X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=78a1f7b6eb9e038a5c24f415dd127a2ddb67c13b;hp=1e133447d381b547f97d9ea93ab7aa7321d862f7;hb=027626db1e449597ba2211a0819f251beda37b88;hpb=16566a8fcf76b9b72b6e746f318f77045df90017 diff --git a/src/search.cpp b/src/search.cpp index 1e133447..78a1f7b6 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,8 +1,6 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 - Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file) Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -65,9 +63,9 @@ namespace { constexpr uint64_t TtHitAverageResolution = 1024; // Razor and futility margins - constexpr int RazorMargin = 531; + constexpr int RazorMargin = 510; Value futility_margin(Depth d, bool improving) { - return Value(217 * (d - improving)); + return Value(223 * (d - improving)); } // Reductions lookup table, initialized at startup @@ -75,16 +73,16 @@ namespace { Depth reduction(bool i, Depth d, int mn) { int r = Reductions[d] * Reductions[mn]; - return (r + 511) / 1024 + (!i && r > 1007); + return (r + 509) / 1024 + (!i && r > 894); } constexpr int futility_move_count(bool improving, Depth depth) { - return (4 + depth * depth) / (2 - improving); + return (3 + depth * depth) / (2 - improving); } // History and stats update bonus, based on depth int stat_bonus(Depth d) { - return d > 15 ? -8 : 19 * d * d + 155 * d - 132; + return d > 13 ? 29 : 17 * d * d + 134 * d - 134; } // Add a small random component to draw evaluations to avoid 3fold-blindness @@ -166,6 +164,8 @@ namespace { uint64_t perft(Position& pos, Depth depth) { StateInfo st; + ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize); + uint64_t cnt, nodes = 0; const bool leaf = (depth == 2); @@ -194,7 +194,7 @@ namespace { void Search::init() { for (int i = 1; i < MAX_MOVES; ++i) - Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i)); + Reductions[i] = int((22.0 + 2 * std::log(Threads.size())) * std::log(i + 0.25 * std::log(i))); } @@ -227,6 +227,8 @@ void MainThread::search() { Time.init(Limits, us, rootPos.game_ply()); TT.new_search(); + Eval::NNUE::verify(); + if (rootMoves.empty()) { rootMoves.emplace_back(MOVE_NONE); @@ -236,14 +238,8 @@ void MainThread::search() { } else { - for (Thread* th : Threads) - { - th->bestMoveChanges = 0; - if (th != this) - th->start_searching(); - } - - Thread::search(); // Let's start searching! + Threads.start_searching(); // start non-main threads + Thread::search(); // main thread start searching } // When we reach the maximum depth, we can arrive here without a raise of @@ -260,9 +256,7 @@ void MainThread::search() { Threads.stop = true; // Wait until all threads have finished - for (Thread* th : Threads) - if (th != this) - th->wait_for_search_finished(); + Threads.wait_for_search_finished(); // When playing in 'nodes as time' mode, subtract the searched nodes from // the available ones before exiting. @@ -271,37 +265,11 @@ void MainThread::search() { Thread* bestThread = this; - // Check if there are threads with a better score than main thread - if ( int(Options["MultiPV"]) == 1 + if ( int(Options["MultiPV"]) == 1 && !Limits.depth && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) - && rootMoves[0].pv[0] != MOVE_NONE) - { - std::map votes; - Value minScore = this->rootMoves[0].score; - - // Find minimum score - for (Thread* th: Threads) - minScore = std::min(minScore, th->rootMoves[0].score); - - // Vote according to score and depth, and select the best thread - for (Thread* th : Threads) - { - votes[th->rootMoves[0].pv[0]] += - (th->rootMoves[0].score - minScore + 14) * int(th->completedDepth); - - if (abs(bestThread->rootMoves[0].score) >= VALUE_TB_WIN_IN_MAX_PLY) - { - // Make sure we pick the shortest mate / TB conversion or stave off mate the longest - if (th->rootMoves[0].score > bestThread->rootMoves[0].score) - bestThread = th; - } - else if ( th->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY - || ( th->rootMoves[0].score > VALUE_TB_LOSS_IN_MAX_PLY - && votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]])) - bestThread = th; - } - } + && rootMoves[0].pv[0] != MOVE_NONE) + bestThread = Threads.get_best_thread(); bestPreviousScore = bestThread->rootMoves[0].score; @@ -369,7 +337,7 @@ void Thread::search() { // for match (TC 60+0.6) results spanning a wide range of k values. PRNG rng(now()); double floatLevel = Options["UCI_LimitStrength"] ? - Utility::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) : + std::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) : double(Options["Skill Level"]); int intLevel = int(floatLevel) + ((floatLevel - int(floatLevel)) * 1024 > rng.rand() % 1024 ? 