X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=4d7195b3e2290905b6d325da28507adcd80ea718;hp=ab3e6f66cdcf9d7988c4dd7e167216bc90b90751;hb=f98385e1297a5d503e4ff933cdadc882465a1e6c;hpb=4c294932e7b4a6ee3604f0c176dd01124524456f diff --git a/src/search.cpp b/src/search.cpp index ab3e6f66..4d7195b3 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -23,6 +23,7 @@ //// #include +#include #include #include #include @@ -47,6 +48,26 @@ namespace { /// Types + // IterationInfoType stores search results for each iteration + // + // Because we use relatively small (dynamic) aspiration window, + // there happens many fail highs and fail lows in root. And + // because we don't do researches in those cases, "value" stored + // here is not necessarily exact. Instead in case of fail high/low + // we guess what the right value might be and store our guess + // as a "speculated value" and then move on. Speculated values are + // used just to calculate aspiration window width, so also if are + // not exact is not big a problem. + + struct IterationInfoType { + + IterationInfoType(Value v = Value(0), Value sv = Value(0)) + : value(v), speculatedValue(sv) {} + + Value value, speculatedValue; + }; + + // 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 @@ -125,17 +146,11 @@ 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); @@ -165,13 +180,14 @@ 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); @@ -198,11 +214,10 @@ namespace { // 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]; + IterationInfoType IterationInfo[PLY_MAX_PLUS_2]; int BestMoveChangesByIteration[PLY_MAX_PLUS_2]; // MultiPV mode @@ -212,7 +227,7 @@ namespace { int SearchStartTime; int MaxNodes, MaxDepth; int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime; - Move BestRootMove, PonderMove, EasyMove; + Move EasyMove; int RootMoveNumber; bool InfiniteSearch; bool PonderSearch; @@ -220,6 +235,7 @@ namespace { bool AbortSearch; bool Quit; bool FailHigh; + bool FailLow; bool Problem; bool PonderingEnabled; int ExactMaxTime; @@ -252,23 +268,19 @@ namespace { /// Functions 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); - Value search(Position &pos, SearchStack ss[], Value beta, - Depth depth, int ply, bool allowNullmove, int threadID); - Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, - Depth depth, int ply, int threadID); + Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta); + 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); + Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, 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 init_node(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); + 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); + Depth extension(const Position &pos, Move m, bool pvNode, bool capture, 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); @@ -291,9 +303,8 @@ namespace { bool thread_is_available(int slave, int master); bool idle_thread_exists(int master); bool split(const Position &pos, SearchStack *ss, int ply, - Value *alpha, Value *beta, Value *bestValue, Depth depth, - int *moves, MovePicker *mp, Bitboard dcCandidates, int master, - bool pvNode); + Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves, + MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode); void wake_sleeping_threads(); #if !defined(_MSC_VER) @@ -326,6 +337,23 @@ History H; // Should be made local? SearchStack EmptySearchStack; +// SearchStack::init() initializes a search stack. Used at the beginning of a +// new search from the root. +void SearchStack::init(int ply) { + + pv[ply] = pv[ply + 1] = MOVE_NONE; + currentMove = threatMove = MOVE_NONE; + reduction = Depth(0); +} + +void SearchStack::initKillers() { + + mateKiller = MOVE_NONE; + for (int i = 0; i < KILLER_MAX; i++) + killers[i] = MOVE_NONE; +} + + //// //// Functions //// @@ -358,8 +386,6 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, // 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++) { @@ -373,6 +399,7 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, AbortSearch = false; Quit = false; FailHigh = false; + FailLow = false; Problem = false; ExactMaxTime = maxTime; @@ -413,13 +440,13 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, 