X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=035dd40a5c7c17d4b92dd11a2ff35f8d1b709cbb;hp=f9579ae0ab4fac374a3f695ba629e20552f6a3fd;hb=4901218d4cc31658942486ccd1dbadf2d2df783a;hpb=44b6697f19ed45a6fb3f542acc83fc5d7111f375 diff --git a/src/search.cpp b/src/search.cpp index f9579ae0..035dd40a 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -2,7 +2,7 @@ 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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -61,10 +61,13 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV }; + constexpr uint64_t ttHitAverageWindow = 4096; + constexpr uint64_t ttHitAverageResolution = 1024; + // Razor and futility margins - constexpr int RazorMargin = 661; + constexpr int RazorMargin = 531; Value futility_margin(Depth d, bool improving) { - return Value(198 * (d - improving)); + return Value(217 * (d - improving)); } // Reductions lookup table, initialized at startup @@ -72,7 +75,7 @@ namespace { Depth reduction(bool i, Depth d, int mn) { int r = Reductions[d] * Reductions[mn]; - return (r + 520) / 1024 + (!i && r > 999); + return (r + 511) / 1024 + (!i && r > 1007); } constexpr int futility_move_count(bool improving, Depth depth) { @@ -81,7 +84,7 @@ namespace { // History and stats update bonus, based on depth int stat_bonus(Depth d) { - return d > 17 ? -8 : 22 * d * d + 151 * d - 140; + return d > 15 ? -8 : 19 * d * d + 155 * d - 132; } // Add a small random component to draw evaluations to avoid 3fold-blindness @@ -191,7 +194,7 @@ namespace { void Search::init() { for (int i = 1; i < MAX_MOVES; ++i) - Reductions[i] = int((23.4 + std::log(Threads.size()) / 2) * std::log(i)); + Reductions[i] = int((24.8 + std::log(Threads.size()) / 2) * std::log(i)); } @@ -332,6 +335,7 @@ void Thread::search() { MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); double timeReduction = 1, totBestMoveChanges = 0; Color us = rootPos.side_to_move(); + int iterIdx = 0; std::memset(ss-7, 0, 10 * sizeof(Stack)); for (int i = 7; i > 0; i--) @@ -342,6 +346,16 @@ void Thread::search() { bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; + if (mainThread) + { + if (mainThread->previousScore == VALUE_INFINITE) + for (int i=0; i<4; ++i) + mainThread->iterValue[i] = VALUE_ZERO; + else + for (int i=0; i<4; ++i) + mainThread->iterValue[i] = mainThread->previousScore; + } + size_t multiPV = Options["MultiPV"]; // Pick integer skill levels, but non-deterministically round up or down @@ -363,6 +377,7 @@ void Thread::search() { multiPV = std::max(multiPV, (size_t)4); multiPV = std::min(multiPV, rootMoves.size()); + ttHitAverage = ttHitAverageWindow * ttHitAverageResolution / 2; int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns @@ -378,6 +393,8 @@ void Thread::search() { contempt = (us == WHITE ? make_score(ct, ct / 2) : -make_score(ct, ct / 2)); + int searchAgainCounter = 0; + // Iterative deepening loop until requested to stop or the target depth is reached while ( ++rootDepth < MAX_PLY && !Threads.stop @@ -395,6 +412,9 @@ void Thread::search() { size_t pvFirst = 0; pvLast = 0; + if (!Threads.increaseDepth) + searchAgainCounter++; + // MultiPV loop. We perform a full root search for each PV line for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx) { @@ -413,12 +433,12 @@ void Thread::search() { if (rootDepth >= 4) { Value previousScore = rootMoves[pvIdx].previousScore; - delta = Value(21 + abs(previousScore) / 128); + delta = Value(21 + abs(previousScore) / 256); alpha = std::max(previousScore - delta,-VALUE_INFINITE); beta = std::min(previousScore + delta, VALUE_INFINITE); // Adjust contempt based on root move's previousScore (dynamic contempt) - int dct = ct + (111 - ct / 2) * previousScore / (abs(previousScore) + 176); + int dct = ct + (102 - ct / 2) * previousScore / (abs(previousScore) + 157); contempt = (us == WHITE ? make_score(dct, dct / 2) : -make_score(dct, dct / 2)); @@ -430,7 +450,7 @@ void Thread::search() { int failedHighCnt = 0; while (true) { - Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt); + Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter); bestValue = ::search(rootPos, ss, alpha, beta, adjustedDepth, false); // Bring the best move to the front. It is critical that sorting @@ -516,12 +536,13 @@ void Thread::search() { && !Threads.stop && !mainThread->stopOnPonderhit) { - double fallingEval = (354 + 10 * (mainThread->previousScore - bestValue)) / 692.0; + double fallingEval = (332 + 6 * (mainThread->previousScore - bestValue) + + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0; fallingEval = clamp(fallingEval, 0.5, 1.5); // If the bestMove is stable over several iterations, reduce time accordingly - timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.97 : 0.98; - double reduction = (1.36 + mainThread->previousTimeReduction) / (2.29 * timeReduction); + timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.94 : 0.91; + double reduction = (1.41 + mainThread->previousTimeReduction) / (2.27 * timeReduction); // Use part of the gained