X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=bce794ca1a30722e0942532f5bdb6e25408a51a3;hp=f5e3b2bb8b3d441a636a94a45c02a2d5118b267d;hb=0a687b2cf06fda0cc8e103c8cf9c3bbd564b02d6;hpb=05c5f08372f2ba6e28eec0c3d66fbb4f27e853b1 diff --git a/src/search.cpp b/src/search.cpp index f5e3b2bb..bce794ca 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -89,8 +89,8 @@ namespace { void idle_loop(int threadID, SplitPoint* sp); template - void split(const Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue, - Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, int master, bool pvNode); + void split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, + Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode); private: friend void poll(); @@ -235,8 +235,8 @@ namespace { const Value EasyMoveMargin = Value(0x200); // Last seconds noise filtering (LSN) - const bool UseLSNFiltering = true; - const int LSNTime = 4000; // In milliseconds + const bool UseLSNFiltering = false; + const int LSNTime = 100; // In milliseconds const Value LSNValue = value_from_centipawns(200); bool loseOnTime = false; @@ -285,10 +285,10 @@ namespace { Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr); template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE); + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID); + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); template void sp_search(SplitPoint* sp, int threadID); @@ -296,15 +296,13 @@ namespace { template Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous); - void init_node(SearchStack* ss, int ply, int threadID); - void update_pv(SearchStack* ss, int ply); - void sp_update_pv(SearchStack* pss, SearchStack* ss, int ply); + void update_pv(SearchStack* ss); + void sp_update_pv(SearchStack* pss, SearchStack* ss); bool connected_moves(const Position& pos, Move m1, Move m2); bool value_is_mate(Value value); bool move_is_killer(Move m, SearchStack* ss); - bool ok_to_do_nullmove(const Position& pos); - bool ok_to_prune(const Position& pos, Move m, Move threat); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); + bool connected_threat(const Position& pos, Move m, Move threat); Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); void update_killers(Move m, SearchStack* ss); @@ -315,7 +313,7 @@ namespace { void poll(); void ponderhit(); void wait_for_stop_or_ponderhit(); - void init_ss_array(SearchStack* ss); + void init_ss_array(SearchStack* ss, int size); void print_pv_info(const Position& pos, SearchStack* ss, Value alpha, Value beta, Value value); #if !defined(_MSC_VER) @@ -339,6 +337,52 @@ void exit_threads() { TM.exit_threads(); } int64_t nodes_searched() { return TM.nodes_searched(); } +/// init_search() is called during startup. It initializes various lookup tables + +void init_search() { + + int d; // depth (OnePly == 2) + int hd; // half depth (OnePly == 1) + int mc; // moveCount + + // Init reductions array + for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++) + { + double pvRed = log(double(hd)) * log(double(mc)) / 3.0; + double nonPVRed = log(double(hd)) * log(double(mc)) / 1.5; + ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0); + ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0); + } + + // Init futility margins array + for (d = 0; d < 16; d++) for (mc = 0; mc < 64; mc++) + FutilityMarginsMatrix[d][mc] = 112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45; + + // Init futility move count array + for (d = 0; d < 32; d++) + FutilityMoveCountArray[d] = 3 + (1 << (3 * d / 8)); +} + + +// SearchStack::init() initializes a search stack entry. +// Called at the beginning of search() when starting to examine a new node. +void SearchStack::init() { + + pv[0] = pv[1] = bestMove = MOVE_NONE; + currentMove = threatMove = MOVE_NONE; + reduction = Depth(0); + eval = VALUE_NONE; +} + +// SearchStack::initKillers() initializes killers for a search stack entry +void SearchStack::initKillers() { + + mateKiller = MOVE_NONE; + for (int i = 0; i < KILLER_MAX; i++) + killers[i] = MOVE_NONE; +} + + /// perft() is our utility to verify move generation is bug free. All the legal /// moves up to given depth are generated and counted and the sum returned. @@ -551,51 +595,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, } -/// init_search() is called during startup. It initializes various lookup tables - -void init_search() { - - // Init our reduction lookup tables - for (int i = 1; i < 64; i++) // i == depth (OnePly = 1) - for (int j = 1; j < 64; j++) // j == moveNumber - { - double pvRed = log(double(i)) * log(double(j)) / 3.0; - double nonPVRed = log(double(i)) * log(double(j)) / 1.5; - ReductionMatrix[PV][i][j] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0); - ReductionMatrix[NonPV][i][j] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0); - } - - // Init futility margins array - for (int i = 0; i < 16; i++) // i == depth (OnePly = 2) - for (int j = 0; j < 64; j++) // j == moveNumber - { - // FIXME: test using log instead of BSR - FutilityMarginsMatrix[i][j] = (i < 2 ? 