X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=d59edbaeefcbf4be8ba40ea965156a21e0bf387a;hp=8581b0b3792819cb392b9913bfe04bd64896ee15;hb=2c237da54647bb7526f3512bea183eb44919cdda;hpb=351844061eddffac59e7a3c2d16af7ea9661bb3e diff --git a/src/search.cpp b/src/search.cpp index 8581b0b3..d59edbae 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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2017 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 @@ -46,7 +46,6 @@ namespace Search { namespace Tablebases { int Cardinality; - uint64_t Hits; bool RootInTB; bool UseRule50; Depth ProbeDepth; @@ -64,18 +63,32 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV }; + // Sizes and phases of the skip-blocks, used for distributing search depths across the threads + const int skipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 }; + const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 }; + // Razoring and futility margin based on depth - const int razor_margin[4] = { 483, 570, 603, 554 }; + // razor_margin[0] is unused as long as depth >= ONE_PLY in search + const int razor_margin[] = { 0, 570, 603, 554 }; Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); } // Futility and reductions lookup tables, initialized at startup int FutilityMoveCounts[2][16]; // [improving][depth] int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] + // Threshold used for countermoves based pruning + const int CounterMovePruneThreshold = 0; + template Depth reduction(bool i, Depth d, int mn) { return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY; } + // History and stats update bonus, based on depth + int stat_bonus(Depth depth) { + int d = depth / ONE_PLY; + return d > 17 ? 0 : d * d + 2 * d - 2; + } + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} @@ -88,8 +101,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager structure is used to detect an 'easy move'. When the PV is - // stable across multiple search iterations, we can quickly return the best move. + // EasyMoveManager structure is used to detect an 'easy move'. When the PV is stable + // across multiple search iterations, we can quickly return the best move. struct EasyMoveManager { void clear() { @@ -114,8 +127,8 @@ namespace { std::copy(newPv.begin(), newPv.begin() + 3, pv); StateInfo st[2]; - pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0])); - pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1])); + pos.do_move(newPv[0], st[0]); + pos.do_move(newPv[1], st[1]); expectedPosKey = pos.key(); pos.undo_move(newPv[1]); pos.undo_move(newPv[0]); @@ -127,49 +140,20 @@ namespace { Move pv[3]; }; - // Set of rows with half bits set to 1 and half to 0. It is used to allocate - // the search depths across the threads. - typedef std::vector Row; - - const Row HalfDensity[] = { - {0, 1}, - {1, 0}, - {0, 0, 1, 1}, - {0, 1, 1, 0}, - {1, 1, 0, 0}, - {1, 0, 0, 1}, - {0, 0, 0, 1, 1, 1}, - {0, 0, 1, 1, 1, 0}, - {0, 1, 1, 1, 0, 0}, - {1, 1, 1, 0, 0, 0}, - {1, 1, 0, 0, 0, 1}, - {1, 0, 0, 0, 1, 1}, - {0, 0, 0, 0, 1, 1, 1, 1}, - {0, 0, 0, 1, 1, 1, 1, 0}, - {0, 0, 1, 1, 1, 1, 0 ,0}, - {0, 1, 1, 1, 1, 0, 0 ,0}, - {1, 1, 1, 1, 0, 0, 0 ,0}, - {1, 1, 1, 0, 0, 0, 0 ,1}, - {1, 1, 0, 0, 0, 0, 1 ,1}, - {1, 0, 0, 0, 0, 1, 1 ,1}, - }; - - const size_t HalfDensitySize = std::extent::value; - EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); template - Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus); - void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus); + void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus); + void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus); void check_time(); } // namespace @@ -183,9 +167,7 @@ void Search::init() { for (int d = 1; d < 64; ++d) for (int mc = 1; mc < 64; ++mc) { - double r = log(d) * log(mc) / 2; - if (r < 0.80) - continue; + double r = log(d) * log(mc) / 1.95; Reductions[NonPV][imp][d][mc] = int(std::round(r)); Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0); @@ -197,13 +179,13 @@ void Search::init() { for (int d = 0; d < 16; ++d) { - FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8)); - FutilityMoveCounts[1][d] = int(2.9 + 1.045 * pow(d + 0.49, 1.8)); + FutilityMoveCounts[0][d] = int(2.4 + 0.74 * pow(d, 1.78)); + FutilityMoveCounts[1][d] = int(5.0 + 1.00 * pow(d, 2.00)); } } -/// Search::clear() resets search state to zero, to obtain reproducible results +/// Search::clear() resets search state to its initial value, to obtain reproducible results void Search::clear() { @@ -211,10 +193,15 @@ void Search::clear() { for (Thread* th : Threads) { - th->history.clear(); - th->counterMoves.clear(); - th->fromTo.clear(); - th->counterMoveHistory.clear(); + th->resetCalls = true; + th->counterMoves.fill(MOVE_NONE); + th->history.fill(0); + + for (auto& to : th->counterMoveHistory) + for (auto& h : to) + h.fill(0); + + th->counterMoveHistory[NO_PIECE][0].fill(CounterMovePruneThreshold - 1); } Threads.main()->previousScore = VALUE_INFINITE; @@ -236,7 +223,7 @@ uint64_t Search::perft(Position& pos, Depth depth) { cnt = 1, nodes++; else { - pos.do_move(m, st, pos.gives_check(m)); + pos.do_move(m, st); cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); nodes += cnt; pos.undo_move(m); @@ -257,6 +244,7 @@ void MainThread::search() { Color us = rootPos.side_to_move(); Time.init(Limits, us, rootPos.game_ply()); + TT.new_search(); int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns DrawValue[ us] = VALUE_DRAW - Value(contempt); @@ -311,9 +299,13 @@ void MainThread::search() { && rootMoves[0].pv[0] != MOVE_NONE) { for (Thread* th : Threads) - if ( th->completedDepth > bestThread->completedDepth - && th->rootMoves[0].score > bestThread->rootMoves[0].score) + { + Depth depthDiff = th->completedDepth - bestThread->completedDepth; + Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score; + + if (scoreDiff > 0 && depthDiff >= 0) bestThread = th; + } } previousScore = bestThread->rootMoves[0].score; @@ -331,18 +323,20 @@ void MainThread::search() { } -// Thread::search() is the main iterative deepening loop. It calls search() -// repeatedly with increasing depth until the allocated thinking time has been -// consumed, the user stops the search, or the maximum search depth is reached. +/// Thread::search() is the main iterative deepening loop. It calls search() +/// repeatedly with increasing depth until the allocated thinking time has been +/// consumed, the user stops the search, or the maximum search depth is reached. void Thread::search() { - Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2) + Stack stack[MAX_PLY+7], *ss = stack+4; // To allow referencing (ss-4) and (ss+2) Value bestValue, alpha, beta, delta; Move easyMove = MOVE_NONE; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - std::memset(ss-5, 0, 8 * sizeof(Stack)); + std::memset(ss-4, 0, 7 * sizeof(Stack)); + for (int i = 4; i > 0; i--) + (ss-i)->history = &this->counterMoveHistory[NO_PIECE][0]; // Use as sentinel bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -354,7 +348,6 @@ void Thread::search() { EasyMove.clear(); mainThread->easyMovePlayed = mainThread->failedLow = false; mainThread->bestMoveChanges = 0; - TT.new_search(); } size_t multiPV = Options["MultiPV"]; @@ -372,13 +365,12 @@ void Thread::search() { && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth)) { - // Set up the new depths for the helper threads skipping on average every - // 2nd ply (using a half-density matrix). - if (!mainThread) + // Distribute search depths across the threads + if (idx) { - const Row& row = HalfDensity[(idx - 1) % HalfDensitySize]; - if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()]) - continue; + int i = (idx - 1) % 20; + if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2) + continue; } // Age out PV variability metric @@ -406,7 +398,7 @@ void Thread::search() { // high/low anymore. while (true) { - bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false, 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 @@ -416,7 +408,7 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // If search has been stopped, break immediately. Sorting and + // If search has been stopped, we break immediately. Sorting and // writing PV back to TT is safe because RootMoves is still // valid, although it refers to the previous iteration. if (Signals.stop) @@ -462,11 +454,7 @@ void Thread::search() { if (!mainThread) continue; - if (Signals.stop) - sync_cout << "info nodes " << Threads.nodes_searched() - << " time " << Time.elapsed() << sync_endl; - - else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000) + if (Signals.