X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=f47507f7e39b6ad6ba7a7ffaf3ebe2f17e1cd6e0;hp=09e3c4fa979efd0620d021e14daacbb51ea8034c;hb=44a7db0f9ac02d2461aff39e25f1ac9107ffbfac;hpb=802fca6fdd562c4c52397521eb0ac05cb2be9046 diff --git a/src/search.cpp b/src/search.cpp index 09e3c4fa..f47507f7 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) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2018 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 @@ -39,7 +39,6 @@ namespace Search { - SignalsType Signals; LimitsType Limits; } @@ -68,17 +67,13 @@ namespace { 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 - // razor_margin[0] is unused as long as depth >= ONE_PLY in search - const int razor_margin[] = { 0, 570, 603, 554 }; + const int razor_margin = 600; 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; } @@ -91,58 +86,15 @@ namespace { // Skill structure is used to implement strength limit struct Skill { - Skill(int l) : level(l) {} + explicit Skill(int l) : level(l) {} bool enabled() const { return level < 20; } bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; } - Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); } Move pick_best(size_t multiPV); int level; 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. - struct EasyMoveManager { - - void clear() { - stableCnt = 0; - expectedPosKey = 0; - pv[0] = pv[1] = pv[2] = MOVE_NONE; - } - - Move get(Key key) const { - return expectedPosKey == key ? pv[2] : MOVE_NONE; - } - - void update(Position& pos, const std::vector& newPv) { - - assert(newPv.size() >= 3); - - // Keep track of how many times in a row the 3rd ply remains stable - stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0; - - if (!std::equal(newPv.begin(), newPv.begin() + 3, pv)) - { - std::copy(newPv.begin(), newPv.begin() + 3, pv); - - StateInfo st[2]; - 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]); - } - } - - int stableCnt; - Key expectedPosKey; - Move pv[3]; - }; - - EasyMoveManager EasyMove; - Value DrawValue[COLOR_NB]; - template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); @@ -152,8 +104,36 @@ namespace { 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, int bonus); + void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus); void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus); + void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCnt, int bonus); + bool pv_is_draw(Position& pos); + + // perft() is our utility to verify move generation. All the leaf nodes up + // to the given depth are generated and counted, and the sum is returned. + template + uint64_t perft(Position& pos, Depth depth) { + + StateInfo st; + uint64_t cnt, nodes = 0; + const bool leaf = (depth == 2 * ONE_PLY); + + for (const auto& m : MoveList(pos)) + { + if (Root && depth <= ONE_PLY) + cnt = 1, nodes++; + else + { + pos.do_move(m, st); + cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); + nodes += cnt; + pos.undo_move(m); + } + if (Root) + sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl; + } + return nodes; + } } // namespace @@ -184,74 +164,42 @@ void Search::init() { } -/// Search::clear() resets search state to its initial value, to obtain reproducible results +/// Search::clear() resets search state to its initial value void Search::clear() { - TT.clear(); - - for (Thread* th : Threads) - { - th->counterMoves.fill(MOVE_NONE); - th->history.fill(0); - - for (auto& to : th->counterMoveHistory) - for (auto& h : to) - h.fill(0); + Threads.main()->wait_for_search_finished(); - th->counterMoveHistory[NO_PIECE][0].fill(CounterMovePruneThreshold - 1); - } - - Threads.main()->callsCnt = 0; - Threads.main()->previousScore = VALUE_INFINITE; -} - - -/// Search::perft() is our utility to verify move generation. All the leaf nodes -/// up to the given depth are generated and counted, and the sum is returned. -template -uint64_t Search::perft(Position& pos, Depth depth) { - - StateInfo st; - uint64_t cnt, nodes = 0; - const bool leaf = (depth == 2 * ONE_PLY); - - for (const auto& m : MoveList(pos)) - { - if (Root && depth <= ONE_PLY) - cnt = 1, nodes++; - else - { - pos.do_move(m, st); - cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); - nodes += cnt; - pos.undo_move(m); - } - if (Root) - sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl; - } - return