X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=d04898e8570a13486f0b11088760138d4d5c768a;hb=559942d64de9497c9d6d13b22307b4b9e1ce8ecf;hp=2c7c6fd671c55e6d9277ca675077f7b4debde2ef;hpb=95f73ff393e5b87b2a3b4195d698b6620fd4a123;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index 2c7c6fd6..d04898e8 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -59,7 +59,7 @@ using namespace Search; namespace { // Different node types, used as a template parameter - enum NodeType { NonPV, PV }; + enum NodeType { NonPV, PV, Root }; constexpr uint64_t TtHitAverageWindow = 4096; constexpr uint64_t TtHitAverageResolution = 1024; @@ -102,10 +102,10 @@ namespace { Move best = MOVE_NONE; }; - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = 0); Value value_to_tt(Value v, int ply); @@ -384,7 +384,7 @@ void Thread::search() { while (true) { Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter); - bestValue = Stockfish::search(rootPos, ss, alpha, beta, adjustedDepth, false); + bestValue = Stockfish::search(rootPos, ss, alpha, beta, adjustedDepth, false); // Bring the best move to the front. It is critical that sorting // is done with a stable algorithm because all the values but the @@ -480,8 +480,8 @@ void Thread::search() { totBestMoveChanges += th->bestMoveChanges; th->bestMoveChanges = 0; } - double bestMoveInstability = 1 + 2 * totBestMoveChanges / Threads.size(); - + double bestMoveInstability = 1.073 + std::max(1.0, 2.25 - 9.9 / rootDepth) + * totBestMoveChanges / Threads.size(); double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability; // Cap used time in case of a single legal move for a better viewer experience in tournaments @@ -527,18 +527,18 @@ namespace { // search<>() is the main search function for both PV and non-PV nodes - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { - constexpr bool PvNode = NT == PV; - const bool rootNode = PvNode && ss->ply == 0; + constexpr bool PvNode = nodeType != NonPV; + constexpr bool rootNode = nodeType == Root; const Depth maxNextDepth = rootNode ? depth : depth + 1; // Check if we have an upcoming move which draws by repetition, or // if the opponent had an alternative move earlier to this position. - if ( pos.rule50_count() >= 3 + if ( !rootNode + && pos.rule50_count() >= 3 && alpha < VALUE_DRAW - && !rootNode && pos.has_game_cycle(ss->ply)) { alpha = value_draw(pos.this_thread()); @@ -548,7 +548,7 @@ namespace { // Dive into quiescence search when the depth reaches zero if (depth <= 0) - return qsearch(pos, ss, alpha, beta); + return qsearch(pos, ss, alpha, beta); assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); @@ -610,10 +610,11 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); - (ss+1)->ttPv = false; + (ss+1)->ttPv = false; (ss+1)->excludedMove = bestMove = MOVE_NONE; - (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; - Square prevSq = to_sq((ss-1)->currentMove); + (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + ss->doubleExtensions = (ss-1)->doubleExtensions; + Square prevSq = to_sq((ss-1)->currentMove); // Initialize statScore to zero for the grandchildren of the current position. // So statScore is shared between all grandchildren and only the first grandchild @@ -1054,9 +1055,9 @@ moves_loop: // When in check, search starts from here // then that move is singular and should be extended. To verify this we do // a reduced search on all the other moves but the ttMove and if the // result is lower than ttValue minus a margin, then we will extend the ttMove. - if ( depth >= 7 + if ( !rootNode + && depth >= 7 && move == ttMove - && !rootNode && !excludedMove // Avoid recursive singular search /* && ttValue != VALUE_NONE Already implicit in the next condition */ && abs(ttValue) < VALUE_KNOWN_WIN @@ -1074,7 +1075,11 @@ moves_loop: // When in check, search starts from here { extension = 1; singularQuietLMR = !ttCapture; - if (!PvNode && value < singularBeta - 93) + + // Avoid search explosion by limiting the number of double extensions to at most 3 + if ( !PvNode + && value < singularBeta - 93 + && ss->doubleExtensions < 3) extension = 2; } @@ -1105,6 +1110,7 @@ moves_loop: // When in check, search starts from here // Add extension to new depth newDepth += extension; + ss->doubleExtensions = (ss-1)->doubleExtensions + (extension == 2); // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); @@ -1132,6 +1138,9 @@ moves_loop: // When in check, search starts from here { Depth r = reduction(improving, depth, moveCount); + if (PvNode) + r--; + // Decrease reduction if the ttHit running average is large (~0 Elo) if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024) r--; @@ -1351,10 +1360,11 @@ moves_loop: // When in check, search starts from here // qsearch() is the quiescence search function, which is called by the main search // function with zero depth, or recursively with further decreasing depth per call. - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { - constexpr bool PvNode = NT == PV; + static_assert(nodeType != Root); + constexpr bool PvNode = nodeType == PV; assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); @@ -1460,7 +1470,7 @@ moves_loop: // When in check, search starts from here // Initialize a MovePicker object for the current position, and prepare // to search the moves. Because the depth is <= 0 here, only captures, - // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS) + // queen promotions, and other checks (only if depth >= DEPTH_QS_CHECKS) // will be generated. MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, @@ -1532,7 +1542,7 @@ moves_loop: // When in check, search starts from here // Make and search the move pos.do_move(move, st, givesCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1); + value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);