X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=3f8436415358e04840d4f54736446ae82efa7874;hp=b3418b257351f6bbe051a913427c6357598b1e95;hb=626b1f8c6adc6c6b1bd7dc30109cd7fa5f3c44d8;hpb=0f50f10327bc1a53d656d5d8c918a9ee413e5e84 diff --git a/src/search.cpp b/src/search.cpp index b3418b25..3f843641 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2009 Marco Costalba + Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -84,10 +84,10 @@ namespace { void put_threads_to_sleep(); void idle_loop(int threadID, SplitPoint* waitSp); bool split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, int* moves, MovePicker* mp, int master, bool pvNode); + Depth depth, bool mateThreat, int* moves, MovePicker* mp, int master, bool pvNode); private: - friend void poll(SearchStack ss[], int ply); + friend void poll(); int ActiveThreads; volatile bool AllThreadsShouldExit, AllThreadsShouldSleep; @@ -165,7 +165,7 @@ namespace { const Depth RazorDepth = 4 * OnePly; // Dynamic razoring margin based on depth - inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * d); } + inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); } // Step 8. Null move search with verification search @@ -182,14 +182,13 @@ namespace { const Depth IIDDepthAtPVNodes = 5 * OnePly; const Depth IIDDepthAtNonPVNodes = 8 * OnePly; - // Internal iterative deepening margin. At Non-PV nodes - // we do an internal iterative deepening - // search when the static evaluation is at most IIDMargin below beta. + // At Non-PV nodes we do an internal iterative deepening search + // when the static evaluation is at most IIDMargin below beta. const Value IIDMargin = Value(0x100); // Step 11. Decide the new search depth - // Extensions. Configurable UCI options. + // Extensions. Configurable UCI options // Array index 0 is used at non-PV nodes, index 1 at PV nodes. Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2]; Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2]; @@ -208,11 +207,11 @@ namespace { const Value FutilityMarginQS = Value(0x80); // Futility lookup tables (initialized at startup) and their getter functions - int32_t FutilityMarginsMatrix[14][64]; // [depth][moveNumber] + int32_t FutilityMarginsMatrix[16][64]; // [depth][moveNumber] int FutilityMoveCountArray[32]; // [depth] - inline Value futility_margin(Depth d, int mn) { return Value(d < 7*OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); } - inline int futility_move_count(Depth d) { return d < 16*OnePly ? FutilityMoveCountArray[d] : 512; } + inline Value futility_margin(Depth d, int mn) { return Value(d < 7 * OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); } + inline int futility_move_count(Depth d) { return d < 16 * OnePly ? FutilityMoveCountArray[d] : 512; } // Step 14. Reduced search @@ -223,7 +222,7 @@ namespace { inline Depth pv_reduction(Depth d, int mn) { return (Depth) PVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; } inline Depth nonpv_reduction(Depth d, int mn) { return (Depth) NonPVReductionMatrix[Min(d / 2, 63)][Min(mn, 63)]; } - // Step. Common adjustments + // Common adjustments // Search depth at iteration 1 const Depth InitialDepth = OnePly; @@ -233,7 +232,7 @@ namespace { const Value EasyMoveMargin = Value(0x200); // Last seconds noise filtering (LSN) - const bool UseLSNFiltering = true; + const bool UseLSNFiltering = false; const int LSNTime = 4000; // In milliseconds const Value LSNValue = value_from_centipawns(200); bool loseOnTime = false; @@ -241,7 +240,7 @@ namespace { /// Global variables - // Iteration counters + // Iteration counter int Iteration; // Scores and number of times the best move changed for each iteration @@ -255,38 +254,32 @@ namespace { int MultiPV; // Time managment variables - int RootMoveNumber; - int SearchStartTime; - int MaxNodes, MaxDepth; - int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime, ExactMaxTime; + int SearchStartTime, MaxNodes, MaxDepth, MaxSearchTime; + int AbsoluteMaxSearchTime, ExtraSearchTime, ExactMaxTime; bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit; - bool AbortSearch, Quit; - bool AspirationFailLow; - - // Show current line? - bool ShowCurrentLine; + bool FirstRootMove, AbortSearch, Quit, AspirationFailLow; // Log file bool UseLogFile; std::ofstream LogFile; - // MP related variables + // Multi-threads related variables Depth MinimumSplitDepth; int MaxThreadsPerSplitPoint; ThreadsManager TM; - // Node counters, used only by thread[0] but try to keep in different - // cache lines (64 bytes each) from the heavy SMP read accessed variables. + // Node counters, used only by thread[0] but try to keep in different cache + // lines (64 bytes each) from the heavy multi-thread read accessed variables. int NodesSincePoll; int NodesBetweenPolls = 30000; // History table History H; - /// Functions + /// Local functions Value id_loop(const Position& pos, Move searchMoves[]); - Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta); + Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr); Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE); Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); @@ -301,7 +294,7 @@ namespace { Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*); bool ok_to_do_nullmove(const Position& pos); bool ok_to_prune(const Position& pos, Move m, Move threat); - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); + bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply, bool allowNullmove); Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); void update_killers(Move m, SearchStack& ss); @@ -309,10 +302,11 @@ namespace { int current_search_time(); int nps(); - void poll(SearchStack ss[], int ply); + void poll(); void ponderhit(); void wait_for_stop_or_ponderhit(); void init_ss_array(SearchStack ss[]); + void print_pv_info(const Position& pos, SearchStack ss[], Value alpha, Value beta, Value value); #if !defined(_MSC_VER) void *init_thread(void *threadID); @@ -340,9 +334,10 @@ int64_t nodes_searched() { return TM.nodes_searched(); } int perft(Position& pos, Depth depth) { + StateInfo st; Move move; int sum = 0; - MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H); + MovePicker mp(pos, MOVE_NONE, depth, H); // If we are at the last ply we don't need to do and undo // the moves, just to count them. @@ -356,7 +351,6 @@ int perft(Position& pos, Depth depth) CheckInfo ci(pos); while ((move = mp.get_next_move()) != MOVE_NONE) { - StateInfo st; pos.do_move(move, st, ci, pos.move_is_check(move, ci)); sum += perft(pos, depth - OnePly); pos.undo_move(move); @@ -375,9 +369,10 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, int maxNodes, int maxTime, Move searchMoves[]) { // Initialize global search variables - StopOnPonderhit = AbortSearch = Quit = false; - AspirationFailLow = false; + StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false; + MaxSearchTime = AbsoluteMaxSearchTime = ExtraSearchTime = 0; NodesSincePoll = 0; + TM.resetNodeCounters(); SearchStartTime = get_system_time(); ExactMaxTime = maxTime; MaxDepth = maxDepth; @@ -389,11 +384,10 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, // Look for a book move, only during games, not tests if (UseTimeManagement && get_option_value_bool("OwnBook")) { - Move bookMove; if (get_option_value_string("Book File") != OpeningBook.file_name()) OpeningBook.open(get_option_value_string("Book File")); - bookMove = OpeningBook.get_move(pos); + Move bookMove = OpeningBook.get_move(pos); if (bookMove != MOVE_NONE) { if (PonderSearch) @@ -404,46 +398,37 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, } } - TM.resetNodeCounters(); - + // Reset loseOnTime flag at the beginning of a new game if (button_was_pressed("New Game")) - loseOnTime = false; // Reset at the beginning of a new game + loseOnTime = false; // Read UCI option values TT.set_size(get_option_value_int("Hash")); if (button_was_pressed("Clear Hash")) TT.clear(); - bool PonderingEnabled = get_option_value_bool("Ponder"); - MultiPV = get_option_value_int("MultiPV"); - - CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)")); - CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)")); - + CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)")); + CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)")); SingleEvasionExtension[1] = Depth(get_option_value_int("Single Evasion Extension (PV nodes)")); SingleEvasionExtension[0] = Depth(get_option_value_int("Single Evasion Extension (non-PV nodes)")); - PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)")); PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)")); + PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)")); + PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)")); + PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)")); + PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)")); + MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)")); + MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)")); + + MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly; + MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point"); + MultiPV = get_option_value_int("MultiPV"); + Chess960 = get_option_value_bool("UCI_Chess960"); + UseLogFile = get_option_value_bool("Use Search Log"); - PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)")); - PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)")); - - PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)")); - PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)")); - - MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)")); - MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)")); - - Chess960 = get_option_value_bool("UCI_Chess960"); - ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine"); - UseLogFile = get_option_value_bool("Use Search Log"); if (UseLogFile) LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app); - MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly; - MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point"); - read_weights(pos.side_to_move()); // Set the number of active threads @@ -452,10 +437,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, { TM.set_active_threads(newActiveThreads); init_eval(TM.active_threads()); - // HACK: init_eval() destroys the static castleRightsMask[] array in the - // Position class. The below line repairs the damage. - Position p(pos.to_fen()); - assert(pos.is_ok()); } // Wake up sleeping threads @@ -493,14 +474,15 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, } } - if (PonderingEnabled) + if (get_option_value_bool("Ponder")) { MaxSearchTime += MaxSearchTime / 4; MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime); } } - // Set best NodesBetweenPolls interval + // Set best NodesBetweenPolls interval to avoid lagging under + // heavy time pressure. if (MaxNodes) NodesBetweenPolls = Min(MaxNodes, 30000); else if (myTime && myTime < 1000) @@ -510,7 +492,7 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, else NodesBetweenPolls = 30000; - // Write information to search log file + // Write search information to log file if (UseLogFile) LogFile << "Searching: " << pos.to_fen() << endl << "infinite: " << infinite @@ -519,7 +501,7 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, << " increment: " << myIncrement << " moves to go: " << movesToGo << endl; - // LSN filtering. Used only for developing purpose. Disabled by default. + // LSN filtering. Used only for developing purposes, disabled by default if ( UseLSNFiltering && loseOnTime) { @@ -574,10 +556,11 @@ void init_search() { } // Init futility margins array - for (int i = 0; i < 14; i++) // i == depth (OnePly = 2) + for (int i = 0; i < 16; i++) // i == depth (OnePly = 2) for (int j = 0; j < 64; j++) // j == moveNumber { - FutilityMarginsMatrix[i][j] = (i < 2 ? 0 : 112 * bitScanReverse32(i * i / 2)) - 8 * j; // FIXME: test using log instead of BSR + // FIXME: test using log instead of BSR + FutilityMarginsMatrix[i][j] = (i < 2 ? 0 : 112 * bitScanReverse32(i * i / 2)) - 8 * j; } // Init futility move count array @@ -614,8 +597,10 @@ namespace { Position p(pos); SearchStack ss[PLY_MAX_PLUS_2]; + Move EasyMove = MOVE_NONE; + Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; - // searchMoves are verified, copied, scored and sorted + // Moves to search are verified, copied, scored and sorted RootMoveList rml(p, searchMoves); // Handle special case of searching on a mate/stale position @@ -624,12 +609,13 @@ namespace { if (PonderSearch) wait_for_stop_or_ponderhit(); - return pos.is_check()? -VALUE_MATE : VALUE_DRAW; + return pos.is_check() ? -VALUE_MATE : VALUE_DRAW; } - // Print RootMoveList c'tor startup scoring to the standard output, - // so that we print information also for iteration 1. - cout << "info depth " << 1 << "\ninfo depth " << 1 + // Print RootMoveList startup scoring to the standard output, + // so to output information also for iteration 1. + cout << "info depth " << 1 + << "\ninfo depth " << 1 << " score " << value_to_string(rml.get_move_score(0)) << " time " << current_search_time() << " nodes " << TM.nodes_searched() @@ -644,7 +630,6 @@ namespace { Iteration = 1; // Is one move significantly better than others after initial scoring ? - Move EasyMove = MOVE_NONE; if ( rml.move_count() == 1 || rml.get_move_score(0) > rml.get_move_score(1) + EasyMoveMargin) EasyMove = rml.get_move(0); @@ -653,17 +638,12 @@ namespace { while (Iteration < PLY_MAX) { // Initialize iteration - rml.sort(); Iteration++; BestMoveChangesByIteration[Iteration] = 0; - if (Iteration <= 5) - ExtraSearchTime = 0; cout << "info depth " << Iteration << endl; - // Calculate dynamic search window based on previous iterations - Value alpha, beta; - + // Calculate dynamic aspiration window based on previous iterations if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN) { int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2]; @@ -675,14 +655,9 @@ namespace { alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE); beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE); } - else - { - alpha = - VALUE_INFINITE; - beta = VALUE_INFINITE; - } - // Search to the current depth - Value value = root_search(p, ss, rml, alpha, beta); + // Search to the current depth, rml is updated and sorted, alpha and beta could change + value = root_search(p, ss, rml, &alpha, &beta); // Write PV to transposition table, in case the relevant entries have // been overwritten during the search. @@ -694,7 +669,7 @@ namespace { //Save info about search result ValueByIteration[Iteration] = value; - // Drop the easy move if it differs from the new best move + // Drop the easy move if differs from the new best move if (ss[0].pv[0] != EasyMove) EasyMove = MOVE_NONE; @@ -714,7 +689,7 @@ namespace { && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) stopSearch = true; - // Stop search early if one move seems to be much better than the rest + // Stop search early if one move seems to be much better than the others int64_t nodes = TM.nodes_searched(); if ( Iteration >= 8 && EasyMove == ss[0].pv[0] @@ -737,10 +712,10 @@ namespace { if (stopSearch) { - if (!PonderSearch) - break; - else + if (PonderSearch) StopOnPonderhit = true; + else + break; } } @@ -748,8 +723,6 @@ namespace { break; } - rml.sort(); - // If we are pondering or in infinite search, we shouldn't print the // best move before we are told to do so. if (!AbortSearch && (PonderSearch || InfiniteSearch)) @@ -767,7 +740,11 @@ namespace { ss[0].pv[0] = rml.get_move(0); ss[0].pv[1] = MOVE_NONE; } + + assert(ss[0].pv[0] != MOVE_NONE); + cout << "bestmove " << ss[0].pv[0]; + if (ss[0].pv[1] != MOVE_NONE) cout << " ponder " << ss[0].pv[1]; @@ -787,7 +764,9 @@ namespace { StateInfo st; p.do_move(ss[0].pv[0], st); - LogFile << "\nPonder move: " << move_to_san(p, ss[0].pv[1]) << endl; + LogFile << "\nPonder move: " + << move_to_san(p, ss[0].pv[1]) // Works also with MOVE_NONE + << endl; } return rml.get_move_score(0); } @@ -795,41 +774,56 @@ namespace { // root_search() is the function which searches the root node. It is // similar to search_pv except that it uses a different move ordering - // scheme and prints some information to the standard output. + // scheme, prints some information to the standard output and handles + // the fail low/high loops. - Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta) { + Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr) { + EvalInfo ei; + StateInfo st; + CheckInfo ci(pos); int64_t nodes; Move move; - StateInfo st; Depth depth, ext, newDepth; - Value value; - CheckInfo ci(pos); - int researchCount = 0; - bool moveIsCheck, captureOrPromotion, dangerous; - Value alpha = oldAlpha; - bool isCheck = pos.is_check(); + Value value, alpha, beta; + bool isCheck, moveIsCheck, captureOrPromotion, dangerous; + int researchCountFH, researchCountFL; - // Evaluate the position statically - EvalInfo ei; - ss[0].eval = !isCheck ? evaluate(pos, ei, 0) : VALUE_NONE; + researchCountFH = researchCountFL = 0; + alpha = *alphaPtr; + beta = *betaPtr; + isCheck = pos.is_check(); + + // Step 1. Initialize node and poll (omitted at root, but I can see no good reason for this, FIXME) + // Step 2. Check for aborted search (omitted at root, because we do not initialize root node) + // Step 3. Mate distance pruning (omitted at root) + // Step 4. Transposition table lookup (omitted at root) - while (1) // Fail low loop + // Step 5. Evaluate the position statically + // At root we do this only to get reference value for child nodes + if (!isCheck) + ss[0].eval = evaluate(pos, ei, 0); + else + ss[0].eval = VALUE_NONE; // HACK because we do not initialize root node + + // Step 6. Razoring (omitted at root) + // Step 7. Static null move pruning (omitted at root) + // Step 8. Null move search with verification search (omitted at root) + // Step 9. Internal iterative deepening (omitted at root) + + // Step extra. Fail low loop + // We start with small aspiration window and in case of fail low, we research + // with bigger window until we are not failing low anymore. + while (1) { + // Sort the moves before to (re)search + rml.sort(); - // Loop through all the moves in the root move list + // Step 10. Loop through all moves in the root move list for (int i = 0; i < rml.move_count() && !AbortSearch; i++) { - if (alpha >= beta) - { - // We failed high, invalidate and skip next moves, leave node-counters - // and beta-counters as they are and quickly return, we will try to do - // a research at the next iteration with a bigger aspiration window. - rml.set_move_score(i, -VALUE_INFINITE); - continue; - } - - RootMoveNumber = i + 1; + // This is used by time management + FirstRootMove = (i == 0); // Save the current node count before the move is searched nodes = TM.nodes_searched(); @@ -843,100 +837,94 @@ namespace { if (current_search_time() >= 1000) cout << "info currmove " << move - << " currmovenumber " << RootMoveNumber << endl; + << " currmovenumber " << i + 1 << endl; - // Decide search depth for this move moveIsCheck = pos.move_is_check(move); captureOrPromotion = pos.move_is_capture_or_promotion(move); + + // Step 11. Decide the new search depth depth = (Iteration - 2) * OnePly + InitialDepth; ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous); newDepth = depth + ext; + // Step 12. Futility pruning (omitted at root) + + // Step extra. Fail high loop + // If move fails high, we research with bigger window until we are not failing + // high anymore. value = - VALUE_INFINITE; - while (1) // Fail high loop + while (1) { - - // Make the move, and search it + // Step 13. Make the move pos.do_move(move, st, ci, moveIsCheck); + // Step extra. pv search + // We do pv search for first moves (i < MultiPV) + // and for fail high research (value > alpha) if (i < MultiPV || value > alpha) { // Aspiration window is disabled in multi-pv case if (MultiPV > 1) alpha = -VALUE_INFINITE; + // Full depth PV search, done on first move or after a fail high value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0); } else { - // Try to reduce non-pv search depth by one ply if move seems not problematic, - // if the move fails high will be re-searched at full depth. + // Step 14. Reduced search + // if the move fails high will be re-searched at full depth bool doFullDepthSearch = true; - if ( depth >= 3*OnePly // FIXME was newDepth + if ( depth >= 3 * OnePly && !dangerous && !captureOrPromotion && !move_is_castle(move)) { - ss[0].reduction = pv_reduction(depth, RootMoveNumber - MultiPV + 1); + ss[0].reduction = pv_reduction(depth, i - MultiPV + 2); if (ss[0].reduction) { + // Reduced depth non-pv search using alpha as upperbound value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0); doFullDepthSearch = (value > alpha); } } + // Step 15. Full depth search if (doFullDepthSearch) { + // Full depth non-pv search using alpha as upperbound ss[0].reduction = Depth(0); value = -search(pos, ss, -alpha, newDepth, 1, true, 0); + // If we are above alpha then research at same depth but as PV + // to get a correct score or eventually a fail high above beta. if (value > alpha) value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0); } } + // Step 16. Undo move pos.undo_move(move); // Can we exit fail high loop ? if (AbortSearch || value < beta) break; - // We are failing high and going to do a research. It's important to update score - // before research in case we run out of time while researching. + // We are failing high and going to do a research. It's important to update + // the score before research in case we run out of time while researching. rml.set_move_score(i, value); update_pv(ss, 0); TT.extract_pv(pos, ss[0].pv, PLY_MAX); rml.set_move_pv(i, ss[0].pv); - // Print search information to the standard output - cout << "info depth " << Iteration - << " score " << value_to_string(value) - << ((value >= beta) ? " lowerbound" : - ((value <= alpha)? " upperbound" : "")) - << " time " << current_search_time() - << " nodes " << TM.nodes_searched() - << " nps " << nps() - << " pv "; - - for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) - cout << ss[0].pv[j] << " "; - - cout << endl; - - if (UseLogFile) - { - ValueType type = (value >= beta ? VALUE_TYPE_LOWER - : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT)); - - LogFile << pretty_pv(pos, current_search_time(), Iteration, - TM.nodes_searched(), value, type, ss[0].pv) << endl; - } + // Print information to the standard output + print_pv_info(pos, ss, alpha, beta, value); // Prepare for a research after a fail high, each time with a wider window - researchCount++; - beta = Min(beta + AspirationDelta * (1 << researchCount), VALUE_INFINITE); + *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE); + researchCountFH++; } // End of fail high loop @@ -949,14 +937,16 @@ namespace { break; // Remember beta-cutoff and searched nodes counts for this move. The - // info is used to sort the root moves at the next iteration. + // info is used to sort the root moves for the next iteration. int64_t our, their; TM.get_beta_counters(pos.side_to_move(), our, their); rml.set_beta_counters(i, our, their); rml.set_move_nodes(i, TM.nodes_searched() - nodes); assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE); + assert(value < beta); + // Step 17. Check for new best move if (value <= alpha && i >= MultiPV) rml.set_move_score(i, -VALUE_INFINITE); else @@ -977,29 +967,10 @@ namespace { if (i > 0) BestMoveChangesByIteration[Iteration]++; - // Print search information to the standard output - cout << "info depth " << Iteration - << " score " << value_to_string(value) - << ((value >= beta) ? " lowerbound" : - ((value <= alpha)? " upperbound" : "")) - << " time " << current_search_time() - << " nodes " << TM.nodes_searched() - << " nps " << nps() - << " pv "; - - for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) - cout << ss[0].pv[j] << " "; - - cout << endl; + // Print information to the standard output + print_pv_info(pos, ss, alpha, beta, value); - if (UseLogFile) - { - ValueType type = (value >= beta ? VALUE_TYPE_LOWER - : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT)); - - LogFile << pretty_pv(pos, current_search_time(), Iteration, - TM.nodes_searched(), value, type, ss[0].pv) << endl; - } + // Raise alpha to setup proper non-pv search upper bound if (value > alpha) alpha = value; } @@ -1010,7 +981,7 @@ namespace { { cout << "info multipv " << j + 1 << " score " << value_to_string(rml.get_move_score(j)) - << " depth " << ((j <= i)? Iteration : Iteration - 1) + << " depth " << (j <= i ? Iteration : Iteration - 1) << " time " << current_search_time() << " nodes " << TM.nodes_searched() << " nps " << nps() @@ -1021,29 +992,31 @@ namespace { cout << endl; } - alpha = rml.get_move_score(Min(i, MultiPV-1)); + alpha = rml.get_move_score(Min(i, MultiPV - 1)); } } // PV move or new best move - assert(alpha >= oldAlpha); + assert(alpha >= *alphaPtr); - AspirationFailLow = (alpha == oldAlpha); + AspirationFailLow = (alpha == *alphaPtr); if (AspirationFailLow && StopOnPonderhit) StopOnPonderhit = false; } // Can we exit fail low loop ? - if (AbortSearch || alpha > oldAlpha) + if (AbortSearch || !AspirationFailLow) break; // Prepare for a research after a fail low, each time with a wider window - researchCount++; - alpha = Max(alpha - AspirationDelta * (1 << researchCount), -VALUE_INFINITE); - oldAlpha = alpha; + *alphaPtr = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE); + researchCountFL++; } // Fail low loop + // Sort the moves before to return + rml.sort(); + return alpha; } @@ -1124,14 +1097,13 @@ namespace { tte = TT.retrieve(pos.get_key()); } - // Step 10. Loop through moves - // Loop through all legal moves until no moves remain or a beta cutoff occurs - // Initialize a MovePicker object for the current position mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]); CheckInfo ci(pos); + // Step 10. Loop through moves + // Loop through all legal moves until no moves remain or a beta cutoff occurs while ( alpha < beta && (move = mp.get_next_move()) != MOVE_NONE && !TM.thread_should_stop(threadID)) @@ -1186,7 +1158,7 @@ namespace { // if the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; - if ( depth >= 3*OnePly + if ( depth >= 3 * OnePly && !dangerous && !captureOrPromotion && !move_is_castle(move) @@ -1239,7 +1211,7 @@ namespace { && !AbortSearch && !TM.thread_should_stop(threadID) && TM.split(pos, ss, ply, &alpha, beta, &bestValue, - depth, &moveCount, &mp, threadID, true)) + depth, mateThreat, &moveCount, &mp, threadID, true)) break; } @@ -1327,7 +1299,7 @@ namespace { tte = TT.retrieve(posKey); ttMove = (tte ? tte->move() : MOVE_NONE); - if (tte && ok_to_use_TT(tte, depth, beta, ply)) + if (tte && ok_to_use_TT(tte, depth, beta, ply, allowNullmove)) { ss[ply].currentMove = ttMove; // Can be MOVE_NONE return value_from_tt(tte->value(), ply); @@ -1348,27 +1320,31 @@ namespace { } // Step 6. Razoring - if ( !value_is_mate(beta) + if ( refinedValue < beta - razor_margin(depth) + && ttMove == MOVE_NONE + && ss[ply - 1].currentMove != MOVE_NULL + && depth < RazorDepth && !isCheck - && depth < RazorDepth - && refinedValue < beta - razor_margin(depth) - && ss[ply - 1].currentMove != MOVE_NULL - && ttMove == MOVE_NONE + && !value_is_mate(beta) && !pos.has_pawn_on_7th(pos.side_to_move())) { Value rbeta = beta - razor_margin(depth); Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID); if (v < rbeta) - return v; //FIXME: Logically should be: return (v + razor_margin(depth)); + // Logically we should return (v + razor_margin(depth)), but + // surprisingly this did slightly weaker in tests. + return v; } // Step 7. Static null move pruning // We're betting that the opponent doesn't have a move that will reduce - // the score by more than fuility_margin(depth) if we do a null move. - if ( !isCheck - && allowNullmove - && depth < RazorDepth - && refinedValue - futility_margin(depth, 0) >= beta) + // the score by more than futility_margin(depth) if we do a null move. + if ( allowNullmove + && depth < RazorDepth + && !isCheck + && !value_is_mate(beta) + && ok_to_do_nullmove(pos) + && refinedValue >= beta + futility_margin(depth, 0)) return refinedValue - futility_margin(depth, 0); // Step 8. Null move search with verification search @@ -1384,8 +1360,6 @@ namespace { { ss[ply].currentMove = MOVE_NULL; - pos.do_null_move(st); - // Null move dynamic reduction based on depth int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0); @@ -1393,19 +1367,30 @@ namespace { if (refinedValue - beta > PawnValueMidgame) R++; + pos.do_null_move(st); + nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID); pos.undo_null_move(); if (nullValue >= beta) { - if (depth < 6 * OnePly) - return beta; + // Do not return unproven mate scores + if (nullValue >= value_mate_in(PLY_MAX)) + nullValue = beta; + + // Do zugzwang verification search for high depths, don't store in TT + // if search was stopped. + if ( ( depth < 6 * OnePly + || search(pos, ss, beta, depth-5*OnePly, ply, false, threadID) >= beta) + && !AbortSearch + && !TM.thread_should_stop(threadID)) + { + assert(value_to_tt(nullValue, ply) == nullValue); - // Do zugzwang verification search - Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID); - if (v >= beta) - return beta; + TT.store(posKey, nullValue, VALUE_TYPE_NS_LO, depth, MOVE_NONE); + return nullValue; + } } else { // The null move failed low, which means that we may be faced with // some kind of threat. If the previous move was reduced, check if @@ -1435,13 +1420,12 @@ namespace { tte = TT.retrieve(posKey); } - // Step 10. Loop through moves - // Loop through all legal moves until no moves remain or a beta cutoff occurs - // Initialize a MovePicker object for the current position MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], beta); CheckInfo ci(pos); + // Step 10. Loop through moves + // Loop through all legal moves until no moves remain or a beta cutoff occurs while ( bestValue < beta && (move = mp.get_next_move()) != MOVE_NONE && !TM.thread_should_stop(threadID)) @@ -1464,7 +1448,7 @@ namespace { if ( depth >= SingularExtensionDepthAtNonPVNodes && tte && move == tte->move() - && !excludedMove // Do not allow recursive single-reply search + && !excludedMove // Do not allow recursive singular extension search && ext < OnePly && is_lower_bound(tte->type()) && tte->depth() >= depth - 3 * OnePly) @@ -1514,8 +1498,8 @@ namespace { // Step 13. Make the move pos.do_move(move, st, ci, moveIsCheck); - // Step 14. Reduced search - // if the move fails high will be re-searched at full depth. + // Step 14. Reduced search, if the move fails high + // will be re-searched at full depth. bool doFullDepthSearch = true; if ( depth >= 3*OnePly @@ -1564,16 +1548,16 @@ namespace { && !AbortSearch && !TM.thread_should_stop(threadID) && TM.split(pos, ss, ply, NULL, beta, &bestValue, - depth, &moveCount, &mp, threadID, false)) + depth, mateThreat, &moveCount, &mp, threadID, false)) break; } // Step 19. Check for mate and stalemate - // All legal moves have been searched and if there were + // All legal moves have been searched and if there are // no legal moves, it must be mate or stalemate. - // If one move was excluded return fail low. + // If one move was excluded return fail low score. if (!moveCount) - return excludedMove ? beta - 1 : (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); + return excludedMove ? beta - 1 : (isCheck ? value_mated_in(ply) : VALUE_DRAW); // Step 20. Update tables // If the search is not aborted, update the transposition table, @@ -1641,7 +1625,7 @@ namespace { tte = TT.retrieve(pos.get_key()); ttMove = (tte ? tte->move() : MOVE_NONE); - if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) + if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply, true)) { assert(tte->type() != VALUE_TYPE_EVAL); @@ -1682,7 +1666,7 @@ namespace { alpha = bestValue; // If we are near beta then try to get a cutoff pushing checks a bit further - bool deepChecks = depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8; + bool deepChecks = (depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8); // Initialize a MovePicker object for the current position, and prepare // to search the moves. Because the depth is <= 0 here, only captures, @@ -1693,8 +1677,7 @@ namespace { enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; futilityBase = staticValue + FutilityMarginQS + ei.futilityMargin[pos.side_to_move()]; - // Loop through the moves until no moves remain or a beta cutoff - // occurs. + // Loop through the moves until no moves remain or a beta cutoff occurs while ( alpha < beta && (move = mp.get_next_move()) != MOVE_NONE) { @@ -1763,7 +1746,7 @@ namespace { // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (!moveCount && pos.is_check()) // Mate! + if (!moveCount && isCheck) // Mate! return value_mated_in(ply); // Update transposition table @@ -1800,7 +1783,6 @@ namespace { // splitting, we don't have to repeat all this work in sp_search(). We // also don't need to store anything to the hash table here: This is taken // care of after we return from the split point. - // FIXME: We are currently ignoring mateThreat flag here void sp_search(SplitPoint* sp, int threadID) { @@ -1837,7 +1819,7 @@ namespace { captureOrPromotion = pos.move_is_capture_or_promotion(move); // Step 11. Decide the new search depth - ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous); + ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous); newDepth = sp->depth - OnePly + ext; // Update current move @@ -1935,7 +1917,6 @@ namespace { // don't have to repeat all this work in sp_search_pv(). We also don't // need to store anything to the hash table here: This is taken care of // after we return from the split point. - // FIXME: We are ignoring mateThreat flag! void sp_search_pv(SplitPoint* sp, int threadID) { @@ -1971,7 +1952,7 @@ namespace { captureOrPromotion = pos.move_is_capture_or_promotion(move); // Step 11. Decide the new search depth - ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous); + ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous); newDepth = sp->depth - OnePly + ext; // Update current move @@ -2070,7 +2051,7 @@ namespace { NodesSincePoll++; if (NodesSincePoll >= NodesBetweenPolls) { - poll(ss, ply); + poll(); NodesSincePoll = 0; } } @@ -2325,14 +2306,18 @@ namespace { } - // ok_to_use_TT() returns true if a transposition table score - // can be used at a given point in search. + // ok_to_use_TT() returns true if a transposition table score can be used at a + // given point in search. To avoid zugzwang issues TT cutoffs at the root node + // of a null move verification search are not allowed if the TT value was found + // by a null search, this is implemented testing allowNullmove and TT entry type. - bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) { + bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply, bool allowNullmove) { Value v = value_from_tt(tte->value(), ply); - return ( tte->depth() >= depth + return (allowNullmove || !(tte->type() & VALUE_TYPE_NULL)) + + && ( tte->depth() >= depth || v >= Max(value_mate_in(PLY_MAX), beta) || v < Min(value_mated_in(PLY_MAX), beta)) @@ -2433,7 +2418,7 @@ namespace { // looks at the time consumed so far and decides if it's time to abort the // search. - void poll(SearchStack ss[], int ply) { + void poll() { static int lastInfoTime; int t = current_search_time(); @@ -2484,23 +2469,13 @@ namespace { cout << "info nodes " << TM.nodes_searched() << " nps " << nps() << " time " << t << " hashfull " << TT.full() << endl; - - // We only support current line printing in single thread mode - if (ShowCurrentLine && TM.active_threads() == 1) - { - cout << "info currline"; - for (int p = 0; p < ply; p++) - cout << " " << ss[p].currentMove; - - cout << endl; - } } // Should we stop the search? if (PonderSearch) return; - bool stillAtFirstMove = RootMoveNumber == 1 + bool stillAtFirstMove = FirstRootMove && !AspirationFailLow && t > MaxSearchTime + ExtraSearchTime; @@ -2523,7 +2498,7 @@ namespace { int t = current_search_time(); PonderSearch = false; - bool stillAtFirstMove = RootMoveNumber == 1 + bool stillAtFirstMove = FirstRootMove && !AspirationFailLow && t > MaxSearchTime + ExtraSearchTime; @@ -2574,6 +2549,36 @@ namespace { } + // print_pv_info() prints to standard output and eventually to log file information on + // the current PV line. It is called at each iteration or after a new pv is found. + + void print_pv_info(const Position& pos, SearchStack ss[], Value alpha, Value beta, Value value) { + + cout << "info depth " << Iteration + << " score " << value_to_string(value) + << ((value >= beta) ? " lowerbound" : + ((value <= alpha)? " upperbound" : "")) + << " time " << current_search_time() + << " nodes " << TM.nodes_searched() + << " nps " << nps() + << " pv "; + + for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) + cout << ss[0].pv[j] << " "; + + cout << endl; + + if (UseLogFile) + { + ValueType type = (value >= beta ? VALUE_TYPE_LOWER + : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT)); + + LogFile << pretty_pv(pos, current_search_time(), Iteration, + TM.nodes_searched(), value, type, ss[0].pv) << endl; + } + } + + // init_thread() is the function which is called when a new thread is // launched. It simply calls the idle_loop() function with the supplied // threadID. There are two versions of this function; one for POSIX @@ -2882,7 +2887,7 @@ namespace { bool ThreadsManager::split(const Position& p, SearchStack* sstck, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, int* moves, MovePicker* mp, int master, bool pvNode) { + Depth depth, bool mateThreat, int* moves, MovePicker* mp, int master, bool pvNode) { assert(p.is_ok()); assert(sstck != NULL); @@ -2917,6 +2922,7 @@ namespace { splitPoint->stopRequest = false; splitPoint->ply = ply; splitPoint->depth = depth; + splitPoint->mateThreat = mateThreat; splitPoint->alpha = pvNode ? *alpha : beta - 1; splitPoint->beta = beta; splitPoint->pvNode = pvNode;