X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=2828ccda35bebb57397034894ce8e434e8de784c;hp=865e477144042c2a99577ac8179e066718016585;hb=0784bd542bf17679febd9d9d87858fd0fd0424f9;hpb=aa0dc16b754f65e5f5b84c7500732476ca1f035b diff --git a/src/search.cpp b/src/search.cpp index 865e4771..2828ccda 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -2,6 +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 Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -37,11 +38,8 @@ namespace Search { - volatile SignalsType Signals; + SignalsType Signals; LimitsType Limits; - RootMoveVector RootMoves; - Position RootPos; - StateStackPtr SetupStates; } namespace Tablebases { @@ -62,11 +60,11 @@ using namespace Search; namespace { - // Different node types, used as template parameter - enum NodeType { Root, PV, NonPV }; + // Different node types, used as a template parameter + enum NodeType { NonPV, PV }; // Razoring and futility margin based on depth - Value razor_margin(Depth d) { return Value(512 + 32 * d); } + const int razor_margin[4] = { 483, 570, 603, 554 }; Value futility_margin(Depth d) { return Value(200 * d); } // Futility and reductions lookup tables, initialized at startup @@ -77,7 +75,7 @@ namespace { return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)]; } - // Skill struct is used to implement strength limiting + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} bool enabled() const { return level < 20; } @@ -89,8 +87,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager struct is used to detect a so called 'easy move'; when PV is - // stable across multiple search iterations we can fast 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() { @@ -107,7 +105,7 @@ namespace { assert(newPv.size() >= 3); - // Keep track of how many times in a row 3rd ply remains stable + // 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)) @@ -128,25 +126,50 @@ namespace { Move pv[3]; }; - size_t PVIdx; + // 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; - double BestMoveChanges; Value DrawValue[COLOR_NB]; - HistoryStats History; - CounterMovesHistoryStats CounterMovesHistory; - MovesStats Countermoves; + CounterMoveHistoryStats CounterMoveHistory; - template + template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - void id_loop(Position& pos); 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_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt); + void check_time(); } // namespace @@ -155,22 +178,21 @@ namespace { void Search::init() { - const double K[][2] = {{ 0.83, 2.25 }, { 0.50, 3.00 }}; - - for (int pv = 0; pv <= 1; ++pv) - for (int imp = 0; imp <= 1; ++imp) - for (int d = 1; d < 64; ++d) - for (int mc = 1; mc < 64; ++mc) - { - double r = K[pv][0] + log(d) * log(mc) / K[pv][1]; + for (int imp = 0; imp <= 1; ++imp) + 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; - if (r >= 1.5) - Reductions[pv][imp][d][mc] = int(r) * ONE_PLY; + Reductions[NonPV][imp][d][mc] = int(std::round(r)) * ONE_PLY; + Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - ONE_PLY, DEPTH_ZERO); - // Increase reduction when eval is not improving - if (!pv && !imp && Reductions[pv][imp][d][mc] >= 2 * ONE_PLY) - Reductions[pv][imp][d][mc] += ONE_PLY; - } + // Increase reduction for non-PV nodes when eval is not improving + if (!imp && Reductions[NonPV][imp][d][mc] >= 2 * ONE_PLY) + Reductions[NonPV][imp][d][mc] += ONE_PLY; + } for (int d = 0; d < 16; ++d) { @@ -180,19 +202,25 @@ void Search::init() { } -/// Search::reset() clears all search memory, to obtain reproducible search results +/// Search::clear() resets search state to zero, to obtain reproducible results -void Search::reset () { +void Search::clear() { TT.clear(); - History.clear(); - CounterMovesHistory.clear(); - Countermoves.clear(); + CounterMoveHistory.clear(); + + for (Thread* th : Threads) + { + th->history.clear(); + th->counterMoves.clear(); + } + + 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 returned. +/// up to the given depth are generated and counted, and the sum is returned. template uint64_t Search::perft(Position& pos, Depth depth) { @@ -218,17 +246,16 @@ uint64_t Search::perft(Position& pos, Depth depth) { return nodes; } -template uint64_t Search::perft(Position& pos, Depth depth); +template uint64_t Search::perft(Position&, Depth); -/// Search::think() is the external interface to Stockfish's search, and is -/// called by the main thread when the program receives the UCI 'go' command. It -/// searches from RootPos and at the end prints the "bestmove" to output. +/// 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 Search::think() { +void MainThread::search() { - Color us = RootPos.side_to_move(); - Time.init(Limits, us, RootPos.game_ply(), now()); + Color us = rootPos.side_to_move(); + Time.init(Limits, us, rootPos.game_ply()); int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns DrawValue[ us] = VALUE_DRAW - Value(contempt); @@ -247,29 +274,30 @@ void Search::think() { TB::ProbeDepth = DEPTH_ZERO; } - if (RootMoves.empty()) + if (rootMoves.empty()) { - RootMoves.push_back(RootMove(MOVE_NONE)); + rootMoves.push_back(RootMove(MOVE_NONE)); sync_cout << "info depth 0 score " - << UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << UCI::value(rootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; } else { - if (TB::Cardinality >= RootPos.count(WHITE) - + RootPos.count(BLACK)) + if ( TB::Cardinality >= rootPos.count(WHITE) + + rootPos.count(BLACK) + && !rootPos.can_castle(ANY_CASTLING)) { - // If the current root position is in the tablebases then RootMoves - // contains only moves that preserve the draw or win. - TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score); + // If the current root position is in the tablebases, then RootMoves + // contains only moves that preserve the draw or the win. + TB::RootInTB = Tablebases::root_probe(rootPos, rootMoves, TB::Score); if (TB::RootInTB) TB::Cardinality = 0; // Do not probe tablebases during the search else // If DTZ tables are missing, use WDL tables as a fallback { - // Filter out moves that do not preserve a draw or win - TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score); + // Filter out moves that do not preserve the draw or the win. + TB::RootInTB = Tablebases::root_probe_wdl(rootPos, rootMoves, TB::Score); // Only probe during search if winning if (TB::Score <= VALUE_DRAW) @@ -278,7 +306,7 @@ void Search::think() { if (TB::RootInTB) { - TB::Hits = RootMoves.size(); + TB::Hits = rootMoves.size(); if (!TB::UseRule50) TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 @@ -288,23 +316,16 @@ void Search::think() { } for (Thread* th : Threads) - { - th->maxPly = 0; - th->notify_one(); // Wake up all the threads - } + if (th != this) + th->start_searching(); - Threads.timer->run = true; - Threads.timer->notify_one(); // Start the recurring timer - - id_loop(RootPos); // Let's start searching ! - - Threads.timer->run = false; + Thread::search(); // Let's start searching! } // When playing in 'nodes as time' mode, subtract the searched nodes from - // the available ones before to exit. + // the available ones before exiting. if (Limits.npmsec) - Time.availableNodes += Limits.inc[us] - RootPos.nodes_searched(); + 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, @@ -314,258 +335,313 @@ void Search::think() { if (!Signals.stop && (Limits.ponder || Limits.infinite)) { Signals.stopOnPonderhit = true; - RootPos.this_thread()->wait_for(Signals.stop); + wait(Signals.stop); + } + + // Stop the threads if not already stopped + Signals.stop = true; + + // Wait until all threads have finished + for (Thread* th : Threads) + if (th != this) + th->wait_for_search_finished(); + + // Check if there are threads with a better score than main thread + Thread* bestThread = this; + if ( !this->easyMovePlayed + && Options["MultiPV"] == 1 + && !Limits.depth + && !Skill(Options["Skill Level"]).enabled() + && rootMoves[0].pv[0] != MOVE_NONE) + { + for (Thread* th : Threads) + if ( th->completedDepth > bestThread->completedDepth + && th->rootMoves[0].score > bestThread->rootMoves[0].score) + bestThread = th; } - sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960()); + previousScore = bestThread->rootMoves[0].score; - if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos)) - std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960()); + // Send new PV when needed + if (bestThread != this) + sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl; + + sync_cout << "bestmove " << UCI::move(bestThread->rootMoves[0].pv[0], rootPos.is_chess960()); + + if (bestThread->rootMoves[0].pv.size() > 1 || bestThread->rootMoves[0].extract_ponder_from_tt(rootPos)) + std::cout << " ponder " << UCI::move(bestThread->rootMoves[0].pv[1], rootPos.is_chess960()); std::cout << sync_endl; } -namespace { +// 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. - // id_loop() is the main iterative deepening loop. It calls search() repeatedly - // with increasing depth until the allocated thinking time has been consumed, - // user stops the search, or the maximum search depth is reached. +void Thread::search() { - void id_loop(Position& pos) { + Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2) + Value bestValue, alpha, beta, delta; + Move easyMove = MOVE_NONE; + MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) - Depth depth; - Value bestValue, alpha, beta, delta; + std::memset(ss-5, 0, 8 * sizeof(Stack)); - Move easyMove = EasyMove.get(pos.key()); - EasyMove.clear(); + bestValue = delta = alpha = -VALUE_INFINITE; + beta = VALUE_INFINITE; + completedDepth = DEPTH_ZERO; - std::memset(ss-2, 0, 5 * sizeof(Stack)); + if (mainThread) + { + easyMove = EasyMove.get(rootPos.key()); + EasyMove.clear(); + mainThread->easyMovePlayed = mainThread->failedLow = false; + mainThread->bestMoveChanges = 0; + TT.new_search(); + } - depth = DEPTH_ZERO; - BestMoveChanges = 0; - bestValue = delta = alpha = -VALUE_INFINITE; - beta = VALUE_INFINITE; + size_t multiPV = Options["MultiPV"]; + Skill skill(Options["Skill Level"]); - TT.new_search(); + // When playing with strength handicap enable MultiPV search that we will + // use behind the scenes to retrieve a set of possible moves. + if (skill.enabled()) + multiPV = std::max(multiPV, (size_t)4); - size_t multiPV = Options["MultiPV"]; - Skill skill(Options["Skill Level"]); + multiPV = std::min(multiPV, rootMoves.size()); - // When playing with strength handicap enable MultiPV search that we will - // use behind the scenes to retrieve a set of possible moves. - if (skill.enabled()) - multiPV = std::max(multiPV, (size_t)4); + // Iterative deepening loop until requested to stop or the target depth is reached. + while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth <= Limits.depth)) + { + // Set up the new depths for the helper threads skipping on average every + // 2nd ply (using a half-density matrix). + if (!mainThread) + { + const Row& row = HalfDensity[(idx - 1) % HalfDensitySize]; + if (row[(rootDepth + rootPos.game_ply()) % row.size()]) + continue; + } - multiPV = std::min(multiPV, RootMoves.size()); + // Age out PV variability metric + if (mainThread) + mainThread->bestMoveChanges *= 0.505, mainThread->failedLow = false; - // Iterative deepening loop until requested to stop or target depth reached - while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) - { - // Age out PV variability metric - BestMoveChanges *= 0.5; + // Save the last iteration's scores before first PV line is searched and + // all the move scores except the (new) PV are set to -VALUE_INFINITE. + for (RootMove& rm : rootMoves) + rm.previousScore = rm.score; - // Save the last iteration's scores before first PV line is searched and - // all the move scores except the (new) PV are set to -VALUE_INFINITE. - for (RootMove& rm : RootMoves) - rm.previousScore = rm.score; + // MultiPV loop. We perform a full root search for each PV line + for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx) + { + // Reset aspiration window starting size + if (rootDepth >= 5 * ONE_PLY) + { + delta = Value(18); + alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); + beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); + } - // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx) - { - // Reset aspiration window starting size - if (depth >= 5 * ONE_PLY) - { - delta = Value(16); - alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); - beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); - } + // Start with a small aspiration window and, in the case of a fail + // high/low, re-search with a bigger window until we're not failing + // high/low anymore. + while (true) + { + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, 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 + // first and eventually the new best one are set to -VALUE_INFINITE + // and we want to keep the same order for all the moves except the + // new PV that goes to the front. Note that in case of MultiPV + // search the already searched PV lines are preserved. + std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); + + // Write PV back to the transposition table in case the relevant + // entries have been overwritten during the search. + for (size_t i = 0; i <= PVIdx; ++i) + rootMoves[i].insert_pv_in_tt(rootPos); + + // If search has been stopped, 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) + break; - // Start with a small aspiration window and, in the case of a fail - // high/low, re-search with a bigger window until we're not failing - // high/low anymore. - while (true) - { - bestValue = search(pos, ss, alpha, beta, depth, 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 - // first and eventually the new best one are set to -VALUE_INFINITE - // and we want to keep the same order for all the moves except the - // new PV that goes to the front. Note that in case of MultiPV - // search the already searched PV lines are preserved. - std::stable_sort(RootMoves.begin() + PVIdx, RootMoves.end()); - - // Write PV back to transposition table in case the relevant - // entries have been overwritten during the search. - for (size_t i = 0; i <= PVIdx; ++i) - RootMoves[i].insert_pv_in_tt(pos); - - // If search has been stopped break immediately. Sorting and - // writing PV back to TT is safe because RootMoves is still - // valid, although it refers to previous iteration. - if (Signals.stop) - break; - - // When failing high/low give some update (without cluttering - // the UI) before a re-search. - if ( multiPV == 1 - && (bestValue <= alpha || bestValue >= beta) - && Time.elapsed() > 3000) - sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl; - - // In case of failing low/high increase aspiration window and - // re-search, otherwise exit the loop. - if (bestValue <= alpha) - { - beta = (alpha + beta) / 2; - alpha = std::max(bestValue - delta, -VALUE_INFINITE); - - Signals.failedLowAtRoot = true; - Signals.stopOnPonderhit = false; - } - else if (bestValue >= beta) - { - alpha = (alpha + beta) / 2; - beta = std::min(bestValue + delta, VALUE_INFINITE); - } - else - break; - - delta += delta / 2; - - assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); - } + // When failing high/low give some update (without cluttering + // the UI) before a re-search. + if ( mainThread + && multiPV == 1 + && (bestValue <= alpha || bestValue >= beta) + && Time.elapsed() > 3000) + sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; + + // In case of failing low/high increase aspiration window and + // re-search, otherwise exit the loop. + if (bestValue <= alpha) + { + beta = (alpha + beta) / 2; + alpha = std::max(bestValue - delta, -VALUE_INFINITE); - // Sort the PV lines searched so far and update the GUI - std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); + if (mainThread) + { + mainThread->failedLow = true; + Signals.stopOnPonderhit = false; + } + } + else if (bestValue >= beta) + { + alpha = (alpha + beta) / 2; + beta = std::min(bestValue + delta, VALUE_INFINITE); + } + else + break; - if (Signals.stop) - sync_cout << "info nodes " << RootPos.nodes_searched() - << " time " << Time.elapsed() << sync_endl; + delta += delta / 4 + 5; - else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000) - sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl; - } + assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); + } - // If skill level is enabled and time is up, pick a sub-optimal best move - if (skill.enabled() && skill.time_to_pick(depth)) - skill.pick_best(multiPV); + // Sort the PV lines searched so far and update the GUI + std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1); - // 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; + if (!mainThread) + continue; - // Do we have time for the next iteration? Can we stop searching now? - if (Limits.use_time_management()) - { - if (!Signals.stop && !Signals.stopOnPonderhit) - { - // Take some extra time if the best move has changed - if (depth > 4 * ONE_PLY && multiPV == 1) - Time.pv_instability(BestMoveChanges); - - // Stop the search if only one legal move is available or all - // of the available time has been used or we matched an easyMove - // from the previous search and just did a fast verification. - if ( RootMoves.size() == 1 - || Time.elapsed() > Time.available() - || ( RootMoves[0].pv[0] == easyMove - && BestMoveChanges < 0.03 - && Time.elapsed() > Time.available() / 10)) - { - // 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; - else - Signals.stop = true; - } - } + if (Signals.stop) + sync_cout << "info nodes " << Threads.nodes_searched() + << " time " << Time.elapsed() << sync_endl; - if (RootMoves[0].pv.size() >= 3) - EasyMove.update(pos, RootMoves[0].pv); - else - EasyMove.clear(); - } - } + else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000) + sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; + } - // 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 || Time.elapsed() < Time.available()) - EasyMove.clear(); + if (!Signals.stop) + completedDepth = rootDepth; - // 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))); + if (!mainThread) + continue; + + // If skill level is enabled and time is up, pick a sub-optimal best move + 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) + { + // 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. + const bool F[] = { !mainThread->failedLow, + bestValue >= mainThread->previousScore }; + + int improvingFactor = 640 - 160*F[0] - 126*F[1] - 124*F[0]*F[1]; + double unstablePvFactor = 1 + mainThread->bestMoveChanges; + + bool doEasyMove = rootMoves[0].pv[0] == easyMove + && mainThread->bestMoveChanges < 0.03 + && Time.elapsed() > Time.optimum() * 25 / 204; + + if ( rootMoves.size() == 1 + || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 634 + || (mainThread->easyMovePlayed = doEasyMove)) + { + // 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; + else + Signals.