X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=fc877f3040d0923943a2a21c34f64af2a24b6bbc;hp=1279fe9c588b837ff1664fbe44d0b9c8459f4567;hb=0c1f119069bf915b85126159d4865c4bcc532239;hpb=52cb3480230cc3142a2adca37a2f5ce733d0769b diff --git a/src/search.cpp b/src/search.cpp index 1279fe9c..fc877f30 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 @@ -63,18 +63,32 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV }; + // Sizes and phases of the skip-blocks, used for distributing search depths across the threads + const int skipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 }; + const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 }; + // Razoring and futility margin based on depth - const int razor_margin[4] = { 483, 570, 603, 554 }; + // razor_margin[0] is unused as long as depth >= ONE_PLY in search + const int razor_margin[] = { 0, 570, 603, 554 }; Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); } // Futility and reductions lookup tables, initialized at startup int FutilityMoveCounts[2][16]; // [improving][depth] int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] + // Threshold used for countermoves based pruning + const int CounterMovePruneThreshold = 0; + template Depth reduction(bool i, Depth d, int mn) { return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY; } + // History and stats update bonus, based on depth + int stat_bonus(Depth depth) { + int d = depth / ONE_PLY ; + return d > 17 ? 0 : d * d + 2 * d - 2; + } + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} @@ -87,8 +101,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager structure is used to detect an 'easy move'. When the PV is - // stable across multiple search iterations, we can quickly return the best move. + // EasyMoveManager structure is used to detect an 'easy move'. When the PV is stable + // across multiple search iterations, we can quickly return the best move. struct EasyMoveManager { void clear() { @@ -113,8 +127,8 @@ namespace { std::copy(newPv.begin(), newPv.begin() + 3, pv); StateInfo st[2]; - pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0])); - pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1])); + pos.do_move(newPv[0], st[0]); + pos.do_move(newPv[1], st[1]); expectedPosKey = pos.key(); pos.undo_move(newPv[1]); pos.undo_move(newPv[0]); @@ -126,49 +140,20 @@ namespace { Move pv[3]; }; - // Set of rows with half bits set to 1 and half to 0. It is used to allocate - // the search depths across the threads. - typedef std::vector Row; - - const Row HalfDensity[] = { - {0, 1}, - {1, 0}, - {0, 0, 1, 1}, - {0, 1, 1, 0}, - {1, 1, 0, 0}, - {1, 0, 0, 1}, - {0, 0, 0, 1, 1, 1}, - {0, 0, 1, 1, 1, 0}, - {0, 1, 1, 1, 0, 0}, - {1, 1, 1, 0, 0, 0}, - {1, 1, 0, 0, 0, 1}, - {1, 0, 0, 0, 1, 1}, - {0, 0, 0, 0, 1, 1, 1, 1}, - {0, 0, 0, 1, 1, 1, 1, 0}, - {0, 0, 1, 1, 1, 1, 0 ,0}, - {0, 1, 1, 1, 1, 0, 0 ,0}, - {1, 1, 1, 1, 0, 0, 0 ,0}, - {1, 1, 1, 0, 0, 0, 0 ,1}, - {1, 1, 0, 0, 0, 0, 1 ,1}, - {1, 0, 0, 0, 0, 1, 1 ,1}, - }; - - const size_t HalfDensitySize = std::extent::value; - EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); template - Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus); - void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus); + void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus); + void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus); void check_time(); } // namespace @@ -182,7 +167,7 @@ void Search::init() { for (int d = 1; d < 64; ++d) for (int mc = 1; mc < 64; ++mc) { - double r = log(d) * log(mc) / 2; + 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); @@ -194,8 +179,8 @@ 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)); } } @@ -208,11 +193,13 @@ void Search::clear() { for (Thread* th : Threads) { - th->history.clear(); th->counterMoves.clear(); - th->fromTo.clear(); + th->history.clear(); th->counterMoveHistory.clear(); th->resetCalls = true; + CounterMoveStats& cm = th->counterMoveHistory[NO_PIECE][0]; + int* t = &cm[NO_PIECE][0]; + std::fill(t, t + sizeof(cm), CounterMovePruneThreshold - 1); } Threads.main()->previousScore = VALUE_INFINITE; @@ -234,7 +221,7 @@ uint64_t Search::perft(Position& pos, Depth depth) { cnt = 1, nodes++; else { - pos.do_move(m, st, pos.gives_check(m)); + pos.do_move(m, st); cnt = leaf ? MoveList(pos).size() : perft(pos, depth - ONE_PLY); nodes += cnt; pos.undo_move(m); @@ -309,9 +296,13 @@ void MainThread::search() { && rootMoves[0].pv[0] != MOVE_NONE) { for (Thread* th : Threads) - if ( th->completedDepth > bestThread->completedDepth - && th->rootMoves[0].score > bestThread->rootMoves[0].score) + { + Depth depthDiff = th->completedDepth - bestThread->completedDepth; + Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score; + + if (scoreDiff > 0 && depthDiff >= 0) bestThread = th; + } } previousScore = bestThread->rootMoves[0].score; @@ -329,18 +320,20 @@ void MainThread::search() { } -// Thread::search() is the main iterative deepening loop. It calls search() -// repeatedly with increasing depth until the allocated thinking time has been -// consumed, the user stops the search, or the maximum search depth is reached. +/// Thread::search() is the main iterative deepening loop. It calls search() +/// repeatedly with increasing depth until the allocated thinking time has been +/// consumed, the user stops the search, or the maximum search depth is reached. void Thread::search() { - Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2) + Stack stack[MAX_PLY+7], *ss = stack+4; // To allow referencing (ss-4) and (ss+2) Value bestValue, alpha, beta, delta; Move easyMove = MOVE_NONE; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - std::memset(ss-5, 0, 8 * sizeof(Stack)); + std::memset(ss-4, 0, 7 * sizeof(Stack)); + for(int i = 4; i > 0; i--) + (ss-i)->counterMoves = &this->counterMoveHistory[NO_PIECE][0]; // Use as sentinel bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -370,13 +363,12 @@ void Thread::search() { && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth)) { - // Set up the new depths for the helper threads skipping on average every - // 2nd ply (using a half-density matrix). - if (!mainThread) + // Distribute search depths across the threads + if (idx) { - const Row& row = HalfDensity[(idx - 1) % HalfDensitySize]; - if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()]) - continue; + int i = (idx - 1) % 20; + if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2) + continue; } // Age out PV variability metric @@ -404,7 +396,7 @@ void Thread::search() { // high/low anymore. while (true) { - bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false, false); // Bring the best move to the front. It is critical that sorting // is done with a stable algorithm because all the values but the @@ -414,7 +406,7 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // If search has been stopped, break immediately. Sorting and + // If search has been stopped, we break immediately. Sorting and // writing PV back to TT is safe because RootMoves is still // valid, although it refers to the previous iteration. if (Signals.stop) @@ -496,7 +488,7 @@ 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 @@ -538,7 +530,7 @@ namespace { // search<>() is the main search function for both PV and non-PV nodes template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) { const bool PvNode = NT == PV; const bool rootNode = PvNode && (ss-1)->ply == 0; @@ -555,17 +547,17 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, nullValue; + Value bestValue, value, ttValue, eval; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets; Piece moved_piece; int moveCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); - moveCount = quietCount = ss->moveCount = 0; - ss->history = VALUE_ZERO; + moveCount = quietCount = ss->moveCount = 0; + ss->history = 0; bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; @@ -573,9 +565,14 @@ namespace { if (thisThread->resetCalls.load(std::memory_order_relaxed)) { thisThread->resetCalls = false; - thisThread->callsCnt = 0; + + // At low node count increase the checking rate to about 0.1% of nodes + // otherwise use a default value. + thisThread->callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) + : 4096; } - if (++thisThread->callsCnt > 4096) + + if (--thisThread->callsCnt <= 0) { for (Thread* th : Threads) th->resetCalls = true; @@ -590,7 +587,7 @@ namespace { if (!rootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) + if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -609,9 +606,9 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->counterMoves = nullptr; - (ss+1)->skipEarlyPruning = false; + ss->counterMoves = &thisThread->counterMoveHistory[NO_PIECE][0]; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + Square prevSq = to_sq((ss-1)->currentMove); // Step 4. Transposition table lookup. We don't want the score of a partial // search to overwrite a previous full search TT value, so we use a different @@ -631,23 +628,24 @@ 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) { - int d = depth / ONE_PLY; - - if (!pos.capture_or_promotion(ttMove)) + if (ttValue >= beta) { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, ttMove, nullptr, 0, bonus); - } + if (!pos.capture_or_promotion(ttMove)) + update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + } + // Penalty for a quiet ttMove that fails low + else if (!pos.capture_or_promotion(ttMove)) { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); + int penalty = -stat_bonus(depth); + thisThread->history.update(pos.side_to_move(), ttMove, penalty); + update_cm_stats(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } return ttValue; @@ -656,10 +654,10 @@ 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)) { @@ -713,20 +711,19 @@ namespace { ss->staticEval, TT.generation()); } - if (ss->skipEarlyPruning) + if (skipEarlyPruning) goto moves_loop; // Step 6. Razoring (skipped when in check) if ( !PvNode && depth < 4 * ONE_PLY - && ttMove == MOVE_NONE && eval + razor_margin[depth / ONE_PLY] <= alpha) { if (depth <= ONE_PLY) - 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; } @@ -745,19 +742,18 @@ 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->counterMoves = &thisThread->counterMoveHistory[NO_PIECE][0]; + pos.do_null_move(st); - (ss+1)->skipEarlyPruning = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); - (ss+1)->skipEarlyPruning = false; + Value nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); pos.undo_null_move(); if (nullValue >= beta) @@ -770,10 +766,8 @@ namespace { return nullValue; // Do verification search at high depths - ss->skipEarlyPruning = true; - Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta, DEPTH_ZERO) - : search(pos, ss, beta-1, beta, depth-R, false); - ss->skipEarlyPruning = false; + Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta) + : search(pos, ss, beta-1, beta, depth-R, false, true); if (v >= beta) return nullValue; @@ -791,8 +785,7 @@ namespace { 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); @@ -801,8 +794,9 @@ namespace { { ss->currentMove = move; ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; - pos.do_move(move, st, pos.gives_check(move)); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + + pos.do_move(move, st); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false); pos.undo_move(move); if (value >= rbeta) return value; @@ -815,9 +809,7 @@ namespace { && (PvNode || ss->staticEval + 256 >= beta)) { Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY; - ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d, cutNode); - ss->skipEarlyPruning = false; + search(pos, ss, alpha, beta, d, cutNode, true); tte = TT.probe(posKey, ttHit); ttMove = ttHit ? tte->move() : MOVE_NONE; @@ -825,9 +817,9 @@ namespace { moves_loop: // When in check search starts from here - const CounterMoveStats* cmh = (ss-1)->counterMoves; - const CounterMoveStats* fmh = (ss-2)->counterMoves; - const CounterMoveStats* fmh2 = (ss-4)->counterMoves; + const CounterMoveStats& cmh = *(ss-1)->counterMoves; + const CounterMoveStats& fmh = *(ss-2)->counterMoves; + const CounterMoveStats& fm2 = *(ss-4)->counterMoves; MovePicker mp(pos, ttMove, depth, ss); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc @@ -842,10 +834,11 @@ moves_loop: // When in check search starts from here && !excludedMove // Recursive singular search is not allowed && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; + skipQuiets = false; // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs - while ((move = mp.next_move()) != MOVE_NONE) + while ((move = mp.next_move(skipQuiets)) != MOVE_NONE) { assert(is_ok(move)); @@ -880,57 +873,57 @@ 