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)"); - 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")); + 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")); @@ -449,7 +476,6 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, // Set thinking time: int myTime = time[side_to_move]; int myIncrement = increment[side_to_move]; - int oppTime = time[1 - side_to_move]; if (!movesToGo) // Sudden death time control { @@ -590,7 +616,8 @@ void init_threads() { } // Init also the empty search stack - init_search_stack(EmptySearchStack); + EmptySearchStack.init(0); + EmptySearchStack.initKillers(); } @@ -642,17 +669,18 @@ namespace { // Initialize TT.new_search(); H.clear(); - init_search_stack(ss); - - ValueByIteration[0] = Value(0); - ValueByIteration[1] = rml.get_move_score(0); + for (int i = 0; i < 3; i++) + { + ss[i].init(i); + ss[i].initKillers(); + } + IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0)); Iteration = 1; - LastIterations = false; EasyMove = rml.scan_for_easy_move(); // Iterative deepening loop - while (!AbortSearch && Iteration < PLY_MAX) + while (Iteration < PLY_MAX) { // Initialize iteration rml.sort(); @@ -663,8 +691,62 @@ namespace { std::cout << "info depth " << Iteration << std::endl; + // Calculate dynamic search window based on previous iterations + Value alpha, beta; + + if (MultiPV == 1 && Iteration >= 6) + { + int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue; + int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue; + + int delta = Max(2 * abs(prevDelta1) + abs(prevDelta2), ProblemMargin); + + alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE); + beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE); + } + else + { + alpha = - VALUE_INFINITE; + beta = VALUE_INFINITE; + } + // Search to the current depth - ValueByIteration[Iteration] = root_search(p, ss, rml); + Value value = root_search(p, ss, rml, alpha, beta); + + // Write PV to transposition table, in case the relevant entries have + // been overwritten during the search. + TT.insert_pv(p, ss[0].pv); + + if (AbortSearch) + break; // Value cannot be trusted. Break out immediately! + + //Save info about search result + Value speculatedValue; + bool fHigh = false; + bool fLow = false; + Value delta = value - IterationInfo[Iteration - 1].value; + + if (value >= beta) + { + assert(delta > 0); + + fHigh = true; + speculatedValue = value + delta; + BestMoveChangesByIteration[Iteration] += 2; // Allocate more time + } + else if (value <= alpha) + { + assert(value == alpha); + assert(delta < 0); + + fLow = true; + speculatedValue = value + delta; + BestMoveChangesByIteration[Iteration] += 3; // Allocate more time + } else + speculatedValue = value; + + speculatedValue = Min(Max(speculatedValue, -VALUE_INFINITE), VALUE_INFINITE); + IterationInfo[Iteration] = IterationInfoType(value, speculatedValue); // Erase the easy move if it differs from the new best move if (ss[0].pv[0] != EasyMove) @@ -683,13 +765,15 @@ namespace { // 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) + && abs(IterationInfo[Iteration].value) >= abs(VALUE_MATE) - 100 + && abs(IterationInfo[Iteration-1].value) >= 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 + && !fLow + && !fHigh && EasyMove == ss[0].pv[0] && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 && current_search_time() > MaxSearchTime / 16) @@ -702,9 +786,6 @@ namespace { 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. @@ -713,15 +794,13 @@ namespace { if (stopSearch) { + //FIXME: Implement fail-low emergency measures 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; @@ -741,6 +820,11 @@ namespace { << " hashfull " << TT.full() << std::endl; // Print the best move and the ponder move to the standard output + if (ss[0].pv[0] == MOVE_NONE) + { + ss[0].pv[0] = rml.get_move(0); + ss[0].pv[1] = MOVE_NONE; + } std::cout << "bestmove " << ss[0].pv[0]; if (ss[0].pv[1] != MOVE_NONE) std::cout << " ponder " << ss[0].pv[1]; @@ -755,12 +839,12 @@ namespace { if (dbg_show_hit_rate) dbg_print_hit_rate(LogFile); - UndoInfo u; + StateInfo st; 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); + p.do_move(ss[0].pv[0], st); LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1]) << std::endl << std::endl; } @@ -773,18 +857,26 @@ namespace { // scheme (perhaps we should try to use this at internal PV nodes, too?) // and prints some information to the standard output. - Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml) { + Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) { - Value alpha = -VALUE_INFINITE; - Value beta = VALUE_INFINITE, value; + Value oldAlpha = alpha; + Value 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++) { + 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; + } int64_t nodes; Move move; - UndoInfo u; + StateInfo st; Depth ext, newDepth; RootMoveNumber = i + 1; @@ -806,20 +898,20 @@ namespace { // Decide search depth for this move bool dangerous; - ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dangerous); + ext = extension(pos, move, true, pos.move_is_capture(move), pos.move_is_check(move), false, false, &dangerous); newDepth = (Iteration - 2) * OnePly + ext + InitialDepth; // Make the move, and search it - pos.do_move(move, u, dcCandidates); + pos.do_move(move, st, dcCandidates); if (i < MultiPV) { - value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0); + value = -search_pv(pos, ss, -beta, -alpha, 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); + Problem = (Iteration >= 2 && value <= IterationInfo[Iteration-1].value - ProblemMargin); if (Problem && StopOnPonderhit) StopOnPonderhit = false; @@ -838,13 +930,13 @@ namespace { } } - pos.undo_move(move, u); + pos.undo_move(move); // 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: + // move and/or PV. if (AbortSearch) break; @@ -863,7 +955,7 @@ namespace { rml.set_move_score(i, -VALUE_INFINITE); else { - // New best move! + // PV move or new best move! // Update PV rml.set_move_score(i, value); @@ -895,11 +987,12 @@ namespace { LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ss[0].pv) << std::endl; - alpha = value; + if (value > alpha) + 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) + if (value > IterationInfo[Iteration - 1].value - NoProblemMargin) Problem = false; } else // MultiPV > 1 @@ -923,7 +1016,11 @@ namespace { } alpha = rml.get_move_score(Min(i, MultiPV-1)); } - } + } // New best move case + + assert(alpha >= oldAlpha); + + FailLow = (alpha == oldAlpha); } return alpha; } @@ -939,16 +1036,17 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); + 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. + init_node(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; @@ -984,8 +1082,9 @@ namespace { int moveCount = 0; Value value, bestValue = -VALUE_INFINITE; Bitboard dcCandidates = mp.discovered_check_candidates(); + Color us = pos.side_to_move(); bool isCheck = pos.is_check(); - bool mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); + bool mateThreat = pos.has_mate_threat(opposite_color(us)); // Loop through all legal moves until no moves remain or a beta cutoff // occurs. @@ -1001,21 +1100,14 @@ namespace { movesSearched[moveCount++] = ss[ply].currentMove = move; - if (moveIsCapture) - ss[ply].currentMoveCaptureValue = pos.midgame_value_of_piece_on(move_to(move)); - else if (move_is_ep(move)) - ss[ply].currentMoveCaptureValue = PawnValueMidgame; - else - ss[ply].currentMoveCaptureValue = Value(0); - // Decide the new search depth bool dangerous; - Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &dangerous); + Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Make and search the move - UndoInfo u; - pos.do_move(move, u, dcCandidates); + StateInfo st; + pos.do_move(move, st, dcCandidates); if (moveCount == 1) // The first move in list is the PV value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID); @@ -1037,7 +1129,7 @@ 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); @@ -1057,7 +1149,7 @@ namespace { } } } - pos.undo_move(move, u); + pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1075,7 +1167,9 @@ 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 <= IterationInfo[Iteration-1].value - ProblemMargin) Problem = true; } @@ -1132,21 +1226,22 @@ 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(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); @@ -1169,39 +1264,31 @@ namespace { Value approximateEval = quick_evaluate(pos); bool mateThreat = false; - bool nullDrivenIID = false; bool isCheck = pos.is_check(); // Null move search if ( allowNullmove && depth > OnePly && !isCheck + && !value_is_mate(beta) && ok_to_do_nullmove(pos) && approximateEval >= beta - NullMoveMargin) { ss[ply].currentMove = MOVE_NULL; - UndoInfo u; - pos.do_null_move(u); - int R = (depth >= 4 * OnePly ? 