1 : 0); @@ -437,12 +405,12 @@ void Thread::search() { if (rootDepth >= 4) { Value prev = rootMoves[pvIdx].previousScore; - delta = Value(21); + delta = Value(17); alpha = std::max(prev - delta,-VALUE_INFINITE); beta = std::min(prev + delta, VALUE_INFINITE); // Adjust contempt based on root move's previousScore (dynamic contempt) - int dct = ct + (102 - ct / 2) * prev / (abs(prev) + 157); + int dct = ct + (105 - ct / 2) * prev / (abs(prev) + 149); contempt = (us == WHITE ? make_score(dct, dct / 2) : -make_score(dct, dct / 2)); @@ -451,7 +419,7 @@ void Thread::search() { // Start with a small aspiration window and, in the case of a fail // high/low, re-search with a bigger window until we don't fail // high/low anymore. - int failedHighCnt = 0; + failedHighCnt = 0; while (true) { Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter); @@ -496,10 +464,7 @@ void Thread::search() { ++failedHighCnt; } else - { - ++rootMoves[pvIdx].bestMoveCount; break; - } delta += delta / 4 + 5; @@ -540,13 +505,13 @@ void Thread::search() { && !Threads.stop && !mainThread->stopOnPonderhit) { - double fallingEval = (332 + 6 * (mainThread->bestPreviousScore - bestValue) - + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0; - fallingEval = Utility::clamp(fallingEval, 0.5, 1.5); + double fallingEval = (318 + 6 * (mainThread->bestPreviousScore - bestValue) + + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0; + fallingEval = std::clamp(fallingEval, 0.5, 1.5); // If the bestMove is stable over several iterations, reduce time accordingly - timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.94 : 0.91; - double reduction = (1.41 + mainThread->previousTimeReduction) / (2.27 * timeReduction); + timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.92 : 0.95; + double reduction = (1.47 + mainThread->previousTimeReduction) / (2.32 * timeReduction); // Use part of the gained time from a previous stable move for the current move for (Thread* th : Threads) @@ -554,11 +519,17 @@ void Thread::search() { totBestMoveChanges += th->bestMoveChanges; th->bestMoveChanges = 0; } - double bestMoveInstability = 1 + totBestMoveChanges / Threads.size(); + double bestMoveInstability = 1 + 2 * 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 + // yielding correct scores and sufficiently fast moves. + if (rootMoves.size() == 1) + totalTime = std::min(500.0, totalTime); - // Stop the search if we have only one legal move, or if available time elapsed - if ( rootMoves.size() == 1 - || Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability) + // Stop the search if we have exceeded the totalTime + if (Time.elapsed() > totalTime) { // If we are allowed to ponder do not stop the search now but // keep pondering until the GUI sends "ponderhit" or "stop". @@ -569,7 +540,7 @@ void Thread::search() { } else if ( Threads.increaseDepth && !mainThread->ponder - && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6) + && Time.elapsed() > totalTime * 0.58) Threads.increaseDepth = false; else Threads.increaseDepth = true; @@ -600,6 +571,7 @@ namespace { constexpr bool PvNode = NT == PV; const bool rootNode = PvNode && ss->ply == 0; + 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. @@ -624,12 +596,14 @@ namespace { Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[64]; StateInfo st; + ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize); + TTEntry* tte; Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, maxValue; - bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture; + Value bestValue, value, ttValue, eval, maxValue, probCutBeta; + bool