X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=6a42cc50b05a233bb181ac884bcefaec6268a062;hp=982f2a2cd279e26273476d955d75e2305857eef2;hb=a86057649364547066f65d088809ae490856587b;hpb=4270aec55886f56d1d588ea329bb5a1c50998c19 diff --git a/src/search.cpp b/src/search.cpp index 982f2a2c..6a42cc50 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 @@ -91,7 +80,7 @@ namespace { 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); + Depth depth, Move threatMove, int moveCount, MovePicker* mp, bool pvNode); private: Depth minimumSplitDepth; @@ -105,7 +94,7 @@ namespace { }; - // 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 +109,8 @@ 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 +118,7 @@ namespace { void extract_pv_from_tt(Position& pos); void insert_pv_in_tt(Position& pos); - std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine); + std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvIdx); int64_t nodes; Value pv_score; @@ -138,7 +127,7 @@ 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 +142,21 @@ 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 +166,6 @@ 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 @@ -203,8 +192,8 @@ 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 */}; @@ -214,7 +203,7 @@ namespace { // 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] @@ -227,7 +216,7 @@ 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. @@ -236,14 +225,14 @@ namespace { /// Namespace variables - // Book object + // Book Book OpeningBook; // Root move list RootMoveList Rml; // MultiPV mode - int MultiPV; + int MultiPV, UCIMultiPV; // Time management variables int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime; @@ -255,7 +244,12 @@ 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 @@ -267,6 +261,7 @@ namespace { // History table History H; + /// Local functions Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove); @@ -280,24 +275,23 @@ namespace { template inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { - return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO, ply) - : search(pos, ss, alpha, beta, depth, ply); + return depth < ONE_PLY ? qsearch(pos, ss, alpha, beta, DEPTH_ZERO, ply) + : search(pos, ss, alpha, beta, depth, ply); } template - Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool 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 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 do_skill_level(Move* best, Move* ponder); int current_search_time(); std::string value_to_uci(Value v); @@ -316,7 +310,7 @@ 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 { @@ -325,10 +319,10 @@ namespace { Move move; Value score = VALUE_ZERO; - // Score root moves using the standard way used in main search, the moves + // 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) @@ -358,9 +352,8 @@ 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(); } @@ -371,8 +364,8 @@ 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 }; @@ -380,20 +373,10 @@ namespace { } // namespace -//// -//// Functions -//// +/// init_threads() is called during startup. It initializes various lookup tables +/// and creates and launches search threads. -/// 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_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) @@ -415,49 +398,56 @@ 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(); @@ -485,14 +475,7 @@ 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(); @@ -501,18 +484,29 @@ 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 + // Wake up needed threads. Main thread, with threadID == 0, is always active for (int i = 1; i < ThreadsMgr.active_threads(); i++) ThreadsMgr.wake_sleeping_thread(i); @@ -522,8 +516,7 @@ 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) @@ -603,16 +596,16 @@ namespace { SearchStack ss[PLY_MAX_PLUS_2]; Value bestValues[PLY_MAX_PLUS_2]; int bestMoveChanges[PLY_MAX_PLUS_2]; - int depth, aspirationDelta; + int depth, aspirationDelta, skillSamplingDepth; Value value, alpha, beta; - Move bestMove, easyMove; + 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 = MOVE_NONE; - depth = aspirationDelta = 0; + *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE; + depth = aspirationDelta = skillSamplingDepth = 0; alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; ss->currentMove = MOVE_NULL; // Hack to skip update_gains() @@ -629,6 +622,11 @@ namespace { return MOVE_NONE; } + // Choose a random sampling depth according to SkillLevel so that at low + // skills there is an higher risk to pick up a blunder. + if (SkillLevelEnabled) + skillSamplingDepth = 4 + SkillLevel + (RK.rand() % 4); + // Iterative deepening loop while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest) { @@ -687,11 +685,16 @@ namespace { // Collect info about search result bestMove = Rml[0].pv[0]; + *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 == skillSamplingDepth) + do_skill_level(&skillBest, &skillPonder); + // Send PV line to GUI and to log file - for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++) + for (int i = 0; i < Min(UCIMultiPV, (int)Rml.size()); i++) cout << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl; if (UseLogFile) @@ -746,7 +749,16 @@ 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; } @@ -777,8 +789,7 @@ 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; @@ -793,7 +804,6 @@ namespace { tte = NULL; ttMove = excludedMove = MOVE_NONE; threatMove = sp->threatMove; - mateThreat = sp->mateThreat; goto split_point_start; } else if (Root) @@ -833,8 +843,8 @@ namespace { ttMove = tte ? tte->move() : MOVE_NONE; // At PV nodes we check for exact scores, 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. + // 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 @@ -845,8 +855,7 @@ namespace { return value_from_tt(tte->value(), 