4 : 3); // Null move dynamic reduction + StateInfo st; + pos.do_null_move(st); + int R = (depth >= 5 * 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 there is a good possibility that this is a cut-node. - // We will do an IID later to find a ttMove. - if ( UseNullDrivenIID - && nullValue < beta - && depth > 6 * OnePly - && 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) + pos.undo_null_move(); + + if (value_is_mate(nullValue)) + { + /* Do not return unproven mates */ + } + else if (nullValue >= beta) { if (depth < 6 * OnePly) return beta; @@ -1218,10 +1305,8 @@ namespace { // 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 @@ -1230,11 +1315,17 @@ namespace { } } // Null move search not allowed, try razoring - else if ( (approximateEval < beta - RazorMargin && depth < RazorDepth) - ||(approximateEval < beta - PawnValueMidgame && depth <= OnePly)) + else if ( !value_is_mate(beta) + && approximateEval < 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 <= 2*OnePly && v < beta - RazorMargin) + || (depth <= OnePly && v < beta - RazorMargin / 2)) return v; } @@ -1245,20 +1336,6 @@ 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 is a cut-node. So it's a good time to search for a ttMove. - 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: @@ -1289,7 +1366,7 @@ namespace { // Decide the new search depth bool dangerous; - Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &dangerous); + Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Futility pruning @@ -1298,15 +1375,18 @@ namespace { && !moveIsCapture && !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) { @@ -1318,8 +1398,8 @@ namespace { } // Make and search the move - UndoInfo u; - pos.do_move(move, u, dcCandidates); + StateInfo st; + pos.do_move(move, st, dcCandidates); // 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. @@ -1342,7 +1422,7 @@ namespace { ss[ply].reduction = Depth(0); value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID); } - pos.undo_move(move, u); + pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1393,6 +1473,9 @@ namespace { } TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER); } + + assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); + return bestValue; } @@ -1410,35 +1493,67 @@ 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(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; - // Transposition table lookup - const TTEntry* tte = TT.retrieve(pos); - if (tte && ok_to_use_TT(tte, depth, beta, ply)) - return value_from_tt(tte->value(), ply); + // Transposition table lookup, only when not in PV + TTEntry* tte = NULL; + bool pvNode = (beta - alpha != 1); + if (!pvNode) + { + tte = TT.retrieve(pos); + if (tte && ok_to_use_TT(tte, depth, beta, ply)) + { + assert(tte->type() != VALUE_TYPE_EVAL); + + return value_from_tt(tte->value(), ply); + } + } + Move ttMove = (tte ? tte->move() : MOVE_NONE); // Evaluate the position statically - Value staticValue = evaluate(pos, ei, threadID); + EvalInfo ei; + Value staticValue; + bool isCheck = pos.is_check(); + ei.futilityMargin = Value(0); // Manually initialize futilityMargin + + if (isCheck) + staticValue = -VALUE_INFINITE; + + else if (tte && tte->type() == VALUE_TYPE_EVAL) + { + // Use the cached evaluation score if possible + assert(tte->value() == evaluate(pos, ei, threadID)); + assert(ei.futilityMargin == Value(0)); + + staticValue = tte->value(); + } + else + staticValue = 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) + { + // Store the score to avoid a future costly evaluation() call + if (!isCheck && !tte && ei.futilityMargin == 0) + TT.store(pos, value_to_tt(bestValue, ply), Depth(-127*OnePly), MOVE_NONE, VALUE_TYPE_EVAL); + return bestValue; + } if (bestValue > alpha) alpha = bestValue; @@ -1446,13 +1561,12 @@ 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, EmptySearchStack, depth, &ei); + MovePicker mp = MovePicker(pos, pvNode, ttMove, EmptySearchStack, depth); Move move; int moveCount = 0; Bitboard dcCandidates = mp.discovered_check_candidates(); - bool isCheck = pos.is_check(); - bool pvNode = (beta - alpha != 1); - bool enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; + Color us = pos.side_to_move(); + bool enoughMaterial = pos.non_pawn_material(us) > RookValueMidgame; // Loop through the moves until no moves remain or a beta cutoff // occurs. @@ -1476,7 +1590,8 @@ namespace { 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) @@ -1496,10 +1611,10 @@ namespace { continue; // Make and search the move. - UndoInfo u; - pos.do_move(move, u, dcCandidates); + StateInfo st; + pos.do_move(move, st, dcCandidates); Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID); - pos.undo_move(move, u); + pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1523,15 +1638,20 @@ namespace { assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); // Update transposition table - TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_EXACT); + Move m = ss[ply].pv[ply]; + if (!pvNode) + { + Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1)); + if (bestValue < beta) + TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER); + else + TT.store(pos, value_to_tt(bestValue, ply), d, m, VALUE_TYPE_LOWER); + } // 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; } @@ -1575,7 +1695,7 @@ namespace { // Decide the new search depth. bool dangerous; - Depth ext = extension(pos, move, false, moveIsCheck, false, false, &dangerous); + Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Prune? @@ -1588,8 +1708,8 @@ namespace { continue; // Make and search the move. - UndoInfo u; - pos.do_move(move, u, sp->dcCandidates); + StateInfo st; + pos.do_move(move, st, sp->dcCandidates); // 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. @@ -1611,7 +1731,7 @@ namespace { ss[sp->ply].reduction = Depth(0); value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID); } - pos.undo_move(move, u); + pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1679,9 +1799,6 @@ namespace { assert(move_is_ok(move)); - ss[sp->ply].currentMoveCaptureValue = move_is_ep(move)? - PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move)); - lock_grab(&(sp->lock)); int moveCount = ++sp->moves; lock_release(&(sp->lock)); @@ -1690,12 +1807,12 @@ namespace { // Decide the new search depth. bool dangerous; - Depth ext = extension(pos, move, true, moveIsCheck, false, false, &dangerous); + Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Make and search the move. - UndoInfo u; - pos.do_move(move, u, sp->dcCandidates); + StateInfo st; + pos.do_move(move, st, sp->dcCandidates); // 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. @@ -1731,7 +1848,7 @@ namespace { Threads[threadID].failHighPly1 = false; } } - pos.undo_move(move, u); + pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1761,8 +1878,10 @@ 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 <= IterationInfo[Iteration-1].value - ProblemMargin) Problem = true; } lock_release(&(sp->lock)); @@ -1771,7 +1890,7 @@ 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]) @@ -1854,15 +1973,15 @@ namespace { if (includeMove) { // Find a quick score for the move - UndoInfo u; + StateInfo st; SearchStack ss[PLY_MAX_PLUS_2]; moves[count].move = mlist[i].move; moves[count].nodes = 0ULL; - pos.do_move(moves[count].move, u); + pos.do_move(moves[count].move, st); moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0); - pos.undo_move(moves[count].move, u); + pos.undo_move(moves[count].move); moves[count].pv[0] = moves[i].move; moves[count].pv[1] = MOVE_NONE; // FIXME count++; @@ -1964,41 +2083,13 @@ 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].threatMove = MOVE_NONE; - ss[i].reduction = Depth(0); - for (int j = 0; j < KILLER_MAX; j++) - ss[i].killers[j] = MOVE_NONE; - } - } - - // init_node() is called at the beginning of all the search functions // (search(), search_pv(), qsearch(), and so on) and initializes the search // stack object corresponding to the current node. Once every // NodesBetweenPolls nodes, init_node() also calls poll(), which polls // for user input and checks whether it is time to stop the search. - void init_node(const Position &pos, SearchStack ss[], int ply, int threadID) { + void init_node(SearchStack ss[], int ply, int threadID) { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); @@ -2011,13 +2102,9 @@ 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].