X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=567f87660197e719cf83ab492191bd3d26945b30;hp=1ffe1e97adb7291f532c1dce631adaad22f6a86c;hb=07b5a28a68b4cc67f1447fce85fc910aa209b319;hpb=847bc0e80fa78a81b028515da03a90ea4dd40458 diff --git a/src/search.cpp b/src/search.cpp index 1ffe1e97..567f8766 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -2,7 +2,7 @@ Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -39,7 +39,6 @@ namespace Search { - SignalsType Signals; LimitsType Limits; } @@ -63,8 +62,13 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV }; + // Sizes and phases of the skip-blocks, used for distributing search depths across the threads + const int skipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 }; + const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 }; + // Razoring and futility margin based on depth - const int razor_margin[4] = { 483, 570, 603, 554 }; + // razor_margin[0] is unused as long as depth >= ONE_PLY in search + const int razor_margin[] = { 0, 570, 603, 554 }; Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); } // Futility and reductions lookup tables, initialized at startup @@ -75,6 +79,12 @@ namespace { return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY; } + // History and stats update bonus, based on depth + int stat_bonus(Depth depth) { + int d = depth / ONE_PLY; + return d > 17 ? 0 : d * d + 2 * d - 2; + } + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} @@ -87,8 +97,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager structure is used to detect an 'easy move'. When the PV is - // stable across multiple search iterations, we can quickly return the best move. + // EasyMoveManager structure is used to detect an 'easy move'. When the PV is stable + // across multiple search iterations, we can quickly return the best move. struct EasyMoveManager { void clear() { @@ -121,43 +131,11 @@ namespace { } } - int stableCnt; Key expectedPosKey; + int stableCnt; Move pv[3]; }; - // Set of rows with half bits set to 1 and half to 0. It is used to allocate - // the search depths across the threads. - typedef std::vector Row; - - const Row HalfDensity[] = { - {0, 1}, - {1, 0}, - {0, 0, 1, 1}, - {0, 1, 1, 0}, - {1, 1, 0, 0}, - {1, 0, 0, 1}, - {0, 0, 0, 1, 1, 1}, - {0, 0, 1, 1, 1, 0}, - {0, 1, 1, 1, 0, 0}, - {1, 1, 1, 0, 0, 0}, - {1, 1, 0, 0, 0, 1}, - {1, 0, 0, 0, 1, 1}, - {0, 0, 0, 0, 1, 1, 1, 1}, - {0, 0, 0, 1, 1, 1, 1, 0}, - {0, 0, 1, 1, 1, 1, 0 ,0}, - {0, 1, 1, 1, 1, 0, 0 ,0}, - {1, 1, 1, 1, 0, 0, 0 ,0}, - {1, 1, 1, 0, 0, 0, 0 ,1}, - {1, 1, 0, 0, 0, 0, 1 ,1}, - {1, 0, 0, 0, 0, 1, 1 ,1}, - }; - - Value bonus(Depth depth) { int d = depth / ONE_PLY ; return Value(d * d + 2 * d - 2); } - Value penalty(Depth depth) { int d = depth / ONE_PLY ; return -Value(d * d + 4 * d + 1); } - - const size_t HalfDensitySize = std::extent::value; - EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; @@ -165,14 +143,39 @@ namespace { Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); template - Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus); - void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus); - void check_time(); + 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); + + // 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 @@ -185,7 +188,7 @@ void Search::init() { for (int d = 1; d < 64; ++d) for (int mc = 1; mc < 64; ++mc) { - double r = log(d) * log(mc) / 2; + double r = log(d) * log(mc) / 1.95; Reductions[NonPV][imp][d][mc] = int(std::round(r)); Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0); @@ -197,67 +200,44 @@ void Search::init() { for (int d = 0; d < 16; ++d) { - FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8)); - FutilityMoveCounts[1][d] = int(2.9 + 1.045 * pow(d + 0.49, 1.8)); + FutilityMoveCounts[0][d] = int(2.4 + 0.74 * pow(d, 1.78)); + FutilityMoveCounts[1][d] = int(5.0 + 1.00 * pow(d, 2.00)); } } -/// Search::clear() resets search state to zero, to obtain reproducible results +/// Search::clear() resets search state to its initial value void Search::clear() { + Threads.main()->wait_for_search_finished(); + + Time.availableNodes = 0; TT.clear(); for (Thread* th : Threads) - { - th->history.clear(); - th->counterMoves.clear(); - th->fromTo.clear(); - th->counterMoveHistory.clear(); - th->resetCalls = true; - } + th->clear(); + 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; -} - -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); @@ -265,7 +245,7 @@ void MainThread::search() { 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; @@ -279,30 +259,30 @@ 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 @@ -312,9 +292,15 @@ void MainThread::search() { && rootMoves[0].pv[0] != MOVE_NONE) { for (Thread* th : Threads) - if ( th->completedDepth > bestThread->completedDepth - && th->rootMoves[0].score > bestThread->rootMoves[0].score) + { + Depth depthDiff = th->completedDepth - bestThread->completedDepth; + Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score; + + // 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; + } } previousScore = bestThread->rootMoves[0].score; @@ -332,22 +318,23 @@ void MainThread::search() { } -// Thread::search() is the main iterative deepening loop. It calls search() -// repeatedly with increasing depth until the allocated thinking time has been -// consumed, the user stops the search, or the maximum search depth is reached. +/// Thread::search() is the main iterative deepening loop. It calls search() +/// repeatedly with increasing depth until the allocated thinking time has been +/// consumed, the user stops the search, or the maximum search depth is reached. void Thread::search() { - Stack stack[MAX_PLY+7], *ss = stack+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; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); std::memset(ss-4, 0, 7 * sizeof(Stack)); + for (int i = 4; i > 0; i--) + (ss-i)->contHistory = &this->contHistory[NO_PIECE][0]; // Use as sentinel bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; - completedDepth = DEPTH_ZERO; if (mainThread) { @@ -355,7 +342,6 @@ void Thread::search() { EasyMove.clear(); mainThread->easyMovePlayed = mainThread->failedLow = false; mainThread->bestMoveChanges = 0; - TT.new_search(); } size_t multiPV = Options["MultiPV"]; @@ -370,16 +356,15 @@ void Thread::search() { // Iterative deepening loop until requested to stop or the target depth is reached while ( (rootDepth += ONE_PLY) < DEPTH_MAX - && !Signals.stop - && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth)) + && !Threads.stop + && !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth)) { - // Set up the new depths for the helper threads skipping on average every - // 2nd ply (using a half-density matrix). - if (!mainThread) + // Distribute search depths across the threads + if (idx) { - const Row& row = HalfDensity[(idx - 1) % HalfDensitySize]; - if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()]) - continue; + int i = (idx - 1) % 20; + if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2) + continue; } // Age out PV variability metric @@ -392,8 +377,11 @@ 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) { @@ -417,10 +405,10 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // If search has been stopped, break immediately. Sorting and + // If search has been stopped, we break immediately. Sorting and // writing PV back to TT is safe because RootMoves is still // valid, although it refers to the previous iteration. - if (Signals.stop) + if (Threads.stop) break; // When failing high/low give some update (without cluttering @@ -441,14 +429,11 @@ 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; @@ -460,16 +445,20 @@ 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; + // 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; @@ -477,16 +466,10 @@ 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 @@ -499,7 +482,7 @@ void Thread::search() { bool doEasyMove = rootMoves[0].pv[0] == easyMove && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.optimum() * 5 / 42; + && Time.elapsed() > Time.optimum() * 5 / 44; if ( rootMoves.size() == 1 || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628 @@ -507,10 +490,10 @@ void Thread::search() { { // 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; } } @@ -544,7 +527,7 @@ 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)); @@ -558,46 +541,31 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, nullValue; + Value bestValue, value, ttValue, eval; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning; - Piece moved_piece; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact; + Piece movedPiece; int moveCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); - moveCount = quietCount = ss->moveCount = 0; - ss->history = VALUE_ZERO; + moveCount = quietCount = ss->moveCount = 0; + ss->statScore = 0; bestValue = -VALUE_INFINITE; - ss->ply = (ss-1)->ply + 1; // Check for the available remaining time - if (thisThread->resetCalls.load(std::memory_order_relaxed)) - { - thisThread->resetCalls = false; - // At low node count increase the checking rate to about 0.1% of nodes - // otherwise use a default value. - thisThread->callsCnt = Limits.nodes ? std::min((int64_t)4096, Limits.nodes / 1024) - : 4096; - } + if (thisThread == Threads.main()) + static_cast(thisThread)->check_time(); - if (--thisThread->callsCnt <= 0) - { - for (Thread* th : Threads) - th->resetCalls = true; - - 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 >= MAX_PLY) + 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) : DrawValue[pos.side_to_move()]; @@ -615,8 +583,9 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); + (ss+1)->ply = ss->ply + 1; ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->counterMoves = nullptr; + ss->contHistory = &thisThread->contHistory[NO_PIECE][0]; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; Square prevSq = to_sq((ss-1)->currentMove); @@ -638,15 +607,25 @@ namespace { && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) { - // If ttMove is quiet, update killers, history, counter move on TT hit - if (ttValue >= beta && ttMove) + // If ttMove is quiet, update move sorting heuristics on TT hit + if (ttMove) { - if (!pos.capture_or_promotion(ttMove)) - update_stats(pos, ss, ttMove, nullptr, 0, bonus(depth)); + if (ttValue >= beta) + { + if (!pos.capture_or_promotion(ttMove)) + update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth)); + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + 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->mainHistory.update(pos.side_to_move(), ttMove, penalty); + update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); + } } return ttValue; } @@ -654,10 +633,10 @@ namespace { // Step 4a. Tablebase probe if (!rootNode && TB::Cardinality) { - int piecesCnt = pos.count(WHITE) + pos.count(BLACK); + int piecesCount = pos.count(); - if ( piecesCnt <= TB::Cardinality - && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) + if ( piecesCount <= TB::Cardinality + && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth) && pos.rule50_count() == 0 && !pos.can_castle(ANY_CASTLING)) { @@ -666,12 +645,12 @@ namespace { if (err != TB::ProbeState::FAIL) { - thisThread->tbHits++; + thisThread->tbHits.fetch_add(1, std::memory_order_relaxed); int drawScore = TB::UseRule50 ? 1 : 0; - value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply - : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply + value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1 + : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1 : VALUE_DRAW + 2 * v * drawScore; tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT, @@ -697,9 +676,9 @@ 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 { @@ -717,14 +696,13 @@ namespace { // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && ttMove == MOVE_NONE && eval + razor_margin[depth / ONE_PLY] <= alpha) { if (depth <= ONE_PLY) - return qsearch(pos, ss, alpha, beta, DEPTH_ZERO); + return qsearch(pos, ss, alpha, alpha+1); Value ralpha = alpha - razor_margin[depth / ONE_PLY]; - Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); + Value v = qsearch(pos, ss, ralpha, ralpha+1); if (v <= ralpha) return v; } @@ -743,17 +721,18 @@ namespace { && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY) && pos.non_pawn_material(pos.side_to_move())) { - ss->currentMove = MOVE_NULL; - ss->counterMoves = nullptr; assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; + ss->currentMove = MOVE_NULL; + ss->contHistory = &thisThread->contHistory[NO_PIECE][0]; + pos.do_null_move(st); - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); + Value nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); pos.undo_null_move(); if (nullValue >= beta) @@ -766,7 +745,7 @@ namespace { return nullValue; // Do verification search at high depths - Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta, DEPTH_ZERO) + Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta) : search(pos, ss, beta-1, beta, depth-R, false, true); if (v >= beta) @@ -782,11 +761,8 @@ namespace { && abs(beta) < VALUE_MATE_IN_MAX_PLY) { Value rbeta = std::min(beta + 200, VALUE_INFINITE); - Depth rdepth = depth - 4 * ONE_PLY; - assert(rdepth >= ONE_PLY); - assert((ss-1)->currentMove != MOVE_NONE); - assert((ss-1)->currentMove != MOVE_NULL); + assert(is_ok((ss-1)->currentMove)); MovePicker mp(pos, ttMove, rbeta - ss->staticEval); @@ -794,9 +770,11 @@ namespace { if (pos.legal(move)) { ss->currentMove = move; - ss->counterMoves = &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); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false); + value = -search(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false); pos.undo_move(move); if (value >= rbeta) return value; @@ -817,11 +795,10 @@ namespace { moves_loop: // When in check search starts from here - const CounterMoveStats* cmh = (ss-1)->counterMoves; - const CounterMoveStats* fmh = (ss-2)->counterMoves; - const CounterMoveStats* fmh2 = (ss-4)->counterMoves; + const PieceToHistory* 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, 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 */ @@ -834,10 +811,13 @@ moves_loop: // When in check search starts from here && !excludedMove // Recursive singular search is not allowed && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; + skipQuiets = false; + 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 - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move(skipQuiets)) != MOVE_NONE) { assert(is_ok(move)); @@ -863,7 +843,7 @@ 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) @@ -872,20 +852,15 @@ moves_loop: // When in check search starts from here moveCountPruning = depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY]; - // Step 12. Extend checks - if ( givesCheck - && !moveCountPruning - && pos.see_ge(move, VALUE_ZERO)) - extension = ONE_PLY; + // Step 12. Singular and Gives Check Extensions // Singular extension search. If all moves but one fail low on a search of // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move // is singular and should be extended. To verify this we do a reduced search // on all the other moves but the ttMove and if the result is lower than - // ttValue minus a margin then we extend the ttMove. + // ttValue minus a margin then we will extend the ttMove. if ( singularExtensionNode && move == ttMove - && !extension && pos.legal(move)) { Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); @@ -897,30 +872,37 @@ moves_loop: // When in check search starts from here if (value < rBeta) extension = ONE_PLY; } + else if ( givesCheck + && !moveCountPruning + && pos.see_ge(move)) + extension = ONE_PLY; - // Update the current move (this must be done after singular extension search) + // Calculate new depth for this move newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth if ( !rootNode + && pos.non_pawn_material(pos.side_to_move()) && bestValue > VALUE_MATED_IN_MAX_PLY) { if ( !captureOrPromotion && !givesCheck - && !pos.advanced_pawn_push(move)) + && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000))) { // Move count based pruning if (moveCountPruning) + { + skipQuiets = true; continue; + } // Reduced depth of the next LMR search int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY; // Countermoves based pruning if ( lmrDepth < 3 - && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh))) + && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold + && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) continue; // Futility pruning: parent node @@ -934,12 +916,10 @@ moves_loop: // When in check search starts from here && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth))) continue; } - else if (depth < 7 * ONE_PLY && !extension) - { - Value v = -Value(400 - 100 * PvNode + 35 * depth / ONE_PLY * depth / ONE_PLY); - if (!pos.see_ge(move, v)) + else if ( depth < 7 * ONE_PLY + && !extension + && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) continue; - } } // Speculative prefetch as early as possible @@ -952,8 +932,12 @@ moves_loop: // When in check search starts from here continue; } + if (move == ttMove && captureOrPromotion) + ttCapture = true; + + // Update the current move (this must be done after singular extension search) ss->currentMove = move; - ss->counterMoves = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; + ss->contHistory = &thisThread->contHistory[movedPiece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -970,6 +954,18 @@ 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; + // Increase reduction for cut nodes if (cutNode) r += 2 * ONE_PLY; @@ -977,26 +973,25 @@ moves_loop: // When in check search starts from here // Decrease reduction for moves that escape a capture. Filter out // castling moves, because they are coded as "king captures rook" and // hence break make_move(). - else if ( type_of(move) == NORMAL - && !