X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=912e7be0dfa0dd2548e69f01e8775d4ace81edd0;hp=abb5116d2cfe3114bfdd74f7c7c48c3161033c5d;hb=9c2b3faec4f4bbc44f4fb8cd1cae52ad642e3ab6;hpb=1b6b711c444362d442f8362d356f668f676ec5cb diff --git a/src/search.cpp b/src/search.cpp index abb5116d..912e7be0 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -42,6 +42,7 @@ namespace Search { LimitsType Limits; std::vector RootMoves; Position RootPosition; + Color RootColor; Time::point SearchTime; StateStackPtr SetupStates; } @@ -55,6 +56,9 @@ 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 }; @@ -62,28 +66,9 @@ namespace { 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 +79,6 @@ 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] @@ -107,22 +87,15 @@ 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; TimeManager TimeMgr; int BestMoveChanges; int SkillLevel; + Move skillBest; bool SkillLevelEnabled, Chess960; + Value DrawValue[COLOR_NB]; History H; - template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); @@ -134,36 +107,10 @@ namespace { 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(); 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; - - // Passed pawn move? - if ( type_of(pos.piece_moved(m)) == PAWN - && pos.pawn_is_passed(pos.side_to_move(), to_sq(m))) - return true; - - // 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; - } - } // namespace @@ -190,7 +137,7 @@ 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)); } @@ -228,7 +175,7 @@ void Search::think() { Position& pos = RootPosition; Chess960 = pos.is_chess960(); - Eval::RootColor = pos.side_to_move(); + RootColor = pos.side_to_move(); TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move()); TT.new_search(); H.clear(); @@ -242,6 +189,16 @@ void Search::think() { goto finalize; } + if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) + { + int cf = Options["Contempt Factor"] * PawnValueMg / 100; // In centipawns + cf = cf * MaterialTable::game_phase(pos) / 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["OwnBook"] && !Limits.infinite) { Move bookMove = book.probe(pos, Options["Book File"], Options["Best Book Move"]); @@ -259,6 +216,7 @@ void Search::think() { // 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); + skillBest = MOVE_NONE; MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV); if (Options["Use Search Log"]) @@ -290,6 +248,15 @@ void Search::think() { Threads.set_timer(0); // Stop timer Threads.sleep(); + // 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)); + } + if (Options["Use Search Log"]) { Time::point elapsed = Time::now() - SearchTime + 1; @@ -331,7 +298,6 @@ 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; @@ -339,7 +305,7 @@ namespace { ss->currentMove = MOVE_NULL; // Hack to skip update gains // 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. @@ -381,37 +347,41 @@ 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 sort multi-PV lines and exit the loop. + if (bestValue > alpha && bestValue < beta) + { + sort(RootMoves.begin(), RootMoves.begin() + PVIdx); + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; 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; @@ -419,15 +389,6 @@ 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); } @@ -437,7 +398,7 @@ namespace { if (SkillLevelEnabled && depth == 1 + SkillLevel) skillBest = do_skill_level(); - 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]) @@ -449,7 +410,7 @@ 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 @@ -469,7 +430,7 @@ namespace { && ( (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); @@ -491,15 +452,6 @@ 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)); - } } @@ -528,16 +480,15 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove, threatMove; Depth ext, newDepth; - Value bestValue, value, oldAlpha, ttValue; - Value refinedValue, nullValue, futilityValue; - bool pvMove, inCheck, singularExtensionNode, givesCheck; + Value bestValue, value, ttValue; + Value eval, nullValue, futilityValue; + bool inCheck, givesCheck, pvMove, singularExtensionNode; bool captureOrPromotion, dangerous, doFullDepthSearch; int moveCount, playedMoveCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); moveCount = playedMoveCount = 0; - oldAlpha = alpha; inCheck = pos.in_check(); if (SpNode) @@ -569,7 +520,7 @@ namespace { { // Step 2. Check for aborted search and immediate draw if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) - return VALUE_DRAW; + 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 @@ -596,9 +547,14 @@ 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 + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { + assert(ttValue != VALUE_NONE); // Due to depth > DEPTH_NONE + TT.refresh(tte); ss->currentMove = ttMove; // Can be MOVE_NONE @@ -615,38 +571,45 @@ namespace { // Step 5. Evaluate the position statically and update parent's gain statistics if (inCheck) - ss->eval = ss->evalMargin = refinedValue = VALUE_NONE; + ss->staticEval = ss->evalMargin = eval = VALUE_NONE; + else if (tte) { assert(tte->static_value() != VALUE_NONE); + assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE); - ss->eval = tte->static_value(); + ss->staticEval = eval = tte->static_value(); ss->evalMargin = tte->static_value_margin(); - refinedValue = refine_eval(tte, ttValue, ss->eval); + + // Can ttValue be used as a better position evaluation? + if ( ((tte->type() & BOUND_LOWER) && ttValue > eval) + || ((tte->type() & BOUND_UPPER) && ttValue < eval)) + eval = ttValue; } 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); + TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, + ss->staticEval, ss->evalMargin); } // 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())) @@ -664,19 +627,19 @@ 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())) { @@ -686,7 +649,7 @@ 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); @@ -723,7 +686,7 @@ namespace { // parent node, which will trigger a re-search with full depth). 