nodes; + Time.availableNodes = 0; + TT.clear(); + Threads.clear(); } -template uint64_t Search::perft(Position&, Depth); - /// MainThread::search() is called by the main thread when the program receives /// the UCI 'go' command. It searches from the root position and outputs the "bestmove". void MainThread::search() { + if (Limits.perft) + { + nodes = perft(rootPos, Limits.perft * ONE_PLY); + sync_cout << "\nNodes searched: " << nodes << "\n" << sync_endl; + return; + } + 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); - DrawValue[~us] = VALUE_DRAW + Value(contempt); + + Eval::Contempt = (us == WHITE ? make_score(contempt, contempt / 2) + : -make_score(contempt, contempt / 2)); if (rootMoves.empty()) { - rootMoves.push_back(RootMove(MOVE_NONE)); + rootMoves.emplace_back(MOVE_NONE); sync_cout << "info depth 0 score " << UCI::value(rootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; @@ -265,34 +213,33 @@ void MainThread::search() { Thread::search(); // Let's start searching! } - // When playing in 'nodes as time' mode, subtract the searched nodes from - // the available ones before exiting. - if (Limits.npmsec) - Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); - // When we reach the maximum depth, we can arrive here without a raise of - // Signals.stop. However, if we are pondering or in an infinite search, + // Threads.stop. However, if we are pondering or in an infinite search, // the UCI protocol states that we shouldn't print the best move before the // GUI sends a "stop" or "ponderhit" command. We therefore simply wait here - // until the GUI sends one of those commands (which also raises Signals.stop). - if (!Signals.stop && (Limits.ponder || Limits.infinite)) - { - Signals.stopOnPonderhit = true; - wait(Signals.stop); - } + // until the GUI sends one of those commands (which also raises Threads.stop). + Threads.stopOnPonderhit = true; - // Stop the threads if not already stopped - Signals.stop = true; + while (!Threads.stop && (Threads.ponder || Limits.infinite)) + {} // Busy wait for a stop or a ponder reset + + // Stop the threads if not already stopped (also raise the stop if + // "ponderhit" just reset Threads.ponder). + Threads.stop = true; // Wait until all threads have finished for (Thread* th : Threads) if (th != this) th->wait_for_search_finished(); + // When playing in 'nodes as time' mode, subtract the searched nodes from + // the available ones before exiting. + if (Limits.npmsec) + Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); + // Check if there are threads with a better score than main thread Thread* bestThread = this; - if ( !this->easyMovePlayed - && Options["MultiPV"] == 1 + if ( Options["MultiPV"] == 1 && !Limits.depth && !Skill(Options["Skill Level"]).enabled() && rootMoves[0].pv[0] != MOVE_NONE) @@ -302,7 +249,9 @@ void MainThread::search() { Depth depthDiff = th->completedDepth - bestThread->completedDepth; Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score; - if (scoreDiff > 0 && depthDiff >= 0) + // Select the thread with the best score, always if it is a mate + if ( scoreDiff > 0 + && (depthDiff >= 0 || th->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY)) bestThread = th; } } @@ -328,28 +277,27 @@ void MainThread::search() { void Thread::search() { - Stack stack[MAX_PLY+7], *ss = stack+4; // To allow referencing (ss-4) and (ss+2) + Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2) Value bestValue, alpha, beta, delta; - Move easyMove = MOVE_NONE; + Move lastBestMove = MOVE_NONE; + Depth lastBestMoveDepth = DEPTH_ZERO; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); + double timeReduction = 1.0; 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 + (ss-i)->contHistory = &this->contHistory[NO_PIECE][0]; // Use as sentinel bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; - completedDepth = DEPTH_ZERO; if (mainThread) { - easyMove = EasyMove.get(rootPos.key()); - EasyMove.clear(); - mainThread->easyMovePlayed = mainThread->failedLow = false; + mainThread->failedLow = false; mainThread->bestMoveChanges = 0; } - size_t multiPV = Options["MultiPV"]; + multiPV = Options["MultiPV"]; Skill skill(Options["Skill Level"]); // When playing with strength handicap enable MultiPV search that we will @@ -361,7 +309,7 @@ void Thread::search() { // Iterative deepening loop until requested to stop or the target depth is reached while ( (rootDepth += ONE_PLY) < DEPTH_MAX - && !Signals.stop + && !Threads.stop && !