X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=45e0888d5efbfb58493075fb0b1c6699615046f6;hp=88d3e8a0b02817d2fc7f07b0318ee6af63c6894c;hb=c97104e8540b72ee2c6c9c13d3773d2c0f9ec32f;hpb=2dbc8feae32e923904a9d05ced4847fd8e6f6724 diff --git a/src/search.cpp b/src/search.cpp index 88d3e8a0..45e0888d 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,13 +1,14 @@ /* - Glaurung, a UCI chess playing engine. - Copyright (C) 2004-2008 Tord Romstad + Stockfish, a UCI chess playing engine derived from Glaurung 2.1 + Copyright (C) 2004-2008 Tord Romstad (Glaurung author) + Copyright (C) 2008 Marco Costalba - Glaurung is free software: you can redistribute it and/or modify + Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. - Glaurung is distributed in the hope that it will be useful, + Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. @@ -46,6 +47,23 @@ namespace { /// Types + // The BetaCounterType class is used to order moves at ply one. + // Apart for the first one that has its score, following moves + // normally have score -VALUE_INFINITE, so are ordered according + // to the number of beta cutoffs occurred under their subtree during + // the last iteration. + + struct BetaCounterType { + + BetaCounterType(); + void clear(); + void add(Color us, Depth d, int threadID); + void read(Color us, int64_t& our, int64_t& their); + + int64_t hits[THREAD_MAX][2]; + }; + + // The RootMove class is used for moves at the root at the tree. For each // root move, we store a score, a node count, and a PV (really a refutation // in the case of moves which fail low). @@ -59,6 +77,7 @@ namespace { Value score; int64_t nodes, cumulativeNodes; Move pv[PLY_MAX_PLUS_2]; + int64_t ourBeta, theirBeta; }; @@ -69,16 +88,17 @@ namespace { public: RootMoveList(Position &pos, Move searchMoves[]); - Move get_move(int moveNum) const; - Value get_move_score(int moveNum) const; - void set_move_score(int moveNum, Value score); - void set_move_nodes(int moveNum, int64_t nodes); + inline Move get_move(int moveNum) const; + inline Value get_move_score(int moveNum) const; + inline void set_move_score(int moveNum, Value score); + inline void set_move_nodes(int moveNum, int64_t nodes); + inline void set_beta_counters(int moveNum, int64_t our, int64_t their); void set_move_pv(int moveNum, const Move pv[]); - Move get_move_pv(int moveNum, int i) const; - int64_t get_move_cumulative_nodes(int moveNum) const; - int move_count() const; + inline Move get_move_pv(int moveNum, int i) const; + inline int64_t get_move_cumulative_nodes(int moveNum) const; + inline int move_count() const; Move scan_for_easy_move() const; - void sort(); + inline void sort(); void sort_multipv(int n); private: @@ -105,14 +125,14 @@ namespace { const bool UseIIDAtPVNodes = true; const bool UseIIDAtNonPVNodes = false; + // Use null move driven internal iterative deepening? + bool UseNullDrivenIID = false; + // Internal iterative deepening margin. At Non-PV moves, when // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search // when the static evaluation is at most IIDMargin below beta. const Value IIDMargin = Value(0x100); - // Use easy moves? - const bool UseEasyMove = true; - // Easy move margin. An easy move candidate must be at least this much // better than the second best move. const Value EasyMoveMargin = Value(0x200); @@ -142,16 +162,23 @@ namespace { bool UseQSearchFutilityPruning = true; bool UseFutilityPruning = true; - // Margins for futility pruning in the quiescence search, at frontier - // nodes, and at pre-frontier nodes: - Value FutilityMargin0 = Value(0x80); - Value FutilityMargin1 = Value(0x100); - Value FutilityMargin2 = Value(0x300); + // Margins for futility pruning in the quiescence search, and at frontier + // and near frontier nodes + Value FutilityMarginQS = Value(0x80); + Value FutilityMargins[6] = { Value(0x100), Value(0x200), Value(0x250), + Value(0x2A0), Value(0x340), Value(0x3A0) }; // Razoring + const bool RazorAtDepthOne = false; Depth RazorDepth = 4*OnePly; Value RazorMargin = Value(0x300); + // Last seconds noise filtering (LSN) + bool UseLSNFiltering = false; + bool looseOnTime = false; + int LSNTime = 4 * 1000; // In milliseconds + Value LSNValue = Value(0x200); + // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes. Depth CheckExtension[2] = {OnePly, OnePly}; Depth SingleReplyExtension[2] = {OnePly / 2, OnePly / 2}; @@ -160,27 +187,29 @@ namespace { Depth PawnEndgameExtension[2] = {OnePly, OnePly}; Depth MateThreatExtension[2] = {Depth(0), Depth(0)}; - // Search depth at iteration 1: + // Search depth at iteration 1 const Depth InitialDepth = OnePly /*+ OnePly/2*/; // Node counters int NodesSincePoll; int NodesBetweenPolls = 30000; - // Iteration counter: + // Iteration counters int Iteration; + bool LastIterations; + BetaCounterType BetaCounter; // Scores and number of times the best move changed for each iteration: Value ValueByIteration[PLY_MAX_PLUS_2]; int BestMoveChangesByIteration[PLY_MAX_PLUS_2]; - // MultiPV mode: + // MultiPV mode int MultiPV = 1; // Time managment variables int SearchStartTime; int MaxNodes, MaxDepth; - int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime, TimeAdvantage; + int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime; Move BestRootMove, PonderMove, EasyMove; int RootMoveNumber; bool InfiniteSearch; @@ -220,7 +249,7 @@ namespace { /// Functions - void id_loop(const Position &pos, Move searchMoves[]); + Value id_loop(const Position &pos, Move searchMoves[]); Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml); Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); @@ -230,19 +259,21 @@ namespace { Depth depth, int ply, int threadID); void sp_search(SplitPoint *sp, int threadID); void sp_search_pv(SplitPoint *sp, int threadID); + void init_search_stack(SearchStack& ss); void init_search_stack(SearchStack ss[]); void init_node(const Position &pos, SearchStack ss[], int ply, int threadID); void update_pv(SearchStack ss[], int ply); void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply); bool connected_moves(const Position &pos, Move m1, Move m2); - Depth extension(const Position &pos, Move m, bool pvNode, bool check, - bool singleReply, bool mateThreat); + bool value_is_mate(Value value); + bool move_is_killer(Move m, const SearchStack& ss); + Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* dangerous); bool ok_to_do_nullmove(const Position &pos); bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); bool ok_to_history(const Position &pos, Move m); - void update_history(const Position& pos, Move m, Depth depth, - Move movesSearched[], int moveCount); + void update_history(const Position& pos, Move m, Depth depth, Move movesSearched[], int moveCount); + void update_killers(Move m, SearchStack& ss); bool fail_high_ply_1(); int current_search_time(); @@ -290,12 +321,15 @@ Lock IOLock; History H; // Should be made local? +// The empty search stack +SearchStack EmptySearchStack; + //// //// Functions //// -/// think() is the external interface to Glaurung's search, and is called when +/// think() is the external interface to Stockfish's search, and is called when /// the program receives the UCI 'go' command. It initializes various /// search-related global variables, and calls root_search() @@ -303,29 +337,33 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, int time[], int increment[], int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) { - // Look for a book move: - if(!infinite && !ponder && get_option_value_bool("OwnBook")) { - Move bookMove; - if(get_option_value_string("Book File") != OpeningBook.file_name()) { - OpeningBook.close(); - OpeningBook.open("book.bin"); - } - bookMove = OpeningBook.get_move(pos); - if(bookMove != MOVE_NONE) { - std::cout << "bestmove " << bookMove << std::endl; - return; - } + // Look for a book move + if (!infinite && !ponder && get_option_value_bool("OwnBook")) + { + Move bookMove; + if (get_option_value_string("Book File") != OpeningBook.file_name()) + { + OpeningBook.close(); + OpeningBook.open("book.bin"); + } + bookMove = OpeningBook.get_move(pos); + if (bookMove != MOVE_NONE) + { + std::cout << "bestmove " << bookMove << std::endl; + return; + } } - // Initialize global search variables: + // Initialize global search variables Idle = false; SearchStartTime = get_system_time(); BestRootMove = MOVE_NONE; PonderMove = MOVE_NONE; EasyMove = MOVE_NONE; - for(int i = 0; i < THREAD_MAX; i++) { - Threads[i].nodes = 0ULL; - Threads[i].failHighPly1 = false; + for (int i = 0; i < THREAD_MAX; i++) + { + Threads[i].nodes = 0ULL; + Threads[i].failHighPly1 = false; } NodesSincePoll = 0; InfiniteSearch = infinite; @@ -337,149 +375,163 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, Problem = false; ExactMaxTime = maxTime; - // Read UCI option values: + // Read UCI option values TT.set_size(get_option_value_int("Hash")); - if(button_was_pressed("Clear Hash")) - TT.clear(); + if (button_was_pressed("Clear Hash")) + TT.clear(); + 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[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)")); + SingleReplyExtension[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)")); - SingleReplyExtension[0] = - Depth(get_option_value_int("Single Reply 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)")); - - LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1; - LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1; - ThreatDepth = get_option_value_int("Threat Depth") * OnePly; + SingleReplyExtension[0] = Depth(get_option_value_int("Single Reply 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)")); + + LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1; + LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1; + ThreatDepth = get_option_value_int("Threat Depth") * OnePly; SelectiveDepth = get_option_value_int("Selective Plies") * OnePly; 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); - - UseQSearchFutilityPruning = - get_option_value_bool("Futility Pruning (Quiescence Search)"); - UseFutilityPruning = - get_option_value_bool("Futility Pruning (Main Search)"); - - FutilityMargin0 = - value_from_centipawns(get_option_value_int("Futility Margin 0")); - FutilityMargin1 = - value_from_centipawns(get_option_value_int("Futility Margin 1")); - FutilityMargin2 = - value_from_centipawns(get_option_value_int("Futility Margin 2")); + if (UseLogFile) + LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app); + + UseNullDrivenIID = get_option_value_bool("Null driven IID"); + UseQSearchFutilityPruning = get_option_value_bool("Futility Pruning (Quiescence Search)"); + UseFutilityPruning = get_option_value_bool("Futility Pruning (Main Search)"); + + FutilityMarginQS = value_from_centipawns(get_option_value_int("Futility Margin (Quiescence Search)")); + int fmScale = get_option_value_int("Futility Margin Scale Factor (Main Search)"); + for (int i = 0; i < 6; i++) + FutilityMargins[i] = (FutilityMargins[i] * fmScale) / 100; RazorDepth = (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly; RazorMargin = value_from_centipawns(get_option_value_int("Razoring Margin")); + UseLSNFiltering = get_option_value_bool("LSN filtering"); + LSNTime = get_option_value_int("LSN Time Margin (sec)") * 1000; + LSNValue = value_from_centipawns(get_option_value_int("LSN Value Margin")); + MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly; - MaxThreadsPerSplitPoint = - get_option_value_int("Maximum Number of Threads per Split Point"); + MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point"); read_weights(pos.side_to_move()); int newActiveThreads = get_option_value_int("Threads"); - if(newActiveThreads != ActiveThreads) { - ActiveThreads = newActiveThreads; - init_eval(ActiveThreads); + if (newActiveThreads != ActiveThreads) + { + ActiveThreads = newActiveThreads; + init_eval(ActiveThreads); } // Wake up sleeping threads: wake_sleeping_threads(); - for(int i = 1; i < ActiveThreads; i++) - assert(thread_is_available(i, 0)); + for (int i = 1; i < ActiveThreads; i++) + assert(thread_is_available(i, 0)); // Set thinking time: int myTime = time[side_to_move]; int myIncrement = increment[side_to_move]; - int oppTime = time[1 - side_to_move]; - - TimeAdvantage = myTime - oppTime; - - if(!movesToGo) { // Sudden death time control - if(increment) { - MaxSearchTime = myTime / 30 + myIncrement; - AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100); - } - else { // Blitz game without increment - MaxSearchTime = myTime / 40; - AbsoluteMaxSearchTime = myTime / 8; - } + + if (!movesToGo) // Sudden death time control + { + if (myIncrement) + { + MaxSearchTime = myTime / 30 + myIncrement; + AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100); + } else { // Blitz game without increment + MaxSearchTime = myTime / 30; + AbsoluteMaxSearchTime = myTime / 8; + } } - else { // (x moves) / (y minutes) - if(movesToGo == 1) { - MaxSearchTime = myTime / 2; - AbsoluteMaxSearchTime = Min(myTime / 2, myTime - 500); - } - else { - MaxSearchTime = myTime / Min(movesToGo, 20); - AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3); - } + else // (x moves) / (y minutes) + { + if (movesToGo == 1) + { + MaxSearchTime = myTime / 2; + AbsoluteMaxSearchTime = Min(myTime / 2, myTime - 500); + } else { + MaxSearchTime = myTime / Min(movesToGo, 20); + AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3); + } } - if(PonderingEnabled) { - MaxSearchTime += MaxSearchTime / 4; - MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime); + + if (PonderingEnabled) + { + MaxSearchTime += MaxSearchTime / 4; + MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime); } // Fixed depth or fixed number of nodes? MaxDepth = maxDepth; - if(MaxDepth) - InfiniteSearch = true; // HACK + if (MaxDepth) + InfiniteSearch = true; // HACK MaxNodes = maxNodes; - if(MaxNodes) { - NodesBetweenPolls = Min(MaxNodes, 30000); - InfiniteSearch = true; // HACK + if (MaxNodes) + { + NodesBetweenPolls = Min(MaxNodes, 30000); + InfiniteSearch = true; // HACK } else - NodesBetweenPolls = 30000; + NodesBetweenPolls = 30000; // Write information to search log file: - if(UseLogFile) { - LogFile << "Searching: " << pos.to_fen() << '\n'; - LogFile << "infinite: " << infinite << " ponder: " << ponder - << " time: " << myTime << " increment: " << myIncrement - << " moves to go: " << movesToGo << '\n'; - } + if (UseLogFile) + LogFile << "Searching: " << pos.to_fen() << std::endl + << "infinite: " << infinite + << " ponder: " << ponder + << " time: " << myTime + << " increment: " << myIncrement + << " moves to go: " << movesToGo << std::endl; + // We're ready to start thinking. Call the iterative deepening loop // function: - id_loop(pos, searchMoves); + if (!looseOnTime) + { + Value v = id_loop(pos, searchMoves); + looseOnTime = ( UseLSNFiltering + && myTime < LSNTime + && myIncrement == 0 + && v < -LSNValue); + } + else + { + looseOnTime = false; // reset for next match + while (SearchStartTime + myTime + 1000 > get_system_time()) + ; // wait here + id_loop(pos, searchMoves); // to fail gracefully + } - if(UseLogFile) - LogFile.close(); + if (UseLogFile) + LogFile.close(); - if(Quit) { - OpeningBook.close(); - stop_threads(); - quit_eval(); - exit(0); + if (Quit) + { + OpeningBook.close(); + stop_threads(); + quit_eval(); + exit(0); } - Idle = true; } @@ -489,13 +541,15 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, /// objects. void init_threads() { + volatile int i; + #if !defined(_MSC_VER) pthread_t pthread[1]; #endif - for(i = 0; i < THREAD_MAX; i++) - Threads[i].activeSplitPoints = 0; + for (i = 0; i < THREAD_MAX; i++) + Threads[i].activeSplitPoints = 0; // Initialize global locks: lock_init(&MPLock, NULL); @@ -507,32 +561,35 @@ void init_threads() { pthread_mutex_init(&WaitLock, NULL); pthread_cond_init(&WaitCond, NULL); #else - for(i = 0; i < THREAD_MAX; i++) - SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0); + for (i = 0; i < THREAD_MAX; i++) + SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0); #endif - // All threads except the main thread should be initialized to idle state: - for(i = 1; i < THREAD_MAX; i++) { - Threads[i].stop = false; - Threads[i].workIsWaiting = false; - Threads[i].idle = true; - Threads[i].running = false; + // All threads except the main thread should be initialized to idle state + for (i = 1; i < THREAD_MAX; i++) + { + Threads[i].stop = false; + Threads[i].workIsWaiting = false; + Threads[i].idle = true; + Threads[i].running = false; } - // Launch the helper threads: - for(i = 1; i < THREAD_MAX; i++) { + // Launch the helper threads + for(i = 1; i < THREAD_MAX; i++) + { #if !defined(_MSC_VER) - pthread_create(pthread, NULL, init_thread, (void*)(&i)); + pthread_create(pthread, NULL, init_thread, (void*)(&i)); #else - { DWORD iID[1]; CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID); - } #endif - // Wait until the thread has finished launching: - while(!Threads[i].running); + // Wait until the thread has finished launching: + while (!Threads[i].running); } + + // Init also the empty search stack + init_search_stack(EmptySearchStack); } @@ -540,13 +597,15 @@ void init_threads() { /// helper threads exit cleanly. void stop_threads() { + ActiveThreads = THREAD_MAX; // HACK Idle = false; // HACK wake_sleeping_threads(); AllThreadsShouldExit = true; - for(int i = 1; i < THREAD_MAX; i++) { - Threads[i].stop = true; - while(Threads[i].running); + for (int i = 1; i < THREAD_MAX; i++) + { + Threads[i].stop = true; + while(Threads[i].running); } destroy_split_point_stack(); } @@ -556,9 +615,10 @@ void stop_threads() { /// the current search. int64_t nodes_searched() { + int64_t result = 0ULL; - for(int i = 0; i < ActiveThreads; i++) - result += Threads[i].nodes; + for (int i = 0; i < ActiveThreads; i++) + result += Threads[i].nodes; return result; } @@ -570,7 +630,8 @@ namespace { // been consumed, the user stops the search, or the maximum search depth is // reached. - void id_loop(const Position &pos, Move searchMoves[]) { + Value id_loop(const Position &pos, Move searchMoves[]) { + Position p(pos); SearchStack ss[PLY_MAX_PLUS_2]; @@ -585,115 +646,124 @@ namespace { ValueByIteration[0] = Value(0); ValueByIteration[1] = rml.get_move_score(0); Iteration = 1; + LastIterations = false; EasyMove = rml.scan_for_easy_move(); // Iterative deepening loop - while(!AbortSearch && Iteration < PLY_MAX) { - - // Initialize iteration - rml.sort(); - Iteration++; - BestMoveChangesByIteration[Iteration] = 0; - if(Iteration <= 5) - ExtraSearchTime = 0; - - std::cout << "info depth " << Iteration << std::endl; - - // Search to the current depth - ValueByIteration[Iteration] = root_search(p, ss, rml); - - // Erase the easy move if it differs from the new best move - if(ss[0].pv[0] != EasyMove) - EasyMove = MOVE_NONE; - - Problem = false; - - if(!InfiniteSearch) { - // Time to stop? - bool stopSearch = false; - - // Stop search early if there is only a single legal move: - if(Iteration >= 6 && rml.move_count() == 1) - stopSearch = true; - - // Stop search early when the last two iterations returned a mate - // score: - if(Iteration >= 6 - && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100 - && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) - stopSearch = true; - - // Stop search early if one move seems to be much better than the - // rest: - int64_t nodes = nodes_searched(); - if(Iteration >= 8 && EasyMove == ss[0].pv[0] && - ((rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 && - current_search_time() > MaxSearchTime / 16) || - (rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100 && - current_search_time() > MaxSearchTime / 32))) - stopSearch = true; - - // Add some extra time if the best move has changed during the last - // two iterations: - if(Iteration > 5 && Iteration <= 50) - ExtraSearchTime = - BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2) + - BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3); - - // If we need some more and we are in time advantage take it. - if (ExtraSearchTime > 0 && TimeAdvantage > 2 * MaxSearchTime) - ExtraSearchTime += MaxSearchTime / 2; - - // Stop search if most of MaxSearchTime is consumed at the end of the - // iteration. We probably don't have enough time to search the first - // move at the next iteration anyway. - if(current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128) - stopSearch = true; - - if(stopSearch) { - if(!PonderSearch) - break; - else - StopOnPonderhit = true; - } - } + while (!AbortSearch && Iteration < PLY_MAX) + { + // Initialize iteration + rml.sort(); + Iteration++; + BestMoveChangesByIteration[Iteration] = 0; + if (Iteration <= 5) + ExtraSearchTime = 0; - // Write PV to transposition table, in case the relevant entries have - // been overwritten during the search: - TT.insert_pv(p, ss[0].pv); + std::cout << "info depth " << Iteration << std::endl; - if(MaxDepth && Iteration >= MaxDepth) - break; + // Search to the current depth + ValueByIteration[Iteration] = root_search(p, ss, rml); + + // Erase the easy move if it differs from the new best move + if (ss[0].pv[0] != EasyMove) + EasyMove = MOVE_NONE; + + Problem = false; + + if (!InfiniteSearch) + { + // Time to stop? + bool stopSearch = false; + + // Stop search early if there is only a single legal move: + if (Iteration >= 6 && rml.move_count() == 1) + stopSearch = true; + + // Stop search early when the last two iterations returned a mate score + if ( Iteration >= 6 + && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100 + && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100) + stopSearch = true; + + // Stop search early if one move seems to be much better than the rest + int64_t nodes = nodes_searched(); + if ( Iteration >= 8 + && EasyMove == ss[0].pv[0] + && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 + && current_search_time() > MaxSearchTime / 16) + ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100 + && current_search_time() > MaxSearchTime / 32))) + stopSearch = true; + + // Add some extra time if the best move has changed during the last two iterations + if (Iteration > 5 && Iteration <= 50) + ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2) + + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3); + + // Try to guess if the current iteration is the last one or the last two + LastIterations = (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*58) / 128); + + // Stop search if most of MaxSearchTime is consumed at the end of the + // iteration. We probably don't have enough time to search the first + // move at the next iteration anyway. + if (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128) + stopSearch = true; + + if (stopSearch) + { + if (!PonderSearch) + break; + else + StopOnPonderhit = true; + } + } + // Write PV to transposition table, in case the relevant entries have + // been overwritten during the search: + TT.insert_pv(p, ss[0].pv); + + if (MaxDepth && Iteration >= MaxDepth) + break; } rml.sort(); // If