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO)) + else if ( type_of(move) == NORMAL + && !pos.see_ge(make_move(to_sq(move), from_sq(move)))) r -= 2 * ONE_PLY; - ss->history = thisThread->history[moved_piece][to_sq(move)] - + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO) - + thisThread->fromTo.get(~pos.side_to_move(), move) - - 8000; // 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->history > VALUE_ZERO && (ss-1)->history < VALUE_ZERO) + if (ss->statScore >= 0 && (ss-1)->statScore < 0) r -= ONE_PLY; - else if (ss->history < VALUE_ZERO && (ss-1)->history > VALUE_ZERO) + else if ((ss-1)->statScore >= 0 && ss->statScore < 0) r += ONE_PLY; // Decrease/increase reduction for moves with a good/bad history - r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->history / 20000) * ONE_PLY); + r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY); } Depth d = std::max(newDepth - r, ONE_PLY); @@ -1011,8 +1006,8 @@ moves_loop: // When in check search starts from here // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha) + : -qsearch(pos, ss+1, -(alpha+1), -alpha) : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false); // For PV nodes only, do a full PV search on the first move or after a fail @@ -1024,8 +1019,8 @@ moves_loop: // When in check search starts from here (ss+1)->pv[0] = MOVE_NONE; value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha) + : -qsearch(pos, ss+1, -beta, -alpha) : - search(pos, ss+1, -beta, -alpha, newDepth, false, false); } @@ -1038,7 +1033,7 @@ 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) @@ -1050,6 +1045,7 @@ 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); @@ -1064,8 +1060,8 @@ 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; } @@ -1076,13 +1072,6 @@ moves_loop: // When in check search starts from here if (value > alpha) { - // If there is an easy move for this position, clear it if unstable - if ( PvNode - && thisThread == Threads.main() - && EasyMove.get(pos.key()) - && (move != EasyMove.get(pos.key()) || moveCount > 1)) - EasyMove.clear(); - bestMove = move; if (PvNode && !rootNode) // Update pv even in fail-high case @@ -1106,7 +1095,7 @@ moves_loop: // When in check search starts from here // 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; */ @@ -1122,25 +1111,25 @@ moves_loop: // When in check search starts from here : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; else if (bestMove) { - - // Quiet best move: update killers, history and countermoves + // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus(depth)); + update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); // Extra penalty for a quiet TT move in previous ply when it gets refuted if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth)); + 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, bonus(depth)); + update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); - tte->save(posKey, value_to_tt(bestValue, ss->ply), - bestValue >= beta ? BOUND_LOWER : - PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval, TT.generation()); + if (!excludedMove) + tte->save(posKey, value_to_tt(bestValue, ss->ply), + bestValue >= beta ? BOUND_LOWER : + PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->staticEval, TT.generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1149,8 +1138,7 @@ moves_loop: // When in check search starts from here // qsearch() is the quiescence search function, which is called by the main - // search function when the remaining depth is zero (or, to be more precise, - // less than ONE_PLY). + // search function with depth zero, or recursively with depth less than ONE_PLY. template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { @@ -1171,6 +1159,7 @@ moves_loop: // When in check search starts from here Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; bool ttHit, givesCheck, evasionPrunable; Depth ttDepth; + int moveCount; if (PvNode) { @@ -1180,10 +1169,11 @@ 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 >= MAX_PLY) + if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -1194,7 +1184,6 @@ 