X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=91b7a867603841eb9612310039ca429b21983b62;hp=6ee1ea02a17b1e45d9dc603a75ec23a6d8e0d50e;hb=9337c6da46dae7c1664f36a4b27e1fedef910b9a;hpb=2572055c87f04832e43d63f30f26de04cadb729c diff --git a/src/search.cpp b/src/search.cpp index 6ee1ea02..91b7a867 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -90,7 +90,7 @@ namespace { 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); + Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode); private: friend void poll(); @@ -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); 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); template void sp_search(SplitPoint* sp, int threadID); @@ -313,7 +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) @@ -603,7 +603,7 @@ 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; @@ -633,7 +633,7 @@ 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; @@ -811,7 +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) @@ -876,7 +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); } else { @@ -892,23 +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); + 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); 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); // 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); } } @@ -1031,26 +1045,27 @@ 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) { 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(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 threadID = pos.thread(); int ply = pos.ply(); refinedValue = bestValue = value = -VALUE_INFINITE; oldAlpha = alpha; @@ -1083,7 +1098,8 @@ 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); @@ -1116,7 +1132,7 @@ 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); @@ -1133,7 +1149,7 @@ namespace { && !pos.has_pawn_on_7th(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)); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -1144,7 +1160,7 @@ 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 @@ -1157,7 +1173,7 @@ 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 @@ -1174,9 +1190,11 @@ namespace { R++; pos.do_null_move(st); + (ss+1)->skipNullMove = true; - nullValue = depth-R*OnePly < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), threadID) - : - search(pos, ss+1, -beta, -alpha, depth-R*OnePly, false, threadID); + nullValue = depth-R*OnePly < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0)) + : - search(pos, ss+1, -beta, -alpha, depth-R*OnePly); + (ss+1)->skipNullMove = false; pos.undo_null_move(); if (nullValue >= beta) @@ -1186,8 +1204,14 @@ namespace { nullValue = beta; // Do zugzwang verification search at high depths - if ( depth < 6 * OnePly - || search(pos, ss, alpha, beta, depth-5*OnePly, false, threadID) >= beta) + if (depth < 6 * OnePly) + return nullValue; + + ss->skipNullMove = true; + Value v = search(pos, ss, alpha, beta, depth-5*OnePly); + ss->skipNullMove = false; + + if (v >= beta) return nullValue; } else @@ -1215,7 +1239,11 @@ namespace { && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) { Depth d = (PvNode ? depth - 2 * OnePly : depth / 2); - search(pos, ss, alpha, beta, d, false, threadID); + + ss->skipNullMove = true; + search(pos, ss, alpha, beta, d); + ss->skipNullMove = false; + ttMove = ss->pv[ply]; tte = TT.retrieve(posKey); } @@ -1263,7 +1291,11 @@ namespace { 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); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; if (v < ttValue - SingularExtensionMargin) ext = OnePly; @@ -1310,8 +1342,8 @@ namespace { // Step extra. pv search (only in PV nodes) // The first move in list is the expected PV if (PvNode && moveCount == 1) - value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), threadID) - : - search(pos, ss+1, -beta, -alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0)) + : - search(pos, ss+1, -beta, -alpha, newDepth); else { // Step 14. Reduced depth search @@ -1328,8 +1360,8 @@ namespace { if (ss->reduction) { Depth d = newDepth - ss->reduction; - value = d < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID) - : - search(pos, ss+1, -(alpha+1), -alpha, d, true, threadID); + value = d < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0)) + : - search(pos, ss+1, -(alpha+1), -alpha, d); doFullDepthSearch = (value > alpha); } @@ -1342,7 +1374,7 @@ namespace { 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); doFullDepthSearch = (value > alpha); } ss->reduction = Depth(0); // Restore original reduction @@ -1351,15 +1383,15 @@ namespace { // Step 15. Full depth search if (doFullDepthSearch) { - value = newDepth < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0)) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); // 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 = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), threadID) - : - search(pos, ss+1, -beta, -alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0)) + : - search(pos, ss+1, -beta, -alpha, newDepth); } } @@ -1393,7 +1425,7 @@ namespace { && !TM.thread_should_stop(threadID) && Iteration <= 99) TM.split(pos, ss, &alpha, beta, &bestValue, depth, - mateThreat, &moveCount, &mp, threadID, PvNode); + mateThreat, &moveCount, &mp, PvNode); } // Step 19. Check for mate and stalemate @@ -1437,26 +1469,27 @@ 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) { 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(pos.thread() >= 0 && pos.thread() < TM.active_threads()); EvalInfo ei; StateInfo st; Move ttMove, move; - Value staticValue, bestValue, value, futilityBase, futilityValue; + Value staticValue, bestValue, value, futilityBase; bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable; const TTEntry* tte = NULL; int moveCount = 0; int ply = pos.ply(); Value oldAlpha = alpha; + Value futilityValue = VALUE_INFINITE; - TM.incrementNodeCounter(threadID); + TM.incrementNodeCounter(pos.thread()); ss->init(ply); // Check for an instant draw or maximum ply reached @@ -1485,7 +1518,7 @@ namespace { ei.kingDanger[pos.side_to_move()] = tte->king_danger(); } else - staticValue = evaluate(pos, ei, threadID); + staticValue = evaluate(pos, ei); if (!isCheck) { @@ -1506,7 +1539,7 @@ namespace { return bestValue; } - if (bestValue > alpha) + if (PvNode && bestValue > alpha) alpha = bestValue; // If we are near beta then try to get a cutoff pushing checks a bit further @@ -1542,6 +1575,11 @@ namespace { && !move_is_promotion(move) && !pos.move_is_passed_pawn_push(move)) { + // Can only decrease from previous move because of + // MVV ordering so we don't need to recheck. + if (futilityValue < alpha) + continue; + futilityValue = futilityBase + pos.endgame_value_of_piece_on(move_to(move)) + (move_is_ep(move) ? PawnValueEndgame : Value(0)); @@ -1571,7 +1609,7 @@ namespace { // 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); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1642,7 +1680,7 @@ 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; @@ -1719,8 +1757,8 @@ namespace { { Value localAlpha = sp->alpha; Depth d = newDepth - ss->reduction; - value = d < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID) - : - search(pos, ss+1, -(localAlpha+1), -localAlpha, d, true, threadID); + value = d < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0)) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, d); doFullDepthSearch = (value > localAlpha); } @@ -1733,7 +1771,7 @@ namespace { 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); doFullDepthSearch = (value > localAlpha); } ss->reduction = Depth(0); // Restore original reduction @@ -1743,15 +1781,15 @@ namespace { if (doFullDepthSearch) { Value localAlpha = sp->alpha; - value = newDepth < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID) - : - search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0)) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth); // 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 = newDepth < OnePly ? -qsearch(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), threadID) - : - search(pos, ss+1, -sp->beta, -sp->alpha, newDepth, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -sp->beta, -sp->alpha, Depth(0)) + : - search(pos, ss+1, -sp->beta, -sp->alpha, newDepth); } // Step 16. Undo move @@ -2213,14 +2251,21 @@ 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(i); + ss->initKillers(); + } } } @@ -2594,16 +2639,18 @@ namespace { 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) { + MovePicker* mp, bool pvNode) { assert(p.is_ok()); 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 @@ -2752,10 +2799,10 @@ 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)); moves[count].pv[0] = cur->move; moves[count].pv[1] = MOVE_NONE; pos.undo_move(cur->move);