we are pondering, we shouldn't print the best move before we // are told to do so - if(PonderSearch) - wait_for_stop_or_ponderhit(); + if (PonderSearch) + wait_for_stop_or_ponderhit(); else - // Print final search statistics - std::cout << "info nodes " << nodes_searched() << " nps " << nps() - << " time " << current_search_time() - << " hashfull " << TT.full() << std::endl; + // Print final search statistics + std::cout << "info nodes " << nodes_searched() + << " nps " << nps() + << " time " << current_search_time() + << " hashfull " << TT.full() << std::endl; - // Print the best move and the ponder move to the standard output: + // Print the best move and the ponder move to the standard output std::cout << "bestmove " << ss[0].pv[0]; - if(ss[0].pv[1] != MOVE_NONE) - std::cout << " ponder " << ss[0].pv[1]; + if (ss[0].pv[1] != MOVE_NONE) + std::cout << " ponder " << ss[0].pv[1]; + std::cout << std::endl; - if(UseLogFile) { - UndoInfo u; - LogFile << "Nodes: " << nodes_searched() << '\n'; - LogFile << "Nodes/second: " << nps() << '\n'; - LogFile << "Best move: " << move_to_san(p, ss[0].pv[0]) << '\n'; - p.do_move(ss[0].pv[0], u); - LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1]) << '\n'; - LogFile << std::endl; + if (UseLogFile) + { + if (dbg_show_mean) + dbg_print_mean(LogFile); + + if (dbg_show_hit_rate) + dbg_print_hit_rate(LogFile); + + UndoInfo u; + LogFile << "Nodes: " << nodes_searched() << std::endl + << "Nodes/second: " << nps() << std::endl + << "Best move: " << move_to_san(p, ss[0].pv[0]) << std::endl; + + p.do_move(ss[0].pv[0], u); + LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1]) + << std::endl << std::endl; } + return rml.get_move_score(0); } @@ -703,134 +773,156 @@ namespace { // and prints some information to the standard output. Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml) { - Value alpha = -VALUE_INFINITE, beta = VALUE_INFINITE, value; + + Value alpha = -VALUE_INFINITE; + Value beta = VALUE_INFINITE, value; Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move()); - // Loop through all the moves in the root move list: - for(int i = 0; i < rml.move_count() && !AbortSearch; i++) { - int64_t nodes; - Move move; - UndoInfo u; - Depth ext, newDepth; + // Loop through all the moves in the root move list + for (int i = 0; i < rml.move_count() && !AbortSearch; i++) + { + int64_t nodes; + Move move; + UndoInfo u; + Depth ext, newDepth; - RootMoveNumber = i + 1; - FailHigh = false; + RootMoveNumber = i + 1; + FailHigh = false; - // Remember the node count before the move is searched. The node counts - // are used to sort the root moves at the next iteration. - nodes = nodes_searched(); + // Remember the node count before the move is searched. The node counts + // are used to sort the root moves at the next iteration. + nodes = nodes_searched(); - // Pick the next root move, and print the move and the move number to - // the standard output: - move = ss[0].currentMove = rml.get_move(i); - if(current_search_time() >= 1000) - std::cout << "info currmove " << move - << " currmovenumber " << i + 1 << std::endl; + // Reset beta cut-off counters + BetaCounter.clear(); - // Decide search depth for this move: - ext = extension(pos, move, true, pos.move_is_check(move), false, false); - newDepth = (Iteration-2)*OnePly + ext + InitialDepth; + // Pick the next root move, and print the move and the move number to + // the standard output. + move = ss[0].currentMove = rml.get_move(i); + if (current_search_time() >= 1000) + std::cout << "info currmove " << move + << " currmovenumber " << i + 1 << std::endl; - // Make the move, and search it. - pos.do_move(move, u, dcCandidates); + // Decide search depth for this move + bool dangerous; + ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dangerous); + newDepth = (Iteration - 2) * OnePly + ext + InitialDepth; - if(i < MultiPV) { - value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0); - // If the value has dropped a lot compared to the last iteration, - // set the boolean variable Problem to true. This variable is used - // for time managment: When Problem is true, we try to complete the - // current iteration before playing a move. - Problem = (Iteration >= 2 && - value <= ValueByIteration[Iteration-1] - ProblemMargin); - if(Problem && StopOnPonderhit) - StopOnPonderhit = false; - } - else { - value = -search(pos, ss, -alpha, newDepth, 1, true, 0); - if(value > alpha) { - // Fail high! Set the boolean variable FailHigh to true, and - // re-search the move with a big window. The variable FailHigh is - // used for time managment: We try to avoid aborting the search - // prematurely during a fail high research. - FailHigh = true; - value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0); + // Make the move, and search it + pos.do_move(move, u, dcCandidates); + + if (i < MultiPV) + { + value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0); + // If the value has dropped a lot compared to the last iteration, + // set the boolean variable Problem to true. This variable is used + // for time managment: When Problem is true, we try to complete the + // current iteration before playing a move. + Problem = (Iteration >= 2 && value <= ValueByIteration[Iteration-1] - ProblemMargin); + + if (Problem && StopOnPonderhit) + StopOnPonderhit = false; + } + else + { + value = -search(pos, ss, -alpha, newDepth, 1, true, 0); + if (value > alpha) + { + // Fail high! Set the boolean variable FailHigh to true, and + // re-search the move with a big window. The variable FailHigh is + // used for time managment: We try to avoid aborting the search + // prematurely during a fail high research. + FailHigh = true; + value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0); + } } - } - pos.undo_move(move, u); + pos.undo_move(move, u); - // Finished searching the move. If AbortSearch is true, the search - // was aborted because the user interrupted the search or because we - // ran out of time. In this case, the return value of the search cannot - // be trusted, and we break out of the loop without updating the best - // move and/or PV: - if(AbortSearch) - break; + // Finished searching the move. If AbortSearch is true, the search + // was aborted because the user interrupted the search or because we + // ran out of time. In this case, the return value of the search cannot + // be trusted, and we break out of the loop without updating the best + // move and/or PV: + if (AbortSearch) + break; - // Remember the node count for this move. The node counts are used to - // sort the root moves at the next iteration. - rml.set_move_nodes(i, nodes_searched() - nodes); + // Remember the node count for this move. The node counts are used to + // sort the root moves at the next iteration. + rml.set_move_nodes(i, nodes_searched() - nodes); - assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE); + // Remember the beta-cutoff statistics + int64_t our, their; + BetaCounter.read(pos.side_to_move(), our, their); + rml.set_beta_counters(i, our, their); - if(value <= alpha && i >= MultiPV) - rml.set_move_score(i, -VALUE_INFINITE); - else { - // New best move! - - // Update PV: - rml.set_move_score(i, value); - update_pv(ss, 0); - rml.set_move_pv(i, ss[0].pv); - - if(MultiPV == 1) { - // We record how often the best move has been changed in each - // iteration. This information is used for time managment: When - // the best move changes frequently, we allocate some more time. - if(i > 0) - BestMoveChangesByIteration[Iteration]++; - - // Print search information to the standard output: - std::cout << "info depth " << Iteration - << " score " << value_to_string(value) - << " time " << current_search_time() - << " nodes " << nodes_searched() - << " nps " << nps() - << " pv "; - for(int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) - std::cout << ss[0].pv[j] << " "; - std::cout << std::endl; - - if(UseLogFile) - LogFile << pretty_pv(pos, current_search_time(), Iteration, - nodes_searched(), value, ss[0].pv) - << std::endl; - - alpha = value; - - // Reset the global variable Problem to false if the value isn't too - // far below the final value from the last iteration. - if(value > ValueByIteration[Iteration - 1] - NoProblemMargin) - Problem = false; - } - else { // MultiPV > 1 - rml.sort_multipv(i); - for(int j = 0; j < Min(MultiPV, rml.move_count()); j++) { - int k; - std::cout << "info multipv " << j + 1 - << " score " << value_to_string(rml.get_move_score(j)) - << " depth " << ((j <= i)? Iteration : Iteration - 1) - << " time " << current_search_time() - << " nodes " << nodes_searched() - << " nps " << nps() - << " pv "; - for(k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++) - std::cout << rml.get_move_pv(j, k) << " "; - std::cout << std::endl; - } - alpha = rml.get_move_score(Min(i, MultiPV-1)); + assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE); + + if (value <= alpha && i >= MultiPV) + rml.set_move_score(i, -VALUE_INFINITE); + else + { + // New best move! + + // Update PV + rml.set_move_score(i, value); + update_pv(ss, 0); + rml.set_move_pv(i, ss[0].pv); + + if (MultiPV == 1) + { + // We record how often the best move has been changed in each + // iteration. This information is used for time managment: When + // the best move changes frequently, we allocate some more time. + if (i > 0) + BestMoveChangesByIteration[Iteration]++; + + // Print search information to the standard output: + std::cout << "info depth " << Iteration + << " score " << value_to_string(value) + << " time " << current_search_time() + << " nodes " << nodes_searched() + << " nps " << nps() + << " pv "; + + for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) + std::cout << ss[0].pv[j] << " "; + + std::cout << std::endl; + + if (UseLogFile) + LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ss[0].pv) + << std::endl; + + alpha = value; + + // Reset the global variable Problem to false if the value isn't too + // far below the final value from the last iteration. + if (value > ValueByIteration[Iteration - 1] - NoProblemMargin) + Problem = false; + } + else // MultiPV > 1 + { + rml.sort_multipv(i); + for (int j = 0; j < Min(MultiPV, rml.move_count()); j++) + { + int k; + std::cout << "info multipv " << j + 1 + << " score " << value_to_string(rml.get_move_score(j)) + << " depth " << ((j <= i)? Iteration : Iteration - 1) + << " time " << current_search_time() + << " nodes " << nodes_searched() + << " nps " << nps() + << " pv "; + + for (k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++) + std::cout << rml.get_move_pv(j, k) << " "; + + std::cout << std::endl; + } + alpha = rml.get_move_score(Min(i, MultiPV-1)); + } } - } } return alpha; } @@ -846,36 +938,35 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); - EvalInfo ei; + if (depth < OnePly) + return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID); // Initialize, and make an early exit in case of an aborted search, // an instant draw, maximum ply reached, etc. - Value oldAlpha = alpha; + init_node(pos, ss, ply, threadID); + // After init_node() that calls poll() if (AbortSearch || thread_should_stop(threadID)) return Value(0); - if (depth < OnePly) - return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID); - - init_node(pos, ss, ply, threadID); - if (pos.is_draw()) return VALUE_DRAW; + EvalInfo ei; + if (ply >= PLY_MAX - 1) return evaluate(pos, ei, threadID); // Mate distance pruning + Value oldAlpha = alpha; alpha = Max(value_mated_in(ply), alpha); beta = Min(value_mate_in(ply+1), beta); if (alpha >= beta) return alpha; - // Transposition table lookup. At PV nodes, we don't use the TT for + // Transposition table lookup. At PV nodes, we don't use the TT for // pruning, but only for move ordering. const TTEntry* tte = TT.retrieve(pos); - Move ttMove = (tte ? tte->move() : MOVE_NONE); // Go with internal iterative deepening if we don't have a TT move @@ -886,16 +977,15 @@ namespace { } // Initialize a MovePicker object for the current position, and prepare - // to search all moves: - MovePicker mp = MovePicker(pos, true, ttMove, ss[ply].mateKiller, - ss[ply].killer1, ss[ply].killer2, depth); + // to search all moves + MovePicker mp = MovePicker(pos, true, ttMove, ss[ply], depth); Move move, movesSearched[256]; int moveCount = 0; Value value, bestValue = -VALUE_INFINITE; Bitboard dcCandidates = mp.discovered_check_candidates(); - bool mateThreat = MateThreatExtension[1] > Depth(0) - && pos.has_mate_threat(opposite_color(pos.side_to_move())); + bool isCheck = pos.is_check(); + bool mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); // Loop through all legal moves until no moves remain or a beta cutoff // occurs. @@ -905,18 +995,21 @@ namespace { { assert(move_is_ok(move)); - bool singleReply = (pos.is_check() && mp.number_of_moves() == 1); + bool singleReply = (isCheck && mp.number_of_moves() == 1); bool moveIsCheck = pos.move_is_check(move, dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); movesSearched[moveCount++] = ss[ply].currentMove = move; - ss[ply].currentMoveCaptureValue = move_is_ep(move) ? - PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move)); + if (moveIsCapture) + ss[ply].currentMoveCaptureValue = + move_is_ep(move)? PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move)); + else + ss[ply].currentMoveCaptureValue = Value(0); // Decide the new search depth - Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat); + bool dangerous; + Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Make and search the move @@ -930,14 +1023,12 @@ namespace { // 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. if ( depth >= 2*OnePly - && ext == Depth(0) && moveCount >= LMRPVMoves + && !dangerous && !moveIsCapture && !move_promotion(move) - && !moveIsPassedPawnPush && !move_is_castle(move) - && move != ss[ply].killer1 - && move != ss[ply].killer2) + && !move_is_killer(move, ss[ply])) { ss[ply].reduction = OnePly; value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true, threadID); @@ -945,7 +1036,7 @@ namespace { else value = alpha + 1; // Just to trigger next condition - if (value > alpha) // Go with full depth pv search + if (value > alpha) // Go with full depth non-pv search { ss[ply].reduction = Depth(0); value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID); @@ -983,7 +1074,9 @@ namespace { // If we are at ply 1, and we are searching the first root move at // ply 0, set the 'Problem' variable if the score has dropped a lot // (from the computer's point of view) since the previous iteration: - if (Iteration >= 2 && -value <= ValueByIteration[Iteration-1] - ProblemMargin) + if ( ply == 1 + && Iteration >= 2 + && -value <= ValueByIteration[Iteration-1] - ProblemMargin) Problem = true; } @@ -1003,7 +1096,7 @@ namespace { // All legal moves have been searched. A special case: If there were // no legal moves, it must be mate or stalemate: if (moveCount == 0) - return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); + return (isCheck ? value_mated_in(ply) : VALUE_DRAW); // If the search is not aborted, update the transposition table, // history counters, and killer moves. @@ -1015,15 +1108,12 @@ namespace { else if (bestValue >= beta) { + BetaCounter.add(pos.side_to_move(), depth, threadID); Move m = ss[ply].pv[ply]; if (ok_to_history(pos, m)) // Only