formerPv, givesCheck, improving, didLMR, priorCapture; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularQuietLMR; Piece movedPiece; @@ -659,7 +633,7 @@ namespace { || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos) - : value_draw(pos.this_thread()); + : value_draw(pos.this_thread()); // 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 @@ -676,6 +650,7 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); (ss+1)->ply = ss->ply + 1; + (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); @@ -685,33 +660,36 @@ namespace { // starts with statScore = 0. Later grandchildren start with the last calculated // statScore of the previous grandchild. This influences the reduction rules in // LMR which are based on the statScore of parent position. - if (rootNode) - (ss+4)->statScore = 0; - else + if (!rootNode) (ss+2)->statScore = 0; // Step 4. Transposition table lookup. 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. excludedMove = ss->excludedMove; - posKey = pos.key() ^ Key(excludedMove << 16); // Isn't a very good hash - tte = TT.probe(posKey, ttHit); - ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; + posKey = excludedMove == MOVE_NONE ? pos.key() : pos.key() ^ make_key(excludedMove); + tte = TT.probe(posKey, ss->ttHit); + ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] - : ttHit ? tte->move() : MOVE_NONE; - ttPv = PvNode || (ttHit && tte->is_pv()); - formerPv = ttPv && !PvNode; - - if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove)) + : ss->ttHit ? tte->move() : MOVE_NONE; + if (!excludedMove) + ss->ttPv = PvNode || (ss->ttHit && tte->is_pv()); + formerPv = ss->ttPv && !PvNode; + + if ( ss->ttPv + && depth > 12 + && ss->ply - 1 < MAX_LPH + && !priorCapture + && is_ok((ss-1)->currentMove)) thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5); // thisThread->ttHitAverage can be used to approximate the running average of ttHit thisThread->ttHitAverage = (TtHitAverageWindow - 1) * thisThread->ttHitAverage / TtHitAverageWindow - + TtHitAverageResolution * ttHit; + + TtHitAverageResolution * ss->ttHit; // At non-PV nodes we check for an early TT cutoff if ( !PvNode - && ttHit + && ss->ttHit && tte->depth() >= depth && ttValue != VALUE_NONE // Possible in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) @@ -776,7 +754,7 @@ namespace { if ( b == BOUND_EXACT || (b == BOUND_LOWER ? value >= beta : value <= alpha)) { - tte->save(posKey, value_to_tt(value, ss->ply), ttPv, b, + tte->save(posKey, value_to_tt(value, ss->ply), ss->ttPv, b, std::min(MAX_PLY - 1, depth + 6), MOVE_NONE, VALUE_NONE); @@ -799,11 +777,12 @@ namespace { // Step 6. Static evaluation of the position if (ss->inCheck) { + // Skip early pruning when in check ss->staticEval = eval = VALUE_NONE; improving = false; - goto moves_loop; // Skip early pruning when in check + goto moves_loop; } - else if (ttHit) + else if (ss->ttHit) { // Never assume anything about values stored in TT ss->staticEval = eval = tte->eval(); @@ -821,15 +800,11 @@ namespace { else { if ((ss-1)->currentMove != MOVE_NULL) - { - int bonus = -(ss-1)->statScore / 512; - - ss->staticEval = eval = evaluate(pos) + bonus; - } + ss->staticEval = eval = evaluate(pos); else ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo; - tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); + tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); } // Step 7. Razoring (~1 Elo) @@ -838,12 +813,13 @@ namespace { && eval <= alpha - RazorMargin) return qsearch(pos, ss, alpha, beta); - improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval > (ss-4)->staticEval - || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval > (ss-2)->staticEval; + improving = (ss-2)->staticEval == VALUE_NONE + ? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE + : ss->staticEval > (ss-2)->staticEval; // Step 8. Futility pruning: child node (~50 Elo) if ( !PvNode - && depth < 6 + && depth < 8 && eval - futility_margin(depth, improving) >= beta && eval < VALUE_KNOWN_WIN) // Do not return unproven wins return eval; @@ -851,10 +827,10 @@ namespace { // Step 9. Null move search with verification search (~40 Elo) if ( !PvNode && (ss-1)->currentMove != MOVE_NULL - && (ss-1)->statScore < 23397 + && (ss-1)->statScore < 22977 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 32 * depth - 30 * improving + 120 * ttPv + 292 + && ss->staticEval >= beta - 30 * depth - 28 * improving + 84 * ss->ttPv + 182 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) @@ -862,7 +838,7 @@ namespace { assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value - Depth R = (854 + 68 * depth) / 258 + std::min(int(eval - beta) / 192, 3); + Depth R = (982 + 85 * depth) / 256 + std::min(int(eval - beta) / 192, 3); ss->currentMove = MOVE_NULL; ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0]; @@ -898,23 +874,41 @@ namespace { } } + probCutBeta = beta + 176 - 49 * improving; + // Step 10. ProbCut (~10 Elo) // If we have a good enough capture and a reduced search returns a value // much above beta, we can (almost) safely prune the previous move. if ( !PvNode - && depth >= 5 - && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY) + && depth > 4 + && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY + // if value from transposition table is lower than probCutBeta, don't attempt probCut + // there and in further interactions with transposition table cutoff depth is set to depth - 3 + // because probCut search has depth set to depth - 4 but we also do a move before it + // so effective depth is equal to depth - 3 + && !( ss->ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE + && ttValue < probCutBeta)) { - Value raisedBeta = beta + 189 - 45 * improving; - assert(raisedBeta < VALUE_INFINITE); - MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory); + // if ttMove is a capture and value from transposition table is good enough produce probCut + // cutoff without digging into actual probCut search + if ( ss->ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE + && ttValue >= probCutBeta + && ttMove + && pos.capture_or_promotion(ttMove)) + return probCutBeta; + + assert(probCutBeta < VALUE_INFINITE); + MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory); int probCutCount = 0; + bool ttPv = ss->ttPv; + ss->ttPv = false; while ( (move = mp.next_move()) != MOVE_NONE - && probCutCount < 2 + 2 * cutNode - && !( move == ttMove - && tte->depth() >= depth - 4 - && ttValue < raisedBeta)) + && probCutCount < 2 + 2 * cutNode) if (move != excludedMove && pos.legal(move)) { assert(pos.capture_or_promotion(move)); @@ -932,28 +926,34 @@ namespace { pos.do_move(move, st); // Perform a preliminary qsearch to verify that the move holds - value = -qsearch(pos, ss+1, -raisedBeta, -raisedBeta+1); + value = -qsearch(pos, ss+1, -probCutBeta, -probCutBeta+1); // If the qsearch held, perform the regular search - if (value >= raisedBeta) - value = -search(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4, !cutNode); + if (value >= probCutBeta) + value = -search(pos, ss+1, -probCutBeta, -probCutBeta+1, depth - 4, !cutNode); pos.undo_move(move); - if (value >= raisedBeta) + if (value >= probCutBeta) + { + // if transposition table doesn't have equal or more deep info write probCut data into it + if ( !(ss->ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE)) + tte->save(posKey, value_to_tt(value, ss->ply), ttPv, + BOUND_LOWER, + depth - 3, move, ss->staticEval); return value; + } } + ss->ttPv = ttPv; } - // Step 11. Internal iterative deepening (~1 Elo) - if (depth >= 7 && !ttMove) - { - search(pos, ss, alpha, beta, depth - 7, cutNode); - - tte = TT.probe(posKey, ttHit); - ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; - ttMove = ttHit ? tte->move() : MOVE_NONE; - } + // Step 11. If the position is not in TT, decrease depth by 2 + if ( PvNode + && depth >= 6 + && !ttMove) + depth -= 2; moves_loop: // When in check, search starts from here @@ -969,7 +969,7 @@ moves_loop: // When in check, search starts from here contHist, countermove, ss->killers, - depth > 12 ? ss->ply : MAX_PLY); + ss->ply); value = bestValue; singularQuietLMR = moveCountPruning = false; @@ -995,6 +995,10 @@ moves_loop: // When in check, search starts from here thisThread->rootMoves.begin() + thisThread->pvLast, move)) continue; + // Check for legality + if (!rootNode && !pos.legal(move)) + continue; + ss->moveCount = ++moveCount; if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000) @@ -1033,16 +1037,17 @@ moves_loop: // When in check, search starts from here continue; // Futility pruning: parent node (~5 Elo) - if ( lmrDepth < 6 + if ( lmrDepth < 7 && !ss->inCheck - && ss->staticEval + 235 + 172 * lmrDepth <= alpha + && ss->staticEval + 283 + 170 * lmrDepth <= alpha && (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] - + (*contHist[3])[movedPiece][to_sq(move)] < 27400) + + (*contHist[3])[movedPiece][to_sq(move)] + + (*contHist[5])[movedPiece][to_sq(move)] / 2 < 27376) continue; // Prune moves with negative SEE (~20 Elo) - if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) + if (!pos.see_ge(move, Value(-(29 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) continue; } else @@ -1053,16 +1058,8 @@ moves_loop: // When in check, search starts from here && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0) continue; - // Futility pruning for captures - if ( !givesCheck - && lmrDepth < 6 - && !(PvNode && abs(bestValue) < 2) - && !ss->inCheck - && ss->staticEval + 270 + 384 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha) - continue; - - // See based pruning - if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo) + // SEE based pruning + if (!pos.see_ge(move, Value(-221) * depth)) // (~25 Elo) continue; } } @@ -1073,16 +1070,15 @@ moves_loop: // When in check, search starts from here // search of (alpha-s, beta-s), and just one fails high on (alpha, beta), // 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 >= 6 + // result is lower than ttValue minus a margin, then we will extend the ttMove. + if ( depth >= 7 && move == ttMove && !rootNode && !excludedMove // Avoid recursive singular search /* && ttValue != VALUE_NONE Already implicit in the next condition */ && abs(ttValue) < VALUE_KNOWN_WIN && (tte->bound() & BOUND_LOWER) - && tte->depth() >= depth - 3 - && pos.legal(move)) + && tte->depth() >= depth - 3) { Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2; Depth singularDepth = (depth - 1 + 3 * formerPv) / 2; @@ -1104,8 +1100,8 @@ moves_loop: // When in check, search starts from here else if (singularBeta >= beta) return singularBeta; - // If the eval of ttMove is greater than beta we try also if there is an other move that - // pushes it over beta, if so also produce a cutoff + // If the eval of ttMove is greater than beta we try also if there is another + // move that pushes it over beta, if so also produce a cutoff. else if (ttValue >= beta) { ss->excludedMove = move; @@ -1122,21 +1118,11 @@ moves_loop: // When in check, search starts from here && (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move))) extension = 1; - // Passed pawn extension - else if ( move == ss->killers[0] - && pos.advanced_pawn_push(move) - && pos.pawn_passed(us, to_sq(move))) - extension = 1; - // Last captures extension else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg && pos.non_pawn_material() <= 2 * RookValueMg) extension = 1; - // Castling extension - if (type_of(move) == CASTLING) - extension = 1; - // Late irreversible move extension if ( move == ttMove && pos.rule50_count() > 80 @@ -1149,13 +1135,6 @@ moves_loop: // When in check, search starts from here // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); - // Check for legality just before making the move - if (!rootNode && !pos.legal(move)) - { - ss->moveCount = --moveCount; - continue; - } - // Update the current move (this must be done after singular extension search) ss->currentMove = move; ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] @@ -1170,37 +1149,40 @@ moves_loop: // When in check, search starts from here // re-searched at full depth. if ( depth >= 3 && moveCount > 1 + 2 * rootNode - && (!rootNode || thisThread->best_move_count(move) == 0) && ( !captureOrPromotion || moveCountPruning || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha || cutNode - || thisThread->ttHitAverage < 375 * TtHitAverageResolution * TtHitAverageWindow / 1024)) + || thisThread->ttHitAverage < 427 * TtHitAverageResolution * TtHitAverageWindow / 