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(); - // search<>() is the main search function for both PV and non-PV nodes and for - // normal and SplitPoint nodes. When called just after a split point the search - // is simpler because we have already probed the hash table, done a null move - // search, and searched the first move before splitting, so we don't have to - // repeat all this work again. We also don't need to store anything to the hash - // table here: This is taken care of after we return from the split point. + // 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))); +} + + +namespace { - template + // 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) { - const bool RootNode = NT == Root; - const bool PvNode = NT == PV || NT == Root; + const bool PvNode = NT == PV; + const bool rootNode = PvNode && (ss-1)->ply == 0; assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); - assert(depth > DEPTH_ZERO); + assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; TTEntry* tte; - SplitPoint* splitPoint; Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth, predictedDepth; Value bestValue, value, ttValue, eval, nullValue, futilityValue; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, dangerous, doFullDepthSearch; + bool captureOrPromotion, doFullDepthSearch; int moveCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); + moveCount = quietCount = ss->moveCount = 0; + bestValue = -VALUE_INFINITE; + ss->ply = (ss-1)->ply + 1; - if (SpNode) + // Check for the available remaining time + if (thisThread->resetCalls.load(std::memory_order_relaxed)) { - splitPoint = ss->splitPoint; - bestMove = splitPoint->bestMove; - bestValue = splitPoint->bestValue; - tte = nullptr; - ttHit = false; - ttMove = excludedMove = MOVE_NONE; - ttValue = VALUE_NONE; - - assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0); - - goto moves_loop; + thisThread->resetCalls = false; + thisThread->callsCnt = 0; } + if (++thisThread->callsCnt > 4096) + { + for (Thread* th : Threads) + th->resetCalls = true; - moveCount = quietCount = 0; - bestValue = -VALUE_INFINITE; - ss->ply = (ss-1)->ply + 1; + check_time(); + } // Used to send selDepth info to GUI if (PvNode && thisThread->maxPly < ss->ply) thisThread->maxPly = ss->ply; - if (!RootNode) + if (!rootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop || pos.is_draw() || ss->ply >= MAX_PLY) - return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; + if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) + return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) + : DrawValue[pos.side_to_move()]; // 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 @@ -581,24 +657,26 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); - ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - (ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO; + ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->counterMoves = nullptr; + (ss+1)->skipEarlyPruning = false; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; - // Step 4. Transposition table lookup - // We don't want the score of a partial search to overwrite a previous full search - // TT value, so we use a different position key in case of an excluded move. + // Step 4. Transposition table lookup. We don't want the score of a partial + // search to overwrite a previous full search TT value, so we use a different + // position key in case of an excluded move. excludedMove = ss->excludedMove; posKey = excludedMove ? pos.exclusion_key() : pos.key(); tte = TT.probe(posKey, ttHit); - ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; + ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] + : ttHit ? tte->move() : MOVE_NONE; - // At non-PV nodes we check for a fail high/low. We don't prune at PV nodes + // At non-PV nodes we check for an early TT cutoff if ( !PvNode && ttHit && tte->depth() >= depth - && ttValue != VALUE_NONE // Only in case of TT access race + && ttValue != VALUE_NONE // Possible in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) { @@ -612,13 +690,14 @@ namespace { } // Step 4a. Tablebase probe - if (!RootNode && TB::Cardinality) + if (!rootNode && TB::Cardinality) { int piecesCnt = pos.count(WHITE) + pos.count(BLACK); if ( piecesCnt <= TB::Cardinality && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) - && pos.rule50_count() == 0) + && pos.rule50_count() == 0 + && !pos.can_castle(ANY_CASTLING)) { int found, v = Tablebases::probe_wdl(pos, &found); @@ -662,9 +741,11 @@ namespace { else { eval = ss->staticEval = - (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo; + (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) + : -(ss-1)->staticEval + 2 * Eval::Tempo; - tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation()); + tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, + ss->staticEval, TT.generation()); } if (ss->skipEarlyPruning) @@ -673,22 +754,21 @@ namespace { // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && eval + razor_margin(depth) <= alpha - && ttMove == MOVE_NONE - && !pos.pawn_on_7th(pos.side_to_move())) + && eval + razor_margin[depth] <= alpha + && ttMove == MOVE_NONE) { if ( depth <= ONE_PLY - && eval + razor_margin(3 * ONE_PLY) <= alpha) + && eval + razor_margin[3 * ONE_PLY] <= alpha) return qsearch(pos, ss, alpha, beta, DEPTH_ZERO); - Value ralpha = alpha - razor_margin(depth); + Value ralpha = alpha - razor_margin[depth]; Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); if (v <= ralpha) return v; } // Step 7. Futility pruning: child node (skipped when in check) - if ( !RootNode + if ( !rootNode && depth < 7 * ONE_PLY && eval - futility_margin(depth) >= beta && eval < VALUE_KNOWN_WIN // Do not return unproven wins @@ -702,6 +782,7 @@ namespace { && pos.non_pawn_material(pos.side_to_move())) { ss->currentMove = MOVE_NULL; + ss->counterMoves = nullptr; assert(eval - beta >= 0); @@ -711,7 +792,7 @@ namespace { 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); + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); (ss+1)->skipEarlyPruning = false; pos.undo_null_move(); @@ -727,7 +808,7 @@ namespace { // 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); + : search(pos, ss, beta-1, beta, depth-R, false); ss->skipEarlyPruning = false; if (v >= beta) @@ -737,8 +818,8 @@ namespace { // Step 9. ProbCut (skipped when in check) // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type]) - // and a reduced search returns a value much above beta, we can (almost) safely - // prune the previous move. + // and a reduced search returns a value much above beta, we can (almost) + // safely prune the previous move. if ( !PvNode && depth >= 5 * ONE_PLY && abs(beta) < VALUE_MATE_IN_MAX_PLY) @@ -750,15 +831,16 @@ namespace { assert((ss-1)->currentMove != MOVE_NONE); assert((ss-1)->currentMove != MOVE_NULL); - MovePicker mp(pos, ttMove, History, CounterMovesHistory, pos.captured_piece_type()); + MovePicker mp(pos, ttMove, PieceValue[MG][pos.captured_piece_type()]); CheckInfo ci(pos); - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) if (pos.legal(move, ci.pinned)) { ss->currentMove = move; + ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)]; pos.do_move(move, st, pos.gives_check(move, ci)); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); pos.undo_move(move); if (value >= rbeta) return value; @@ -770,29 +852,28 @@ namespace { && !ttMove && (PvNode || ss->staticEval + 256 >= beta)) { - Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2); + Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4); ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d / 2, true); + search(pos, ss, alpha, beta, d, true); ss->skipEarlyPruning = false; tte = TT.probe(posKey, ttHit); ttMove = ttHit ? tte->move() : MOVE_NONE; } -moves_loop: // When in check and at SpNode search starts from here +moves_loop: // When in check search starts from here - Square prevMoveSq = to_sq((ss-1)->currentMove); - Move countermove = Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq]; + Square prevSq = to_sq((ss-1)->currentMove); + const CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq]; - MovePicker mp(pos, ttMove, depth, History, CounterMovesHistory, countermove, ss); + MovePicker mp(pos, ttMove, depth, ss); CheckInfo ci(pos); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc improving = ss->staticEval >= (ss-2)->staticEval || ss->staticEval == VALUE_NONE ||(ss-2)->staticEval == VALUE_NONE; - singularExtensionNode = !RootNode - && !SpNode + singularExtensionNode = !rootNode && depth >= 8 * ONE_PLY && ttMove != MOVE_NONE /* && ttValue != VALUE_NONE Already implicit in the next condition */ @@ -803,7 +884,7 @@ moves_loop: // When in check and at SpNode search starts from here // 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()) != MOVE_NONE) { assert(is_ok(move)); @@ -813,30 +894,16 @@ moves_loop: // When in check and at SpNode search starts from here // 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(RootMoves.begin() + PVIdx, RootMoves.end(), move)) + if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, + thisThread->rootMoves.end(), move)) continue; - if (SpNode) - { - // Shared counter cannot be decremented later if the move turns out to be illegal - if (!pos.legal(move, ci.pinned)) - continue; - - moveCount = ++splitPoint->moveCount; - splitPoint->spinlock.release(); - } - else - ++moveCount; + ss->moveCount = ++moveCount; - if (RootNode) - { - Signals.firstRootMove = (moveCount == 1); - - if (thisThread == Threads.main() && Time.elapsed() > 3000) - sync_cout << "info depth " << depth / ONE_PLY - << " currmove " << UCI::move(move, pos.is_chess960()) - << " currmovenumber " << moveCount + PVIdx << sync_endl; - } + if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000) + sync_cout << "info depth " << depth / ONE_PLY + << " currmove " << UCI::move(move, pos.is_chess960()) + << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl; if (PvNode) (ss+1)->pv = nullptr; @@ -848,10 +915,6 @@ moves_loop: // When in check and at SpNode search starts from here ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move) : pos.gives_check(move, ci); - dangerous = givesCheck - || type_of(move) != NORMAL - || pos.advanced_pawn_push(move); - // Step 12. Extend checks if (givesCheck && pos.see_sign(move) >= VALUE_ZERO) extension = ONE_PLY; @@ -869,7 +932,7 @@ moves_loop: // When in check and at SpNode search starts from here Value rBeta = ttValue - 2 * depth / ONE_PLY; ss->excludedMove = move; ss->skipEarlyPruning = true; - value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); + value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); ss->skipEarlyPruning = false; ss->excludedMove = MOVE_NONE; @@ -881,23 +944,26 @@ moves_loop: // When in check and at SpNode search starts from here newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth - if ( !RootNode + if ( !rootNode && !captureOrPromotion && !inCheck - && !dangerous + && !givesCheck + && !pos.advanced_pawn_push(move) && bestValue > VALUE_MATED_IN_MAX_PLY) { // Move count based pruning if ( depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth]) - { - if (SpNode) - splitPoint->spinlock.acquire(); + continue; + // History based pruning + if ( depth <= 4 * ONE_PLY + && move != ss->killers[0] + && thisThread->history[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO + && cmh[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO) continue; - } - predictedDepth = newDepth - reduction(improving, depth, moveCount); + predictedDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO); // Futility pruning: parent node if (predictedDepth < 7 * ONE_PLY) @@ -907,38 +973,27 @@ moves_loop: // When in check and at SpNode search starts from here if (futilityValue <= alpha) { bestValue = std::max(bestValue, futilityValue); - - if (SpNode) - { - splitPoint->spinlock.acquire(); - if (bestValue > splitPoint->bestValue) - splitPoint->bestValue = bestValue; - } continue; } } // Prune moves with negative SEE at low depths if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO) - { - if (SpNode) - splitPoint->spinlock.acquire(); - continue; - } } // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); // Check for legality just before making the move - if (!RootNode && !SpNode && !pos.legal(move, ci.pinned)) + if (!rootNode && !pos.legal(move, ci.pinned)) { - moveCount--; + ss->moveCount = --moveCount; continue; } ss->currentMove = move; + ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -947,59 +1002,55 @@ moves_loop: // When in check and at SpNode search starts from here // re-searched at full depth. if ( depth >= 3 * ONE_PLY && moveCount > 1 - && !captureOrPromotion - && move != ss->killers[0] - && move != ss->killers[1]) + && !captureOrPromotion) { - ss->reduction = reduction(improving, depth, moveCount); - - if ( (!PvNode && cutNode) - || ( History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO - && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq] - [pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO)) - ss->reduction += ONE_PLY; - - if ( move == countermove - || ( History[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO - && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq] - [pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO)) - ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); - - // Decrease reduction for moves that escape a capture - if ( ss->reduction + Depth r = reduction(improving, depth, moveCount); + Value hValue = thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)]; + Value cmhValue = cmh[pos.piece_on(to_sq(move))][to_sq(move)]; + + const CounterMoveStats* fm = (ss - 2)->counterMoves; + const CounterMoveStats* fm2 = (ss - 4)->counterMoves; + Value fmValue = (fm ? (*fm)[pos.piece_on(to_sq(move))][to_sq(move)] : VALUE_ZERO); + Value fm2Value = (fm2 ? (*fm2)[pos.piece_on(to_sq(move))][to_sq(move)] : VALUE_ZERO); + + // Increase reduction for cut nodes + if (!PvNode && cutNode) + r += ONE_PLY; + + // Decrease/increase reduction for moves with a good/bad history + int rHist = (hValue + cmhValue + fmValue + fm2Value - 10000) / 20000; + r = std::max(DEPTH_ZERO, r - rHist * ONE_PLY); + + // 