non capture moves are considered { update_history(pos, m, depth, movesSearched, moveCount); - if (m != ss[ply].killer1) - { - ss[ply].killer2 = ss[ply].killer1; - ss[ply].killer1 = m; - } + update_killers(m, ss[ply]); } TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER); } @@ -1043,21 +1133,22 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); - EvalInfo ei; + if (depth < OnePly) + return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); // Initialize, and make an early exit in case of an aborted search, // an instant draw, maximum ply reached, etc. + init_node(pos, ss, ply, threadID); + + // After init_node() that calls poll() if (AbortSearch || thread_should_stop(threadID)) return Value(0); - if (depth < OnePly) - return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); - - init_node(pos, ss, ply, threadID); - if (pos.is_draw()) return VALUE_DRAW; + EvalInfo ei; + if (ply >= PLY_MAX - 1) return evaluate(pos, ei, threadID); @@ -1070,21 +1161,24 @@ namespace { // Transposition table lookup const TTEntry* tte = TT.retrieve(pos); - Move ttMove = (tte ? tte->move() : MOVE_NONE); if (tte && ok_to_use_TT(tte, depth, beta, ply)) { - ss[ply].currentMove = ttMove; // can be MOVE_NONE ? + ss[ply].currentMove = ttMove; // can be MOVE_NONE return value_from_tt(tte->value(), ply); } Value approximateEval = quick_evaluate(pos); bool mateThreat = false; + bool nullDrivenIID = false; + bool isCheck = pos.is_check(); // Null move search if ( allowNullmove - && !pos.is_check() + && depth > OnePly + && !isCheck + && !value_is_mate(beta) && ok_to_do_nullmove(pos) && approximateEval >= beta - NullMoveMargin) { @@ -1092,10 +1186,30 @@ namespace { UndoInfo u; pos.do_null_move(u); - Value nullValue = -search(pos, ss, -(beta-1), depth-4*OnePly, ply+1, false, threadID); + int R = (depth >= 4 * OnePly ? 4 : 3); // Null move dynamic reduction + + Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID); + + // Check for a null capture artifact, if the value without the null capture + // is above beta then mark the node as a suspicious failed low. We will verify + // later if we are really under threat. + if ( UseNullDrivenIID + && nullValue < beta + && depth > 6 * OnePly + &&!value_is_mate(nullValue) + && ttMove == MOVE_NONE + && ss[ply + 1].currentMove != MOVE_NONE + && pos.move_is_capture(ss[ply + 1].currentMove) + && pos.see(ss[ply + 1].currentMove) + nullValue >= beta) + nullDrivenIID = true; + pos.undo_null_move(u); - if (nullValue >= beta) + if (value_is_mate(nullValue)) + { + /* Do not return unproven mates */ + } + else if (nullValue >= beta) { if (depth < 6 * OnePly) return beta; @@ -1106,14 +1220,16 @@ namespace { return beta; } 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 + // some kind of threat. If the previous move was reduced, check if // the move that refuted the null move was somehow connected to the - // move which was reduced. If a connection is found, return a fail + // 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; - + nullDrivenIID = false; + } ss[ply].threatMove = ss[ply + 1].currentMove; if ( depth < ThreatDepth && ss[ply - 1].reduction @@ -1122,12 +1238,17 @@ namespace { } } // Null move search not allowed, try razoring - else if ( depth < RazorDepth + else if ( !value_is_mate(beta) && approximateEval < beta - RazorMargin - && evaluate(pos, ei, threadID) < beta - RazorMargin) + && depth < RazorDepth + && (RazorAtDepthOne || depth > OnePly) + && ttMove == MOVE_NONE + && !pos.has_pawn_on_7th(pos.side_to_move())) { Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); - if (v < beta) + if ( (v < beta - RazorMargin - RazorMargin / 4) + || (depth < 3*OnePly && v < beta - RazorMargin) + || (depth < 2*OnePly && v < beta - RazorMargin / 2)) return v; } @@ -1138,18 +1259,32 @@ namespace { search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID); ttMove = ss[ply].pv[ply]; } + else if (nullDrivenIID) + { + // The null move failed low due to a suspicious capture. Perhaps we + // are facing a null capture artifact due to the side to move change + // and this position should fail high. So do a normal search with a + // reduced depth to get a good ttMove to use in the following full + // depth search. + Move tm = ss[ply].threatMove; + + assert(tm != MOVE_NONE); + assert(ttMove == MOVE_NONE); + + search(pos, ss, beta, depth/2, ply, false, threadID); + ttMove = ss[ply].pv[ply]; + ss[ply].threatMove = tm; + } // Initialize a MovePicker object for the current position, and prepare // to search all moves: - MovePicker mp = MovePicker(pos, false, ttMove, ss[ply].mateKiller, - ss[ply].killer1, ss[ply].killer2, depth); + MovePicker mp = MovePicker(pos, false, ttMove, ss[ply], depth); Move move, movesSearched[256]; int moveCount = 0; Value value, bestValue = -VALUE_INFINITE; Bitboard dcCandidates = mp.discovered_check_candidates(); Value futilityValue = VALUE_NONE; - bool isCheck = pos.is_check(); bool useFutilityPruning = UseFutilityPruning && depth < SelectiveDepth && !isCheck; @@ -1165,30 +1300,32 @@ namespace { bool singleReply = (isCheck && mp.number_of_moves() == 1); bool moveIsCheck = pos.move_is_check(move, dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); movesSearched[moveCount++] = ss[ply].currentMove = move; // Decide the new search depth - Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat); + bool dangerous; + Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Futility pruning if ( useFutilityPruning - && ext == Depth(0) + && !dangerous && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move)) { + // History pruning. See ok_to_prune() definition if ( moveCount >= 2 + int(depth) && ok_to_prune(pos, move, ss[ply].threatMove, depth)) continue; - if (depth < 3 * OnePly && approximateEval < beta) + // Value based pruning + if (depth < 7 * OnePly && approximateEval < beta) { if (futilityValue == VALUE_NONE) futilityValue = evaluate(pos, ei, threadID) - + (depth < 2 * OnePly ? FutilityMargin1 : FutilityMargin2); + + FutilityMargins[int(depth)/2 - 1] + + 32 * (depth & 1); if (futilityValue < beta) { @@ -1205,15 +1342,13 @@ namespace { // 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. - if ( depth >= 2*OnePly - && ext == Depth(0) - && moveCount >= LMRNonPVMoves + if ( depth >= 2*OnePly + && moveCount >= LMRNonPVMoves + && !dangerous && !moveIsCapture && !move_promotion(move) - && !moveIsPassedPawnPush && !move_is_castle(move) - && move != ss[ply].killer1 - && move != ss[ply].killer2) + && !move_is_killer(move, ss[ply])) { ss[ply].reduction = OnePly; value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true, threadID); @@ -1255,7 +1390,7 @@ namespace { } // All legal moves have been searched. A special case: If there were - // no legal moves, it must be mate or stalemate: + // no legal moves, it must be mate or stalemate. if (moveCount == 0) return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); @@ -1268,15 +1403,12 @@ namespace { TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER); else { + BetaCounter.add(pos.side_to_move(), depth, threadID); Move m = ss[ply].pv[ply]; if (ok_to_history(pos, m)) // Only non capture moves are considered { update_history(pos, m, depth, movesSearched, moveCount); - if (m != ss[ply].killer1) - { - ss[ply].killer2 = ss[ply].killer1; - ss[ply].killer1 = m; - } + update_killers(m, ss[ply]); } TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER); } @@ -1297,15 +1429,14 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); - EvalInfo ei; - // Initialize, and make an early exit in case of an aborted search, // an instant draw, maximum ply reached, etc. + init_node(pos, ss, ply, threadID); + + // After