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth)) { // Distribute search depths across the threads @@ -382,8 +330,11 @@ void Thread::search() { rm.previousScore = rm.score; // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx) + for (PVIdx = 0; PVIdx < multiPV && !Threads.stop; ++PVIdx) { + // Reset UCI info selDepth for each depth and each PV line + selDepth = 0; + // Reset aspiration window starting size if (rootDepth >= 5 * ONE_PLY) { @@ -410,7 +361,7 @@ void Thread::search() { // 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) + if (Threads.stop) break; // When failing high/low give some update (without cluttering @@ -431,14 +382,11 @@ void Thread::search() { if (mainThread) { mainThread->failedLow = true; - Signals.stopOnPonderhit = false; + Threads.stopOnPonderhit = false; } } else if (bestValue >= beta) - { - alpha = (alpha + beta) / 2; beta = std::min(bestValue + delta, VALUE_INFINITE); - } else break; @@ -450,16 +398,25 @@ void Thread::search() { // Sort the PV lines searched so far and update the GUI std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1); - if (!mainThread) - continue; - - if (Signals.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000) + if ( mainThread + && (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000)) sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; } - if (!Signals.stop) + if (!Threads.stop) completedDepth = rootDepth; + if (rootMoves[0].pv[0] != lastBestMove) { + lastBestMove = rootMoves[0].pv[0]; + lastBestMoveDepth = rootDepth; + } + + // Have we found a "mate in x"? + if ( Limits.mate + && bestValue >= VALUE_MATE_IN_MAX_PLY + && VALUE_MATE - bestValue <= 2 * Limits.mate) + Threads.stop = true; + if (!mainThread) continue; @@ -467,62 +424,56 @@ void Thread::search() { if (skill.enabled() && skill.time_to_pick(rootDepth)) skill.pick_best(multiPV); - // Have we found a "mate in x"? - if ( Limits.mate - && bestValue >= VALUE_MATE_IN_MAX_PLY - && VALUE_MATE - bestValue <= 2 * Limits.mate) - Signals.stop = true; - // Do we have time for the next iteration? Can we stop searching now? if (Limits.use_time_management()) { - if (!Signals.stop && !Signals.stopOnPonderhit) + if (!Threads.stop && !Threads.stopOnPonderhit) { // Stop the search if only one legal move is available, or if all - // of the available time has been used, or if we matched an easyMove - // from the previous search and just did a fast verification. + // of the available time has been used const int F[] = { mainThread->failedLow, bestValue - mainThread->previousScore }; - int improvingFactor = std::max(229, std::min(715, 357 + 119 * F[0] - 6 * F[1])); - double unstablePvFactor = 1 + mainThread->bestMoveChanges; - bool doEasyMove = rootMoves[0].pv[0] == easyMove - && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.optimum() * 5 / 44; + Color us = rootPos.side_to_move(); + bool thinkHard = bestValue == VALUE_DRAW + && Limits.time[us] - Time.elapsed() > Limits.time[~us] + && ::pv_is_draw(rootPos); + + double unstablePvFactor = 1 + mainThread->bestMoveChanges + thinkHard; + + // if the bestMove is stable over several iterations, reduce time for this move, + // the longer the move has been stable, the more. + // Use part of the gained time from a previous stable move for the current move. + timeReduction = 1; + for (int i : {3, 4, 5}) + if (lastBestMoveDepth * i < completedDepth && !thinkHard) + timeReduction *= 1.3; + unstablePvFactor *= std::pow(mainThread->previousTimeReduction, 0.51) / timeReduction; if ( rootMoves.size() == 1 - || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628 - || (mainThread->easyMovePlayed = doEasyMove, doEasyMove)) + || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628) { // If we are allowed to ponder do not stop the search now but // keep pondering until the GUI sends "ponderhit" or "stop". - if (Limits.ponder) - Signals.stopOnPonderhit = true; + if (Threads.ponder) + Threads.stopOnPonderhit = true; else - Signals.stop = true; + Threads.stop = true; } } - - if (rootMoves[0].pv.size() >= 3) - EasyMove.update(rootPos, rootMoves[0].pv); - else - EasyMove.clear(); } } if (!mainThread) return; - // Clear any candidate easy move that wasn't stable for the last search - // iterations; the second condition prevents consecutive fast moves. - if (EasyMove.stableCnt < 6 || mainThread->easyMovePlayed) - EasyMove.clear(); + mainThread->previousTimeReduction = timeReduction; // If skill level is enabled, swap best PV line with the sub-optimal one if (skill.enabled()) - std::swap(rootMoves[0], *std::find(rootMoves.begin(), - rootMoves.end(), skill.best_move(multiPV))); + std::swap(rootMoves[0], *std::find(rootMoves.begin(), rootMoves.end(), + skill.best ? skill.best : skill.pick_best(multiPV))); } @@ -534,7 +485,7 @@ namespace { 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; + const bool rootNode = PvNode && ss->ply == 0; assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); @@ -542,40 +493,39 @@ namespace { assert(!(PvNode && cutNode)); assert(depth / ONE_PLY * ONE_PLY == depth); - Move pv[MAX_PLY+1], quietsSearched[64]; + Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[64]; StateInfo st; TTEntry* tte; Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval; + Value bestValue, value, ttValue, eval, maxValue; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture; - Piece moved_piece; - int moveCount, quietCount; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact; + Piece movedPiece; + int moveCount, captureCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); - moveCount = quietCount = ss->moveCount = 0; + moveCount = captureCount = quietCount = ss->moveCount = 0; ss->statScore = 0; bestValue = -VALUE_INFINITE; - ss->ply = (ss-1)->ply + 1; + maxValue = VALUE_INFINITE; // Check for the available remaining time if (thisThread == Threads.main()) static_cast(thisThread)->check_time(); - // Used to send selDepth info to GUI - if (PvNode && thisThread->maxPly < ss->ply) - thisThread->maxPly = ss->ply; + // Used to send selDepth info to GUI (selDepth counts from 1, ply from 0) + if (PvNode && thisThread->selDepth < ss->ply + 1) + thisThread->selDepth = ss->ply + 1; if (!rootNode) { // Step 2. Check for aborted search and immediate draw - 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()]; + if (Threads.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) + return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : VALUE_DRAW; // 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 @@ -591,8 +541,9 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); + (ss+1)->ply = ss->ply + 1; ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->history = &thisThread->counterMoveHistory[NO_PIECE][0]; + ss->contHistory = &thisThread->contHistory[NO_PIECE][0]; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; Square prevSq = to_sq((ss-1)->currentMove); @@ -600,7 +551,7 @@ namespace { // 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); + 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) : VALUE_NONE; ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] @@ -624,14 +575,14 @@ namespace { // 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)); + update_continuation_histories(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)) { 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); + thisThread->mainHistory.update(pos.side_to_move(), ttMove, penalty); + update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } return ttValue; @@ -648,7 +599,7 @@ namespace { && !pos.can_castle(ANY_CASTLING)) { TB::ProbeState err; - TB::WDLScore v = Tablebases::probe_wdl(pos, &err); + TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err); if (err != TB::ProbeState::FAIL) { @@ -656,15 +607,30 @@ namespace { int drawScore = TB::UseRule50 ? 