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000) sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; } @@ -502,7 +490,7 @@ void Thread::search() { bool doEasyMove = rootMoves[0].pv[0] == easyMove && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.optimum() * 5 / 42; + && Time.elapsed() > Time.optimum() * 5 / 44; if ( rootMoves.size() == 1 || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628 @@ -544,7 +532,7 @@ namespace { // search<>() is the main search function for both PV and non-PV nodes template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) { const bool PvNode = NT == PV; const bool rootNode = PvNode && (ss-1)->ply == 0; @@ -561,16 +549,17 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, nullValue; + Value bestValue, value, ttValue, eval; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets; Piece moved_piece; int moveCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); - moveCount = quietCount = ss->moveCount = 0; + moveCount = quietCount = ss->moveCount = 0; + ss->statScore = 0; bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; @@ -578,9 +567,14 @@ namespace { if (thisThread->resetCalls.load(std::memory_order_relaxed)) { thisThread->resetCalls = false; - thisThread->callsCnt = 0; + + // At low node count increase the checking rate to about 0.1% of nodes + // otherwise use a default value. + thisThread->callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) + : 4096; } - if (++thisThread->callsCnt > 4096) + + if (--thisThread->callsCnt <= 0) { for (Thread* th : Threads) th->resetCalls = true; @@ -595,7 +589,7 @@ namespace { if (!rootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) + if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -614,9 +608,9 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->counterMoves = nullptr; - (ss+1)->skipEarlyPruning = false; + ss->history = &thisThread->counterMoveHistory[NO_PIECE][0]; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + Square prevSq = to_sq((ss-1)->currentMove); // 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 @@ -636,25 +630,24 @@ namespace { && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) { - ss->currentMove = ttMove; // Can be MOVE_NONE - - // If ttMove is quiet, update killers, history, counter move on TT hit - if (ttValue >= beta && ttMove) + // If ttMove is quiet, update move sorting heuristics on TT hit + if (ttMove) { - int d = depth / ONE_PLY; - - if (!pos.capture_or_promotion(ttMove)) + if (ttValue >= beta) { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, ttMove, nullptr, 0, bonus); - } + if (!pos.capture_or_promotion(ttMove)) + update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + } + // Penalty for a quiet ttMove that fails low + else if (!pos.capture_or_promotion(ttMove)) { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); + int penalty = -stat_bonus(depth); + thisThread->history.update(pos.side_to_move(), ttMove, penalty); + update_cm_stats(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } return ttValue; @@ -663,18 +656,19 @@ namespace { // Step 4a. Tablebase probe if (!rootNode && TB::Cardinality) { - int piecesCnt = pos.count(WHITE) + pos.count(BLACK); + int piecesCount = pos.count(); - if ( piecesCnt <= TB::Cardinality - && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) + if ( piecesCount <= TB::Cardinality + && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth) && pos.rule50_count() == 0 && !pos.can_castle(ANY_CASTLING)) { - int found, v = Tablebases::probe_wdl(pos, &found); + TB::ProbeState err; + TB::WDLScore v = Tablebases::probe_wdl(pos, &err); - if (found) + if (err != TB::ProbeState::FAIL) { - TB::Hits++; + thisThread->tbHits++; int drawScore = TB::UseRule50 ? 1 : 0; @@ -719,21 +713,19 @@ namespace { ss->staticEval, TT.generation()); } - if (ss->skipEarlyPruning) + if (skipEarlyPruning) goto moves_loop; // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && ttMove == MOVE_NONE && eval + razor_margin[depth / ONE_PLY] <= alpha) { - if ( depth <= ONE_PLY - && eval + razor_margin[3 * ONE_PLY] <= alpha) - return qsearch(pos, ss, alpha, beta, DEPTH_ZERO); + if (depth <= ONE_PLY) + return qsearch(pos, ss, alpha, alpha+1); Value ralpha = alpha - razor_margin[depth / ONE_PLY]; - Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); + Value v = qsearch(pos, ss, ralpha, ralpha+1); if (v <= ralpha) return v; } @@ -744,7 +736,7 @@ namespace { && eval - futility_margin(depth) >= beta && eval < VALUE_KNOWN_WIN // Do not return unproven wins && pos.non_pawn_material(pos.side_to_move())) - return