1024)) { Depth r = reduction(improving, depth, moveCount); // Decrease reduction if the ttHit running average is large - if (thisThread->ttHitAverage > 500 * TtHitAverageResolution * TtHitAverageWindow / 1024) + if (thisThread->ttHitAverage > 509 * TtHitAverageResolution * TtHitAverageWindow / 1024) r--; - // Reduction if other threads are searching this position. + // Increase reduction if other threads are searching this position if (th.marked()) r++; // Decrease reduction if position is or has been on the PV (~10 Elo) - if (ttPv) + if (ss->ttPv) r -= 2; + // Increase reduction at root and non-PV nodes when the best move does not change frequently + if ((rootNode || !PvNode) && depth > 10 && thisThread->bestMoveChanges <= 2) + r++; + if (moveCountPruning && !formerPv) r++; // Decrease reduction if opponent's move count is high (~5 Elo) - if ((ss-1)->moveCount > 14) + if ((ss-1)->moveCount > 13) r--; // Decrease reduction if ttMove has been singularly extended (~3 Elo) if (singularQuietLMR) - r -= 1 + formerPv; + r--; if (!captureOrPromotion) { @@ -1208,6 +1190,9 @@ moves_loop: // When in check, search starts from here if (ttCapture) r++; + // Increase reduction at root if failing high + r += rootNode ? thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512 : 0; + // Increase reduction for cut nodes (~10 Elo) if (cutNode) r += 2; @@ -1217,37 +1202,37 @@ moves_loop: // When in check, search starts from here // hence break make_move(). (~2 Elo) else if ( type_of(move) == NORMAL && !pos.see_ge(reverse_move(move))) - r -= 2 + ttPv; + r -= 2 + ss->ttPv - (type_of(movedPiece) == PAWN); ss->statScore = thisThread->mainHistory[us][from_to(move)] + (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)] - - 4926; + - 5287; // Decrease/increase reduction by comparing opponent's stat score (~10 Elo) - if (ss->statScore >= -102 && (ss-1)->statScore < -114) + if (ss->statScore >= -106 && (ss-1)->statScore < -104) r--; - else if ((ss-1)->statScore >= -116 && ss->statScore < -154) + else if ((ss-1)->statScore >= -119 && ss->statScore < -140) r++; // Decrease/increase reduction for moves with a good/bad history (~30 Elo) - r -= ss->statScore / 16434; + r -= ss->statScore / 14884; } else { - // Increase reduction for captures/promotions if late move and at low depth - if (depth < 8 && moveCount > 2) - r++; - - // Unless giving check, this capture is likely bad - if ( !givesCheck - && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 200 * depth <= alpha) - r++; + // Increase reduction for captures/promotions if late move and at low depth + if (depth < 8 && moveCount > 2) + r++; + + // Unless giving check, this capture is likely bad + if ( !givesCheck + && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 213 * depth <= alpha) + r++; } - Depth d = Utility::clamp(newDepth - r, 1, newDepth); + Depth d = std::clamp(newDepth - r, 1, newDepth); value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); @@ -1287,7 +1272,8 @@ moves_loop: // When in check, search starts from here (ss+1)->pv = pv; (ss+1)->pv[0] = MOVE_NONE; - value = -search(pos, ss+1, -beta, -alpha, newDepth, false); + value = -search(pos, ss+1, -beta, -alpha, + std::min(maxNextDepth, newDepth), false); } // Step 18. Undo move @@ -1320,7 +1306,7 @@ moves_loop: // When in check, search starts from here rm.pv.push_back(*m); // We record how often the best move has been changed in each - // iteration. This information is used for time management: When + // iteration. This information is used for time management: when // the best move changes frequently, we allocate some more time. if (moveCount > 1) ++thisThread->bestMoveChanges; @@ -1395,8 +1381,17 @@ moves_loop: // When in check, search starts from here if (PvNode) bestValue = std::min(bestValue, maxValue); + // If no good move is found and the previous position was ttPv, then the previous + // opponent move is probably good and the new position is added to the search tree. + if (bestValue <= alpha) + ss->ttPv = ss->ttPv || ((ss-1)->ttPv && depth > 3); + // Otherwise, a counter move has been found and if the position is the last leaf + // in the search tree, remove the position from the search tree. + else if (depth > 3) + ss->ttPv = ss->ttPv && (ss+1)->ttPv; + if (!excludedMove && !