X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=085d124ee66b994819a1e8e71e20bf99eb3532cd;hp=29dc00a996d2e97337c819b29a99681c49f9806f;hb=db097921bc0f631d770c3437569f105579823471;hpb=e5463eb3ae6c1a035fe1da717fb88568ee654237 diff --git a/src/search.cpp b/src/search.cpp index 29dc00a9..085d124e 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -41,7 +41,8 @@ namespace Search { volatile SignalsType Signals; LimitsType Limits; std::vector RootMoves; - Position RootPosition; + Position RootPos; + Color RootColor; Time::point SearchTime; StateStackPtr SetupStates; } @@ -55,35 +56,15 @@ namespace { // Set to true to force running with one thread. Used for debugging const bool FakeSplit = false; + // This is the minimum interval in msec between two check_time() calls + const int TimerResolution = 5; + // Different node types, used as template parameter enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; - // Lookup table to check if a Piece is a slider and its access function - const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; - inline bool piece_is_slider(Piece p) { return Slidings[p]; } - - // Maximum depth for razoring - const Depth RazorDepth = 4 * ONE_PLY; - // Dynamic razoring margin based on depth inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } - // Maximum depth for use of dynamic threat detection when null move fails low - const Depth ThreatDepth = 5 * ONE_PLY; - - // Minimum depth for use of internal iterative deepening - const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY }; - - // At Non-PV nodes we do an internal iterative deepening search - // when the static evaluation is bigger then beta - IIDMargin. - const Value IIDMargin = Value(256); - - // Minimum depth for use of singular extension - const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY }; - - // Futility margin for quiescence search - const Value FutilityMarginQS = Value(128); - // Futility lookup tables (initialized at startup) and their access functions Value FutilityMargins[16][64]; // [depth][moveNumber] int FutilityMoveCounts[32]; // [depth] @@ -94,11 +75,6 @@ namespace { : 2 * VALUE_INFINITE; } - inline int futility_move_count(Depth d) { - - return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES; - } - // Reduction lookup tables (initialized at startup) and their access function int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] @@ -107,62 +83,41 @@ namespace { return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; } - // Easy move margin. An easy move candidate must be at least this much better - // than the second best move. - const Value EasyMoveMargin = Value(0x150); - - // This is the minimum interval in msec between two check_time() calls - const int TimerResolution = 5; - - - size_t MultiPV, UCIMultiPV, PVIdx; + size_t PVSize, PVIdx; TimeManager TimeMgr; int BestMoveChanges; - int SkillLevel; - bool SkillLevelEnabled, Chess960; + Value DrawValue[COLOR_NB]; History H; - template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); void id_loop(Position& pos); - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta); - bool connected_moves(const Position& pos, Move m1, Move m2); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool can_return_tt(const TTEntry* tte, Depth depth, Value ttValue, Value beta); - bool connected_threat(const Position& pos, Move m, Move threat); - Value refine_eval(const TTEntry* tte, Value ttValue, Value defaultEval); - Move do_skill_level(); + bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta); + bool allows_move(const Position& pos, Move first, Move second); + bool prevents_move(const Position& pos, Move first, Move second); string uci_pv(const Position& pos, int depth, Value alpha, Value beta); - // is_dangerous() checks whether a move belongs to some classes of known - // 'dangerous' moves so that we avoid to prune it. - FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) { - - // Castle move? - if (type_of(m) == CASTLE) - return true; + struct Skill { + Skill(int l) : level(l), best(MOVE_NONE) {} + ~Skill() { + if (enabled()) // Swap best PV line with the sub-optimal one + std::swap(RootMoves[0], *std::find(RootMoves.begin(), + RootMoves.end(), best ? best : pick_move())); + } - // Passed pawn move? - if ( type_of(pos.piece_moved(m)) == PAWN - && pos.pawn_is_passed(pos.side_to_move(), to_sq(m))) - return true; + bool enabled() const { return level < 20; } + bool time_to_pick(int depth) const { return depth == 1 + level; } + Move pick_move(); - // Entering a pawn endgame? - if ( captureOrPromotion - && type_of(pos.piece_on(to_sq(m))) != PAWN - && type_of(m) == NORMAL - && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) - - PieceValue[Mg][pos.piece_on(to_sq(m))] == VALUE_ZERO)) - return true; - - return false; - } + int level; + Move best; + }; } // namespace @@ -190,7 +145,7 @@ void Search::init() { // Init futility move count array for (d = 0; d < 32; d++) - FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(d, 2.0)); + FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(double(d), 2.0)); } @@ -220,31 +175,28 @@ size_t Search::perft(Position& pos, Depth depth) { /// Search::think() is the external interface to Stockfish's search, and is /// called by the main thread when the program receives the UCI 'go' command. It -/// searches from RootPosition and at the end prints the "bestmove" to output. +/// searches from RootPos and at the end prints the "bestmove" to output. void Search::think() { static PolyglotBook book; // Defined static to initialize the PRNG only once - Position& pos = RootPosition; - Chess960 = pos.is_chess960(); - Eval::RootColor = pos.side_to_move(); - TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move()); - TT.new_search(); - H.clear(); + RootColor = RootPos.side_to_move(); + TimeMgr.init(Limits, RootPos.startpos_ply_counter(), RootColor); if (RootMoves.empty()) { + RootMoves.push_back(MOVE_NONE); sync_cout << "info depth 0 score " - << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; + << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << sync_endl; - RootMoves.push_back(MOVE_NONE); goto finalize; } if (Options["OwnBook"] && !Limits.infinite) { - Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]); + Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]); if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove)) { @@ -253,22 +205,24 @@ void Search::think() { } } - UCIMultiPV = Options["MultiPV"]; - SkillLevel = Options["Skill Level"]; - - // Do we have to play with skill handicap? In this case enable MultiPV that - // we will use behind the scenes to retrieve a set of possible moves. - SkillLevelEnabled = (SkillLevel < 20); - MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV); + if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) + { + int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns + cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase + DrawValue[ RootColor] = VALUE_DRAW - Value(cf); + DrawValue[~RootColor] = VALUE_DRAW + Value(cf); + } + else + DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW; if (Options["Use Search Log"]) { Log log(Options["Search Log Filename"]); - log << "\nSearching: " << pos.to_fen() + log << "\nSearching: " << RootPos.fen() << "\ninfinite: " << Limits.infinite << " ponder: " << Limits.ponder - << " time: " << Limits.time[pos.side_to_move()] - << " increment: " << Limits.inc[pos.side_to_move()] + << " time: " << Limits.time[RootColor] + << " increment: " << Limits.inc[RootColor] << " moves to go: " << Limits.movestogo << std::endl; } @@ -278,12 +232,14 @@ void Search::think() { // Set best timer interval to avoid lagging under time pressure. Timer is // used to check for remaining available thinking time. if (Limits.use_time_management()) - Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 16, TimerResolution))); + Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 16, + TimerResolution))); + else if (Limits.nodes) + Threads.set_timer(2 * TimerResolution); else Threads.set_timer(100); - // We're ready to start searching. Call the iterative deepening loop function - id_loop(pos); + id_loop(RootPos); // Let's start searching ! Threads.set_timer(0); // Stop timer Threads.sleep(); @@ -293,14 +249,14 @@ void Search::think() { Time::point elapsed = Time::now() - SearchTime + 1; Log log(Options["Search Log Filename"]); - log << "Nodes: " << pos.nodes_searched() - << "\nNodes/second: " << pos.nodes_searched() * 1000 / elapsed - << "\nBest move: " << move_to_san(pos, RootMoves[0].pv[0]); + log << "Nodes: " << RootPos.nodes_searched() + << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed + << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]); StateInfo st; - pos.do_move(RootMoves[0].pv[0], st); - log << "\nPonder move: " << move_to_san(pos, RootMoves[0].pv[1]) << std::endl; - pos.undo_move(RootMoves[0].pv[0]); + RootPos.do_move(RootMoves[0].pv[0], st); + log << "\nPonder move: " << move_to_san(RootPos, RootMoves[0].pv[1]) << std::endl; + RootPos.undo_move(RootMoves[0].pv[0]); } finalize: @@ -309,11 +265,12 @@ finalize: // but if we are pondering or in infinite search, we shouldn't print the best // move before we are told to do so. if (!Signals.stop && (Limits.ponder || Limits.infinite)) - pos.this_thread()->wait_for_stop_or_ponderhit(); + RootPos.this_thread()->wait_for_stop_or_ponderhit(); // Best move could be MOVE_NONE when searching on a stalemate position - sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], Chess960) - << " ponder " << move_to_uci(RootMoves[0].pv[1], Chess960) << sync_endl; + sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960()) + << " ponder " << move_to_uci(RootMoves[0].pv[1], RootPos.is_chess960()) + << sync_endl; } @@ -329,26 +286,37 @@ namespace { int depth, prevBestMoveChanges; Value bestValue, alpha, beta, delta; bool bestMoveNeverChanged = true; - Move skillBest = MOVE_NONE; memset(ss, 0, 4 * sizeof(Stack)); depth = BestMoveChanges = 0; bestValue = delta = -VALUE_INFINITE; ss->currentMove = MOVE_NULL; // Hack to skip update gains + TT.new_search(); + H.clear(); + + PVSize = Options["MultiPV"]; + Skill skill(Options["Skill Level"]); + + // Do we have to play with skill handicap? In this case enable MultiPV search + // that we will use behind the scenes to retrieve a set of possible moves. + if (skill.enabled() && PVSize < 4) + PVSize = 4; + + PVSize = std::min(PVSize, RootMoves.size()); // Iterative deepening loop until requested to stop or target depth reached - while (!Signals.stop && ++depth <= MAX_PLY && (!Limits.depth || depth <= Limits.depth)) + while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) { // Save last iteration's scores before first PV line is searched and all // the move scores but the (new) PV are set to -VALUE_INFINITE. for (size_t i = 0; i < RootMoves.size(); i++) RootMoves[i].prevScore = RootMoves[i].score; - prevBestMoveChanges = BestMoveChanges; + prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1 BestMoveChanges = 0; // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < std::min(MultiPV, RootMoves.size()); PVIdx++) + for (PVIdx = 0; PVIdx < PVSize; PVIdx++) { // Set aspiration window default width if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN) @@ -379,37 +347,37 @@ namespace { // the already searched PV lines are preserved. sort(RootMoves.begin() + PVIdx, RootMoves.end()); - // In case we have found an exact score and we are going to leave - // the fail high/low loop then reorder the PV moves, otherwise - // leave the last PV move in its position so to be searched again. - // Of course this is needed only in MultiPV search. - if (PVIdx && bestValue > alpha && bestValue < beta) - sort(RootMoves.begin(), RootMoves.begin() + PVIdx); - // Write PV back to transposition table in case the relevant // entries have been overwritten during the search. for (size_t i = 0; i <= PVIdx; i++) RootMoves[i].insert_pv_in_tt(pos); - // If search has been stopped exit the aspiration window loop. - // Sorting and writing PV back to TT is safe becuase RootMoves - // is still valid, although refers to previous iteration. + // If search has been stopped return immediately. Sorting and + // writing PV back to TT is safe becuase RootMoves is still + // valid, although refers to previous iteration. if (Signals.stop) + return; + + // In case of failing high/low increase aspiration window and + // research, otherwise exit the loop. + if (bestValue > alpha && bestValue < beta) break; - // Send full PV info to GUI if we are going to leave the loop or - // if we have a fail high/low and we are deep in the search. - if ((bestValue > alpha && bestValue < beta) || Time::now() - SearchTime > 2000) + // Give some update (without cluttering the UI) before to research + if (Time::now() - SearchTime > 3000) sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; - // In case of failing high/low increase aspiration window and - // research, otherwise exit the fail high/low loop. - if (bestValue >= beta) + if (abs(bestValue) >= VALUE_KNOWN_WIN) + { + alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; + } + else if (bestValue >= beta) { beta += delta; delta += delta / 2; } - else if (bestValue <= alpha) + else { Signals.failedLowAtRoot = true; Signals.stopOnPonderhit = false; @@ -417,25 +385,21 @@ namespace { alpha -= delta; delta += delta / 2; } - else - break; - - // Search with full window in case we have a win/mate score - if (abs(bestValue) >= VALUE_KNOWN_WIN) - { - alpha = -VALUE_INFINITE; - beta = VALUE_INFINITE; - } assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); } + + // Sort the PV lines searched so far and update the GUI + sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); + if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000) + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; } - // Skills: Do we need to pick now the best move ? - if (SkillLevelEnabled && depth == 1 + SkillLevel) - skillBest = do_skill_level(); + // Do we need to pick now the sub-optimal best move ? + if (skill.enabled() && skill.time_to_pick(depth)) + skill.pick_move(); - if (!Signals.stop && Options["Use Search Log"]) + if (Options["Use Search Log"]) { Log log(Options["Search Log Filename"]); log << pretty_pv(pos, depth, bestValue, Time::now() - SearchTime, &RootMoves[0].pv[0]) @@ -447,12 +411,12 @@ namespace { bestMoveNeverChanged = false; // Do we have time for the next iteration? Can we stop searching now? - if (!Signals.stop && !Signals.stopOnPonderhit && Limits.use_time_management()) + if (Limits.use_time_management() && !Signals.stopOnPonderhit) { bool stop = false; // Local variable, not the volatile Signals.stop // Take in account some extra time if the best move has changed - if (depth > 4 && depth < 50) + if (depth > 4 && depth < 50 && PVSize == 1) TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges); // Stop search if most of available time is already consumed. We @@ -464,10 +428,11 @@ namespace { // Stop search early if one move seems to be much better than others if ( depth >= 12 && !stop + && PVSize == 1 && ( (bestMoveNeverChanged && pos.captured_piece_type()) || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100)) { - Value rBeta = bestValue - EasyMoveMargin; + Value rBeta = bestValue - 2 * PawnValueMg; (ss+1)->excludedMove = RootMoves[0].pv[0]; (ss+1)->skipNullMove = true; Value v = search(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY); @@ -489,15 +454,6 @@ namespace { } } } - - // When using skills swap best PV line with the sub-optimal one - if (SkillLevelEnabled) - { - if (skillBest == MOVE_NONE) // Still unassigned ? - skillBest = do_skill_level(); - - std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), skillBest)); - } } @@ -526,55 +482,48 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove, threatMove; Depth ext, newDepth; - Bound bt; - Value bestValue, value, oldAlpha, ttValue; - Value refinedValue, nullValue, futilityValue; - bool pvMove, inCheck, singularExtensionNode, givesCheck; - bool captureOrPromotion, dangerous, doFullDepthSearch; + Value bestValue, value, ttValue; + Value eval, nullValue, futilityValue; + bool inCheck, givesCheck, pvMove, singularExtensionNode; + bool captureOrPromotion, dangerous, doFullDepthSearch, threatExtension; int moveCount, playedMoveCount; + // Step 1. Initialize node Thread* thisThread = pos.this_thread(); moveCount = playedMoveCount = 0; - oldAlpha = alpha; - inCheck = pos.in_check(); - ss->ply = (ss-1)->ply + 1; - - // Used to send selDepth info to GUI - if (PvNode && thisThread->maxPly < ss->ply) - thisThread->maxPly = ss->ply; + threatExtension = false; + inCheck = pos.checkers(); - // Step 1. Initialize node if (SpNode) { + sp = ss->sp; + bestMove = sp->bestMove; + threatMove = sp->threatMove; + bestValue = sp->bestValue; tte = NULL; ttMove = excludedMove = MOVE_NONE; ttValue = VALUE_NONE; - sp = ss->sp; - bestMove = sp->bestMove; - threatMove = sp->threatMove; - bestValue = sp->bestValue; - assert(bestValue > -VALUE_INFINITE && sp->moveCount > 0); + assert(sp->bestValue > -VALUE_INFINITE && sp->moveCount > 0); goto split_point_start; } - else - { - bestValue = -VALUE_INFINITE; - ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; - (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; - } - // Enforce node limit here. FIXME: This only works with 1 search thread. - if (Limits.nodes && pos.nodes_searched() >= Limits.nodes) - Signals.stop = true; + bestValue = -VALUE_INFINITE; + ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->ply = (ss-1)->ply + 1; + (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; + (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + + // Used to send selDepth info to GUI + if (PvNode && thisThread->maxPly < ss->ply) + thisThread->maxPly = ss->ply; if (!RootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) - return VALUE_DRAW; + if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) + return DrawValue[pos.side_to_move()]; // Step 3. Mate distance pruning. Even if we mate at the next move our score // would be at best mate_in(ss->ply+1), but if alpha is already bigger because @@ -601,8 +550,13 @@ namespace { // a fail high/low. Biggest advantage at probing at PV nodes is to have a // smooth experience in analysis mode. We don't probe at Root nodes otherwise // we should also update RootMoveList to avoid bogus output. - if (!RootNode && tte && (PvNode ? tte->depth() >= depth && tte->type() == BOUND_EXACT - : can_return_tt(tte, depth, ttValue, beta))) + if ( !RootNode + && tte + && tte->depth() >= depth + && ttValue != VALUE_NONE // Only in case of TT access race + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { TT.refresh(tte); ss->currentMove = ttMove; // Can be MOVE_NONE @@ -620,44 +574,43 @@ namespace { // Step 5. Evaluate the position statically and update parent's gain statistics if (inCheck) - ss->eval = ss->evalMargin = refinedValue = VALUE_NONE; - else if (tte) - { - assert(tte->static_value() != VALUE_NONE); - - ss->eval = tte->static_value(); - ss->evalMargin = tte->static_value_margin(); - refinedValue = refine_eval(tte, ttValue, ss->eval); - } + ss->staticEval = ss->evalMargin = eval = VALUE_NONE; else { - refinedValue = ss->eval = evaluate(pos, ss->evalMargin); - TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin); + eval = ss->staticEval = evaluate(pos, ss->evalMargin); + + // Can ttValue be used as a better position evaluation? + if (tte && ttValue != VALUE_NONE) + { + if ( ((tte->type() & BOUND_LOWER) && ttValue > eval) + || ((tte->type() & BOUND_UPPER) && ttValue < eval)) + eval = ttValue; + } } // Update gain for the parent non-capture move given the static position // evaluation before and after the move. - if ( (move = (ss-1)->currentMove) != MOVE_NULL - && (ss-1)->eval != VALUE_NONE - && ss->eval != VALUE_NONE + if ( (move = (ss-1)->currentMove) != MOVE_NULL + && (ss-1)->staticEval != VALUE_NONE + && ss->staticEval != VALUE_NONE && !pos.captured_piece_type() && type_of(move) == NORMAL) { Square to = to_sq(move); - H.update_gain(pos.piece_on(to), to, -(ss-1)->eval - ss->eval); + H.update_gain(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval); } // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode - && depth < RazorDepth + && depth < 4 * ONE_PLY && !inCheck - && refinedValue + razor_margin(depth) < beta + && eval + razor_margin(depth) < beta && ttMove == MOVE_NONE && abs(beta) < VALUE_MATE_IN_MAX_PLY && !pos.pawn_on_7th(pos.side_to_move())) { Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); + Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -669,19 +622,19 @@ namespace { // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode && !ss->skipNullMove - && depth < RazorDepth + && depth < 4 * ONE_PLY && !inCheck - && refinedValue - futility_margin(depth, 0) >= beta + && eval - FutilityMargins[depth][0] >= beta && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) - return refinedValue - futility_margin(depth, 0); + return eval - FutilityMargins[depth][0]; // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode && !ss->skipNullMove && depth > ONE_PLY && !inCheck - && refinedValue >= beta + && eval >= beta && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) { @@ -691,12 +644,12 @@ namespace { Depth R = 3 * ONE_PLY + depth / 4; // Null move dynamic reduction based on value - if (refinedValue - PawnValueMg > beta) + if (eval - PawnValueMg > beta) R += ONE_PLY; pos.do_null_move(st); (ss+1)->skipNullMove = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) : - search(pos, ss+1, -beta, -alpha, depth-R); (ss+1)->skipNullMove = false; pos.do_null_move(st); @@ -723,16 +676,15 @@ namespace { // 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 // the move that refuted the null move was somehow connected to the - // 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). + // move which was reduced. If a connection is found extend moves that + // defend against threat. threatMove = (ss+1)->currentMove; - if ( depth < ThreatDepth + if ( depth < 5 * ONE_PLY && (ss-1)->reduction && threatMove != MOVE_NONE - && connected_moves(pos, (ss-1)->currentMove, threatMove)) - return beta - 1; + && allows_move(pos, (ss-1)->currentMove, threatMove)) + threatExtension = true; } } @@ -741,7 +693,7 @@ namespace { // and a reduced search returns a value much above beta, we can (almost) safely // prune the previous move. if ( !PvNode - && depth >= RazorDepth + ONE_PLY + && depth >= 5 * ONE_PLY && !inCheck && !ss->skipNullMove && excludedMove == MOVE_NONE @@ -770,9 +722,9 @@ namespace { } // Step 10. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] + if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) && ttMove == MOVE_NONE - && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta))) + && (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta))) { Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2); @@ -791,7 +743,7 @@ split_point_start: // At split points actual search starts from here value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc singularExtensionNode = !RootNode && !SpNode - && depth >= SingularExtensionDepth[PvNode] + && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY) && ttMove != MOVE_NONE && !excludedMove // Recursive singular search is not allowed && (tte->type() & BOUND_LOWER) @@ -799,10 +751,7 @@ split_point_start: // At split points actual search starts from here // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs - while ( bestValue < beta - && (move = mp.next_move()) != MOVE_NONE - && !thisThread->cutoff_occurred() - && !Signals.stop) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); @@ -831,21 +780,31 @@ split_point_start: // At split points actual search starts from here { Signals.firstRootMove = (moveCount == 1); - if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000) + if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000) sync_cout << "info depth " << depth / ONE_PLY - << " currmove " << move_to_uci(move, Chess960) + << " currmove " << move_to_uci(move, pos.is_chess960()) << " currmovenumber " << moveCount + PVIdx << sync_endl; } + ext = DEPTH_ZERO; captureOrPromotion = pos.is_capture_or_promotion(move); givesCheck = pos.move_gives_check(move, ci); - dangerous = givesCheck || is_dangerous(pos, move, captureOrPromotion); - ext = DEPTH_ZERO; + dangerous = givesCheck + || pos.is_passed_pawn_push(move) + || type_of(move) == CASTLE + || ( captureOrPromotion // Entering a pawn endgame? + && type_of(pos.piece_on(to_sq(move))) != PAWN + && type_of(move) == NORMAL + && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) + - PieceValue[MG][pos.piece_on(to_sq(move))] == VALUE_ZERO)); // Step 12. Extend checks and, in PV nodes, also dangerous moves if (PvNode && dangerous) ext = ONE_PLY; + else if (threatExtension && prevents_move(pos, move, threatMove)) + ext = ONE_PLY; + else if (givesCheck && pos.see_sign(move) >= 0) ext = ONE_PLY / 2; @@ -855,11 +814,13 @@ split_point_start: // At split points actual search starts from here // on all the other moves but the ttMove, if result is lower than ttValue minus // a margin then we extend ttMove. if ( singularExtensionNode - && !ext && move == ttMove + && !ext && pos.pl_move_is_legal(move, ci.pinned) && abs(ttValue) < VALUE_KNOWN_WIN) { + assert(ttValue != VALUE_NONE); + Value rBeta = ttValue - int(depth); ss->excludedMove = move; ss->skipNullMove = true; @@ -868,7 +829,7 @@ split_point_start: // At split points actual search starts from here ss->excludedMove = MOVE_NONE; if (value < rBeta) - ext = ONE_PLY; + ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY; } // Update current move (this must be done after singular extension search) @@ -880,11 +841,13 @@ split_point_start: // At split points actual search starts from here && !inCheck && !dangerous && move != ttMove - && (bestValue > VALUE_MATED_IN_MAX_PLY || bestValue == -VALUE_INFINITE)) + && (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE + && alpha > VALUE_MATED_IN_MAX_PLY))) { // Move count based pruning - if ( moveCount >= futility_move_count(depth) - && (!threatMove || !connected_threat(pos, move, threatMove))) + if ( depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[depth] + && (!threatMove || !prevents_move(pos, move, threatMove))) { if (SpNode) sp->mutex.lock(); @@ -896,7 +859,7 @@ split_point_start: // At split points actual search starts from here // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth, // but fixing this made program slightly weaker. Depth predictedDepth = newDepth - reduction(depth, moveCount); - futilityValue = ss->eval + ss->evalMargin + futility_margin(predictedDepth, moveCount) + futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount) + H.gain(pos.piece_moved(move), to_sq(move)); if (futilityValue < beta) @@ -919,7 +882,7 @@ split_point_start: // At split points actual search starts from here } // Check for legality only before to do the move - if (!pos.pl_move_is_legal(move, ci.pinned)) + if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned)) { moveCount--; continue; @@ -958,7 +921,9 @@ split_point_start: // At split points actual search starts from here if (doFullDepthSearch) { alpha = SpNode ? sp->alpha : alpha; - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + value = newDepth < ONE_PLY ? + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); } @@ -966,9 +931,10 @@ split_point_start: // At split points actual search starts from here // high, in the latter case search only if value < beta, otherwise let the // parent node to fail low with value <= alpha and to try another move. if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta)))) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + value = newDepth < ONE_PLY ? + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) : - search(pos, ss+1, -beta, -alpha, newDepth); - // Step 