eval - futility_margin(depth); + return eval; // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode @@ -752,19 +744,18 @@ namespace { && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY) && pos.non_pawn_material(pos.side_to_move())) { - ss->currentMove = MOVE_NULL; - ss->counterMoves = nullptr; assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; + ss->currentMove = MOVE_NULL; + ss->history = &thisThread->counterMoveHistory[NO_PIECE][0]; + pos.do_null_move(st); - (ss+1)->skipEarlyPruning = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); - (ss+1)->skipEarlyPruning = false; + Value nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); pos.undo_null_move(); if (nullValue >= beta) @@ -777,10 +768,8 @@ namespace { return nullValue; // Do verification search at high depths - ss->skipEarlyPruning = true; - Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta, DEPTH_ZERO) - : search(pos, ss, beta-1, beta, depth-R, false); - ss->skipEarlyPruning = false; + Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta) + : search(pos, ss, beta-1, beta, depth-R, false, true); if (v >= beta) return nullValue; @@ -795,11 +784,8 @@ namespace { && abs(beta) < VALUE_MATE_IN_MAX_PLY) { Value rbeta = std::min(beta + 200, VALUE_INFINITE); - Depth rdepth = depth - 4 * ONE_PLY; - assert(rdepth >= ONE_PLY); - assert((ss-1)->currentMove != MOVE_NONE); - assert((ss-1)->currentMove != MOVE_NULL); + assert(is_ok((ss-1)->currentMove)); MovePicker mp(pos, ttMove, rbeta - ss->staticEval); @@ -807,9 +793,11 @@ namespace { if (pos.legal(move)) { ss->currentMove = move; - ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; - pos.do_move(move, st, pos.gives_check(move)); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + ss->history = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; + + assert(depth >= 5 * ONE_PLY); + pos.do_move(move, st); + value = -search(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false); pos.undo_move(move); if (value >= rbeta) return value; @@ -822,9 +810,7 @@ namespace { && (PvNode || ss->staticEval + 256 >= beta)) { Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY; - ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d, cutNode); - ss->skipEarlyPruning = false; + search(pos, ss, alpha, beta, d, cutNode, true); tte = TT.probe(posKey, ttHit); ttMove = ttHit ? tte->move() : MOVE_NONE; @@ -832,9 +818,9 @@ namespace { moves_loop: // When in check search starts from here - const CounterMoveStats* cmh = (ss-1)->counterMoves; - const CounterMoveStats* fmh = (ss-2)->counterMoves; - const CounterMoveStats* fmh2 = (ss-4)->counterMoves; + const PieceToHistory& cmh = *(ss-1)->history; + const PieceToHistory& fmh = *(ss-2)->history; + const PieceToHistory& fm2 = *(ss-4)->history; MovePicker mp(pos, ttMove, depth, ss); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc @@ -849,10 +835,11 @@ moves_loop: // When in check search starts from here && !excludedMove // Recursive singular search is not allowed && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; + skipQuiets = false; // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move(skipQuiets)) != MOVE_NONE) { assert(is_ok(move)); @@ -887,72 +874,73 @@ moves_loop: // When in check search starts from here moveCountPruning = depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY]; - // Step 12. Extend checks - if ( givesCheck - && !moveCountPruning - && pos.see_sign(move) >= VALUE_ZERO) - extension = ONE_PLY; + // Step 12. Singular and Gives Check Extensions // Singular extension search. 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 result is lower than - // ttValue minus a margin then we extend the ttMove. + // ttValue minus a margin then we will extend the ttMove. if ( singularExtensionNode && move == ttMove - && !extension && pos.legal(move)) { Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY; ss->excludedMove = move; - ss->skipEarlyPruning = true; - value = search(pos, ss, rBeta - 1, rBeta, d, cutNode); - ss->skipEarlyPruning = false; + value = search(pos, ss, rBeta - 1, rBeta, d, cutNode, true); ss->excludedMove = MOVE_NONE; if (value < rBeta) extension = ONE_PLY; } + else if ( givesCheck + && !moveCountPruning + && pos.see_ge(move)) + extension = ONE_PLY; - // Update the current move (this must be done after singular extension search) + // Calculate new depth for this move newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth if ( !rootNode - && !inCheck - && bestValue > VALUE_MATED_IN_MAX_PLY) + && pos.non_pawn_material(pos.side_to_move()) + && bestValue > VALUE_MATED_IN_MAX_PLY) { if ( !captureOrPromotion && !givesCheck - && !pos.advanced_pawn_push(move)) + && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000))) { // Move count based pruning if (moveCountPruning) + { + skipQuiets = true; continue; + } // Reduced depth of the next LMR search int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY; // Countermoves based pruning if ( lmrDepth < 3 - && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh))) + && (cmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold) + && (fmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold)) continue; // Futility pruning: parent node if ( lmrDepth < 7 + && !inCheck && ss->staticEval + 256 + 200 * lmrDepth <= alpha) continue; // Prune moves with negative SEE if ( lmrDepth < 8 - && pos.see_sign(move) < Value(-35 * lmrDepth * lmrDepth)) + && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth))) continue; } - else if ( depth < 7 * ONE_PLY - && pos.see_sign(move) < Value(-35 * depth / ONE_PLY * depth / ONE_PLY)) + else if ( depth < 7 * ONE_PLY + && !extension + && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) continue; } @@ -966,8 +954,9 @@ moves_loop: // When in check search starts from here continue; } + // Update the current move (this must be done after singular extension search) ss->currentMove = move; - ss->counterMoves = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; + ss->history = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -990,26 +979,31 @@ moves_loop: // When in check search starts from here // 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(). Also use see() instead of see_sign(), - // because the destination square is empty. - else if ( type_of(move) == NORMAL - && type_of(pos.piece_on(to_sq(move))) != PAWN - && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO) + // hence break make_move(). + else if ( type_of(move) == NORMAL + && !pos.see_ge(make_move(to_sq(move), from_sq(move)))) r -= 2 * ONE_PLY; + ss->statScore = cmh[moved_piece][to_sq(move)] + + fmh[moved_piece][to_sq(move)] + + fm2[moved_piece][to_sq(move)] + + thisThread->history[~pos.side_to_move()][from_to(move)] + - 4000; // Correction factor + + // Decrease/increase reduction by comparing opponent's stat score + if (ss->statScore > 0 && (ss-1)->statScore < 0) + r -= ONE_PLY; + + else if (ss->statScore < 0 && (ss-1)->statScore > 0) + r += ONE_PLY; + // Decrease/increase reduction for moves with a good/bad history - Value val = thisThread->history[moved_piece][to_sq(move)] - + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO) - + thisThread->fromTo.get(~pos.side_to_move(), move); - int rHist = (val - 8000) / 20000; - r = std::max(DEPTH_ZERO, (r / ONE_PLY - rHist) * ONE_PLY); + r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY); } Depth d = std::max(newDepth - r, ONE_PLY); - value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true, false); doFullDepthSearch = (value > alpha && d != newDepth); } @@ -1019,9 +1013,9 @@ moves_loop: // When in check search starts from here // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha) + : -qsearch(pos, ss+1, -(alpha+1), -alpha) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false); // For PV nodes only, do a full PV search on the first move or after a fail // high (in the latter case search only if value < beta), otherwise let the @@ -1032,9 +1026,9 @@ moves_loop: // When in check search starts from here (ss+1)->pv[0] = MOVE_NONE; value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth, false); + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha) + : -qsearch(pos, ss+1, -beta, -alpha) + : - search(pos, ss+1, -beta, -alpha, newDepth, false, false); } // Step 17. Undo move @@ -1084,13 +1078,6 @@ moves_loop: // When in check search starts from here if (value > alpha) { - // If there is an easy move for this position, clear it if unstable - if ( PvNode - && thisThread == Threads.main() - && EasyMove.get(pos.key()) - && (move != EasyMove.get(pos.key()) || moveCount > 1)) - EasyMove.clear(); - bestMove = move; if (PvNode && !rootNode) // Update pv even in fail-high case @@ -1122,43 +1109,33 @@ moves_loop: // When in check search starts from here // All