + search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth); assert(threads[threadID].state == THREAD_SEARCHING); @@ -2152,8 +2105,10 @@ split_point_start: // At split points actual search starts from here // Wake up master thread so to allow it to return from the idle loop in // case we are the last slave of the split point. - if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE) - wake_sleeping_thread(tsp->master); + if ( useSleepingThreads + && threadID != tsp->master + && threads[tsp->master].state == THREAD_AVAILABLE) + threads[tsp->master].wake_up(); } // If this thread is the master of a split point and all slaves have @@ -2179,41 +2134,36 @@ split_point_start: // At split points actual search starts from here } - // init_threads() is called during startup. It launches all helper threads, - // and initializes the split point stack and the global locks and condition - // objects. + // init_threads() is called during startup. Initializes locks and condition + // variables and launches all threads sending them immediately to sleep. void ThreadsManager::init_threads() { int i, arg[MAX_THREADS]; bool ok; - // Initialize global locks + // This flag is needed to properly end the threads when program exits + allThreadsShouldExit = false; + + // Threads will sent to sleep as soon as created, only main thread is kept alive + activeThreads = 1; + lock_init(&mpLock); for (i = 0; i < MAX_THREADS; i++) { - lock_init(&sleepLock[i]); - cond_init(&sleepCond[i]); - } + // Initialize thread and split point locks + lock_init(&threads[i].sleepLock); + cond_init(&threads[i].sleepCond); - // Initialize splitPoints[] locks - for (i = 0; i < MAX_THREADS; i++) for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) lock_init(&(threads[i].splitPoints[j].lock)); - // Will be set just before program exits to properly end the threads - allThreadsShouldExit = false; - - // Threads will be put all threads to sleep as soon as created - activeThreads = 1; - - // All threads except the main thread should be initialized to THREAD_INITIALIZING - threads[0].state = THREAD_SEARCHING; - for (i = 1; i < MAX_THREADS; i++) - threads[i].state = THREAD_INITIALIZING; + // All threads but first should be set to THREAD_INITIALIZING + threads[i].state = (i == 0 ? THREAD_SEARCHING : THREAD_INITIALIZING); + } - // Launch the helper threads + // Create and startup the threads for (i = 1; i < MAX_THREADS; i++) { arg[i] = i; @@ -2242,28 +2192,27 @@ split_point_start: // At split points actual search starts from here void ThreadsManager::exit_threads() { - allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop() + // Force the woken up threads to exit idle_loop() and hence terminate + allThreadsShouldExit = true; - // Wake up all the threads and waits for termination - for (int i = 1; i < MAX_THREADS; i++) + for (int i = 0; i < MAX_THREADS; i++) { - wake_sleeping_thread(i); - while (threads[i].state != THREAD_TERMINATED) {} - } + // Wake up all the threads and waits for termination + if (i != 0) + { + threads[i].wake_up(); + while (threads[i].state != THREAD_TERMINATED) {} + } + + // Now we can safely destroy the locks and wait conditions + lock_destroy(&threads[i].sleepLock); + cond_destroy(&threads[i].sleepCond); - // 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(&mpLock); - - // Now we can safely destroy the wait conditions - for (int i = 0; i < MAX_THREADS; i++) - { - lock_destroy(&sleepLock[i]); - cond_destroy(&sleepCond[i]); - } } @@ -2343,11 +2292,10 @@ split_point_start: // At split points actual search starts from here // call search().When all threads have returned from search() then split() returns. template - void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha, - const Value beta, Value* bestValue, Depth depth, Move threatMove, - bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) { + void ThreadsManager::split(Position& pos, SearchStack* ss, Value* alpha, const Value beta, + Value* bestValue, Depth depth, Move threatMove, + int moveCount, MovePicker* mp, bool pvNode) { assert(pos.is_ok()); - assert(ply > 0 && ply < PLY_MAX); assert(*bestValue >= -VALUE_INFINITE); assert(*bestValue <= *alpha); assert(*alpha < beta); @@ -2377,10 +2325,8 @@ split_point_start: // At split points actual search starts from here splitPoint.parent = masterThread.splitPoint; splitPoint.master = master; splitPoint.betaCutoff = false; - splitPoint.ply = ply; splitPoint.depth = depth; splitPoint.threatMove = threatMove; - splitPoint.mateThreat = mateThreat; splitPoint.alpha = *alpha; splitPoint.beta = beta; splitPoint.pvNode = pvNode; @@ -2389,7 +2335,7 @@ split_point_start: // At split points actual search starts from here splitPoint.moveCount = moveCount; splitPoint.pos = &pos; splitPoint.nodes = 0; - splitPoint.parentSstack = ss; + splitPoint.ss = ss; for (i = 0; i < activeThreads; i++) splitPoint.slaves[i] = 0; @@ -2416,18 +2362,16 @@ split_point_start: // At split points actual search starts from here lock_release(&mpLock); // 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. + // their idle loop. for (i = 0; i < activeThreads; i++) if (i == master || splitPoint.slaves[i]) { - 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() if (useSleepingThreads && i != master) - wake_sleeping_thread(i); + threads[i].wake_up(); } // Everything is set up. The master thread enters the idle loop, from @@ -2451,17 +2395,6 @@ split_point_start: // At split points actual search starts from here } - // wake_sleeping_thread() wakes up the thread with the given threadID - // when it is time to start a new search. - - void ThreadsManager::wake_sleeping_thread(int threadID) { - - lock_grab(&sleepLock[threadID]); - cond_signal(&sleepCond[threadID]); - lock_release(&sleepLock[threadID]); - } - - /// RootMove and RootMoveList method's definitions RootMove::RootMove() { @@ -2496,13 +2429,13 @@ split_point_start: // At split points actual search starts from here TTEntry* tte; int ply = 1; - assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0])); + assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0])); pos.do_move(pv[0], *st++); while ( (tte = TT.retrieve(pos.get_key())) != NULL && tte->move() != MOVE_NONE - && move_is_legal(pos, tte->move()) + && pos.move_is_legal(tte->move()) && ply < PLY_MAX && (!pos.is_draw() || ply < 2)) { @@ -2526,13 +2459,13 @@ split_point_start: // At split points actual search starts from here Value v, m = VALUE_NONE; int ply = 0; - assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0])); + assert(pv[0] != MOVE_NONE && pos.move_is_legal(pv[0])); do { k = pos.get_key(); tte = TT.retrieve(k); - // Don't overwrite exsisting correct entries + // Don't overwrite existing correct entries if (!tte || tte->move() != pv[ply]) { v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m)); @@ -2546,34 +2479,23 @@ split_point_start: // At split points actual search starts from here } // pv_info_to_uci() returns a string with information on the current PV line - // formatted according to UCI specification and eventually writes the info - // to a log file. It is called at each iteration or after a new pv is found. + // formatted according to UCI specification. - std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) { - - std::stringstream s, l; - Move* m = pv; - - while (*m != MOVE_NONE) - l << *m++ << " "; + std::string RootMove::pv_info_to_uci(Position& pos, int depth, int selDepth, Value alpha, + Value beta, int pvIdx) { + std::stringstream s; - s << "info depth " << depth / ONE_PLY - << " seldepth " << int(m - pv) - << " multipv " << pvLine + 1 + s << "info depth " << depth + << " seldepth " << selDepth + << " multipv " << pvIdx + 1 << " score " << value_to_uci(pv_score) << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "") - << " time " << current_search_time() - << " nodes " << pos.nodes_searched() - << " nps " << nps(pos) - << " pv " << l.str(); + << speed_to_uci(pos.nodes_searched()) + << " pv "; - if (UseLogFile && pvLine == 0) - { - ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER : - pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT; + for (Move* m = pv; *m != MOVE_NONE; m++) + s << *m << " "; - LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl; - } return s.str(); } @@ -2586,11 +2508,8 @@ split_point_start: // At split points actual search starts from here clear(); bestMoveChanges = 0; - // Generate all legal moves and score them + // Generate all legal moves and add them to RootMoveList MoveStack* last = generate(pos, mlist); - qsearch_scoring(pos, mlist, last); - - // Add each move to the RootMoveList's vector for (MoveStack* cur = mlist; cur != last; cur++) { // If we have a searchMoves[] list then verify cur->move @@ -2603,10 +2522,51 @@ split_point_start: // At split points actual search starts from here RootMove rm; rm.pv[0] = cur->move; rm.pv[1] = MOVE_NONE; - rm.pv_score = Value(cur->score); + rm.pv_score = -VALUE_INFINITE; push_back(rm); } - sort(); + } + + + // When playing with strength handicap choose best move among the MultiPV set + // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen. + void do_skill_level(Move* best, Move* ponder) { + + assert(MultiPV > 1); + + // Rml list is already sorted by pv_score in descending order + int s; + int max_s = -VALUE_INFINITE; + int size = Min(MultiPV, (int)Rml.size()); + int max = Rml[0].pv_score; + int var = Min(max - Rml[size - 1].pv_score, PawnValueMidgame); + int wk = 120 - 2 * SkillLevel; + + // PRNG sequence should be non deterministic + for (int i = abs(get_system_time() % 50); i > 0; i--) + RK.rand(); + + // Choose best move. For each move's score we add two terms both dependent + // on wk, one deterministic and bigger for weaker moves, and one random, + // then we choose the move with the resulting highest score. + for (int i = 0; i < size; i++) + { + s = Rml[i].pv_score; + + // Don't allow crazy blunders even at very low skills + if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin) + break; + + // This is our magical formula + s += ((max - s) * wk + var * (RK.rand() % wk)) / 128; + + if (s > max_s) + { + max_s = s; + *best = Rml[i].pv[0]; + *ponder = Rml[i].pv[1]; + } + } } } // namespace