1 : 0; - value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply - : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - : VALUE_DRAW + 2 * v * drawScore; + value = wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1 + : wdl > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1 + : VALUE_DRAW + 2 * wdl * drawScore; + + Bound b = wdl < -drawScore ? BOUND_UPPER + : wdl > drawScore ? BOUND_LOWER : BOUND_EXACT; - tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT, - std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY), - MOVE_NONE, VALUE_NONE, TT.generation()); + if ( b == BOUND_EXACT + || (b == BOUND_LOWER ? value >= beta : value <= alpha)) + { + tte->save(posKey, value_to_tt(value, ss->ply), b, + std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY), + MOVE_NONE, VALUE_NONE, TT.generation()); - return value; + return value; + } + + if (PvNode) + { + if (b == BOUND_LOWER) + bestValue = value, alpha = std::max(alpha, bestValue); + else + maxValue = value; + } } } } @@ -683,9 +649,9 @@ namespace { eval = ss->staticEval = evaluate(pos); // Can ttValue be used as a better position evaluation? - if (ttValue != VALUE_NONE) - if (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)) - eval = ttValue; + if ( ttValue != VALUE_NONE + && (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER))) + eval = ttValue; } else { @@ -697,18 +663,18 @@ namespace { ss->staticEval, TT.generation()); } - if (skipEarlyPruning) + if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move())) goto moves_loop; // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && eval + razor_margin[depth / ONE_PLY] <= alpha) + && eval + razor_margin <= alpha) { if (depth <= ONE_PLY) return qsearch(pos, ss, alpha, alpha+1); - Value ralpha = alpha - razor_margin[depth / ONE_PLY]; + Value ralpha = alpha - razor_margin; Value v = qsearch(pos, ss, ralpha, ralpha+1); if (v <= ralpha) return v; @@ -718,15 +684,14 @@ namespace { if ( !rootNode && depth < 7 * ONE_PLY && eval - futility_margin(depth) >= beta - && eval < VALUE_KNOWN_WIN // Do not return unproven wins - && pos.non_pawn_material(pos.side_to_move())) + && eval < VALUE_KNOWN_WIN) // Do not return unproven wins return eval; // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode && eval >= beta - && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY) - && pos.non_pawn_material(pos.side_to_move())) + && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225 + && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd)) { assert(eval - beta >= 0); @@ -735,7 +700,7 @@ namespace { 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]; + ss->contHistory = &thisThread->contHistory[NO_PIECE][0]; pos.do_null_move(st); Value nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) @@ -748,13 +713,19 @@ namespace { if (nullValue >= VALUE_MATE_IN_MAX_PLY) nullValue = beta; - if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN) + if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply)) return nullValue; // Do verification search at high depths + // disable null move pruning for side to move for the first part of the remaining search tree + thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4; + thisThread->nmp_odd = ss->ply % 2; + Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta) : search(pos, ss, beta-1, beta, depth-R, false, true); + thisThread->nmp_odd = thisThread->nmp_ply = 0; + if (v >= beta) return nullValue; } @@ -771,13 +742,13 @@ namespace { assert(is_ok((ss-1)->currentMove)); - MovePicker mp(pos, ttMove, rbeta - ss->staticEval); + MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory); while ((move = mp.next_move()) != MOVE_NONE) if (pos.legal(move)) { ss->currentMove = move; - ss->history = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; + ss->contHistory = &thisThread->contHistory[pos.moved_piece(move)][to_sq(move)]; assert(depth >= 5 * ONE_PLY); pos.do_move(move, st); @@ -802,11 +773,10 @@ namespace { moves_loop: // When in check search starts from here - const PieceToHistory& cmh = *(ss-1)->history; - const PieceToHistory& fmh = *(ss-2)->history; - const PieceToHistory& fm2 = *(ss-4)->history; + const PieceToHistory* contHist[] = { (ss-1)->contHistory, (ss-2)->contHistory, nullptr, (ss-4)->contHistory }; + Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]; - MovePicker mp(pos, ttMove, depth, ss); + MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, contHist, countermove, ss->killers); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc improving = ss->staticEval >= (ss-2)->staticEval /* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */ @@ -821,6 +791,7 @@ moves_loop: // When in check search starts from here && tte->depth() >= depth - 3 * ONE_PLY; skipQuiets = false; ttCapture = false; + pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT; // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs @@ -831,12 +802,20 @@ moves_loop: // When