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) @@ -870,9 +879,9 @@ 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); @@ -890,8 +899,8 @@ 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); @@ -901,7 +910,7 @@ 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; @@ -910,7 +919,7 @@ 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); @@ -922,7 +931,7 @@ namespace { 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) @@ -944,10 +953,8 @@ 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 @@ -959,7 +966,7 @@ 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); @@ -971,10 +978,6 @@ namespace { 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 @@ -1030,24 +1033,24 @@ split_point_start: // At split points actual search starts from here 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; } - // At Root and at first iteration do a PV search on all the moves - // to score root moves. Otherwise only the first one is the PV. - isPvMove = (PvNode && moveCount <= (Root ? MultiPV + 1000 * (depth <= ONE_PLY) : 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 than 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) @@ -1056,14 +1059,14 @@ split_point_start: // At split points actual search starts from here if (abs(ttValue) < VALUE_KNOWN_WIN) { - Value b = ttValue - depth; + 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, ply); ss->skipNullMove = false; ss->excludedMove = MOVE_NONE; ss->bestMove = MOVE_NONE; - if (v < b) + if (v < rBeta) ext = ONE_PLY; } } @@ -1082,8 +1085,8 @@ 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)); @@ -1114,7 +1117,7 @@ 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) @@ -1124,6 +1127,16 @@ 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); @@ -1145,6 +1158,7 @@ split_point_start: // At split points actual search starts from here // 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 @@ -1165,6 +1179,18 @@ split_point_start: // At split points actual search starts from here 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, ply+1); + doFullDepthSearch = (value > rAlpha); + ss->reduction = DEPTH_ZERO; // Restore original reduction + } + // Step 15. Full depth search if (doFullDepthSearch) { @@ -1272,7 +1298,7 @@ split_point_start: // At split points actual search starts from here && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID)) ThreadsMgr.split(pos, ss, ply, &alpha, beta, &bestValue, depth, - threatMove, mateThreat, moveCount, &mp, PvNode); + threatMove, moveCount, &mp, PvNode); } // Step 19. Check for mate and stalemate @@ -1297,8 +1323,12 @@ split_point_start: // At split points actual search starts from here 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); } } @@ -1442,7 +1472,7 @@ split_point_start: // At split points actual search starts from here // 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()); @@ -1616,28 +1646,16 @@ 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; @@ -1649,10 +1667,10 @@ 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; @@ -1667,21 +1685,15 @@ 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; - - if (*dangerous) - { - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; + *dangerous = moveIsCheck; - 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) { @@ -1709,15 +1721,6 @@ 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); } @@ -1771,8 +1774,8 @@ split_point_start: // At split points actual search starts from here 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)); @@ -1817,19 +1820,6 @@ 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. @@ -1843,6 +1833,7 @@ split_point_start: // At split points actual search starts from here H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after)); } + // current_search_time() returns the number of milliseconds which have passed // since the beginning of the current search. @@ -1866,7 +1857,7 @@ 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(); } @@ -1903,10 +1894,7 @@ 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; @@ -1945,11 +1933,8 @@ 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; @@ -1984,20 +1969,12 @@ 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 } @@ -2314,7 +2291,7 @@ split_point_start: // At split points actual search starts from here 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) { + int moveCount, MovePicker* mp, bool pvNode) { assert(pos.is_ok()); assert(ply > 0 && ply < PLY_MAX); assert(*bestValue >= -VALUE_INFINITE); @@ -2349,7 +2326,6 @@ split_point_start: // At split points actual search starts from here splitPoint.ply = ply; splitPoint.depth = depth; splitPoint.threatMove = threatMove; - splitPoint.mateThreat = mateThreat; splitPoint.alpha = *alpha; splitPoint.beta = beta; splitPoint.pvNode = pvNode; @@ -2463,13 +2439,13 @@ 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)) { @@ -2493,7 +2469,7 @@ 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(); @@ -2513,11 +2489,10 @@ 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. It is called at each iteration - // or after a new pv is found. - - std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) { + // formatted according to UCI specification. + std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, + Value beta, int pvIdx) { std::stringstream s, l; Move* m = pv; @@ -2526,7 +2501,7 @@ split_point_start: // At split points actual search starts from here s << "info depth " << depth << " seldepth " << int(m - pv) - << " multipv " << pvLine + 1 + << " multipv " << pvIdx + 1 << " score " << value_to_uci(pv_score) << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "") << speed_to_uci(pos.nodes_searched()) @@ -2563,4 +2538,46 @@ split_point_start: // At split points actual search starts from here } } + + // 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