init_node() that calls poll() if (AbortSearch || thread_should_stop(threadID)) return Value(0); - init_node(pos, ss, ply, threadID); - if (pos.is_draw()) return VALUE_DRAW; @@ -1314,15 +1445,17 @@ namespace { if (tte && ok_to_use_TT(tte, depth, beta, ply)) return value_from_tt(tte->value(), ply); - // Evaluate the position statically: - Value staticValue = evaluate(pos, ei, threadID); + // Evaluate the position statically + EvalInfo ei; + bool isCheck = pos.is_check(); + Value staticValue = (isCheck ? -VALUE_INFINITE : evaluate(pos, ei, threadID)); if (ply == PLY_MAX - 1) - return staticValue; + return evaluate(pos, ei, threadID); // Initialize "stand pat score", and return it immediately if it is // at least beta. - Value bestValue = (pos.is_check() ? -VALUE_INFINITE : staticValue); + Value bestValue = staticValue; if (bestValue >= beta) return bestValue; @@ -1333,12 +1466,12 @@ namespace { // Initialize a MovePicker object for the current position, and prepare // to search the moves. Because the depth is <= 0 here, only captures, // queen promotions and checks (only if depth == 0) will be generated. - MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE, - MOVE_NONE, depth); + bool pvNode = (beta - alpha != 1); + MovePicker mp = MovePicker(pos, pvNode, MOVE_NONE, EmptySearchStack, depth, isCheck ? NULL : &ei); Move move; int moveCount = 0; Bitboard dcCandidates = mp.discovered_check_candidates(); - bool isCheck = pos.is_check(); + bool enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; // Loop through the moves until no moves remain or a beta cutoff // occurs. @@ -1347,25 +1480,23 @@ namespace { { assert(move_is_ok(move)); - bool moveIsCheck = pos.move_is_check(move, dcCandidates); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); - moveCount++; ss[ply].currentMove = move; // Futility pruning if ( UseQSearchFutilityPruning + && enoughMaterial && !isCheck - && !moveIsCheck + && !pvNode && !move_promotion(move) - && !moveIsPassedPawnPush - && beta - alpha == 1 - && pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame) + && !pos.move_is_check(move, dcCandidates) + && !pos.move_is_passed_pawn_push(move)) { Value futilityValue = staticValue + Max(pos.midgame_value_of_piece_on(move_to(move)), pos.endgame_value_of_piece_on(move_to(move))) - + FutilityMargin0 + + (move_is_ep(move) ? PawnValueEndgame : Value(0)) + + FutilityMarginQS + ei.futilityMargin; if (futilityValue < alpha) @@ -1376,7 +1507,7 @@ namespace { } } - // Don't search captures and checks with negative SEE values. + // Don't search captures and checks with negative SEE values if ( !isCheck && !move_promotion(move) && (pos.midgame_value_of_piece_on(move_from(move)) > @@ -1414,6 +1545,13 @@ namespace { // Update transposition table TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_EXACT); + // Update killers only for good check moves + Move m = ss[ply].currentMove; + if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered + { + // Wrong to update history when depth is <= 0 + update_killers(m, ss[ply]); + } return bestValue; } @@ -1448,7 +1586,6 @@ namespace { bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); lock_grab(&(sp->lock)); int moveCount = ++sp->moves; @@ -1457,14 +1594,14 @@ namespace { ss[sp->ply].currentMove = move; // Decide the new search depth. - Depth ext = extension(pos, move, false, moveIsCheck, false, false); + bool dangerous; + Depth ext = extension(pos, move, false, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Prune? if ( useFutilityPruning - && ext == Depth(0) + && !dangerous && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && moveCount >= 2 + int(sp->depth) && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth)) @@ -1476,14 +1613,12 @@ namespace { // 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. - if ( ext == Depth(0) + if ( !dangerous && moveCount >= LMRNonPVMoves && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && !move_is_castle(move) - && move != ss[sp->ply].killer1 - && move != ss[sp->ply].killer2) + && !move_is_killer(move, ss[sp->ply])) { ss[sp->ply].reduction = OnePly; value = -search(pos, ss, -(sp->beta-1), newDepth - OnePly, sp->ply+1, true, threadID); @@ -1561,12 +1696,14 @@ namespace { { bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); assert(move_is_ok(move)); - ss[sp->ply].currentMoveCaptureValue = move_is_ep(move)? - PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move)); + if (moveIsCapture) + ss[sp->ply].currentMoveCaptureValue = + move_is_ep(move)? PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move)); + else + ss[sp->ply].currentMoveCaptureValue = Value(0); lock_grab(&(sp->lock)); int moveCount = ++sp->moves; @@ -1575,7 +1712,8 @@ namespace { ss[sp->ply].currentMove = move; // Decide the new search depth. - Depth ext = extension(pos, move, true, moveIsCheck, false, false); + bool dangerous; + Depth ext = extension(pos, move, true, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Make and search the move. @@ -1584,14 +1722,12 @@ namespace { // 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. - if ( ext == Depth(0) + if ( !dangerous && moveCount >= LMRPVMoves && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && !move_is_castle(move) - && move != ss[sp->ply].killer1 - && move != ss[sp->ply].killer2) + && !move_is_killer(move, ss[sp->ply])) { ss[sp->ply].reduction = OnePly; value = -search(pos, ss, -sp->alpha, newDepth - OnePly, sp->ply+1, true, threadID); @@ -1648,8 +1784,10 @@ namespace { } // If we are at ply 1, and we are searching the first root move at // ply 0, set the 'Problem' variable if the score has dropped a lot - // (from the computer's point of view) since the previous iteration: - if (Iteration >= 2 && -value <= ValueByIteration[Iteration-1] - ProblemMargin) + // (from the computer's point of view) since the previous iteration. + if ( sp->ply == 1 + && Iteration >= 2 + && -value <= ValueByIteration[Iteration-1] - ProblemMargin) Problem = true; } lock_release(&(sp->lock)); @@ -1658,7 +1796,7 @@ namespace { lock_grab(&(sp->lock)); // If this is the master thread and we have been asked to stop because of - // a beta cutoff higher up in the tree, stop all slave threads: + // a beta cutoff higher up in the tree, stop all slave threads. if (sp->master == threadID && thread_should_stop(threadID)) for (int i = 0; i < ActiveThreads; i++) if (sp->slaves[i]) @@ -1670,6 +1808,32 @@ namespace { lock_release(&(sp->lock)); } + /// The BetaCounterType class + + BetaCounterType::BetaCounterType() { clear(); } + + void BetaCounterType::clear() { + + for (int i = 0; i < THREAD_MAX; i++) + hits[i][WHITE] = hits[i][BLACK] = 0ULL; + } + + void BetaCounterType::add(Color us, Depth d, int threadID) { + + // Weighted count based on depth + hits[threadID][us] += int(d); + } + + void BetaCounterType::read(Color us, int64_t& our, int64_t& their) { + + our = their = 0UL; + for (int i = 0; i < THREAD_MAX; i++) + { + our += hits[i][us]; + their += hits[i][opposite_color(us)]; + } + } + /// The RootMove class @@ -1689,7 +1853,7 @@ namespace { if (score != m.score) return (score < m.score); - return nodes <= m.nodes; + return theirBeta <= m.theirBeta; } /// The RootMoveList class @@ -1752,6 +1916,11 @@ namespace { moves[moveNum].cumulativeNodes += nodes; } + inline void RootMoveList::set_beta_counters(int moveNum, int64_t our, int64_t their) { + moves[moveNum].ourBeta = our; + moves[moveNum].theirBeta = their; + } + void RootMoveList::set_move_pv(int moveNum, const Move pv[]) { int j; for(j = 0; pv[j] != MOVE_NONE; j++) @@ -1822,17 +1991,28 @@ namespace { // init_search_stack() initializes a search stack at the beginning of a // new search