in check search starts from here if (move == excludedMove) continue; - // At root obey the "searchmoves" option and skip moves not listed in Root - // Move List. As a consequence any illegal move is also skipped. In MultiPV - // mode we also skip PV moves which have been already searched. - if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, - thisThread->rootMoves.end(), move)) - continue; + if (rootNode) + { + // At root obey the "searchmoves" option and skip moves not listed in Root + // Move List. As a consequence any illegal move is also skipped. + if (!std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, + thisThread->rootMoves.end(), move)) + continue; + + // In MultiPV mode we not only skip PV moves which have already been searched, + // but also any other move except we have reached the last PV line. + if ( thisThread->PVIdx + 1 < thisThread->multiPV + && move != ttMove) + continue; + } ss->moveCount = ++moveCount; @@ -850,10 +829,10 @@ moves_loop: // When in check search starts from here extension = DEPTH_ZERO; captureOrPromotion = pos.capture_or_promotion(move); - moved_piece = pos.moved_piece(move); + movedPiece = pos.moved_piece(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.check_squares(type_of(movedPiece)) & to_sq(move) : pos.gives_check(move); moveCountPruning = depth < 16 * ONE_PLY @@ -908,8 +887,8 @@ moves_loop: // When in check search starts from here // Countermoves based pruning if ( lmrDepth < 3 - && (cmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold) - && (fmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold)) + && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold + && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) continue; // Futility pruning: parent node @@ -944,7 +923,7 @@ moves_loop: // When in check search starts from here // Update the current move (this must be done after singular extension search) ss->currentMove = move; - ss->history = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; + ss->contHistory = &thisThread->contHistory[movedPiece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -961,6 +940,14 @@ moves_loop: // When in check search starts from here r -= r ? ONE_PLY : DEPTH_ZERO; else { + // Decrease reduction if opponent's move count is high + if ((ss-1)->moveCount > 15) + r -= ONE_PLY; + + // Decrease reduction for exact PV nodes + if (pvExact) + r -= ONE_PLY; + // Increase reduction if ttMove is a capture if (ttCapture) r += ONE_PLY; @@ -976,17 +963,17 @@ moves_loop: // When in check search starts from here && !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 + ss->statScore = thisThread->mainHistory[~pos.side_to_move()][from_to(move)] + + (*contHist[0])[movedPiece][to_sq(move)] + + (*contHist[1])[movedPiece][to_sq(move)] + + (*contHist[3])[movedPiece][to_sq(move)] + - 4000; // Decrease/increase reduction by comparing opponent's stat score - if (ss->statScore > 0 && (ss-1)->statScore < 0) + if (ss->statScore >= 0 && (ss-1)->statScore < 0) r -= ONE_PLY; - else if (ss->statScore < 0 && (ss-1)->statScore > 0) + else if ((ss-1)->statScore >= 0 && ss->statScore < 0) r += ONE_PLY; // Decrease/increase reduction for moves with a good/bad history @@ -1032,7 +1019,7 @@ moves_loop: // When in check search starts from here // Finished searching the move. If a stop occurred, the return value of // the search cannot be trusted, and we return immediately without // updating best move, PV and TT. - if (Signals.stop.load(std::memory_order_relaxed)) + if (Threads.stop.load(std::memory_order_relaxed)) return VALUE_ZERO; if (rootNode) @@ -1044,6 +1031,7 @@ moves_loop: // When in check search starts from here if (moveCount == 1 || value > alpha) { rm.score = value; + rm.selDepth = thisThread->selDepth; rm.pv.resize(1); assert((ss+1)->pv); @@ -1058,8 +1046,8 @@ moves_loop: // When in check search starts from here ++static_cast(thisThread)->bestMoveChanges; } else - // All other moves but the PV are set to the lowest value: this is - // not a problem when sorting because the sort is stable and the + // All other moves but the PV are set to the lowest value: this + // is not a problem when sorting because the sort is stable and the // move position in the list is preserved - just the PV is pushed up. rm.score = -VALUE_INFINITE; } @@ -1087,13 +1075,15 @@ moves_loop: // When in check search starts from here if (!captureOrPromotion && move != bestMove && quietCount < 64) quietsSearched[quietCount++] = move; + else if (captureOrPromotion && move != bestMove && captureCount < 32) + capturesSearched[captureCount++] = move; } // The following condition would detect a stop only after move loop has been // completed. But in this case bestValue is valid because we have fully // searched our subtree, and we can anyhow save the result in TT. /* - if (Signals.stop) + if (Threads.stop) return VALUE_DRAW; */ @@ -1106,22 +1096,27 @@ moves_loop: // When in check search starts from here if (!moveCount) bestValue = excludedMove ? alpha - : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; + : inCheck ? mated_in(ss->ply) : VALUE_DRAW; else if (bestMove) { // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); + else + update_capture_stats(pos, bestMove, capturesSearched, captureCount, 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()) - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + update_continuation_histories(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)) - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); + update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); + + if (PvNode) + bestValue = std::min(bestValue, maxValue); if (!excludedMove) tte->save(posKey, value_to_tt(bestValue, ss->ply), @@ -1143,7 +1138,7 @@ moves_loop: // When in check search starts from here const bool PvNode = NT == PV; - assert(InCheck == !!pos.checkers()); + assert(InCheck == bool(pos.checkers())); assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(depth <= DEPTH_ZERO); @@ -1167,13 +1162,12 @@ moves_loop: // When in check search starts from here } ss->currentMove = bestMove = MOVE_NONE; - ss->ply = (ss-1)->ply + 1; + (ss+1)->ply = ss->ply + 1; moveCount = 0; // Check for an instant draw or if the maximum ply has been reached if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) - return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) - : DrawValue[pos.side_to_move()]; + return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : VALUE_DRAW; assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -1182,7 +1176,6 @@ moves_loop: // When in check search starts from here // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS; - // Transposition table lookup posKey = pos.key(); tte = TT.probe(posKey, ttHit); @@ -1212,9 +1205,9 @@ moves_loop: // When in check search starts from here ss->staticEval = bestValue = evaluate(pos); // Can ttValue be used as a better position evaluation? - if (ttValue != VALUE_NONE) - if (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER)) - bestValue = ttValue; + if ( ttValue != VALUE_NONE + && (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER))) + bestValue = ttValue; } else ss->staticEval = bestValue = @@ -1225,7 +1218,7 @@ moves_loop: // When in check search starts from here if (bestValue >= beta) { if (!ttHit) - tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, + tte->save(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation()); return bestValue; @@ -1241,7 +1234,7 @@ moves_loop: // When in check search starts from here // 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. - MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove)); + MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory, &pos.this_thread()->captureHistory, to_sq((ss-1)->currentMove)); // Loop through the moves until no moves remain or a beta cutoff occurs while ((move = mp.next_move()) != MOVE_NONE) @@ -1249,7 +1242,7 @@ moves_loop: // When in check search starts from here assert(is_ok(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.check_squares(type_of(pos.moved_piece(move))) & to_sq(move) : pos.gives_check(move); moveCount++; @@ -1285,7 +1278,6 @@ moves_loop: // When in check search starts from here // Don't search moves with negative SEE values if ( (!InCheck || evasionPrunable) - && type_of(move) != PROMOTION && !pos.see_ge(move)) continue; @@ -1385,13 +1377,34 @@ moves_loop: // When in check search starts from here } - // update_cm_stats() updates countermove and follow-up move history + // update_continuation_histories() updates histories of the move pairs formed + // by moves at ply -1, -2, and -4 