0 : 112 * bitScanReverse32(i * i / 2)) - 8 * j + 45; - } - - // Init futility move count array - for (int i = 0; i < 32; i++) // i == depth (OnePly = 2) - FutilityMoveCountArray[i] = 3 + (1 << (3 * i / 8)); -} - - -// SearchStack::init() initializes a search stack. Used at the beginning of a -// new search from the root. -void SearchStack::init(int ply) { - - pv[ply] = pv[ply + 1] = MOVE_NONE; - currentMove = threatMove = MOVE_NONE; - reduction = Depth(0); - eval = VALUE_NONE; -} - -void SearchStack::initKillers() { - - mateKiller = MOVE_NONE; - for (int i = 0; i < KILLER_MAX; i++) - killers[i] = MOVE_NONE; -} - namespace { // id_loop() is the main iterative deepening loop. It calls root_search @@ -605,7 +604,7 @@ namespace { Value id_loop(const Position& pos, Move searchMoves[]) { - Position p(pos); + Position p(pos, pos.thread()); SearchStack ss[PLY_MAX_PLUS_2]; Move EasyMove = MOVE_NONE; Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; @@ -635,9 +634,8 @@ namespace { // Initialize TT.new_search(); H.clear(); - init_ss_array(ss); + init_ss_array(ss, PLY_MAX_PLUS_2); ValueByIteration[1] = rml.get_move_score(0); - p.reset_ply(); Iteration = 1; // Is one move significantly better than others after initial scoring ? @@ -813,7 +811,7 @@ namespace { // Step 5. Evaluate the position statically // At root we do this only to get reference value for child nodes if (!isCheck) - ss->eval = evaluate(pos, ei, 0); + ss->eval = evaluate(pos, ei); // Step 6. Razoring (omitted at root) // Step 7. Static null move pruning (omitted at root) @@ -878,7 +876,7 @@ namespace { alpha = -VALUE_INFINITE; // Full depth PV search, done on first move or after a fail high - value = -search(pos, ss+1, -beta, -alpha, newDepth, false, 0); + value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); } else { @@ -894,23 +892,37 @@ namespace { ss->reduction = reduction(depth, i - MultiPV + 2); if (ss->reduction) { + assert(newDepth-ss->reduction >= OnePly); + // Reduced depth non-pv search using alpha as upperbound - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, 0); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); + doFullDepthSearch = (value > alpha); + } + + // The move failed high, but if reduction is very big we could + // face a false positive, retry with a less aggressive reduction, + // if the move fails high again then go with full depth search. + if (doFullDepthSearch && ss->reduction > 2 * OnePly) + { + assert(newDepth - OnePly >= OnePly); + + ss->reduction = OnePly; + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); doFullDepthSearch = (value > alpha); } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { // Full depth non-pv search using alpha as upperbound - ss->reduction = Depth(0); - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, true, 0); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, 1); // If we are above alpha then research at same depth but as PV // to get a correct score or eventually a fail high above beta. if (value > alpha) - value = -search(pos, ss+1, -beta, -alpha, newDepth, false, 0); + value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); } } @@ -924,7 +936,7 @@ namespace { // We are failing high and going to do a research. It's important to update // the score before research in case we run out of time while researching. rml.set_move_score(i, value); - update_pv(ss, 0); + update_pv(ss); TT.extract_pv(pos, ss->pv, PLY_MAX); rml.set_move_pv(i, ss->pv); @@ -964,7 +976,7 @@ namespace { // Update PV rml.set_move_score(i, value); - update_pv(ss, 0); + update_pv(ss); TT.extract_pv(pos, ss->pv, PLY_MAX); rml.set_move_pv(i, ss->pv); @@ -1033,36 +1045,40 @@ namespace { // search<>() is the main search function for both PV and non-PV nodes