X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=12cbffe020b25f7bf92921dc860e23e83eb3d919;hp=31e8b0b661f46392453d097c39e137ba52bead57;hb=77342126d8417469bd6a398cfc6c0594b1f02f82;hpb=3627348e2b4633604a878b0e5397acb6218a6afc diff --git a/src/search.cpp b/src/search.cpp index 31e8b0b6..12cbffe0 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -63,22 +63,30 @@ 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 - Value stat_bonus(Depth depth) { - int d = depth / ONE_PLY ; - return Value(d * d + 2 * d - 2); + 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 @@ -93,8 +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() { @@ -132,19 +140,6 @@ namespace { Move pv[3]; }; - // skip half of the plies in blocks depending on the helper thread idx. - bool skip_ply(int idx, int ply) { - - idx = (idx - 1) % 20 + 1; // cycle after 20 threads. - - // number of successive plies to skip, depending on idx. - int ones = 1; - while (ones * (ones + 1) < idx) - ones++; - - return ((ply + idx - 1) / ones - ones) % 2 == 0; - } - EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; @@ -157,8 +152,8 @@ namespace { Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); - void update_cm_stats(Stack* ss, Piece pc, Square s, 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 @@ -172,7 +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); @@ -184,13 +179,13 @@ void Search::init() { for (int d = 0; d < 16; ++d) { - FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8)); - FutilityMoveCounts[1][d] = int(2.9 + 1.045 * pow(d + 0.49, 1.8)); + FutilityMoveCounts[0][d] = int(2.4 + 0.74 * pow(d, 1.78)); + FutilityMoveCounts[1][d] = int(5.0 + 1.00 * pow(d, 2.00)); } } -/// Search::clear() resets search state to zero, to obtain reproducible results +/// Search::clear() resets search state to its initial value, to obtain reproducible results void Search::clear() { @@ -198,10 +193,15 @@ void Search::clear() { for (Thread* th : Threads) { - th->counterMoves.clear(); - th->history.clear(); - th->counterMoveHistory.clear(); th->resetCalls = true; + th->counterMoves.fill(MOVE_NONE); + th->history.fill(0); + + for (auto& to : th->counterMoveHistory) + for (auto& h : to) + h.fill(0); + + th->counterMoveHistory[NO_PIECE][0].fill(CounterMovePruneThreshold - 1); } Threads.main()->previousScore = VALUE_INFINITE; @@ -244,6 +244,7 @@ void MainThread::search() { Color us = rootPos.side_to_move(); Time.init(Limits, us, rootPos.game_ply()); + TT.new_search(); int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns DrawValue[ us] = VALUE_DRAW - Value(contempt); @@ -322,9 +323,9 @@ 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() { @@ -334,6 +335,8 @@ void Thread::search() { 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)->history = &this->counterMoveHistory[NO_PIECE][0]; // Use as sentinel bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -345,7 +348,6 @@ void Thread::search() { EasyMove.clear(); mainThread->easyMovePlayed = mainThread->failedLow = false; mainThread->bestMoveChanges = 0; - TT.new_search(); } size_t multiPV = Options["MultiPV"]; @@ -359,13 +361,17 @@ void Thread::search() { multiPV = std::min(multiPV, rootMoves.size()); // Iterative deepening loop until requested to stop or the target depth is reached - while ( (rootDepth += ONE_PLY) < DEPTH_MAX + while ( (rootDepth = rootDepth + ONE_PLY) < DEPTH_MAX && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth)) { - // skip plies for helper threads - if (idx && skip_ply(idx, rootDepth / ONE_PLY + rootPos.game_ply())) - continue; + // Distribute search depths across the threads + if (idx) + { + int i = (idx - 1) % 20; + if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2) + continue; + } // Age out PV variability metric if (mainThread) @@ -394,6 +400,9 @@ void Thread::search() { { bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false, false); + this->tbHits = rootPos.tb_hits(); + this->nodes = rootPos.nodes_searched(); + // 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 @@ -545,15 +554,15 @@ namespace { Depth extension, newDepth; Value bestValue, value, ttValue, eval; bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture; 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->statScore = 0; bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; @@ -561,9 +570,13 @@ namespace { if (thisThread->resetCalls.load(std::memory_order_relaxed)) { thisThread->resetCalls = false; + + thisThread->tbHits = pos.tb_hits(); + thisThread->nodes = pos.nodes_searched(); + // 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) + thisThread->callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) : 4096; } @@ -601,7 +614,7 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->counterMoves = nullptr; + ss->history = &thisThread->counterMoveHistory[NO_PIECE][0]; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; Square prevSq = to_sq((ss-1)->currentMove); @@ -638,7 +651,7 @@ namespace { // Penalty for a quiet ttMove that fails low else if (!pos.capture_or_promotion(ttMove)) { - Value penalty = -stat_bonus(depth + ONE_PLY); + 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); } @@ -649,7 +662,7 @@ namespace { // Step 4a. Tablebase probe if (!rootNode && TB::Cardinality) { - int piecesCount = pos.count(WHITE) + pos.count(BLACK); + int piecesCount = pos.count(); if ( piecesCount <= TB::Cardinality && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth) @@ -661,7 +674,7 @@ namespace { if (err != TB::ProbeState::FAIL) { - thisThread->tbHits++; + pos.increment_tbHits(); int drawScore = TB::UseRule50 ? 