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)) @@ -736,7 +699,7 @@ 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 @@ -765,9 +728,9 @@ 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); @@ -786,7 +749,7 @@ 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) @@ -794,10 +757,7 @@ 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)); @@ -832,10 +792,17 @@ split_point_start: // At split points actual search starts from here << " 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) @@ -850,11 +817,13 @@ 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; @@ -863,7 +832,7 @@ 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) @@ -875,10 +844,12 @@ 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) + if ( depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[depth] && (!threatMove || !connected_threat(pos, move, threatMove))) { if (SpNode) @@ -891,7 +862,7 @@ 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) @@ -981,7 +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 bestValue; + + if (RootNode) { RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); @@ -1007,37 +981,41 @@ split_point_start: // At split points actual search starts from here if (value > bestValue) { bestValue = value; - bestMove = move; - - if ( PvNode - && value > alpha - && value < beta) // We want always alpha < beta - { - alpha = bestValue; // Update alpha here! - } + if (SpNode) sp->bestValue = value; - if (SpNode && !thisThread->cutoff_occurred()) + if (value > alpha) { - sp->bestValue = bestValue; - sp->bestMove = bestMove; - sp->alpha = alpha; + bestMove = move; + if (SpNode) sp->bestMove = move; - if (bestValue >= beta) - sp->cutoff = true; + if (PvNode && value < beta) + { + alpha = value; // Update alpha here! Always alpha < beta + if (SpNode) sp->alpha = value; + } + else // 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)) + { bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove, depth, threatMove, moveCount, mp, NT); + 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 @@ -1045,8 +1023,9 @@ split_point_start: // At split points actual search starts from here // 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 (!SpNode && !moveCount) - return excludedMove ? alpha : inCheck ? mated_in(ss->ply) : VALUE_DRAW; + if (!moveCount) + 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) @@ -1056,20 +1035,12 @@ split_point_start: // At split points actual search starts from here 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 ttm = bestValue <= oldAlpha ? MOVE_NONE : bestMove; - Bound bt = bestValue <= oldAlpha ? BOUND_UPPER - : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT; + TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, + bestMove, ss->staticEval, ss->evalMargin); - TT.store(posKey, value_to_tt(bestValue, ss->ply), bt, depth, ttm, ss->eval, ss->evalMargin); - - // Update killers and history for non capture cut-off moves - if ( bestValue >= beta - && !pos.is_capture_or_promotion(bestMove) - && !inCheck) + if (!pos.is_capture_or_promotion(bestMove) && !inCheck) { if (bestMove != ss->killers[0]) { @@ -1089,6 +1060,10 @@ 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, ss->staticEval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1107,39 +1082,44 @@ split_point_start: // At split points actual search starts from here assert(NT == PV || NT == NonPV); 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; + bool inCheck, givesCheck, enoughMaterial, evasionPrunable; Depth ttDepth; - Bound bt; - Value oldAlpha = alpha; + inCheck = pos.in_check(); ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; // 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); + 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 + && ( PvNode ? tte->type() == BOUND_EXACT + : ttValue >= beta ? (tte->type() & BOUND_LOWER) + : (tte->type() & BOUND_UPPER))) { + assert(ttValue != VALUE_NONE); // Due to ttDepth > DEPTH_NONE + ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; } @@ -1147,8 +1127,8 @@ split_point_start: // At split points actual search starts from here // Evaluate the position statically if (inCheck) { + ss->staticEval = ss->evalMargin = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; - ss->eval = evalMargin = VALUE_NONE; enoughMaterial = false; } else @@ -1157,17 +1137,18 @@ split_point_start: // At split points actual search starts from here { assert(tte->static_value() != VALUE_NONE); - evalMargin = tte->static_value_margin(); - ss->eval = bestValue = tte->static_value(); + ss->staticEval = bestValue = tte->static_value(); + ss->evalMargin = tte->static_value_margin(); } 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, ss->staticEval, ss->evalMargin); return bestValue; } @@ -1175,7 +1156,7 @@ 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; } @@ -1187,8 +1168,7 @@ 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)); @@ -1204,7 +1184,7 @@ 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) @@ -1243,7 +1223,7 @@ split_point_start: // At split points actual search starts from here && 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; @@ -1255,21 +1235,31 @@ 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 = -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, ss->staticEval, ss->evalMargin); + + return value; + } + } } } @@ -1278,12 +1268,9 @@ split_point_start: // At split points actual search starts from here 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 && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove, ss->staticEval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1328,7 +1315,7 @@ split_point_start: // At split points actual search starts from here 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; } @@ -1390,13 +1377,10 @@ split_point_start: // At split points actual search starts from here 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; + assert(v != VALUE_NONE); - return v; + return v >= VALUE_MATE_IN_MAX_PLY ? v + ply + : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; } @@ -1406,13 +1390,9 @@ split_point_start: // At split points actual search starts from here Value value_from_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; + return v == VALUE_NONE ? VALUE_NONE + : v >= VALUE_MATE_IN_MAX_PLY ? v - ply + : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v; } @@ -1440,7 +1420,7 @@ split_point_start: // At split points actual search starts from here // 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)] + && ( 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; @@ -1456,35 +1436,6 @@ split_point_start: // At split points actual search starts from here } - // 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. @@ -1513,7 +1464,7 @@ split_point_start: // At split points actual search starts from here 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