template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, - bool allowNullmove, int threadID, Move excludedMove) { + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta > alpha && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); - assert(pos.ply() > 0 && pos.ply() < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); + assert(ply > 0 && ply < PLY_MAX); + assert(pos.thread() >= 0 && pos.thread() < TM.active_threads()); Move movesSearched[256]; EvalInfo ei; StateInfo st; const TTEntry* tte; - Move ttMove, move; + Key posKey; + Move ttMove, move, excludedMove; Depth ext, newDepth; Value bestValue, value, oldAlpha; Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous; bool mateThreat = false; int moveCount = 0; - int ply = pos.ply(); + int threadID = pos.thread(); refinedValue = bestValue = value = -VALUE_INFINITE; oldAlpha = alpha; - if (depth < OnePly) - return qsearch(pos, ss, alpha, beta, Depth(0), threadID); + // Step 1. Initialize node and poll. Polling can abort search + TM.incrementNodeCounter(threadID); + ss->init(); + (ss+2)->initKillers(); - // Step 1. Initialize node and poll - // Polling can abort search. - init_node(ss, ply, threadID); + if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls) + { + NodesSincePoll = 0; + poll(); + } // Step 2. Check for aborted search and immediate draw if (AbortSearch || TM.thread_should_stop(threadID)) @@ -1081,7 +1097,8 @@ namespace { // We don't want the score of a partial search to overwrite a previous full search // TT value, so we use a different position key in case of an excluded move exists. - Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); + excludedMove = ss->excludedMove; + posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); tte = TT.retrieve(posKey); ttMove = (tte ? tte->move() : MOVE_NONE); @@ -1114,7 +1131,7 @@ namespace { ei.kingDanger[pos.side_to_move()] = tte->king_danger(); } else - ss->eval = evaluate(pos, ei, threadID); + ss->eval = evaluate(pos, ei); refinedValue = refine_eval(tte, ss->eval, ply); // Enhance accuracy with TT value if possible update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); @@ -1122,16 +1139,20 @@ namespace { // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode + && depth < RazorDepth + && !isCheck && refinedValue < beta - razor_margin(depth) && ttMove == MOVE_NONE && (ss-1)->currentMove != MOVE_NULL - && depth < RazorDepth - && !isCheck && !value_is_mate(beta) && !pos.has_pawn_on_7th(pos.side_to_move())) { + // Pass ss->eval to qsearch() and avoid an evaluate call + if (!tte || tte->static_value() == VALUE_NONE) + TT.store(posKey, ss->eval, VALUE_TYPE_EXACT, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); + Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), threadID); + Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -1142,12 +1163,12 @@ namespace { // We're betting that the opponent doesn't have a move that will reduce // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode - && allowNullmove + && !ss->skipNullMove && depth < RazorDepth + && refinedValue >= beta + futility_margin(depth, 0) && !isCheck && !value_is_mate(beta) - && ok_to_do_nullmove(pos) - && refinedValue >= beta + futility_margin(depth, 0)) + && pos.non_pawn_material(pos.side_to_move())) return refinedValue - futility_margin(depth, 0); // Step 8. Null move search with verification search (is omitted in PV nodes) @@ -1155,12 +1176,12 @@ namespace { // at least beta. Otherwise we do a null move if static value is not more than // NullMoveMargin under beta. if ( !PvNode - && allowNullmove + && !ss->skipNullMove && depth > OnePly + && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0) && !isCheck && !value_is_mate(beta) - && ok_to_do_nullmove(pos) - && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0)) + && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; @@ -1172,9 +1193,11 @@ namespace { R++; pos.do_null_move(st); + (ss+1)->skipNullMove = true; - nullValue = -search(pos, ss+1, -beta, -alpha, depth-R*OnePly, false, threadID); - + nullValue = depth-R*OnePly < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, depth-R*OnePly, ply+1); + (ss+1)->skipNullMove = false; pos.undo_null_move(); if (nullValue >= beta) @@ -1183,14 +1206,19 @@ namespace { if (nullValue >= value_mate_in(PLY_MAX)) nullValue = beta; + // Do zugzwang verification search at high depths if (depth < 6 * OnePly) return nullValue; - // Do zugzwang