X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=da306a1a6150a487b3f6a734375e12023fd55862;hp=8099787ec71980751e8fa826f641e058326e0609;hb=44643c277007e3902586418541c0c22ff110fde1;hpb=d29a68f5854d0b529f2e0447fddcc6a61200c5aa diff --git a/src/search.cpp b/src/search.cpp index 8099787e..da306a1a 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, 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 @@ -20,30 +20,43 @@ #include #include #include -#include +#include // For std::memset #include #include #include "evaluate.h" +#include "misc.h" #include "movegen.h" #include "movepick.h" -#include "rkiss.h" #include "search.h" #include "timeman.h" #include "thread.h" #include "tt.h" #include "uci.h" +#include "syzygy/tbprobe.h" namespace Search { volatile SignalsType Signals; LimitsType Limits; - std::vector RootMoves; + RootMoveVector RootMoves; Position RootPos; Time::point SearchTime; StateStackPtr SetupStates; } +namespace Tablebases { + + int Cardinality; + uint64_t Hits; + bool RootInTB; + bool UseRule50; + Depth ProbeDepth; + Value Score; +} + +namespace TB = Tablebases; + using std::string; using Eval::evaluate; using namespace Search; @@ -57,7 +70,7 @@ namespace { inline Value razor_margin(Depth d) { return Value(512 + 32 * d); } // Futility lookup tables (initialized at startup) and their access functions - int FutilityMoveCounts[2][32]; // [improving][depth] + int FutilityMoveCounts[2][16]; // [improving][depth] inline Value futility_margin(Depth d) { return Value(200 * d); @@ -87,8 +100,9 @@ namespace { void id_loop(Position& pos); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); + void update_pv(Move* pv, Move move, Move* childPv); void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt); - string uci_pv(const Position& pos, int depth, Value alpha, Value beta); + string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta); struct Skill { Skill(int l, size_t rootSize) : level(l), @@ -101,7 +115,7 @@ namespace { } size_t candidates_size() const { return candidates; } - bool time_to_pick(int depth) const { return depth == 1 + level; } + bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; } Move pick_move(); int level; @@ -116,28 +130,26 @@ namespace { void Search::init() { - int d; // depth (ONE_PLY == 2) - int hd; // half depth (ONE_PLY == 1) - int mc; // moveCount - // Init reductions array - for (hd = 1; hd < 64; ++hd) for (mc = 1; mc < 64; ++mc) - { - double pvRed = 0.00 + log(double(hd)) * log(double(mc)) / 3.00; - double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25; + for (int d = 1; d < 64; ++d) + for (int mc = 1; mc < 64; ++mc) + { + double pvRed = 0.00 + log(double(d)) * log(double(mc)) / 3.00; + double nonPVRed = 0.33 + log(double(d)) * log(double(mc)) / 2.25; - Reductions[1][1][hd][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0); - Reductions[0][1][hd][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0); + Reductions[1][1][d][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0); + Reductions[0][1][d][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0); - Reductions[1][0][hd][mc] = Reductions[1][1][hd][mc]; - Reductions[0][0][hd][mc] = Reductions[0][1][hd][mc]; + Reductions[1][0][d][mc] = Reductions[1][1][d][mc]; + Reductions[0][0][d][mc] = Reductions[0][1][d][mc]; - if (Reductions[0][0][hd][mc] >= 2) - Reductions[0][0][hd][mc] += 1; - } + // Increase reduction when eval is not improving + if (Reductions[0][0][d][mc] >= 2) + Reductions[0][0][d][mc] += 1; + } // Init futility move count array - for (d = 0; d < 32; ++d) + 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)); @@ -167,7 +179,7 @@ uint64_t Search::perft(Position& pos, Depth depth) { pos.undo_move(*it); } if (Root) - sync_cout << UCI::format_move(*it, pos.is_chess960()) << ": " << cnt << sync_endl; + sync_cout << UCI::move(*it, pos.is_chess960()) << ": " << cnt << sync_endl; } return nodes; } @@ -181,38 +193,75 @@ template uint64_t Search::perft(Position& pos, Depth depth); void Search::think() { - TimeMgr.init(Limits, RootPos.game_ply(), RootPos.side_to_move()); + TimeMgr.init(Limits, RootPos.side_to_move(), RootPos.game_ply()); - int