time from a previous stable move for the current move for (Thread* th : Threads) @@ -542,7 +563,16 @@ void Thread::search() { else Threads.stop = true; } + else if ( Threads.increaseDepth + && !mainThread->ponder + && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6) + Threads.increaseDepth = false; + else + Threads.increaseDepth = true; } + + mainThread->iterValue[iterIdx] = bestValue; + iterIdx = (iterIdx + 1) & 3; } if (!mainThread) @@ -665,6 +695,9 @@ namespace { ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; ttPv = PvNode || (ttHit && tte->is_pv()); + // thisThread->ttHitAverage can be used to approximate the running average of ttHit + thisThread->ttHitAverage = (ttHitAverageWindow - 1) * thisThread->ttHitAverage / ttHitAverageWindow + + ttHitAverageResolution * ttHit; // At non-PV nodes we check for an early TT cutoff if ( !PvNode @@ -694,7 +727,9 @@ namespace { update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } - return ttValue; + + if (pos.rule50_count() < 90) + return ttValue; } // Step 5. Tablebases probe @@ -784,18 +819,18 @@ namespace { tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); } - // Step 7. Razoring (~2 Elo) + // Step 7. Razoring (~1 Elo) if ( !rootNode // The required rootNode PV handling is not available in qsearch && depth < 2 && eval <= alpha - RazorMargin) return qsearch(pos, ss, alpha, beta); - improving = ss->staticEval >= (ss-2)->staticEval - || (ss-2)->staticEval == VALUE_NONE; + 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 (~30 Elo) + // Step 8. Futility pruning: child node (~50 Elo) if ( !PvNode - && depth < 7 + && depth < 6 && eval - futility_margin(depth, improving) >= beta && eval < VALUE_KNOWN_WIN) // Do not return unproven wins return eval; @@ -803,10 +838,10 @@ namespace { // Step 9. Null move search with verification search (~40 Elo) if ( !PvNode && (ss-1)->currentMove != MOVE_NULL - && (ss-1)->statScore < 22661 + && (ss-1)->statScore < 23397 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 33 * depth + 299 - improving * 30 + && ss->staticEval >= beta - 32 * depth + 292 - improving * 30 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) @@ -814,7 +849,7 @@ namespace { assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value - Depth R = (835 + 70 * depth) / 256 + std::min(int(eval - beta) / 185, 3); + Depth R = (854 + 68 * depth) / 258 + std::min(int(eval - beta) / 192, 3); ss->currentMove = MOVE_NULL; ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0]; @@ -857,7 +892,7 @@ namespace { && depth >= 5 && abs(beta) < VALUE_MATE_IN_MAX_PLY) { - Value raisedBeta = std::min(beta + 191 - 46 * improving, VALUE_INFINITE); + Value raisedBeta = std::min(beta + 189 - 45 * improving, VALUE_INFINITE); MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory); int probCutCount = 0; @@ -893,7 +928,7 @@ namespace { } } - // Step 11. Internal iterative deepening (~2 Elo) + // Step 11. Internal iterative deepening (~1 Elo) if (depth >= 7 && !ttMove) { search(pos, ss, alpha, beta, depth - 7, cutNode); @@ -955,9 +990,50 @@ moves_loop: // When in check, search starts from here movedPiece = pos.moved_piece(move); givesCheck = pos.gives_check(move); - // Step 13. Extensions (~70 Elo) + // Calculate new depth for this move + newDepth = depth - 1; + + // Step 13. Pruning at shallow depth (~200 Elo) + if ( !rootNode + && pos.non_pawn_material(us) + && bestValue > VALUE_MATED_IN_MAX_PLY) + { + // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold + moveCountPruning = moveCount >= futility_move_count(improving, depth); + + if ( !captureOrPromotion + && !givesCheck) + { + // Reduced depth of the next LMR search + int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0); + + // Countermoves based pruning (~20 Elo) + if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1) + && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold + && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) + continue; + + // Futility pruning: parent node (~5 Elo) + if ( lmrDepth < 6 + && !inCheck + && ss->staticEval + 235 + 172 * lmrDepth <= alpha + && thisThread->mainHistory[us][from_to(move)] + + (*contHist[0])[movedPiece][to_sq(move)] + + (*contHist[1])[movedPiece][to_sq(move)] + + (*contHist[3])[movedPiece][to_sq(move)] < 25000) + continue; + + // Prune moves with negative SEE (~20 Elo) + if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) + continue; + } + else if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo) + continue; + } + + // Step 14. Extensions (~75 Elo) - // Singular extension search (~60 Elo). If all moves but one fail low on a + // Singular extension search (~70 Elo). If all moves but one fail low on a // 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 @@ -989,8 +1065,7 @@ moves_loop: // When in check, search starts from here // search without the ttMove. So we assume this expected Cut-node is not singular, // that multiple moves fail high, and we can prune the whole subtree by returning // a soft bound. - else if ( eval >= beta - && singularBeta >= beta) + else if (singularBeta >= beta) return singularBeta; } @@ -1005,48 +1080,17 @@ moves_loop: // When in check, search starts from here && 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; - // Calculate new depth for this move - newDepth = depth - 1 + extension; - - // Step 14. Pruning at shallow depth (~170 Elo) - if ( !rootNode - && pos.non_pawn_material(us) - && bestValue > VALUE_MATED_IN_MAX_PLY) - { - // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold - moveCountPruning = moveCount >= futility_move_count(improving, depth); - - if ( !captureOrPromotion - && !givesCheck - && (!pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg)) - { - // Reduced depth of the next LMR search - int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0); - - // Countermoves based pruning (~20 Elo) - if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1) - && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold - && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) - continue; - - // Futility pruning: parent node (~2 Elo) - if ( lmrDepth < 6 - && !inCheck - && ss->staticEval + 250 + 211 * lmrDepth <= alpha) - continue; - - // Prune moves with negative SEE (~10 Elo) - if (!pos.see_ge(move, Value(-(31 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) - continue; - } - else if ( !(givesCheck && extension) - && !pos.see_ge(move, Value(-199) * depth)) // (~20 Elo) - continue; - } + // Add extension to new depth + newDepth += extension; // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); @@ -1068,7 +1112,7 @@ moves_loop: // When in check, search starts from here // Step 15. Make the move pos.do_move(move, st, givesCheck); - // Step 16. Reduced depth search (LMR). If the move fails high it will be + // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be // re-searched at full depth. if ( depth >= 3 && moveCount > 1 + 2 * rootNode @@ -1076,39 +1120,44 @@ moves_loop: // When in check, search starts from here && ( !captureOrPromotion || moveCountPruning || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha - || cutNode)) + || cutNode + || thisThread->ttHitAverage < 375 * 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) + r--; + // Reduction if other threads are searching this position. if (th.marked()) r++; - // Decrease reduction if position is or has been on the PV + // Decrease reduction if position is or has been on the PV (~10 Elo) if (ttPv) r -= 2; - // Decrease reduction if opponent's move count is high (~10 Elo) - if ((ss-1)->moveCount > 15) + // Decrease reduction if opponent's move count is high (~5 Elo) + if ((ss-1)->moveCount > 14) r--; - // Decrease reduction if ttMove has been singularly extended + // Decrease reduction if ttMove has been singularly extended (~3 Elo) if (singularLMR) r -= 2; if (!captureOrPromotion) { - // Increase reduction if ttMove is a capture (~0 Elo) + // Increase reduction if ttMove is a capture (~5 Elo) if (ttCapture) r++; - // Increase reduction for cut nodes (~5 Elo) + // Increase reduction for cut nodes (~10 Elo) if (cutNode) r += 2; // Decrease reduction for moves that escape a capture. Filter out // castling moves, because they are coded as "king captures rook" and - // hence break make_move(). (~5 Elo) + // hence break make_move(). (~2 Elo) else if ( type_of(move) == NORMAL && !pos.see_ge(reverse_move(move))) r -= 2; @@ -1117,7 +1166,7 @@ moves_loop: // When in check, search starts from here + (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)] - - 4729; + - 4926; // Reset statScore to zero if negative and most stats shows >= 0 if ( ss->statScore < 0 @@ -1127,10 +1176,10 @@ moves_loop: // When in check, search starts from here ss->statScore = 0; // Decrease/increase reduction by comparing opponent's stat score (~10 Elo) - if (ss->statScore >= -99 && (ss-1)->statScore < -116) + if (ss->statScore >= -102 && (ss-1)->statScore < -114) r--; - else if ((ss-1)->statScore >= -117 && ss->statScore < -144) + else if ((ss-1)->statScore >= -116 && ss->statScore < -154) r++; // Decrease/increase reduction for moves with a good/bad history (~30 Elo) @@ -1389,7 +1438,7 @@ moves_loop: // When in check, search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = bestValue + 153; + futilityBase = bestValue + 154; } const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, @@ -1445,9 +1494,7 @@ moves_loop: // When in check, search starts from here && !pos.capture(move); // Don't search moves with negative SEE values - if ( (!inCheck || evasionPrunable) - && !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move)) - && !pos.see_ge(move)) + if ( (!inCheck || evasionPrunable) && !pos.see_ge(move)) continue; // Speculative prefetch as early as possible @@ -1708,7 +1755,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { for (size_t i = 0; i < multiPV; ++i) { - bool updated = (i <= pvIdx && rootMoves[i].score != -VALUE_INFINITE); + bool updated = rootMoves[i].score != -VALUE_INFINITE; if (depth == 1 && !updated) continue;