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; + + ss[ply].init(ply); + ss[ply+2].initKillers(); if(Threads[threadID].printCurrentLine) print_current_line(ss, ply, threadID); @@ -2088,7 +2175,7 @@ namespace { // Case 4: The destination square for m2 is attacked by the moving piece // in m1: - if(pos.piece_attacks_square(t1, t2)) + if(pos.piece_attacks_square(pos.piece_on(t1), t1, t2)) return true; // Case 5: Discovered check, checking piece is the piece moved in m1: @@ -2120,6 +2207,18 @@ 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. @@ -2141,9 +2240,11 @@ namespace { // 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, + Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous) { + assert(m != MOVE_NONE); + Depth result = Depth(0); *dangerous = check || singleReply || mateThreat; @@ -2156,28 +2257,33 @@ namespace { if (mateThreat) result += MateThreatExtension[pvNode]; - if (pos.move_is_pawn_push_to_7th(m)) + if (pos.type_of_piece_on(move_from(m)) == PAWN) { - result += PawnPushTo7thExtension[pvNode]; - *dangerous = true; - } - if (pos.move_is_passed_pawn_push(m)) - { - result += PassedPawnExtension[pvNode]; - *dangerous = true; + 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.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame + if ( capture + && 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_promotion(m) + && !move_is_ep(m)) { result += PawnEndgameExtension[pvNode]; *dangerous = true; } if ( pvNode - && pos.move_is_capture(m) + && capture && pos.type_of_piece_on(move_to(m)) != PAWN && pos.see(m) >= 0) { @@ -2236,7 +2342,7 @@ namespace { // value of the threatening piece, don't prune move which defend it. if ( !PruneDefendingMoves && threat != MOVE_NONE - && pos.type_of_piece_on(tto) != NO_PIECE_TYPE + && 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)) @@ -2251,7 +2357,8 @@ namespace { if ( !PruneBlockingMoves && threat != MOVE_NONE && piece_is_slider(pos.piece_on(tfrom)) - && bit_is_set(squares_between(tfrom, tto), mto) && pos.see(m) >= 0) + && bit_is_set(squares_between(tfrom, tto), mto) + && pos.see(m) >= 0) return false; return true; @@ -2403,11 +2510,11 @@ namespace { return; bool overTime = t > AbsoluteMaxSearchTime - || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime) - || ( !FailHigh && !fail_high_ply_1() && !Problem + || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow) //FIXME: We are not checking any problem flags, BUG? + || ( !FailHigh && !FailLow && !fail_high_ply_1() && !Problem && t > 6*(MaxSearchTime + ExtraSearchTime)); - if ( (Iteration >= 2 && (!InfiniteSearch && overTime)) + if ( (Iteration >= 3 && (!InfiniteSearch && overTime)) || (ExactMaxTime && t >= ExactMaxTime) || (Iteration >= 3 && MaxNodes && nodes_searched() >= MaxNodes)) AbortSearch = true; @@ -2421,12 +2528,12 @@ namespace { void ponderhit() { int t = current_search_time(); PonderSearch = false; - if(Iteration >= 2 && + if(Iteration >= 3 && (!InfiniteSearch && (StopOnPonderhit || t > AbsoluteMaxSearchTime || (RootMoveNumber == 1 && - t > MaxSearchTime + ExtraSearchTime) || - (!FailHigh && !fail_high_ply_1() && !Problem && + t > MaxSearchTime + ExtraSearchTime && !FailLow) || + (!FailHigh && !FailLow && !fail_high_ply_1() && !Problem && t > 6*(MaxSearchTime + ExtraSearchTime))))) AbortSearch = true; } @@ -2629,9 +2736,9 @@ namespace { // splitPoint->cpus becomes 0), split() returns true. bool split(const Position &p, SearchStack *sstck, int ply, - Value *alpha, Value *beta, Value *bestValue, - Depth depth, int *moves, + Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves, MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) { + assert(p.is_ok()); assert(sstck != NULL); assert(ply >= 0 && ply < PLY_MAX);