cf = Options["Contempt"] * PawnValueEg / 100; // From centipawns - DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(cf); - DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(cf); + int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns + DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(contempt); + DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(contempt); + + TB::Hits = 0; + TB::RootInTB = false; + TB::UseRule50 = Options["Syzygy50MoveRule"]; + TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; + TB::Cardinality = Options["SyzygyProbeLimit"]; + + // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality + if (TB::Cardinality > TB::MaxCardinality) + { + TB::Cardinality = TB::MaxCardinality; + TB::ProbeDepth = DEPTH_ZERO; + } if (RootMoves.empty()) { RootMoves.push_back(MOVE_NONE); sync_cout << "info depth 0 score " - << UCI::format_value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) + << UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; - - goto finalize; } + else + { + if (TB::Cardinality >= RootPos.count(WHITE) + + RootPos.count(BLACK)) + { + // If the current root position is in the tablebases then RootMoves + // contains only moves that preserve the draw or win. + TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score); + + if (TB::RootInTB) + TB::Cardinality = 0; // Do not probe tablebases during the search + + else // If DTZ tables are missing, use WDL tables as a fallback + { + // Filter out moves that do not preserve a draw or win + TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score); - // Reset the threads, still sleeping: will wake up at split time - for (size_t i = 0; i < Threads.size(); ++i) - Threads[i]->maxPly = 0; + // Only probe during search if winning + if (TB::Score <= VALUE_DRAW) + TB::Cardinality = 0; + } - Threads.timer->run = true; - Threads.timer->notify_one(); // Wake up the recurring timer + if (TB::RootInTB) + { + TB::Hits = RootMoves.size(); - id_loop(RootPos); // Let's start searching ! + if (!TB::UseRule50) + TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1 + : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1 + : VALUE_DRAW; + } + } - Threads.timer->run = false; // Stop the timer + for (size_t i = 0; i < Threads.size(); ++i) + Threads[i]->maxPly = 0; -finalize: + Threads.timer->run = true; + Threads.timer->notify_one(); // Wake up the recurring timer - // When search is stopped this info is not printed - sync_cout << "info nodes " << RootPos.nodes_searched() - << " time " << Time::now() - SearchTime + 1 << sync_endl; + id_loop(RootPos); // Let's start searching ! + + Threads.timer->run = false; + } // 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, @@ -225,10 +274,12 @@ finalize: RootPos.this_thread()->wait_for(Signals.stop); } - // Best move could be MOVE_NONE when searching on a stalemate position - sync_cout << "bestmove " << UCI::format_move(RootMoves[0].pv[0], RootPos.is_chess960()) - << " ponder " << UCI::format_move(RootMoves[0].pv[1], RootPos.is_chess960()) - << sync_endl; + sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960()); + + if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos)) + std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960()); + + std::cout << sync_endl; } @@ -241,12 +292,12 @@ namespace { void id_loop(Position& pos) { Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2) - int depth; + Depth depth; Value bestValue, alpha, beta, delta; std::memset(ss-2, 0, 5 * sizeof(Stack)); - depth = 0; + depth = DEPTH_ZERO; BestMoveChanges = 0; bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -265,7 +316,7 @@ namespace { multiPV = std::max(multiPV, skill.candidates_size()); // Iterative deepening loop until requested to stop or target depth reached - while (++depth < MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) + while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth)) { // Age out PV variability metric BestMoveChanges *= 0.5; @@ -273,17 +324,17 @@ namespace { // Save the last