verification search - Value v = search(pos, ss, alpha, beta, depth-5*OnePly, false, threadID); + ss->skipNullMove = true; + Value v = search(pos, ss, alpha, beta, depth-5*OnePly, ply); + ss->skipNullMove = false; + if (v >= beta) return nullValue; - } else { + } + else + { // The null move failed low, which means that we may be faced with // some kind of threat. If the previous move was reduced, check if // the move that refuted the null move was somehow connected to the @@ -1210,12 +1238,16 @@ namespace { // Step 9. Internal iterative deepening if ( depth >= IIDDepth[PvNode] - && (ttMove == MOVE_NONE || (PvNode && tte->depth() <= depth - 4 * OnePly)) + && ttMove == MOVE_NONE && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) { Depth d = (PvNode ? depth - 2 * OnePly : depth / 2); - search(pos, ss, alpha, beta, d, false, threadID); - ttMove = ss->pv[ply]; + + ss->skipNullMove = true; + search(pos, ss, alpha, beta, d, ply); + ss->skipNullMove = false; + + ttMove = ss->bestMove; tte = TT.retrieve(posKey); } @@ -1226,6 +1258,11 @@ namespace { // Initialize a MovePicker object for the current position MovePicker mp = MovePicker(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta)); CheckInfo ci(pos); + bool singularExtensionNode = depth >= SingularExtensionDepth[PvNode] + && tte && tte->move() + && !excludedMove // Do not allow recursive singular extension search + && is_lower_bound(tte->type()) + && tte->depth() >= depth - 3 * OnePly; // Step 10. Loop through moves // Loop through all legal moves until no moves remain or a beta cutoff occurs @@ -1248,21 +1285,20 @@ namespace { // Singular extension search. We extend the TT move if its value is much better than // its siblings. To verify this we do a reduced search on all the other moves but the // ttMove, if result is lower then ttValue minus a margin then we extend ttMove. - if ( depth >= SingularExtensionDepth[PvNode] - && tte + if ( singularExtensionNode && move == tte->move() - && !excludedMove // Do not allow recursive singular extension search - && ext < OnePly - && is_lower_bound(tte->type()) - && tte->depth() >= depth - 3 * OnePly) + && ext < OnePly) { Value ttValue = value_from_tt(tte->value(), ply); if (abs(ttValue) < VALUE_KNOWN_WIN) { Value b = ttValue - SingularExtensionMargin; - Value v = search(pos, ss, b - 1, b, depth / 2, false, threadID, move); - + ss->excludedMove = move; + ss->skipNullMove = true; + Value v = search(pos, ss, b - 1, b, depth / 2, ply); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; if (v < ttValue - SingularExtensionMargin) ext = OnePly; } @@ -1275,15 +1311,15 @@ namespace { // Step 12. Futility pruning (is omitted in PV nodes) if ( !PvNode + && !captureOrPromotion && !isCheck && !dangerous - && !captureOrPromotion - && !move_is_castle(move) - && move != ttMove) + && move != ttMove + && !move_is_castle(move)) { // Move count based pruning if ( moveCount >= futility_move_count(depth) - && ok_to_prune(pos, move, ss->threatMove) + && !(ss->threatMove && connected_threat(pos, move, ss->threatMove)) && bestValue > value_mated_in(PLY_MAX)) continue; @@ -1308,7 +1344,8 @@ namespace { // Step extra. pv search (only in PV nodes) // The first move in list is the expected PV if (PvNode && moveCount == 1) - value = -search(pos, ss+1, -beta, -alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); else { // Step 14. Reduced depth search @@ -1316,15 +1353,18 @@ namespace { bool doFullDepthSearch = true; if ( depth >= 3 * OnePly - && !dangerous && !captureOrPromotion + && !dangerous && !move_is_castle(move) && !move_is_killer(move, ss)) { ss->reduction = reduction(depth, moveCount); if (ss->reduction) { - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, threadID); + Depth d = newDepth - ss->reduction; + value = d < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -(alpha+1), -alpha, d, ply+1); + doFullDepthSearch = (value > alpha); } @@ -1333,23 +1373,27 @@ namespace { // if the move fails high again then go with full depth search. if (doFullDepthSearch && ss->reduction > 2 * OnePly) { + assert(newDepth - OnePly >= OnePly); + ss->reduction = OnePly; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, threadID); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1); doFullDepthSearch = (value > alpha); } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { - ss->reduction = Depth(0); - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1); // Step