from the root. + void init_search_stack(SearchStack& ss) { + + ss.pv[0] = MOVE_NONE; + ss.pv[1] = MOVE_NONE; + ss.currentMove = MOVE_NONE; + ss.threatMove = MOVE_NONE; + ss.reduction = Depth(0); + for (int j = 0; j < KILLER_MAX; j++) + ss.killers[j] = MOVE_NONE; + } void init_search_stack(SearchStack ss[]) { - for(int i = 0; i < 3; i++) { - ss[i].pv[i] = MOVE_NONE; - ss[i].pv[i+1] = MOVE_NONE; - ss[i].currentMove = MOVE_NONE; - ss[i].mateKiller = MOVE_NONE; - ss[i].killer1 = MOVE_NONE; - ss[i].killer2 = MOVE_NONE; - ss[i].threatMove = MOVE_NONE; - ss[i].reduction = Depth(0); + + for (int i = 0; i < 3; i++) + { + ss[i].pv[i] = MOVE_NONE; + ss[i].pv[i+1] = MOVE_NONE; + ss[i].currentMove = MOVE_NONE; + ss[i].threatMove = MOVE_NONE; + ss[i].reduction = Depth(0); + for (int j = 0; j < KILLER_MAX; j++) + ss[i].killers[j] = MOVE_NONE; } } @@ -1856,13 +2036,13 @@ namespace { NodesSincePoll = 0; } } - ss[ply].pv[ply] = ss[ply].pv[ply+1] = ss[ply].currentMove = MOVE_NONE; ss[ply+2].mateKiller = MOVE_NONE; - ss[ply+2].killer1 = ss[ply+2].killer2 = MOVE_NONE; ss[ply].threatMove = MOVE_NONE; ss[ply].reduction = Depth(0); ss[ply].currentMoveCaptureValue = Value(0); + for (int j = 0; j < KILLER_MAX; j++) + ss[ply+2].killers[j] = MOVE_NONE; if(Threads[threadID].printCurrentLine) print_current_line(ss, ply, threadID); @@ -1965,32 +2145,89 @@ namespace { } + // 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); + } + + + // move_is_killer() checks if the given move is among the + // killer moves of that ply. + + bool move_is_killer(Move m, const SearchStack& ss) { + + const Move* k = ss.killers; + for (int i = 0; i < KILLER_MAX; i++, k++) + if (*k == m) + return true; + + return false; + } + + // extension() decides whether a move should be searched with normal depth, // or with extended depth. Certain classes of moves (checking moves, in - // particular) are searched with bigger depth than ordinary moves. + // particular) are searched with bigger depth than ordinary moves and in + // any case are marked as 'dangerous'. Note that also if a move is not + // extended, as example because the corresponding UCI option is set to zero, + // the move is marked as 'dangerous' so, at least, we avoid to prune it. + + Depth extension(const Position &pos, Move m, bool pvNode, bool check, + bool singleReply, bool mateThreat, bool* dangerous) { + + assert(m != MOVE_NONE); - Depth extension(const Position &pos, Move m, bool pvNode, - bool check, bool singleReply, bool mateThreat) { Depth result = Depth(0); + *dangerous = check || singleReply || mateThreat; + + if (check) + result += CheckExtension[pvNode]; - if(check) - result += CheckExtension[pvNode]; - if(singleReply) - result += SingleReplyExtension[pvNode]; - if(pos.move_is_pawn_push_to_7th(m)) - result += PawnPushTo7thExtension[pvNode]; - if(pos.move_is_passed_pawn_push(m)) - result += PassedPawnExtension[pvNode]; - if(mateThreat) - result += MateThreatExtension[pvNode]; - if(pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame - && (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) - - pos.midgame_value_of_piece_on(move_to(m)) == Value(0)) - && !move_promotion(m)) - result += PawnEndgameExtension[pvNode]; - if(pvNode && pos.move_is_capture(m) - && pos.type_of_piece_on(move_to(m)) != PAWN && pos.see(m) >= 0) - result += OnePly/2; + if (singleReply) + result += SingleReplyExtension[pvNode]; + + if (mateThreat) + result += MateThreatExtension[pvNode]; + + if (pos.type_of_piece_on(move_from(m)) == PAWN) + { + if (pos.move_is_pawn_push_to_7th(m)) + { + result += PawnPushTo7thExtension[pvNode]; + *dangerous = true; + } + if (pos.move_is_passed_pawn_push(m)) + { + result += PassedPawnExtension[pvNode]; + *dangerous = true; + } + } + + if ( pos.move_is_capture(m) + && pos.type_of_piece_on(move_to(m)) != PAWN + && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) + - pos.midgame_value_of_piece_on(move_to(m)) == Value(0)) + && !move_promotion(m) + && !move_is_ep(m)) + { + result += PawnEndgameExtension[pvNode]; + *dangerous = true; + } + + if ( pvNode + && pos.move_is_capture(m) + && pos.type_of_piece_on(move_to(m)) != PAWN + && pos.see(m) >= 0) + { + result += OnePly/2; + *dangerous = true; + } return Min(result, OnePly); } @@ -2032,31 +2269,35 @@ namespace { tto = move_to(threat); // Case 1: Castling moves are never pruned. - if(move_is_castle(m)) - return false; + if (move_is_castle(m)) + return false; // Case 2: Don't prune moves which move the threatened piece - if(!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto) - return false; + if (!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto) + return false; // Case 3: If the threatened piece has value less than or equal to the // value of the threatening piece, don't prune move which defend it. - if(!PruneDefendingMoves && threat != MOVE_NONE - && (piece_value_midgame(pos.piece_on(tfrom)) - >= piece_value_midgame(pos.piece_on(tto))) - && pos.move_attacks_square(m, tto)) + if ( !PruneDefendingMoves + && threat != MOVE_NONE + && pos.move_is_capture(threat) + && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) + || pos.type_of_piece_on(tfrom) == KING) + && pos.move_attacks_square(m, tto)) return false; // Case 4: Don't prune moves with good history. - if(!H.ok_to_prune(pos.piece_on(move_from(m)), m, d)) - return false; + if (!H.ok_to_prune(pos.piece_on(move_from(m)), m, d)) + return false; // Case 5: If the moving piece in the threatened move is a slider, don't // prune safe moves which block its ray. - if(!PruneBlockingMoves && threat != MOVE_NONE - && piece_is_slider(pos.piece_on(tfrom)) - && bit_is_set(squares_between(tfrom, tto), mto) && pos.see(m) >= 0) - return false; + if ( !PruneBlockingMoves + && threat != MOVE_NONE + && piece_is_slider(pos.piece_on(tfrom)) + && bit_is_set(squares_between(tfrom, tto), mto) + && pos.see(m) >= 0) + return false; return true; } @@ -2079,13 +2320,11 @@ namespace { // ok_to_history() returns true if a move m can be stored - // in history. Should be a non capturing move. + // in history. Should be a non capturing move nor a promotion. bool ok_to_history(const Position& pos, Move m) { - return pos.square_is_empty(move_to(m)) - && !move_promotion(m) - && !move_is_ep(m); + return !pos.move_is_capture(m) && !move_promotion(m); } @@ -2098,8 +2337,26 @@ namespace { H.success(pos.piece_on(move_from(m)), m, depth); for (int i = 0; i < moveCount - 1; i++) - if (ok_to_history(pos, movesSearched[i]) && m != movesSearched[i]) + { + assert(m != movesSearched[i]); + if (ok_to_history(pos, movesSearched[i])) H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]); + } + } + + + // update_killers() add a good move that produced a beta-cutoff + // among the killer moves of that ply. + + void update_killers(Move m, SearchStack& ss) { + + if (m == ss.killers[0]) + return; + + for (int i = KILLER_MAX - 1; i > 0; i--) + ss.killers[i] = ss.killers[i - 1]; + + ss.killers[0] = m; } // fail_high_ply_1() checks if some thread is currently resolving a fail @@ -2174,6 +2431,12 @@ namespace { { lastInfoTime = t; lock_grab(&IOLock); + if (dbg_show_mean) + dbg_print_mean(); + + if (dbg_show_hit_rate) + dbg_print_hit_rate(); + std::cout << "info nodes " << nodes_searched() << " nps " << nps() << " time " << t << " hashfull " << TT.full() << std::endl; lock_release(&IOLock); @@ -2186,7 +2449,7 @@ namespace { bool overTime = t > AbsoluteMaxSearchTime || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime) - || ( !FailHigh && !fail_high_ply_1() && !Problem + || ( !FailHigh && !fail_high_ply_1() && !Problem && t > 6*(MaxSearchTime + ExtraSearchTime)); if ( (Iteration >= 2 && (!InfiniteSearch && overTime))