with current move. - void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus) { + void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) { for (int i : {1, 2, 4}) if (is_ok((ss-i)->currentMove)) - (ss-i)->history->update(pc, s, bonus); + (ss-i)->contHistory->update(pc, to, bonus); + } + + + // update_capture_stats() updates move sorting heuristics when a new capture best move is found + + void update_capture_stats(const Position& pos, Move move, + Move* captures, int captureCnt, int bonus) { + + CapturePieceToHistory& captureHistory = pos.this_thread()->captureHistory; + Piece moved_piece = pos.moved_piece(move); + PieceType captured = type_of(pos.piece_on(to_sq(move))); + captureHistory.update(moved_piece, to_sq(move), captured, bonus); + + // Decrease all the other played capture moves + for (int i = 0; i < captureCnt; ++i) + { + moved_piece = pos.moved_piece(captures[i]); + captured = type_of(pos.piece_on(to_sq(captures[i]))); + captureHistory.update(moved_piece, to_sq(captures[i]), captured, -bonus); + } } @@ -1408,24 +1421,42 @@ moves_loop: // When in check search starts from here Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - thisThread->history.update(c, move, bonus); - update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); + thisThread->mainHistory.update(c, move, bonus); + update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus); if (is_ok((ss-1)->currentMove)) { Square prevSq = to_sq((ss-1)->currentMove); - thisThread->counterMoves[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->history.update(c, quiets[i], -bonus); - update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + thisThread->mainHistory.update(c, quiets[i], -bonus); + update_continuation_histories(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } } + // Is the PV leading to a draw position? Assumes all pv moves are legal + bool pv_is_draw(Position& pos) { + + StateInfo st[MAX_PLY]; + auto& pv = pos.this_thread()->rootMoves[0].pv; + + for (size_t i = 0; i < pv.size(); ++i) + pos.do_move(pv[i], st[i]); + + bool isDraw = pos.is_draw(pv.size()); + + for (size_t i = pv.size(); i > 0; --i) + pos.undo_move(pv[i-1]); + + return isDraw; + } + + // When playing with strength handicap, choose best move among a set of RootMoves // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. @@ -1449,7 +1480,7 @@ moves_loop: // When in check search starts from here int push = ( weakness * int(topScore - rootMoves[i].score) + delta * (rng.rand() % weakness)) / 128; - if (rootMoves[i].score + push > maxScore) + if (rootMoves[i].score + push >= maxScore) { maxScore = rootMoves[i].score + push; best = rootMoves[i].pv[0]; @@ -1485,13 +1516,13 @@ moves_loop: // When in check search starts from here } // An engine may not stop pondering until told so by the GUI - if (Limits.ponder) + if (Threads.ponder) return; if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10) || (Limits.movetime && elapsed >= Limits.movetime) || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes)) - Signals.stop = true; + Threads.stop = true; } @@ -1504,7 +1535,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { int elapsed = Time.elapsed() + 1; 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()); + size_t multiPV = pos.this_thread()->multiPV; uint64_t nodesSearched = Threads.nodes_searched(); uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0); @@ -1526,7 +1557,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { ss << "info" << " depth " << d / ONE_PLY - << " seldepth " << pos.this_thread()->maxPly + << " seldepth " << rootMoves[i].selDepth << " multipv " << i + 1 << " score " << UCI::value(v); @@ -1597,6 +1628,10 @@ void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING)) return; + // Don't filter any moves if the user requested analysis on multiple + if (Options["MultiPV"] != 1) + return; + // If the current root position is in the tablebases, then RootMoves // contains only moves that preserve the draw or the win. RootInTB = root_probe(pos, rootMoves, TB::Score); @@ -1618,4 +1653,9 @@ void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 : VALUE_DRAW; + + // Since root_probe() and root_probe_wdl() dirty the root move scores, + // we reset them to -VALUE_INFINITE + for (RootMove& rm : rootMoves) + rm.score = -VALUE_INFINITE; }