extra. pv search (only in PV nodes) // Search only for possible new PV nodes, if instead value >= beta then // parent node fails low with value <= alpha and tries another move. if (PvNode && value > alpha && value < beta) - value = -search(pos, ss+1, -beta, -alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); } } @@ -1367,7 +1411,7 @@ namespace { if (PvNode && value < beta) // This guarantees that always: alpha < beta alpha = value; - update_pv(ss, ply); + update_pv(ss); if (value == value_mate_in(ply + 1)) ss->mateKiller = move; @@ -1375,15 +1419,15 @@ namespace { } // Step 18. Check for split - if ( TM.active_threads() > 1 + if ( depth >= MinimumSplitDepth + && TM.active_threads() > 1 && bestValue < beta - && depth >= MinimumSplitDepth - && Iteration <= 99 && TM.available_thread_exists(threadID) && !AbortSearch - && !TM.thread_should_stop(threadID)) - TM.split(pos, ss, &alpha, beta, &bestValue, depth, - mateThreat, &moveCount, &mp, threadID, PvNode); + && !TM.thread_should_stop(threadID) + && Iteration <= 99) + TM.split(pos, ss, ply, &alpha, beta, &bestValue, depth, + mateThreat, &moveCount, &mp, PvNode); } // Step 19. Check for mate and stalemate @@ -1399,22 +1443,20 @@ namespace { if (AbortSearch || TM.thread_should_stop(threadID)) return bestValue; - if (bestValue <= oldAlpha) - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); + ValueType f = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); + move = (bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove); + TT.store(posKey, value_to_tt(bestValue, ply), f, depth, move, ss->eval, ei.kingDanger[pos.side_to_move()]); - else if (bestValue >= beta) + // Update killers and history only for non capture moves that fails high + if (bestValue >= beta) { TM.incrementBetaCounter(pos.side_to_move(), depth, threadID); - move = ss->pv[ply]; - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move, ss->eval, ei.kingDanger[pos.side_to_move()]); if (!pos.move_is_capture_or_promotion(move)) { update_history(pos, move, depth, movesSearched, moveCount); update_killers(move, ss); } } - else - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss->pv[ply], ss->eval, ei.kingDanger[pos.side_to_move()]); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1427,33 +1469,28 @@ namespace { // less than OnePly). template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID) { + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); assert(depth <= 0); - assert(pos.ply() > 0 && pos.ply() < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); + assert(ply > 0 && ply < PLY_MAX); + assert(pos.thread() >= 0 && pos.thread() < TM.active_threads()); EvalInfo ei; StateInfo st; Move ttMove, move; - Value staticValue, bestValue, value, futilityBase, futilityValue; - bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable; - const TTEntry* tte = NULL; - int moveCount = 0; - int ply = pos.ply(); + Value bestValue, value, futilityValue, futilityBase; + bool isCheck, deepChecks, enoughMaterial, moveIsCheck, evasionPrunable; + const TTEntry* tte; Value oldAlpha = alpha; - // Initialize, and make an early exit in case of an aborted search, - // an instant draw, maximum ply reached, etc. - init_node(ss, ply, threadID); - - // After init_node() that calls poll() - if (AbortSearch || TM.thread_should_stop(threadID)) - return Value(0); + TM.incrementNodeCounter(pos.thread()); + ss->pv[0] = ss->pv[1] = ss->bestMove = ss->currentMove = MOVE_NONE; + ss->eval = VALUE_NONE; + // Check for an instant draw or maximum ply reached if (pos.is_draw() || ply >= PLY_MAX - 1) return VALUE_DRAW; @@ -1472,39 +1509,42 @@ namespace { // Evaluate the position statically if (isCheck) - staticValue = -VALUE_INFINITE; - else if (tte && tte->static_value() != VALUE_NONE) { - staticValue = tte->static_value(); - ei.kingDanger[pos.side_to_move()] = tte->king_danger(); + bestValue = futilityBase = -VALUE_INFINITE; + deepChecks = enoughMaterial = false; } else - staticValue = evaluate(pos, ei, threadID); - - if (!isCheck) { - ss->eval = staticValue; + if (tte && tte->static_value() != VALUE_NONE) + { + ei.kingDanger[pos.side_to_move()] = tte->king_danger(); + bestValue = tte->static_value(); + } + else + bestValue = evaluate(pos, ei); + + ss->eval = bestValue; update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); - } - // Initialize "stand pat score", and return it immediately if it