1 : 0; @@ -737,14 +750,15 @@ namespace { && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY) && pos.non_pawn_material(pos.side_to_move())) { - ss->currentMove = MOVE_NULL; - ss->counterMoves = nullptr; assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; + ss->currentMove = MOVE_NULL; + ss->history = &thisThread->counterMoveHistory[NO_PIECE][0]; + pos.do_null_move(st); Value nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); @@ -776,11 +790,8 @@ 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); @@ -788,9 +799,11 @@ namespace { if (pos.legal(move)) { ss->currentMove = move; - ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; + ss->history = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; + + assert(depth >= 5 * ONE_PLY); pos.do_move(move, st); - value = -search(pos, ss+1, -rbeta, -rbeta+1, 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; @@ -811,9 +824,9 @@ namespace { moves_loop: // When in check search starts from here - const CounterMoveStats* cmh = (ss-1)->counterMoves; - const CounterMoveStats* fmh = (ss-2)->counterMoves; - const CounterMoveStats* fmh2 = (ss-4)->counterMoves; + const PieceToHistory& cmh = *(ss-1)->history; + const PieceToHistory& fmh = *(ss-2)->history; + const PieceToHistory& fm2 = *(ss-4)->history; MovePicker mp(pos, ttMove, depth, ss); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc @@ -828,10 +841,12 @@ 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; // 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)); @@ -866,21 +881,15 @@ moves_loop: // When in check search starts from here moveCountPruning = depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY]; - // Step 12. Extensions - // 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); @@ -892,30 +901,37 @@ 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; // 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.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 5000)) + && (!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 @@ -944,10 +960,13 @@ moves_loop: // When in check search starts from here ss->moveCount = --moveCount; 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->history = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; // Step 14. Make the move pos.do_move(move, st, givesCheck); @@ -964,6 +983,11 @@ moves_loop: // When in check search starts from here r -= r ? ONE_PLY : DEPTH_ZERO; else { + + // Increase reduction if ttMove is a capture + if (ttCapture) + r += ONE_PLY; + // Increase reduction for cut nodes if (cutNode) r += 2 * ONE_PLY; @@ -971,25 +995,25 @@ 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 = (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->history.get(~pos.side_to_move(), move) - - 4000; // Correction factor + ss->statScore = cmh[moved_piece][to_sq(move)] + + fmh[moved_piece][to_sq(move)] + + fm2[moved_piece][to_sq(move)] + + thisThread->history[~pos.side_to_move()][from_to(move)] + - 4000; // Correction factor // Decrease/increase reduction by comparing opponent's stat score - if (ss->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->statScore < 0 && (ss-1)->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); @@ -1108,7 +1132,6 @@ 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 move sorting heuristics if (!pos.capture_or_promotion(bestMove)) update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); @@ -1123,10 +1146,11 @@ moves_loop: // When in check search starts from here && is_ok((ss-1)->currentMove)) 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); @@ -1156,6 +1180,7 @@ 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) { @@ -1166,6 +1191,7 @@ moves_loop: // When in check search starts from here ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; + moveCount = 0; // Check for an instant draw or if the maximum ply has been reached if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) @@ -1249,6 +1275,8 @@ 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 @@ -1274,13 +1302,14 @@ 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 @@ -1288,7 +1317,10 @@ 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; @@ -1378,27 +1410,18 @@ 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)->history->update(pc, s, bonus); } // 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) { @@ -1411,10 +1434,10 @@ moves_loop: // When in check search starts from here thisThread->history.update(c, move, bonus); update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); - if ((ss-1)->counterMoves) + if (is_ok((ss-1)->currentMove)) { Square prevSq = to_sq((ss-1)->currentMove); - thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move); + thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]=move; } // Decrease all the other played quiet moves @@ -1465,7 +1488,7 @@ moves_loop: // When in check search starts from here void check_time() { - static TimePoint lastInfoTime = now(); + static std::atomic lastInfoTime = { now() }; int elapsed = Time.elapsed(); TimePoint tick = Limits.startTime + elapsed; @@ -1504,7 +1527,7 @@ 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;