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. + if ( r && 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) - ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); + r = std::max(DEPTH_ZERO, r - ONE_PLY); - Depth d = std::max(newDepth - ss->reduction, ONE_PLY); - if (SpNode) - alpha = splitPoint->alpha; + 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); - doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); - ss->reduction = DEPTH_ZERO; + doFullDepthSearch = (value > alpha && r != DEPTH_ZERO); } else doFullDepthSearch = !PvNode || moveCount > 1; - // Step 16. Full depth search, when LMR is skipped or fails high + // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) - { - if (SpNode) - alpha = splitPoint->alpha; - 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); - } + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); // 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 - // parent node fail low with value <= alpha and to try another move. - if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta)))) + // parent node fail low with value <= alpha and try another move. + if (PvNode && (moveCount == 1 || (value > alpha && (rootNode || value < beta)))) { (ss+1)->pv = pv; (ss+1)->pv[0] = MOVE_NONE; @@ -1007,7 +1058,7 @@ moves_loop: // When in check and at SpNode search starts from here 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); + : - search(pos, ss+1, -beta, -alpha, newDepth, false); } // Step 17. Undo move @@ -1015,23 +1066,17 @@ moves_loop: // When in check and at SpNode search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 18. Check for new best move - if (SpNode) - { - splitPoint->spinlock.acquire(); - bestValue = splitPoint->bestValue; - alpha = splitPoint->alpha; - } - - // Finished searching the move. If a stop or a cutoff occurred, the return - // value of the search cannot be trusted, and we return immediately without + // Step 18. Check for a new best move + // 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 || thisThread->cutoff_occurred()) + if (Signals.stop.load(std::memory_order_relaxed)) return VALUE_ZERO; - if (RootNode) + if (rootNode) { - RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); + RootMove& rm = *std::find(thisThread->rootMoves.begin(), + thisThread->rootMoves.end(), move); // PV move or new best move ? if (moveCount == 1 || value > alpha) @@ -1047,8 +1092,8 @@ moves_loop: // When in check and at SpNode search starts from here // We record how often the best move has been changed in each // iteration. This information is used for time management: When // the best move changes frequently, we allocate some more time. - if (moveCount > 1) - ++BestMoveChanges; + if (moveCount > 1 && thisThread == Threads.main()) + ++static_cast(thisThread)->bestMoveChanges; } else // All other moves but the PV are set to the lowest value: this is @@ -1059,75 +1104,47 @@ moves_loop: // When in check and at SpNode search starts from here if (value > bestValue) { - bestValue = SpNode ? splitPoint->bestValue = value : value; + bestValue = value; 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 = SpNode ? splitPoint->bestMove = move : move; + bestMove = move; - if (PvNode && !RootNode) // Update pv even in fail-high case - update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv); + if (PvNode && !rootNode) // Update pv even in fail-high case + update_pv(ss->pv, move, (ss+1)->pv); if (PvNode && value < beta) // Update alpha! Always alpha < beta - alpha = SpNode ? splitPoint->alpha = value : value; + alpha = value; else { assert(value >= beta); // Fail high - - if (SpNode) - splitPoint->cutoff = true; - break; } } } - if (!SpNode && !captureOrPromotion && move != bestMove && quietCount < 64) + if (!captureOrPromotion && move != bestMove && quietCount < 64) quietsSearched[quietCount++] = move; - - // Step 19. Check for splitting the search - if ( !SpNode - && Threads.size() >= 2 - && depth >= Threads.minimumSplitDepth - && ( !thisThread->activeSplitPoint - || !thisThread->activeSplitPoint->allSlavesSearching - || ( Threads.size() > MAX_SLAVES_PER_SPLITPOINT - && thisThread->activeSplitPoint->slavesMask.count() == MAX_SLAVES_PER_SPLITPOINT)) - && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD) - { - assert(bestValue > -VALUE_INFINITE && bestValue < beta); - - thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove, - depth, moveCount, &mp, NT, cutNode); - - if (Signals.stop || thisThread->cutoff_occurred()) - return VALUE_ZERO; - - if (bestValue >= beta) - break; - } } - if (SpNode) - return bestValue; - - // Following condition would detect a stop or a cutoff set 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. + // 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 || thisThread->cutoff_occurred()) + if (Signals.stop) return VALUE_DRAW; */ // Step 20. Check for mate and stalemate // All legal moves have been searched and if there are no legal moves, it - // must be mate or stalemate. If we are in a singular extension search then + // must be a mate or a stalemate. If we are in a singular extension search then // return a fail low score. if (!moveCount) bestValue = excludedMove ? alpha @@ -1137,6 +1154,24 @@ moves_loop: // When in check and at SpNode search starts from here else if (bestMove && !pos.capture_or_promotion(bestMove)) update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount); + // Bonus for prior countermove that caused the fail low + else if ( depth >= 3 * ONE_PLY + && !bestMove + && !inCheck + && !pos.captured_piece_type() + && is_ok((ss-1)->currentMove)) + { + Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); + if ((ss-2)->counterMoves) + (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); + + if ((ss-3)->counterMoves) + (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); + + if ((ss-5)->counterMoves) + (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus); + } + tte->save(posKey, value_to_tt(bestValue, ss->ply), bestValue >= beta ? BOUND_LOWER : PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, @@ -1157,7 +1192,6 @@ moves_loop: // When in check and at SpNode search starts from here const bool PvNode = NT == PV; - assert(NT == PV || NT == NonPV); assert(InCheck == !!pos.checkers()); assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); @@ -1184,7 +1218,8 @@ moves_loop: // When in check and at SpNode search starts from here // Check for an instant draw or if the maximum ply has been reached if (pos.is_draw() || 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) + : DrawValue[pos.side_to_move()]; assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -1232,7 +1267,8 @@ moves_loop: // When in check and at SpNode search starts from here } else ss->staticEval = bestValue = - (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo; + (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) + : -(ss-1)->staticEval + 2 * Eval::Tempo; // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) @@ -1254,11 +1290,11 @@ moves_loop: // When in check and at SpNode 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, History, CounterMovesHistory, to_sq((ss-1)->currentMove)); + MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove)); CheckInfo ci(pos); // Loop through the moves until no moves remain or a beta cutoff occurs - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); @@ -1317,7 +1353,7 @@ moves_loop: // When in check and at SpNode search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Check for new best move + // Check for a new best move if (value > bestValue) { bestValue = value; @@ -1327,7 +1363,7 @@ moves_loop: // When in check and at SpNode search starts from here if (PvNode) // Update pv even in fail-high case update_pv(ss->pv, move, (ss+1)->pv); - if (PvNode && value < beta) // Update alpha here! Always alpha < beta + if (PvNode && value < beta) // Update alpha here! { alpha = value; bestMove = move; @@ -1393,8 +1429,8 @@ moves_loop: // When in check and at SpNode search starts from here } - // update_stats() updates killers, history, countermove history and - // countermoves stats for a quiet best move. + // update_stats() updates killers, history, countermove and countermove plus + // follow-up move history when a new quiet best move is found. void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) { @@ -1405,34 +1441,54 @@ moves_loop: // When in check and at SpNode search starts from here ss->killers[0] = move; } - Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY)); + Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); Square prevSq = to_sq((ss-1)->currentMove); - HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq]; + CounterMoveStats* cmh = (ss-1)->counterMoves; + CounterMoveStats* fmh = (ss-2)->counterMoves; + CounterMoveStats* fmh2 = (ss-4)->counterMoves; + Thread* thisThread = pos.this_thread(); - History.update(pos.moved_piece(move), to_sq(move), bonus); + thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); - if (is_ok((ss-1)->currentMove)) + if (cmh) { - Countermoves.update(pos.piece_on(prevSq), prevSq, move); - cmh.update(pos.moved_piece(move), to_sq(move), bonus); + thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); + cmh->update(pos.moved_piece(move), to_sq(move), bonus); } + if (fmh) + fmh->update(pos.moved_piece(move), to_sq(move), bonus); + + if (fmh2) + fmh2->update(pos.moved_piece(move), to_sq(move), bonus); + // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { - History.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + + if (cmh) + cmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); - if (is_ok((ss-1)->currentMove)) - cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + if (fmh) + fmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + + if (fmh2) + fmh2->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } - // Extra penalty for TT move in previous ply when it gets refuted - if (is_ok((ss-2)->currentMove) && (ss-1)->currentMove == (ss-1)->ttMove && !pos.captured_piece_type()) + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece_type()) { - Square prevPrevSq = to_sq((ss-2)->currentMove); - HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; - ttMoveCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1); + if ((ss-2)->counterMoves) + (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); + + if ((ss-3)->counterMoves) + (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); + + if ((ss-5)->counterMoves) + (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); } } @@ -1442,32 +1498,61 @@ moves_loop: // When in check and at SpNode search starts from here Move Skill::pick_best(size_t multiPV) { - // PRNG sequence should be non-deterministic, so we seed it with the time at init - static PRNG rng(now()); + const RootMoves& rootMoves = Threads.main()->rootMoves; + static PRNG rng(now()); // PRNG sequence should be non-deterministic // RootMoves are already sorted by score in descending order - int variance = std::min(RootMoves[0].score - RootMoves[multiPV - 1].score, PawnValueMg); + Value topScore = rootMoves[0].score; + int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValueMg); int weakness = 120 - 2 * level; int maxScore = -VALUE_INFINITE; - // Choose best move. For each move score we add two terms both dependent on - // weakness. One deterministic and bigger for weaker levels, and one random, - // then we choose the move with the resulting highest score. + // Choose best move. For each move score we add two terms, both dependent on + // weakness. One is deterministic and bigger for weaker levels, and one is + // random. Then we choose the move with the resulting highest score. for (size_t i = 0; i < multiPV; ++i) { // This is our magic formula - int push = ( weakness * int(RootMoves[0].score - RootMoves[i].score) - + variance * (rng.rand() % weakness)) / 128; + 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]; + maxScore = rootMoves[i].score + push; + best = rootMoves[i].pv[0]; } } + return best; } + + // check_time() is used to print debug info and, more importantly, to detect + // when we are out of available time and thus stop the search. + + void check_time() { + + static TimePoint lastInfoTime = now(); + + int elapsed = Time.elapsed(); + TimePoint tick = Limits.startTime + elapsed; + + if (tick - lastInfoTime >= 1000) + { + lastInfoTime = tick; + dbg_print(); + } + + // An engine may not stop pondering until told so by the GUI + if (Limits.ponder) + return; + + if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10) + || (Limits.movetime && elapsed >= Limits.movetime) + || (Limits.nodes && Threads.nodes_searched() >= Limits.nodes)) + Signals.stop = true; + } + } // namespace @@ -1478,12 +1563,10 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { std::stringstream ss; int elapsed = Time.elapsed() + 1; - size_t multiPV = std::min((size_t)Options["MultiPV"], RootMoves.size()); - int selDepth = 0; - - for (Thread* th : Threads) - if (th->maxPly > selDepth) - selDepth = th->maxPly; + 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(); for (size_t i = 0; i < multiPV; ++i) { @@ -1493,7 +1576,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { continue; Depth d = updated ? depth : depth - ONE_PLY; - Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore; + Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore; bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; v = tb ? TB::Score : v; @@ -1503,15 +1586,15 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { ss << "info" << " depth " << d / ONE_PLY - << " seldepth " << selDepth + << " seldepth " << pos.this_thread()->maxPly << " multipv " << i + 1 << " score " << UCI::value(v); if (!tb && i == PVIdx) ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); - ss << " nodes " << pos.nodes_searched() - << " nps " << pos.nodes_searched() * 1000 / elapsed; + ss << " nodes " << nodes_searched + << " nps " << nodes_searched * 1000 / elapsed; if (elapsed > 1000) // Earlier makes little sense ss << " hashfull " << TT.hashfull(); @@ -1520,7 +1603,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { << " time " << elapsed << " pv"; - for (Move m : RootMoves[i].pv) + for (Move m : rootMoves[i].pv) ss << " " << UCI::move(m, pos.is_chess960()); } @@ -1544,7 +1627,8 @@ void RootMove::insert_pv_in_tt(Position& pos) { TTEntry* tte = TT.probe(pos.key(), ttHit); if (!ttHit || tte->move() != m) // Don't overwrite correct entries - tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, m, VALUE_NONE, TT.generation()); + tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, + m, VALUE_NONE, TT.generation()); pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos))); } @@ -1554,10 +1638,10 @@ void RootMove::insert_pv_in_tt(Position& pos) { } -/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move before -/// exiting the search, for instance in case we stop the search during a 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. +/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move +/// before exiting the search, for instance, in case we stop the search during a +/// 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) { @@ -1579,197 +1663,3 @@ bool RootMove::extract_ponder_from_tt(Position& pos) return false; } - - -/// Thread::idle_loop() is where the thread is parked when it has no work to do - -void Thread::idle_loop() { - - // Pointer 'this_sp' is not null only if we are called from split(), and not - // at the thread creation. This means we are the split point's master. - SplitPoint* this_sp = activeSplitPoint; - - assert(!this_sp || (this_sp->master == this && searching)); - - while (!exit && !(this_sp && this_sp->slavesMask.none())) - { - // If this thread has been assigned work, launch a search - while (searching) - { - spinlock.acquire(); - - assert(activeSplitPoint); - SplitPoint* sp = activeSplitPoint; - - spinlock.release(); - - Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) - Position pos(*sp->pos, this); - - std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack)); - ss->splitPoint = sp; - - sp->spinlock.acquire(); - - assert(activePosition == nullptr); - - activePosition = &pos; - - if (sp->nodeType == NonPV) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else if (sp->nodeType == PV) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else if (sp->nodeType == Root) - search(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode); - - else - assert(false); - - assert(searching); - - searching = false; - activePosition = nullptr; - sp->slavesMask.reset(idx); - sp->allSlavesSearching = false; - sp->nodes += pos.nodes_searched(); - - // After releasing the lock we can't access any SplitPoint related data - // in a safe way because it could have been released under our feet by - // the sp master. - sp->spinlock.release(); - - // Try to late join to another split point if none of its slaves has - // already finished. - SplitPoint* bestSp = NULL; - int minLevel = INT_MAX; - - for (Thread* th : Threads) - { - const size_t size = th->splitPointsSize; // Local copy - sp = size ? &th->splitPoints[size - 1] : nullptr; - - if ( sp - && sp->allSlavesSearching - && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT - && can_join(sp)) - { - assert(this != th); - assert(!(this_sp && this_sp->slavesMask.none())); - assert(Threads.size() > 2); - - // Prefer to join to SP with few parents to reduce the probability - // that a cut-off occurs above us, and hence we waste our work. - int level = 0; - for (SplitPoint* p = th->activeSplitPoint; p; p = p->parentSplitPoint) - level++; - - if (level < minLevel) - { - bestSp = sp; - minLevel = level; - } - } - } - - if (bestSp) - { - sp = bestSp; - - // Recheck the conditions under lock protection - sp->spinlock.acquire(); - - if ( sp->allSlavesSearching - && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT) - { - spinlock.acquire(); - - if (can_join(sp)) - { - sp->slavesMask.set(idx); - activeSplitPoint = sp; - searching = true; - } - - spinlock.release(); - } - - sp->spinlock.release(); - } - } - - // If search is finished then sleep, otherwise just yield - if (!Threads.main()->thinking) - { - assert(!this_sp); - - std::unique_lock lk(mutex); - while (!exit && !Threads.main()->thinking) - sleepCondition.wait(lk); - } - else - std::this_thread::yield(); // Wait for a new job or for our slaves to finish - } -} - - -/// check_time() is called by the timer thread when the timer triggers. It is -/// used to print debug info and, more importantly, to detect when we are out of -/// available time and thus stop the search. - -void check_time() { - - static TimePoint lastInfoTime = now(); - int elapsed = Time.elapsed(); - - if (now() - lastInfoTime >= 1000) - { - lastInfoTime = now(); - dbg_print(); - } - - // An engine may not stop pondering until told so by the GUI - if (Limits.ponder) - return; - - if (Limits.use_time_management()) - { - bool stillAtFirstMove = Signals.firstRootMove - && !Signals.failedLowAtRoot - && elapsed > Time.available() * 75 / 100; - - if ( stillAtFirstMove - || elapsed > Time.maximum() - 2 * TimerThread::Resolution) - Signals.stop = true; - } - else if (Limits.movetime && elapsed >= Limits.movetime) - Signals.stop = true; - - else if (Limits.nodes) - { - int64_t nodes = RootPos.nodes_searched(); - - // Loop across all split points and sum accumulated SplitPoint nodes plus - // all the currently active positions nodes. - // FIXME: Racy... - for (Thread* th : Threads) - for (size_t i = 0; i < th->splitPointsSize; ++i) - { - SplitPoint& sp = th->splitPoints[i]; - - sp.spinlock.acquire(); - - nodes += sp.nodes; - - for (size_t idx = 0; idx < Threads.size(); ++idx) - if (sp.slavesMask.test(idx) && Threads[idx]->activePosition) - nodes += Threads[idx]->activePosition->nodes_searched(); - - sp.spinlock.release(); - } - - if (nodes >= Limits.nodes) - Signals.stop = true; - } -}