is - // at least beta. - bestValue = staticValue; + // Stand pat. Return immediately if static value is at least beta + if (bestValue >= beta) + { + if (!tte) + TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); - if (bestValue >= beta) - { - // Store the score to avoid a future costly evaluation() call - if (!isCheck && !tte) - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); + return bestValue; + } - return bestValue; - } + if (PvNode && bestValue > alpha) + alpha = bestValue; - if (bestValue > alpha) - alpha = bestValue; + // If we are near beta then try to get a cutoff pushing checks a bit further + deepChecks = (depth == -OnePly && bestValue >= beta - PawnValueMidgame / 8); - // If we are near beta then try to get a cutoff pushing checks a bit further - bool deepChecks = (depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8); + // Futility pruning parameters, not needed when in check + futilityBase = bestValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()]; + enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; + } // Initialize a MovePicker object for the current position, and prepare // to search the moves. Because the depth is <= 0 here, only captures, @@ -1512,8 +1552,6 @@ namespace { // and we are near beta) will be generated. MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H); CheckInfo ci(pos); - enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; - futilityBase = staticValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()]; // Loop through the moves until no moves remain or a beta cutoff occurs while ( alpha < beta @@ -1523,16 +1561,12 @@ namespace { moveIsCheck = pos.move_is_check(move, ci); - // Update current move - moveCount++; - ss->currentMove = move; - // Futility pruning if ( !PvNode - && enoughMaterial && !isCheck && !moveIsCheck && move != ttMove + && enoughMaterial && !move_is_promotion(move) && !pos.move_is_passed_pawn_push(move)) { @@ -1563,9 +1597,12 @@ namespace { && pos.see_sign(move) < 0) continue; + // Update current move + ss->currentMove = move; + // Make and search the move pos.do_move(move, st, ci, moveIsCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth-OnePly, threadID); + value = -qsearch(pos, ss+1, -beta, -alpha, depth-OnePly, ply+1); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1577,35 +1614,25 @@ namespace { if (value > alpha) { alpha = value; - update_pv(ss, ply); + update_pv(ss); } } } // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (!moveCount && isCheck) // Mate! + if (isCheck && bestValue == -VALUE_INFINITE) return value_mated_in(ply); // Update transposition table Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1)); - if (bestValue <= oldAlpha) - { - // If bestValue isn't changed it means it is still the static evaluation - // of the node, so keep this info to avoid a future evaluation() call. - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, d, MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); - } - else if (bestValue >= beta) - { - move = ss->pv[ply]; - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move, ss->eval, ei.kingDanger[pos.side_to_move()]); + ValueType f = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); + TT.store(pos.get_key(), value_to_tt(bestValue, ply), f, d, ss->bestMove, ss->eval, ei.kingDanger[pos.side_to_move()]); - // Update killers only for good checking moves - if (!pos.move_is_capture_or_promotion(move)) - update_killers(move, ss); - } - else - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, d, ss->pv[ply], ss->eval, ei.kingDanger[pos.side_to_move()]); + // Update killers only for checking moves that fails high + if ( bestValue >= beta + && !pos.move_is_capture_or_promotion(ss->bestMove)) + update_killers(ss->bestMove, ss); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1636,9 +1663,8 @@ namespace { int moveCount; value = -VALUE_INFINITE; - Position pos(*sp->pos); + Position pos(*sp->pos, threadID); CheckInfo ci(pos); - int ply = pos.ply(); SearchStack* ss = sp->sstack[threadID] + 1; isCheck = pos.is_check(); @@ -1667,14 +1693,14 @@ namespace { // Step 12. Futility pruning (is omitted in PV nodes) if ( !PvNode + && !captureOrPromotion && !isCheck && !dangerous - && !captureOrPromotion && !move_is_castle(move)) { // Move count based pruning if ( moveCount >= futility_move_count(sp->depth) - && ok_to_prune(pos, move, ss->threatMove) + && !