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); Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY; ss->excludedMove = move; - ss->skipEarlyPruning = true; - value = search(pos, ss, rBeta - 1, rBeta, d, cutNode); - ss->skipEarlyPruning = false; + value = search(pos, ss, rBeta - 1, rBeta, d, cutNode, true); ss->excludedMove = MOVE_NONE; if (value < rBeta) extension = ONE_PLY; } + else if ( givesCheck + && !moveCountPruning + && pos.see_ge(move)) + extension = ONE_PLY; - // Update the current move (this must be done after singular extension search) + // Calculate new depth for this move newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth if ( !rootNode + && pos.non_pawn_material(pos.side_to_move()) && bestValue > VALUE_MATED_IN_MAX_PLY) { if ( !captureOrPromotion && !givesCheck - && !pos.advanced_pawn_push(move)) + && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000))) { // Move count based pruning if (moveCountPruning) + { + skipQuiets = true; continue; + } // Reduced depth of the next LMR search int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY; // Countermoves based pruning if ( lmrDepth < 3 - && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO) - && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh))) + && (cmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold) + && (fmh[moved_piece][to_sq(move)] < CounterMovePruneThreshold)) continue; // Futility pruning: parent node @@ -944,9 +937,9 @@ moves_loop: // When in check search starts from here && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth))) continue; } - else if ( depth < 7 * ONE_PLY + else if ( depth < 7 * ONE_PLY && !extension - && !pos.see_ge(move, Value(-35 * depth / ONE_PLY * depth / ONE_PLY))) + && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) continue; } @@ -960,6 +953,7 @@ moves_loop: // When in check search starts from here continue; } + // Update the current move (this must be done after singular extension search) ss->currentMove = move; ss->counterMoves = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; @@ -984,25 +978,22 @@ moves_loop: // When in check search starts from here // Decrease reduction for moves that escape a capture. Filter out // castling moves, because they are coded as "king captures rook" and - // hence break make_move(). Also use see() instead of see_sign(), - // because the destination square is empty. - else if ( type_of(move) == NORMAL - && type_of(pos.piece_on(to_sq(move))) != PAWN - && !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO)) + // hence break make_move(). + else if ( type_of(move) == NORMAL + && !pos.see_ge(make_move(to_sq(move), from_sq(move)))) r -= 2 * ONE_PLY; - ss->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->history = cmh[moved_piece][to_sq(move)] + + fmh[moved_piece][to_sq(move)] + + fm2[moved_piece][to_sq(move)] + + thisThread->history.get(~pos.side_to_move(), move) + - 4000; // Correction factor // Decrease/increase reduction by comparing opponent's stat score - if (ss->history > VALUE_ZERO && (ss-1)->history < VALUE_ZERO) + if (ss->history > 0 && (ss-1)->history < 0) r -= ONE_PLY; - else if (ss->history < VALUE_ZERO && (ss-1)->history > VALUE_ZERO) + else if (ss->history < 0 && (ss-1)->history > 0) r += ONE_PLY; // Decrease/increase reduction for moves with a good/bad history @@ -1011,7 +1002,7 @@ moves_loop: // When in check search starts from here Depth d = std::max(newDepth - r, ONE_PLY); - value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true, false); doFullDepthSearch = (value > alpha && d != newDepth); } @@ -1021,9 +1012,9 @@ moves_loop: // When in check search starts from here // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha) + : -qsearch(pos, ss+1, -(alpha+1), -alpha) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false); // For PV nodes only, do a full PV search on the first move or after a fail // high (in the latter case search only if value < beta), otherwise let the @@ -1034,9 +1025,9 @@ moves_loop: // When in check search starts from here (ss+1)->pv[0] = MOVE_NONE; value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth, false); + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha) + : -qsearch(pos, ss+1, -beta, -alpha) + : - search(pos, ss+1, -beta, -alpha, newDepth, false, false); } // Step 