17. Undo move pos.undo_move(move); @@ -986,7 +952,10 @@ split_point_start: // At split points actual search starts from here // 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 don't update the best move and/or PV. - if (RootNode && !Signals.stop) + if (Signals.stop || thisThread->cutoff_occurred()) + return value; // To avoid returning VALUE_INFINITE + + if (RootNode) { RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); @@ -999,7 +968,7 @@ split_point_start: // At split points actual search starts from here // We record how often the best move has been changed in each // iteration. This information is used for time management: When // the best move changes frequently, we allocate some more time. - if (!pvMove && MultiPV == 1) + if (!pvMove) BestMoveChanges++; } else @@ -1007,82 +976,84 @@ split_point_start: // At split points actual search starts from here // is not a problem when sorting becuase sort is stable and move // position in the list is preserved, just the PV is pushed up. rm.score = -VALUE_INFINITE; - } if (value > bestValue) { bestValue = value; - bestMove = move; - - if ( PvNode - && value > alpha - && value < beta) // We want always alpha < beta - alpha = value; + if (SpNode) sp->bestValue = value; - if (SpNode && !thisThread->cutoff_occurred()) + if (value > alpha) { - sp->bestValue = value; - sp->bestMove = move; - sp->alpha = alpha; - - if (value >= beta) - sp->cutoff = true; + bestMove = move; + if (SpNode) sp->bestMove = move; + + if (PvNode && value < beta) + { + alpha = value; // Update alpha here! Always alpha < beta + if (SpNode) sp->alpha = value; + } + else + { + assert(value >= beta); // Fail high + + if (SpNode) sp->cutoff = true; + break; + } } } - // Step 19. Check for split + // Step 19. Check for splitting the search if ( !SpNode && depth >= Threads.min_split_depth() - && bestValue < beta - && Threads.available_slave_exists(thisThread) - && !Signals.stop - && !thisThread->cutoff_occurred()) + && Threads.available_slave_exists(thisThread)) + { + assert(bestValue < beta); + bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove, - depth, threatMove, moveCount, &mp, NT); + depth, threatMove, moveCount, mp, NT); + if (bestValue >= beta) + break; + } } + if (SpNode) + return bestValue; + // Step 20. Check for mate and stalemate // All legal moves have been searched and if there are no legal moves, it // must be mate or stalemate. Note that we can have a false positive in // case of Signals.stop or thread.cutoff_occurred() are set, but this is // harmless because return value is discarded anyhow in the parent nodes. // If we are in a singular extension search then return a fail low score. + // A split node has at least one move, the one tried before to be splitted. if (!moveCount) - return excludedMove ? oldAlpha : inCheck ? mated_in(ss->ply) : VALUE_DRAW; + return excludedMove ? alpha + : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; // If we have pruned all the moves without searching return a fail-low score if (bestValue == -VALUE_INFINITE) { assert(!playedMoveCount); - bestValue = oldAlpha; + bestValue = alpha; } - // Step 21. Update tables - // Update transposition table entry, killers and history - if (!SpNode && !Signals.stop && !thisThread->cutoff_occurred()) + if (bestValue >= beta) // Failed high { - move = bestValue <= oldAlpha ? MOVE_NONE : bestMove; - bt = bestValue <= oldAlpha ? BOUND_UPPER - : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT; + TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, bestMove); - TT.store(posKey, value_to_tt(bestValue, ss->ply), bt, depth, move, ss->eval, ss->evalMargin); - - // Update killers and history for non capture cut-off moves - if ( bestValue >= beta - && !pos.is_capture_or_promotion(move) - && !inCheck) + if (!pos.is_capture_or_promotion(bestMove) && !inCheck) { - if (move != ss->killers[0]) + if (bestMove != ss->killers[0]) { ss->killers[1] = ss->killers[0]; - ss->killers[0] = move; + ss->killers[0] = bestMove; } // Increase history value of the cut-off move Value bonus = Value(int(depth) * int(depth)); - H.add(pos.piece_moved(move), to_sq(move), bonus); + H.add(pos.piece_moved(bestMove), to_sq(bestMove), bonus); // Decrease history of all the other played non-capture moves for (int i = 0; i < playedMoveCount - 1; i++) @@ -1092,6 +1063,10 @@ split_point_start: // At split points actual search starts from here } } } + else // Failed low or PV search + TT.store(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1103,74 +1078,83 @@ split_point_start: // At split points actual search starts from here // search function when the remaining depth is zero (or, to be more precise, // less than ONE_PLY). - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { const bool PvNode = (NT == PV); assert(NT == PV || NT == NonPV); + assert(InCheck == !!pos.checkers()); assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); - assert((alpha == beta - 1) || PvNode); + assert(PvNode || (alpha == beta - 1)); assert(depth <= DEPTH_ZERO); StateInfo st; - Move ttMove, move, bestMove; - Value ttValue, bestValue, value, evalMargin, futilityValue, futilityBase; - bool inCheck, enoughMaterial, givesCheck, evasionPrunable; const TTEntry* tte; + Key posKey; + Move ttMove, move, bestMove; + Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; + bool givesCheck, enoughMaterial, evasionPrunable, fromNull; Depth ttDepth; - Bound bt; - Value oldAlpha = alpha; + + // To flag BOUND_EXACT a node with eval above alpha and no available moves + if (PvNode) + oldAlpha = alpha; ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; + fromNull = (ss-1)->currentMove == MOVE_NULL; // Check for an instant draw or maximum ply reached - if (pos.is_draw() || ss->ply > MAX_PLY) - return VALUE_DRAW; - - // Decide whether or not to include checks, this fixes also the type of - // TT entry depth that we are going to use. Note that in qsearch we use - // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. - inCheck = pos.in_check(); - ttDepth = (inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS); + if (pos.is_draw() || ss->ply > MAX_PLY) + return DrawValue[pos.side_to_move()]; // Transposition table lookup. At PV nodes, we don't use the TT for // pruning, but only for move ordering. - tte = TT.probe(pos.key()); - ttMove = (tte ? tte->move() : MOVE_NONE); - ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_ZERO; + posKey = pos.key(); + tte = TT.probe(posKey); + ttMove = tte ? tte->move() : MOVE_NONE; + ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE; - if (!PvNode && tte && can_return_tt(tte, ttDepth, ttValue, beta)) + // Decide whether or not to include checks, this fixes also the type of + // TT entry depth that we are going to use. Note that in qsearch we use + // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. + ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS + : DEPTH_QS_NO_CHECKS; + if ( tte + && tte->depth() >= ttDepth + && ttValue != VALUE_NONE // Only in case of TT access race + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; } // Evaluate the position statically - if (inCheck) + if (InCheck) { + ss->staticEval = ss->evalMargin = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; - ss->eval = evalMargin = VALUE_NONE; enoughMaterial = false; } else { - if (tte) + if (fromNull) { - assert(tte->static_value() != VALUE_NONE); - - evalMargin = tte->static_value_margin(); - ss->eval = bestValue = tte->static_value(); + // Approximated score. Real one is slightly higher due to tempo + ss->staticEval = bestValue = -(ss-1)->staticEval; + ss->evalMargin = VALUE_ZERO; } else - ss->eval = bestValue = evaluate(pos, evalMargin); + ss->staticEval = bestValue = evaluate(pos, ss->evalMargin); // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { if (!tte) - TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin); + TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE); return bestValue; } @@ -1178,7 +1162,7 @@ split_point_start: // At split points actual search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = ss->eval + evalMargin + FutilityMarginQS; + futilityBase = ss->staticEval + ss->evalMargin + Value(128); enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg; } @@ -1190,8 +1174,7 @@ split_point_start: // At split points actual search starts from here CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs - while ( bestValue < beta - && (move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); @@ -1199,7 +1182,8 @@ split_point_start: // At split points actual search starts from here // Futility pruning if ( !PvNode - && !inCheck + && !InCheck + && !fromNull && !givesCheck && move != ttMove && enoughMaterial @@ -1207,14 +1191,12 @@ split_point_start: // At split points actual search starts from here && !pos.is_passed_pawn_push(move)) { futilityValue = futilityBase - + PieceValue[Eg][pos.piece_on(to_sq(move))] + + PieceValue[EG][pos.piece_on(to_sq(move))] + (type_of(move) == ENPASSANT ? PawnValueEg : VALUE_ZERO); if (futilityValue < beta) { - if (futilityValue > bestValue) - bestValue = futilityValue; - + bestValue = std::max(bestValue, futilityValue); continue; } @@ -1222,19 +1204,22 @@ split_point_start: // At split points actual search starts from here if ( futilityBase < beta && depth < DEPTH_ZERO && pos.see(move) <= 0) + { + bestValue = std::max(bestValue, futilityBase); continue; + } } // Detect non-capture evasions that are candidate to be pruned evasionPrunable = !PvNode - && inCheck + && InCheck && bestValue > VALUE_MATED_IN_MAX_PLY && !pos.is_capture(move) && !pos.can_castle(pos.side_to_move()); // Don't search moves with negative SEE values if ( !PvNode - && (!inCheck || evasionPrunable) + && (!InCheck || evasionPrunable) && move != ttMove && type_of(move) != PROMOTION && pos.see_sign(move) < 0) @@ -1242,11 +1227,11 @@ split_point_start: // At split points actual search starts from here // Don't search useless checks if ( !PvNode - && !inCheck + && !InCheck && givesCheck && move != ttMove && !pos.is_capture_or_promotion(move) - && ss->eval + PawnValueMg / 4 < beta + && ss->staticEval + PawnValueMg / 4 < beta && !check_is_dangerous(pos, move, futilityBase, beta)) continue; @@ -1258,35 +1243,41 @@ split_point_start: // At split points actual search starts from here // Make and search the move pos.do_move(move, st, ci, givesCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY); + value = givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY) + : -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // New best move? + // Check for new best move if (value > bestValue) { bestValue = value; - bestMove = move; - if ( PvNode - && value > alpha - && value < beta) // We want always alpha < beta - alpha = value; + if (value > alpha) + { + if (PvNode && value < beta) // Update alpha here! Always alpha < beta + { + alpha = value; + bestMove = move; + } + else // Fail high + { + TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, ttDepth, move); + return value; + } + } } } // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (inCheck && bestValue == -VALUE_INFINITE) + if (InCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root - // Update transposition table - move = bestValue <= oldAlpha ? MOVE_NONE : bestMove; - bt = bestValue <= oldAlpha ? BOUND_UPPER - : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT; - - TT.store(pos.key(), value_to_tt(bestValue, ss->ply), bt, ttDepth, move, ss->eval, evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1294,44 +1285,60 @@ split_point_start: // At split points actual search starts from here } - // check_is_dangerous() tests if a checking move can be pruned in qsearch(). - // bestValue is updated only when returning false because in that case move - // will be pruned. + // value_to_tt() adjusts a mate score from "plies to mate from the root" to + // "plies to mate from the current position". Non-mate scores are unchanged. + // The function is called before storing a value to the transposition table. + + Value value_to_tt(Value v, int ply) { + + assert(v != VALUE_NONE); + + return v >= VALUE_MATE_IN_MAX_PLY ? v + ply + : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; + } + + + // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score + // from the transposition table (where refers to the plies to mate/be mated + // from current position) to "plies to mate/be mated from the root". + + Value value_from_tt(Value v, int ply) { + + return v == VALUE_NONE ? VALUE_NONE + : v >= VALUE_MATE_IN_MAX_PLY ? v - ply + : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v; + } + + + // check_is_dangerous() tests if a checking move can be pruned in qsearch() - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta) + bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta) { - Bitboard b, occ, oldAtt, newAtt, kingAtt; - Square from, to, ksq; - Piece pc; - Color them; - - from = from_sq(move); - to = to_sq(move); - them = ~pos.side_to_move(); - ksq = pos.king_square(them); - kingAtt = pos.attacks_from(ksq); - pc = pos.piece_moved(move); - - occ = pos.pieces() ^ from ^ ksq; - oldAtt = pos.attacks_from(pc, from, occ); - newAtt = pos.attacks_from(pc, to, occ); - - // Rule 1. Checks which give opponent's king at most one escape square are dangerous - b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to); - - if (!more_than_one(b)) + Piece pc = pos.piece_moved(move); + Square from = from_sq(move); + Square to = to_sq(move); + Color them = ~pos.side_to_move(); + Square ksq = pos.king_square(them); + Bitboard enemies = pos.pieces(them); + Bitboard kingAtt = pos.attacks_from(ksq); + Bitboard occ = pos.pieces() ^ from ^ ksq; + Bitboard oldAtt = pos.attacks_from(pc, from, occ); + Bitboard newAtt = pos.attacks_from(pc, to, occ); + + // Checks which give opponent's king at most one escape square are dangerous + if (!more_than_one(kingAtt & ~(enemies | newAtt | to))) return true; - // Rule 2. Queen contact check is very dangerous + // Queen contact check is very dangerous if (type_of(pc) == QUEEN && (kingAtt & to)) return true; - // Rule 3. Creating new double threats with checks - b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq); + // Creating new double threats with checks is dangerous + Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt; while (b) { // Note that here we generate illegal "double move"! - if (futilityBase + PieceValue[Eg][pos.piece_on(pop_lsb(&b))] >= beta) + if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta) return true; } @@ -1339,161 +1346,103 @@ split_point_start: // At split points actual search starts from here } - // connected_moves() tests whether two moves are 'connected' in the sense - // that the first move somehow made the second move possible (for instance - // if the moving piece is the same in both moves). The first move is assumed - // to be the move that was made to reach the current position, while the - // second move is assumed to be a move from the current position. + // allows_move() tests whether the move at previous ply (first) somehow makes a + // second move possible, for instance if the moving piece is the same in both + // moves. Normally the second move is the threat move (the best move returned + // from a null search that fails low). - bool connected_moves(const Position& pos, Move m1, Move m2) { + bool allows_move(const Position& pos, Move first, Move second) { - Square f1, t1, f2, t2; - Piece p1, p2; - Square ksq; + assert(is_ok(first)); + assert(is_ok(second)); + assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move()); + assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move()); - assert(is_ok(m1)); - assert(is_ok(m2)); + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); - // Case 1: The moving piece is the same in both moves - f2 = from_sq(m2); - t1 = to_sq(m1); - if (f2 == t1) + // The piece is the same or second's destination was vacated by the first move + if (m1to == m2from || m2to == m1from) return true; - // Case 2: The destination square for m2 was vacated by m1 - t2 = to_sq(m2); - f1 = from_sq(m1); - if (t2 == f1) - return true; - - // Case 3: Moving through the vacated square - p2 = pos.piece_on(f2); - if (piece_is_slider(p2) && (between_bb(f2, t2) & f1)) + // Second one moves through the square vacated by first one + if (between_bb(m2from, m2to) & m1from) return true; - // Case 4: The destination square for m2 is defended by the moving piece in m1 - p1 = pos.piece_on(t1); - if (pos.attacks_from(p1, t1) & t2) + // Second's destination is defended by the first move's piece + Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from); + if (m1att & m2to) return true; - // Case 5: Discovered check, checking piece is the piece moved in m1 - ksq = pos.king_square(pos.side_to_move()); - if ( piece_is_slider(p1) - && (between_bb(t1, ksq) & f2) - && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq)) + // Second move gives a discovered check through the first's checking piece + if (m1att & pos.king_square(pos.side_to_move())) + { + assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from); return true; + } return false; } - // value_to_tt() adjusts a mate score from "plies to mate from the root" to - // "plies to mate from the current position". Non-mate scores are unchanged. - // The function is called before storing a value to the transposition table. - - Value value_to_tt(Value v, int ply) { - - if (v >= VALUE_MATE_IN_MAX_PLY) - return v + ply; - - if (v <= VALUE_MATED_IN_MAX_PLY) - return v - ply; - - return v; - } + // prevents_move() tests whether a move (first) is able to defend against an + // opponent's move (second). In this case will not be pruned. Normally the + // second move is the threat move (the best move returned from a null search + // that fails low). + bool prevents_move(const Position& pos, Move first, Move second) { - // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score - // from the transposition table (where refers to the plies to mate/be mated - // from current position) to "plies to mate/be mated from the root". - - Value value_from_tt(Value v, int ply) { + assert(is_ok(first)); + assert(is_ok(second)); + assert(!pos.is_capture_or_promotion(first)); + assert(!pos.is_passed_pawn_push(first)); - if (v >= VALUE_MATE_IN_MAX_PLY) - return v - ply; + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); - if (v <= VALUE_MATED_IN_MAX_PLY) - return v + ply; - - return v; - } - - - // connected_threat() tests whether it is safe to forward prune a move or if - // is somehow connected to the threat move returned by null search. - - bool connected_threat(const Position& pos, Move m, Move threat) { - - assert(is_ok(m)); - assert(is_ok(threat)); - assert(!pos.is_capture_or_promotion(m)); - assert(!pos.is_passed_pawn_push(m)); + // Don't prune moves of the threatened piece + if (m1from == m2to) + return true; - Square mfrom, mto, tfrom, tto; + // If the threatened piece has value less than or equal to the value of the + // threat piece, don't prune moves which defend it. + if ( pos.is_capture(second) + && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)] + || type_of(pos.piece_on(m2from)) == KING)) + { + // Update occupancy as if the piece and the threat are moving + Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from; + Piece piece = pos.piece_on(m1from); - mfrom = from_sq(m); - mto = to_sq(m); - tfrom = from_sq(threat); - tto = to_sq(threat); + // The moved piece attacks the square 'tto' ? + if (pos.attacks_from(piece, m1to, occ) & m2to) + return true; - // Case 1: Don't prune moves which move the threatened piece - if (mfrom == tto) - return true; + // Scan for possible X-ray attackers behind the moved piece + Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, ROOK)) + | (attacks_bb(m2to, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP)); - // Case 2: If the threatened piece has value less than or equal to the - // value of the threatening piece, don't prune moves which defend it. - if ( pos.is_capture(threat) - && ( PieceValue[Mg][pos.piece_on(tfrom)] >= PieceValue[Mg][pos.piece_on(tto)] - || type_of(pos.piece_on(tfrom)) == KING) - && pos.move_attacks_square(m, tto)) - return true; + // Verify attackers are triggered by our move and not already existing + if (xray && (xray ^ (xray & pos.attacks_from(m2to)))) + return true; + } - // Case 3: If the moving piece in the threatened move is a slider, don't - // prune safe moves which block its ray. - if ( piece_is_slider(pos.piece_on(tfrom)) - && (between_bb(tfrom, tto) & mto) - && pos.see_sign(m) >= 0) + // Don't prune safe moves which block the threat path + if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0) return true; return false; } - // can_return_tt() returns true if a transposition table score can be used to - // cut-off at a given point in search. - - bool