(ss->threatMove && connected_threat(pos, move, ss->threatMove)) && sp->bestValue > value_mated_in(PLY_MAX)) { lock_grab(&(sp->lock)); @@ -1703,8 +1729,8 @@ namespace { // If the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; - if ( !dangerous - && !captureOrPromotion + if ( !captureOrPromotion + && !dangerous && !move_is_castle(move) && !move_is_killer(move, ss)) { @@ -1712,7 +1738,10 @@ namespace { if (ss->reduction) { Value localAlpha = sp->alpha; - value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, true, threadID); + Depth d = newDepth - ss->reduction; + value = d < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, d, sp->ply+1); + doFullDepthSearch = (value > localAlpha); } @@ -1721,22 +1750,29 @@ namespace { // if the move fails high again then go with full depth search. if (doFullDepthSearch && ss->reduction > 2 * OnePly) { + assert(newDepth - OnePly >= OnePly); + ss->reduction = OnePly; Value localAlpha = sp->alpha; - value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, true, threadID); + value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, sp->ply+1); doFullDepthSearch = (value > localAlpha); } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { - ss->reduction = Depth(0); Value localAlpha = sp->alpha; - value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1); + // Step extra. pv search (only in PV nodes) + // Search only for possible new PV nodes, if instead value >= beta then + // parent node fails low with value <= alpha and tries another move. if (PvNode && value > localAlpha && value < sp->beta) - value = -search(pos, ss+1, -sp->beta, -sp->alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -sp->beta, -sp->alpha, newDepth, sp->ply+1); } // Step 16. Undo move @@ -1759,7 +1795,7 @@ namespace { if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta sp->alpha = value; - sp_update_pv(sp->parentSstack, ss, ply); + sp_update_pv(sp->parentSstack, ss); } } } @@ -1771,48 +1807,20 @@ namespace { lock_release(&(sp->lock)); } - // init_node() is called at the beginning of all the search functions - // (search() qsearch(), and so on) and initializes the - // search stack object corresponding to the current node. Once every - // NodesBetweenPolls nodes, init_node() also calls poll(), which polls - // for user input and checks whether it is time to stop the search. - - void init_node(SearchStack* ss, int ply, int threadID) { - - assert(ply >= 0 && ply < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); - - TM.incrementNodeCounter(threadID); - - if (threadID == 0) - { - NodesSincePoll++; - if (NodesSincePoll >= NodesBetweenPolls) - { - poll(); - NodesSincePoll = 0; - } - } - ss->init(ply); - (ss + 2)->initKillers(); - } - // update_pv() is called whenever a search returns a value > alpha. // It updates the PV in the SearchStack object corresponding to the // current node. - void update_pv(SearchStack* ss, int ply) { - - assert(ply >= 0 && ply < PLY_MAX); - - int p; + void update_pv(SearchStack* ss) { - ss->pv[ply] = ss->currentMove; + Move* src = (ss+1)->pv; + Move* dst = ss->pv; - for (p = ply + 1; (ss+1)->pv[p] != MOVE_NONE; p++) - ss->pv[p] = (ss+1)->pv[p]; + *dst = ss->bestMove = ss->currentMove; - ss->pv[p] = MOVE_NONE; + do + *++dst = *src; + while (*src++ != MOVE_NONE); } @@ -1820,18 +1828,17 @@ namespace { // difference between the two functions is that sp_update_pv also updates // the PV at the parent node. - void sp_update_pv(SearchStack* pss, SearchStack* ss, int ply) { + void sp_update_pv(SearchStack* pss, SearchStack* ss) { - assert(ply >= 0 && ply < PLY_MAX); + Move* src = (ss+1)->pv; + Move* dst = ss->pv; + Move* pdst = pss->pv; - int p; + *dst = *pdst = pss->bestMove = ss->bestMove = ss->currentMove; - ss->pv[ply] = pss->pv[ply] = ss->currentMove; - - for (p = ply + 1; (ss+1)->pv[p] != MOVE_NONE; p++) - ss->pv[p] = pss->pv[p] = (ss+1)->pv[p]; - - ss->pv[p] = pss->pv[p] = MOVE_NONE; + do + *++dst = *++pdst = *src; + while (*src++ != MOVE_NONE); } @@ -1934,7 +1941,7 @@ namespace { if (*dangerous) { - if (moveIsCheck) + if (moveIsCheck && pos.see_sign(m) >= 0) result += CheckExtension[PvNode]; if (singleEvasion) @@ -1983,38 +1990,19 @@ namespace { } - // ok_to_do_nullmove() looks at the current position and decides whether - // doing a 'null move' should be allowed. In order to avoid zugzwang - // problems, null moves are not allowed when the side to move has very - // little