17. Undo move @@ -1086,13 +1077,6 @@ 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 @@ -1132,38 +1116,25 @@ moves_loop: // When in check search starts from here : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; else if (bestMove) { - int d = depth / ONE_PLY; - - // Quiet best move: update killers, history and countermoves + // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus); - } + update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); // Extra penalty for a quiet TT move in previous ply when it gets refuted if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); - } + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); } // Bonus for prior countermove that caused the fail low else if ( depth >= 3 * ONE_PLY && !pos.captured_piece() && is_ok((ss-1)->currentMove)) - { - int d = depth / ONE_PLY; - Value bonus = Value(d * d + 2 * d - 2); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus); - } + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); - tte->save(posKey, value_to_tt(bestValue, ss->ply), - bestValue >= beta ? BOUND_LOWER : - PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval, TT.generation()); + if (!excludedMove) + tte->save(posKey, value_to_tt(bestValue, ss->ply), + bestValue >= beta ? BOUND_LOWER : + PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, + depth, bestMove, ss->staticEval, TT.generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1172,8 +1143,7 @@ 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) { @@ -1206,7 +1176,7 @@ moves_loop: // When in check search starts from here ss->ply = (ss-1)->ply + 1; // 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()]; @@ -1312,13 +1282,14 @@ moves_loop: // When in check search starts from here // Detect non-capture evasions that are candidates to be pruned evasionPrunable = InCheck + && depth != DEPTH_ZERO && 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 @@ -1416,28 +1387,18 @@ moves_loop: // When in check search starts from here // update_cm_stats() updates countermove and follow-up move history - void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) { - - CounterMoveStats* cmh = (ss-1)->counterMoves; - CounterMoveStats* fmh1 = (ss-2)->counterMoves; - CounterMoveStats* fmh2 = (ss-4)->counterMoves; - - if (cmh) - cmh->update(pc, s, bonus); - - if (fmh1) - fmh1->update(pc, s, bonus); + void update_cm_stats(Stack* ss, Piece pc, Square s, int bonus) { - if (fmh2) - fmh2->update(pc, s, bonus); + for (int i : {1, 2, 4}) + if (is_ok((ss-i)->currentMove)) + (ss-i)->counterMoves->update(pc, s, bonus); } - // update_stats() updates killers, history, countermove and countermove plus - // follow-up move history when a new quiet best move is found. + // update_stats() updates move sorting heuristics when a new quiet best move is found void update_stats(const Position& pos, Stack* ss, Move move, - Move* quiets, int quietsCnt, Value bonus) { + Move* quiets, int quietsCnt, int bonus) { if (ss->killers[0] != move) { @@ -1447,11 +1408,10 @@ moves_loop: // When in check search starts from here Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - thisThread->fromTo.update(c, move, bonus); - thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); + thisThread->history.update(c, move, bonus); update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); - if ((ss-1)->counterMoves) + if (is_ok((ss-1)->currentMove)) { Square prevSq = to_sq((ss-1)->currentMove); thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); @@ -1460,8 +1420,7 @@ moves_loop: // When in check search starts from here // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { - thisThread->fromTo.update(c, quiets[i], -bonus); - thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + thisThread->history.update(c, quiets[i], -bonus); update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } } @@ -1545,7 +1504,7 @@ 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; @@ -1601,7 +1560,7 @@ bool RootMove::extract_ponder_from_tt(Position& pos) { if (!pv[0]) return false; - pos.do_move(pv[0], st, pos.gives_check(pv[0])); + pos.do_move(pv[0], st); TTEntry* tte = TT.probe(pos.key(), ttHit); if (ttHit)