(rootNode && thisThread->pvIdx)) - tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv, + tte->save(posKey, value_to_tt(bestValue, ss->ply), ss->ttPv, bestValue >= beta ? BOUND_LOWER : PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, depth, bestMove, ss->staticEval); @@ -1420,12 +1415,14 @@ moves_loop: // When in check, search starts from here Move pv[MAX_PLY+1]; StateInfo st; + ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize); + TTEntry* tte; Key posKey; Move ttMove, move, bestMove; Depth ttDepth; Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; - bool ttHit, pvHit, givesCheck, captureOrPromotion; + bool pvHit, givesCheck, captureOrPromotion; int moveCount; if (PvNode) @@ -1455,13 +1452,13 @@ moves_loop: // When in check, search starts from here : DEPTH_QS_NO_CHECKS; // Transposition table lookup posKey = pos.key(); - tte = TT.probe(posKey, ttHit); - ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; - ttMove = ttHit ? tte->move() : MOVE_NONE; - pvHit = ttHit && tte->is_pv(); + tte = TT.probe(posKey, ss->ttHit); + ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; + ttMove = ss->ttHit ? tte->move() : MOVE_NONE; + pvHit = ss->ttHit && tte->is_pv(); if ( !PvNode - && ttHit + && ss->ttHit && tte->depth() >= ttDepth && ttValue != VALUE_NONE // Only in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) @@ -1476,7 +1473,7 @@ moves_loop: // When in check, search starts from here } else { - if (ttHit) + if (ss->ttHit) { // Never assume anything about values stored in TT if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE) @@ -1495,7 +1492,7 @@ moves_loop: // When in check, search starts from here // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { - if (!ttHit) + if (!ss->ttHit) tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->staticEval); @@ -1505,7 +1502,7 @@ moves_loop: // When in check, search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = bestValue + 154; + futilityBase = bestValue + 145; } const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, @@ -1514,8 +1511,8 @@ 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 promotions and checks (only if depth >= DEPTH_QS_CHECKS) will - // be generated. + // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS) + // will be generated. MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, contHist, @@ -1532,13 +1529,17 @@ moves_loop: // When in check, search starts from here moveCount++; // Futility pruning - if ( !ss->inCheck + if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY && !givesCheck && futilityBase > -VALUE_KNOWN_WIN && !pos.advanced_pawn_push(move)) { assert(type_of(move) != ENPASSANT); // Due to !pos.advanced_pawn_push + // moveCount pruning + if (moveCount > 2) + continue; + futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))]; if (futilityValue <= alpha) @@ -1554,8 +1555,10 @@ moves_loop: // When in check, search starts from here } } - // Don't search moves with negative SEE values - if ( !ss->inCheck && !pos.see_ge(move)) + // Do not search moves with negative SEE values + if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY + && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move)) + && !pos.see_ge(move)) continue; // Speculative prefetch as early as possible @@ -1574,6 +1577,13 @@ moves_loop: // When in check, search starts from here [pos.moved_piece(move)] [to_sq(move)]; + // CounterMove based pruning + if ( !captureOrPromotion + && bestValue > VALUE_TB_LOSS_IN_MAX_PLY + && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold + && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold) + continue; + // Make and search the move pos.do_move(move, st, givesCheck); value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1); @@ -1601,10 +1611,14 @@ moves_loop: // When in check, search starts from here } } - // All legal moves have been searched. A special case: If we're in check + // All legal moves have been searched. A special case: if we're in check // and no legal moves were found, it is checkmate. if (ss->inCheck && bestValue == -VALUE_INFINITE) + { + assert(!MoveList(pos).size()); + return mated_in(ss->ply); // Plies to mate from the root + } tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, bestValue >= beta ? BOUND_LOWER : @@ -1618,7 +1632,7 @@ moves_loop: // When in check, search starts from here // value_to_tt() adjusts a mate or TB score from "plies to mate from the root" to - // "plies to mate from the current position". standard scores are unchanged. + // "plies to mate from the current position". Standard scores are unchanged. // The function is called before storing a value in the transposition table. Value value_to_tt(Value v, int ply) { @@ -1630,11 +1644,11 @@ moves_loop: // When in check, search starts from here } - // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate or TB score - // from the transposition table (which refers to the plies to mate/be mated - // from current position) to "plies to mate/be mated (TB win/loss) from the root". - // However, for mate scores, to avoid potentially false mate scores related to the 50 moves rule, - // and the graph history interaction, return an optimal TB score instead. + // value_from_tt() is the inverse of value_to_tt(): it adjusts a mate or TB score + // from the transposition table (which refers to the plies to mate/be mated from + // current position) to "plies to mate/be mated (TB win/loss) from the root". However, + // for mate scores, to avoid potentially false mate scores related to the 50 moves rule + // and the graph history interaction, we return an optimal TB score instead. Value value_from_tt(Value v, int ply, int r50c) { @@ -1701,8 +1715,8 @@ moves_loop: // When in check, search starts from here else captureHistory[moved_piece][to_sq(bestMove)][captured] << bonus1; - // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted - if ( ((ss-1)->moveCount == 1 || ((ss-1)->currentMove == (ss-1)->killers[0])) + // Extra penalty for a quiet early move that was not a TT move or main killer move in previous ply when it gets refuted + if ( ((ss-1)->moveCount == 1 + (ss-1)->ttHit || ((ss-1)->currentMove == (ss-1)->killers[0])) && !pos.captured_piece()) update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -bonus1); @@ -1755,7 +1769,7 @@ moves_loop: // When in check, search starts from here thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move; } - if (depth > 12 && ss->ply < MAX_LPH) + if (depth > 11 && ss->ply < MAX_LPH) thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7); } @@ -1794,6 +1808,7 @@ moves_loop: // When in check, search starts from here } // namespace + /// MainThread::check_time() is used to print debug info and, more importantly, /// to detect when we are out of available time and thus stop the search. @@ -1844,12 +1859,15 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { { bool updated = rootMoves[i].score != -VALUE_INFINITE; - if (depth == 1 && !updated) + if (depth == 1 && !updated && i > 0) continue; - Depth d = updated ? depth : depth - 1; + Depth d = updated ? depth : std::max(1, depth - 1); Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore; + if (v == -VALUE_INFINITE) + v = VALUE_ZERO; + bool tb = TB::RootInTB && abs(v) < VALUE_MATE_IN_MAX_PLY; v = tb ? rootMoves[i].tbScore : v; @@ -1862,6 +1880,9 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { << " multipv " << i + 1 << " score " << UCI::value(v); + if (Options["UCI_ShowWDL"]) + ss << UCI::wdl(v, pos.game_ply()); + if (!tb && i == pvIdx) ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); @@ -1891,6 +1912,8 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { bool RootMove::extract_ponder_from_tt(Position& pos) { StateInfo st; + ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize); + bool ttHit; assert(pv.size() == 1); @@ -1944,7 +1967,7 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) { if (RootInTB) { // Sort moves according to TB rank - std::sort(rootMoves.begin(), rootMoves.end(), + std::stable_sort(rootMoves.begin(), rootMoves.end(), [](const RootMove &a, const RootMove &b) { return a.tbRank > b.tbRank; } ); // Probe during search only if DTZ is not available and we are winning