material left. Currently, the test is a bit too simple: Null - // moves are avoided only when the side to move has only pawns left. - // It's probably a good idea to avoid null moves in at least some more - // complicated endgames, e.g. KQ vs KR. FIXME - - bool ok_to_do_nullmove(const Position& pos) { - - return pos.non_pawn_material(pos.side_to_move()) != Value(0); - } - + // connected_threat() tests whether it is safe to forward prune a move or if + // is somehow coonected to the threat move returned by null search. - // ok_to_prune() tests whether it is safe to forward prune a move. Only - // non-tactical moves late in the move list close to the leaves are - // candidates for pruning. - - bool ok_to_prune(const Position& pos, Move m, Move threat) { + bool connected_threat(const Position& pos, Move m, Move threat) { assert(move_is_ok(m)); - assert(threat == MOVE_NONE || move_is_ok(threat)); + assert(threat && move_is_ok(threat)); assert(!pos.move_is_check(m)); assert(!pos.move_is_capture_or_promotion(m)); assert(!pos.move_is_passed_pawn_push(m)); Square mfrom, mto, tfrom, tto; - // Prune if there isn't any threat move - if (threat == MOVE_NONE) - return true; - mfrom = move_from(m); mto = move_to(m); tfrom = move_from(threat); @@ -2022,7 +2010,7 @@ namespace { // Case 1: Don't prune moves which move the threatened piece if (mfrom == tto) - return false; + return true; // Case 2: If the threatened piece has value less than or equal to the // value of the threatening piece, don't prune move which defend it. @@ -2030,16 +2018,16 @@ namespace { && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) || pos.type_of_piece_on(tfrom) == KING) && pos.move_attacks_square(m, tto)) - return false; + 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)) && bit_is_set(squares_between(tfrom, tto), mto) && pos.see_sign(m) >= 0) - return false; + return true; - return true; + return false; } @@ -2243,14 +2231,21 @@ namespace { } - // init_ss_array() does a fast reset of the first entries of a SearchStack array + // init_ss_array() does a fast reset of the first entries of a SearchStack + // array and of all the excludedMove and skipNullMove entries. - void init_ss_array(SearchStack* ss) { + void init_ss_array(SearchStack* ss, int size) { - for (int i = 0; i < 3; i++, ss++) + for (int i = 0; i < size; i++, ss++) { - ss->init(i); - ss->initKillers(); + ss->excludedMove = MOVE_NONE; + ss->skipNullMove = false; + + if (i < 3) + { + ss->init(); + ss->initKillers(); + } } } @@ -2530,7 +2525,7 @@ namespace { // Wait for thread termination for (int i = 1; i < MAX_THREADS; i++) - while (threads[i].state != THREAD_TERMINATED); + while (threads[i].state != THREAD_TERMINATED) {} // Now we can safely destroy the locks for (int i = 0; i < MAX_THREADS; i++) @@ -2622,18 +2617,21 @@ namespace { // split() returns. template - void ThreadsManager::split(const Position& p, SearchStack* ss, Value* alpha, const Value beta, - Value* bestValue, Depth depth, bool mateThreat, int* moveCount, - MovePicker* mp, int master, bool pvNode) { + void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha, + const Value beta, Value* bestValue, Depth depth, bool mateThreat, + int* moveCount, MovePicker* mp, bool pvNode) { assert(p.is_ok()); + assert(ply > 0 && ply < PLY_MAX); assert(*bestValue >= -VALUE_INFINITE); assert(*bestValue <= *alpha); assert(*alpha < beta); assert(beta <= VALUE_INFINITE); assert(depth > Depth(0)); - assert(master >= 0 && master < ActiveThreads); + assert(p.thread() >= 0 && p.thread() < ActiveThreads); assert(ActiveThreads > 1); + int master = p.thread(); + lock_grab(&MPLock); // If no other thread is available to help us, or if we have too many @@ -2651,6 +2649,7 @@ namespace { // Initialize the split point object splitPoint->parent = threads[master].splitPoint; splitPoint->stopRequest = false; + splitPoint->ply = ply; splitPoint->depth = depth; splitPoint->mateThreat = mateThreat; splitPoint->alpha = *alpha; @@ -2782,10 +2781,10 @@ namespace { continue; // Find a quick score for the move - init_ss_array(ss); + init_ss_array(ss, PLY_MAX_PLUS_2); pos.do_move(cur->move, st); moves[count].move = cur->move; - moves[count].score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 0); + moves[count].score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1); moves[count].pv[0] = cur->move; moves[count].pv[1] = MOVE_NONE; pos.undo_move(cur->move);