can_return_tt(const TTEntry* tte, Depth depth, Value v, Value beta) { - - return ( tte->depth() >= depth - || v >= std::max(VALUE_MATE_IN_MAX_PLY, beta) - || v < std::min(VALUE_MATED_IN_MAX_PLY, beta)) - - && ( ((tte->type() & BOUND_LOWER) && v >= beta) - || ((tte->type() & BOUND_UPPER) && v < beta)); - } - - - // refine_eval() returns the transposition table score if possible, otherwise - // falls back on static position evaluation. - - Value refine_eval(const TTEntry* tte, Value v, Value defaultEval) { - - assert(tte); - - if ( ((tte->type() & BOUND_LOWER) && v >= defaultEval) - || ((tte->type() & BOUND_UPPER) && v < defaultEval)) - return v; - - return defaultEval; - } - - // When playing with strength handicap choose best move among the MultiPV set - // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen. - - Move do_skill_level() { + // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. - assert(MultiPV > 1); + Move Skill::pick_move() { static RKISS rk; @@ -1502,21 +1451,20 @@ split_point_start: // At split points actual search starts from here rk.rand(); // RootMoves are already sorted by score in descending order - size_t size = std::min(MultiPV, RootMoves.size()); - int variance = std::min(RootMoves[0].score - RootMoves[size - 1].score, PawnValueMg); - int weakness = 120 - 2 * SkillLevel; + int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg); + int weakness = 120 - 2 * level; int max_s = -VALUE_INFINITE; - Move best = MOVE_NONE; + best = MOVE_NONE; // Choose best move. For each move score we add two terms both dependent on // weakness, one deterministic and bigger for weaker moves, and one random, // then we choose the move with the resulting highest score. - for (size_t i = 0; i < size; i++) + for (size_t i = 0; i < PVSize; i++) { int s = RootMoves[i].score; // Don't allow crazy blunders even at very low skills - if (i > 0 && RootMoves[i-1].score > s + EasyMoveMargin) + if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg) break; // This is our magic formula @@ -1541,23 +1489,24 @@ split_point_start: // At split points actual search starts from here std::stringstream s; Time::point elaspsed = Time::now() - SearchTime + 1; + size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size()); int selDepth = 0; for (size_t i = 0; i < Threads.size(); i++) if (Threads[i].maxPly > selDepth) selDepth = Threads[i].maxPly; - for (size_t i = 0; i < std::min(UCIMultiPV, RootMoves.size()); i++) + for (size_t i = 0; i < uciPVSize; i++) { bool updated = (i <= PVIdx); if (depth == 1 && !updated) continue; - int d = (updated ? depth : depth - 1); - Value v = (updated ? RootMoves[i].score : RootMoves[i].prevScore); + int d = updated ? depth : depth - 1; + Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore; - if (s.rdbuf()->in_avail()) + if (s.rdbuf()->in_avail()) // Not at first line s << "\n"; s << "info depth " << d @@ -1570,7 +1519,7 @@ split_point_start: // At split points actual search starts from here << " pv"; for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++) - s << " " << move_to_uci(RootMoves[i].pv[j], Chess960); + s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960()); } return s.str(); @@ -1588,29 +1537,28 @@ void RootMove::extract_pv_from_tt(Position& pos) { StateInfo state[MAX_PLY_PLUS_2], *st = state; TTEntry* tte; - int ply = 1; + int ply = 0; Move m = pv[0]; - assert(m != MOVE_NONE && pos.is_pseudo_legal(m)); - pv.clear(); - pv.push_back(m); - pos.do_move(m, *st++); - - while ( (tte = TT.probe(pos.key())) != NULL - && (m = tte->move()) != MOVE_NONE // Local copy, TT entry could change - && pos.is_pseudo_legal(m) - && pos.pl_move_is_legal(m, pos.pinned_pieces()) - && ply < MAX_PLY - && (!pos.is_draw() || ply < 2)) - { + + do { pv.push_back(m); - pos.do_move(m, *st++); - ply++; - } - pv.push_back(MOVE_NONE); - do pos.undo_move(pv[--ply]); while (ply); + assert(MoveList(pos).contains(pv[ply])); + + pos.do_move(pv[ply++], *st++); + tte = TT.probe(pos.key()); + + } while ( tte + && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change + && pos.pl_move_is_legal(m, pos.pinned_pieces()) + && ply < MAX_PLY + && (!pos.is_draw() || ply < 2)); + + pv.push_back(MOVE_NONE); // Must be zero-terminating + + while (ply) pos.undo_move(pv[--ply]); } @@ -1622,27 +1570,21 @@ void RootMove::insert_pv_in_tt(Position& pos) { StateInfo state[MAX_PLY_PLUS_2], *st = state; TTEntry* tte; - Key k; - Value v, m = VALUE_NONE; int ply = 0; - assert(pv[ply] != MOVE_NONE && pos.is_pseudo_legal(pv[ply])); - do { - k = pos.key(); - tte = TT.probe(k); + tte = TT.probe(pos.key()); - // Don't overwrite existing correct entries - if (!tte || tte->move() != pv[ply]) - { - v = (pos.in_check() ? VALUE_NONE : evaluate(pos, m)); - TT.store(k, VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m); - } - pos.do_move(pv[ply], *st++); + if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries + TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply]); + + assert(MoveList(pos).contains(pv[ply])); + + pos.do_move(pv[ply++], *st++); - } while (pv[++ply] != MOVE_NONE); + } while (pv[ply] != MOVE_NONE); - do pos.undo_move(pv[--ply]); while (ply); + while (ply) pos.undo_move(pv[--ply]); } @@ -1712,6 +1654,10 @@ void Thread::idle_loop() { sp->mutex.lock(); + assert(sp->activePositions[idx] == NULL); + + sp->activePositions[idx] = &pos; + if (sp->nodeType == Root) search(pos, ss+1, sp->alpha, sp->beta, sp->depth); else if (sp->nodeType == PV) @@ -1724,6 +1670,7 @@ void Thread::idle_loop() { assert(is_searching); is_searching = false; + sp->activePositions[idx] = NULL; sp->slavesMask &= ~(1ULL << idx); sp->nodes += pos.nodes_searched(); @@ -1754,6 +1701,7 @@ void Thread::idle_loop() { void check_time() { static Time::point lastInfoTime = Time::now(); + int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning if (Time::now() - lastInfoTime >= 1000) { @@ -1764,6 +1712,35 @@ void check_time() { if (Limits.ponder) return; + if (Limits.nodes) + { + Threads.mutex.lock(); + + nodes = RootPos.nodes_searched(); + + // Loop across all split points and sum accumulated SplitPoint nodes plus + // all the currently active slaves positions. + for (size_t i = 0; i < Threads.size(); i++) + for (int j = 0; j < Threads[i].splitPointsCnt; j++) + { + SplitPoint& sp = Threads[i].splitPoints[j]; + + sp.mutex.lock(); + + nodes += sp.nodes; + Bitboard sm = sp.slavesMask; + while (sm) + { + Position* pos = sp.activePositions[pop_lsb(&sm)]; + nodes += pos ? pos->nodes_searched() : 0; + } + + sp.mutex.unlock(); + } + + Threads.mutex.unlock(); + } + Time::point elapsed = Time::now() - SearchTime; bool stillAtFirstMove = Signals.firstRootMove && !Signals.failedLowAtRoot @@ -1773,6 +1750,7 @@ void check_time() { || stillAtFirstMove; if ( (Limits.use_time_management() && noMoreTime) - || (Limits.movetime && elapsed >= Limits.movetime)) + || (Limits.movetime && elapsed >= Limits.movetime) + || (Limits.nodes && nodes >= Limits.nodes)) Signals.stop = true; }