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); @@ -1224,9 +1213,9 @@ 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 = @@ -1253,7 +1242,7 @@ 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, 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) @@ -1264,6 +1253,8 @@ moves_loop: // When in check search starts from here ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move) : pos.gives_check(move); + moveCount++; + // Futility pruning if ( !InCheck && !givesCheck @@ -1289,13 +1280,14 @@ moves_loop: // When in check search starts from here // Detect non-capture evasions that are candidates to be pruned evasionPrunable = InCheck + && (depth != DEPTH_ZERO || moveCount > 2) && bestValue > VALUE_MATED_IN_MAX_PLY && !pos.capture(move); // Don't search moves with negative SEE values if ( (!InCheck || evasionPrunable) && type_of(move) != PROMOTION - && !pos.see_ge(move, VALUE_ZERO)) + && !pos.see_ge(move)) continue; // Speculative prefetch as early as possible @@ -1303,7 +1295,10 @@ moves_loop: // When in check search starts from here // Check for legality just before making the move if (!pos.legal(move)) + { + moveCount--; continue; + } ss->currentMove = move; @@ -1391,30 +1386,21 @@ moves_loop: // When in check search starts from here } - // update_cm_stats() updates countermove and follow-up move history - - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) { - - CounterMoveStats* cmh = (ss-1)->counterMoves; - CounterMoveStats* fmh1 = (ss-2)->counterMoves; - CounterMoveStats* fmh2 = (ss-4)->counterMoves; + // update_continuation_histories() updates histories of the move pairs formed + // by moves at ply -1, -2, and -4 with current move. - if (cmh) - cmh->update(pc, s, bonus); + void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) { - if (fmh1) - fmh1->update(pc, s, bonus); - - if (fmh2) - fmh2->update(pc, s, bonus); + for (int i : {1, 2, 4}) + if (is_ok((ss-i)->currentMove)) + (ss-i)->contHistory->update(pc, to, bonus); } - // update_stats() updates killers, history, countermove and countermove plus - // follow-up move history when a new quiet best move is found. + // update_stats() updates move sorting heuristics when a new quiet best move is found void update_stats(const Position& pos, Stack* ss, Move move, - Move* quiets, int quietsCnt, Value bonus) { + Move* quiets, int quietsCnt, int bonus) { if (ss->killers[0] != move) { @@ -1424,22 +1410,20 @@ moves_loop: // When in check search starts from here Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - thisThread->fromTo.update(c, move, bonus); - thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); - 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 ((ss-1)->counterMoves) + if (is_ok((ss-1)->currentMove)) { Square prevSq = to_sq((ss-1)->currentMove); - thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); + thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move; } // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { - thisThread->fromTo.update(c, quiets[i], -bonus); - thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); - 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); } } @@ -1477,11 +1461,19 @@ moves_loop: // When in check search starts from here return best; } +} // namespace // 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() { + void MainThread::check_time() { + + if (--callsCnt > 0) + return; + + // At low node count increase the checking rate to about 0.1% of nodes + // otherwise use a default value. + callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) : 4096; static TimePoint lastInfoTime = now(); @@ -1495,17 +1487,15 @@ 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) + if ( (Limits.use_time_management() && elapsed > Time.maximum()) || (Limits.movetime && elapsed >= Limits.movetime) || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes)) - Signals.stop = true; + Threads.stop = true; } -} // namespace - /// UCI::pv() formats PV information according to the UCI protocol. UCI requires /// that all (if any) unsearched PV lines are sent using a previous search score. @@ -1522,7 +1512,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { for (size_t i = 0; i < multiPV; ++i) { - bool updated = (i <= PVIdx); + bool updated = (i <= PVIdx && rootMoves[i].score != -VALUE_INFINITE); if (depth == ONE_PLY && !updated) continue; @@ -1538,7 +1528,7 @@ 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);