legal moves have been searched and if there are no legal moves, it // must be a mate or a stalemate. If we are in a singular extension search then // return a fail low score. + + assert(moveCount || !inCheck || excludedMove || !MoveList(pos).size()); + if (!moveCount) bestValue = excludedMove ? alpha : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; else if (bestMove) { - int d = depth / ONE_PLY; - - // Quiet best move: update killers, history and countermoves + // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus); - } + update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); // Extra penalty for a quiet TT move in previous ply when it gets refuted if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); - } + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); } // Bonus for prior countermove that caused the fail low else if ( depth >= 3 * ONE_PLY && !pos.captured_piece() && is_ok((ss-1)->currentMove)) - { - int d = depth / ONE_PLY; - Value bonus = Value(d * d + 2 * d - 2); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus); - } + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); - tte->save(posKey, value_to_tt(bestValue, ss->ply), - bestValue >= beta ? BOUND_LOWER : - PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval, TT.generation()); + if (!excludedMove) + tte->save(posKey, value_to_tt(bestValue, ss->ply), + bestValue >= beta ? BOUND_LOWER : + PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->staticEval, TT.generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1167,8 +1144,7 @@ moves_loop: // When in check search starts from here // qsearch() is the quiescence search function, which is called by the main - // search function when the remaining depth is zero (or, to be more precise, - // less than ONE_PLY). + // search function with depth zero, or recursively with depth less than ONE_PLY. template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { @@ -1189,6 +1165,7 @@ moves_loop: // When in check search starts from here Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; bool ttHit, givesCheck, evasionPrunable; Depth ttDepth; + int moveCount; if (PvNode) { @@ -1199,9 +1176,10 @@ moves_loop: // When in check search starts from here ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; + moveCount = 0; // Check for an instant draw or if the maximum ply has been reached - if (pos.is_draw() || ss->ply >= MAX_PLY) + if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -1225,10 +1203,7 @@ moves_loop: // When in check search starts from here && ttValue != VALUE_NONE // Only in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) - { - ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; - } // Evaluate the position statically if (InCheck) @@ -1281,10 +1256,15 @@ moves_loop: // When in check search starts from here { assert(is_ok(move)); + // Speculative prefetch as early as possible + prefetch(TT.first_entry(pos.key_after(move))); + givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates() ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move) : pos.gives_check(move); + moveCount++; + // Futility pruning if ( !InCheck && !givesCheck @@ -1301,7 +1281,7 @@ moves_loop: // When in check search starts from here continue; } - if (futilityBase <= alpha && pos.see(move) <= VALUE_ZERO) + if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1)) { bestValue = std::max(bestValue, futilityBase); continue; @@ -1310,21 +1290,22 @@ moves_loop: // When in check search starts from here // Detect non-capture evasions that are candidates to be pruned evasionPrunable = InCheck + && (depth != DEPTH_ZERO || moveCount > 2) && bestValue > VALUE_MATED_IN_MAX_PLY && !pos.capture(move); // Don't search moves with negative SEE values if ( (!InCheck || evasionPrunable) && type_of(move) != PROMOTION - && pos.see_sign(move) < VALUE_ZERO) + && !pos.see_ge(move)) continue; - // Speculative prefetch as early as possible - prefetch(TT.first_entry(pos.key_after(move))); - // Check for legality just before making the move if (!pos.legal(move)) + { + moveCount--; continue; + } ss->currentMove = move; @@ -1414,28 +1395,18 @@ moves_loop: // When in check search starts from here // update_cm_stats() updates countermove and follow-up move history - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) { + void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus) { - CounterMoveStats* cmh = (ss-1)->counterMoves; - CounterMoveStats* fmh1 = (ss-2)->counterMoves; - CounterMoveStats* fmh2 = (ss-4)->counterMoves; - - if (cmh) - cmh->update(pc, s, bonus); - - if (fmh1) - fmh1->update(pc, s, bonus); - - if (fmh2) - fmh2->update(pc, s, bonus); + for (int i : {1, 2, 4}) + if (is_ok((ss-i)->currentMove)) + (ss-i)->history->update(pc, s, bonus); } - // update_stats() updates killers, history, countermove and countermove plus - // follow-up move history when a new quiet best move is found. + // update_stats() updates move sorting heuristics when a new quiet best move is found void update_stats(const Position& pos, Stack* ss, Move move, - Move* quiets, int quietsCnt, Value bonus) { + Move* quiets, int quietsCnt, int bonus) { if (ss->killers[0] != move) { @@ -1445,21 +1416,19 @@ moves_loop: // When in check search starts from here Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - thisThread->fromTo.update(c, move, bonus); - thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); + thisThread->history.update(c, move, bonus); update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); - if ((ss-1)->counterMoves) + if (is_ok((ss-1)->currentMove)) { Square prevSq = to_sq((ss-1)->currentMove); - thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); + thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]=move; } // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { - thisThread->fromTo.update(c, quiets[i], -bonus); - thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + thisThread->history.update(c, quiets[i], -bonus); update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } } @@ -1521,7 +1490,7 @@ moves_loop: // When in check search starts from here if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10) || (Limits.movetime && elapsed >= Limits.movetime) - || (Limits.nodes && Threads.nodes_searched() >= Limits.nodes)) + || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes)) Signals.stop = true; } @@ -1538,11 +1507,12 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { const RootMoves& rootMoves = pos.this_thread()->rootMoves; size_t PVIdx = pos.this_thread()->PVIdx; size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size()); - uint64_t nodes_searched = Threads.nodes_searched(); + uint64_t nodesSearched = Threads.nodes_searched(); + uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0); for (size_t i = 0; i < multiPV; ++i) { - bool updated = (i <= PVIdx); + bool updated = (i <= PVIdx && rootMoves[i].score != -VALUE_INFINITE); if (depth == ONE_PLY && !updated) continue; @@ -1565,13 +1535,13 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { if (!tb && i == PVIdx) ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); - ss << " nodes " << nodes_searched - << " nps " << nodes_searched * 1000 / elapsed; + ss << " nodes " << nodesSearched + << " nps " << nodesSearched * 1000 / elapsed; if (elapsed > 1000) // Earlier makes little sense ss << " hashfull " << TT.hashfull(); - ss << " tbhits " << TB::Hits + ss << " tbhits " << tbHits << " time " << elapsed << " pv"; @@ -1588,8 +1558,8 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { /// fail high at root. We try hard to have a ponder move to return to the GUI, /// otherwise in case of 'ponder on' we have nothing to think on. -bool RootMove::extract_ponder_from_tt(Position& pos) -{ +bool RootMove::extract_ponder_from_tt(Position& pos) { + StateInfo st; bool ttHit; @@ -1598,7 +1568,7 @@ bool RootMove::extract_ponder_from_tt(Position& pos) if (!pv[0]) return false; - pos.do_move(pv[0], st, pos.gives_check(pv[0])); + pos.do_move(pv[0], st); TTEntry* tte = TT.probe(pos.key(), ttHit); if (ttHit) @@ -1614,7 +1584,6 @@ bool RootMove::extract_ponder_from_tt(Position& pos) void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) { - Hits = 0; RootInTB = false; UseRule50 = Options["Syzygy50MoveRule"]; ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; @@ -1647,13 +1616,8 @@ void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) Cardinality = 0; } - if (RootInTB) - { - Hits = rootMoves.size(); - - if (!UseRule50) - TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 - : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 - : VALUE_DRAW; - } + if (RootInTB && !UseRule50) + TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 + : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 + : VALUE_DRAW; }