iteration's scores before first PV line is searched and // all the move scores except the (new) PV are set to -VALUE_INFINITE. for (size_t i = 0; i < RootMoves.size(); ++i) - RootMoves[i].prevScore = RootMoves[i].score; + RootMoves[i].previousScore = RootMoves[i].score; // MultiPV loop. We perform a full root search for each PV line for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx) { // Reset aspiration window starting size - if (depth >= 5) + if (depth >= 5 * ONE_PLY) { delta = Value(16); - alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE); - beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE); + alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE); + beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE); } // Start with a small aspiration window and, in the case of a fail @@ -291,7 +342,7 @@ namespace { // high/low anymore. while (true) { - bestValue = search(pos, ss, alpha, beta, depth * ONE_PLY, false); + bestValue = search(pos, ss, alpha, beta, depth, false); // Bring the best move to the front. It is critical that sorting // is done with a stable algorithm because all the values but the @@ -314,7 +365,8 @@ namespace { // When failing high/low give some update (without cluttering // the UI) before a re-search. - if ( (bestValue <= alpha || bestValue >= beta) + if ( multiPV == 1 + && (bestValue <= alpha || bestValue >= beta) && Time::now() - SearchTime > 3000) sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; @@ -322,18 +374,21 @@ namespace { // re-search, otherwise exit the loop. if (bestValue <= alpha) { + beta = (alpha + beta) / 2; alpha = std::max(bestValue - delta, -VALUE_INFINITE); Signals.failedLowAtRoot = true; Signals.stopOnPonderhit = false; } else if (bestValue >= beta) + { + alpha = (alpha + beta) / 2; beta = std::min(bestValue + delta, VALUE_INFINITE); - + } else break; - delta += 3 * delta / 8; + delta += delta / 2; assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); } @@ -341,9 +396,12 @@ namespace { // Sort the PV lines searched so far and update the GUI std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); - if ( !Signals.stop - && ( PVIdx + 1 == std::min(multiPV, RootMoves.size()) - || Time::now() - SearchTime > 3000)) + if (Signals.stop) + sync_cout << "info nodes " << RootPos.nodes_searched() + << " time " << Time::now() - SearchTime << sync_endl; + + else if ( PVIdx + 1 == std::min(multiPV, RootMoves.size()) + || Time::now() - SearchTime > 3000) sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; } @@ -361,7 +419,7 @@ namespace { if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit) { // Take some extra time if the best move has changed - if (depth > 4 && multiPV == 1) + if (depth > 4 * ONE_PLY && multiPV == 1) TimeMgr.pv_instability(BestMoveChanges); // Stop the search if only one legal move is available or all @@ -398,15 +456,15 @@ namespace { assert(PvNode || (alpha == beta - 1)); assert(depth > DEPTH_ZERO); - Move quietsSearched[64]; + Move pv[MAX_PLY+1], quietsSearched[64]; StateInfo st; - const TTEntry *tte; + TTEntry* tte; SplitPoint* splitPoint; Key posKey; Move ttMove, move, excludedMove, bestMove; - Depth ext, newDepth, predictedDepth; + Depth extension, newDepth, predictedDepth; Value bestValue, value, ttValue, eval, nullValue, futilityValue; - bool inCheck, givesCheck, pvMove, singularExtensionNode, improving; + bool ttHit, inCheck, givesCheck, singularExtensionNode, improving; bool captureOrPromotion, dangerous, doFullDepthSearch; int moveCount, quietCount; @@ -420,6 +478,7 @@ namespace { bestMove = splitPoint->bestMove; bestValue = splitPoint->bestValue; tte = NULL; + ttHit = false; ttMove = excludedMove = MOVE_NONE; ttValue = VALUE_NONE; @@ -457,7 +516,7 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; + (ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; // Step 4. Transposition table lookup @@ -465,21 +524,17 @@ namespace { // TT value, so we use a different position key in case of an excluded move. excludedMove = ss->excludedMove; posKey = excludedMove ? pos.exclusion_key() : pos.key(); - tte = TT.probe(posKey); - ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE; - ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - - // At PV nodes we check for exact scores, whilst at non-PV nodes we check for - // a fail high/low. The biggest advantage to probing at PV nodes is to have a - // smooth experience in analysis mode. We don't probe at Root nodes otherwise - // we should also update RootMoveList to avoid bogus output. - if ( !RootNode - && tte + tte = TT.probe(posKey, ttHit); + ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; + ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; + + // At non-PV nodes we check for a fail high/low. We don't probe at PV nodes + if ( !PvNode + && ttHit && tte->depth() >= depth && ttValue != VALUE_NONE // Only in case of TT access race - && ( PvNode ? tte->bound() == BOUND_EXACT - : ttValue >= beta ? (tte->bound() & BOUND_LOWER) - : (tte->bound() & BOUND_UPPER))) + && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { ss->currentMove = ttMove; // Can be MOVE_NONE @@ -490,6 +545,36 @@ namespace { return ttValue; } + // Step 4a. Tablebase probe + if (!RootNode && TB::Cardinality) + { + int piecesCnt = pos.count(WHITE) + pos.count(BLACK); + + if ( piecesCnt <= TB::Cardinality + && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) + && pos.rule50_count() == 0) + { + int found, v = Tablebases::probe_wdl(pos, &found); + + if (found) + { + TB::Hits++; + + int drawScore = TB::UseRule50 ? 1 : 0; + + value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply + : VALUE_DRAW + 2 * v * drawScore; + + tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT, + std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY), + MOVE_NONE, VALUE_NONE, TT.generation()); + + return value; + } + } + } + // Step 5. Evaluate the position statically and update parent's gain statistics if (inCheck) { @@ -497,10 +582,10 @@ namespace { goto moves_loop; } - else if (tte) + else if (ttHit) { // Never assume anything on values stored in TT - if ((ss->staticEval = eval = tte->eval_value()) == VALUE_NONE) + if ((ss->staticEval = eval = tte->eval()) == VALUE_NONE) eval = ss->staticEval = evaluate(pos); // Can ttValue be used as a better position evaluation? @@ -513,9 +598,12 @@ namespace { eval = ss->staticEval = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo; - TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval); + tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation()); } + if (ss->skipEarlyPruning) + goto moves_loop; + if ( !pos.captured_piece_type() && ss->staticEval != VALUE_NONE && (ss-1)->staticEval != VALUE_NONE @@ -545,8 +633,7 @@ namespace { } // Step 7. Futility pruning: child node (skipped when in check) - if ( !PvNode - && !ss->skipNullMove + if ( !RootNode && depth < 7 * ONE_PLY && eval - futility_margin(depth) >= beta && eval < VALUE_KNOWN_WIN // Do not return unproven wins @@ -555,7 +642,6 @@ namespace { // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode - && !ss->skipNullMove && depth >= 2 * ONE_PLY && eval >= beta && pos.non_pawn_material(pos.side_to_move())) @@ -565,13 +651,13 @@ namespace { assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value - Depth R = (3 + depth / 4 + std::min(int(eval - beta) / PawnValueMg, 3)) * ONE_PLY; + Depth R = ((823 + 67 * depth) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; pos.do_null_move(st); - (ss+1)->skipNullMove = true; + (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)->skipNullMove = false; + (ss+1)->skipEarlyPruning = false; pos.undo_null_move(); if (nullValue >= beta) @@ -584,10 +670,10 @@ namespace { return nullValue; // Do verification search at high depths - ss->skipNullMove = true; + 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->skipNullMove = false; + ss->skipEarlyPruning = false; if (v >= beta) return nullValue; @@ -600,7 +686,6 @@ namespace { // prune the previous move. if ( !PvNode && depth >= 5 * ONE_PLY - && !ss->skipNullMove && abs(beta) < VALUE_MATE_IN_MAX_PLY) { Value rbeta = std::min(beta + 200, VALUE_INFINITE); @@ -631,12 +716,12 @@ namespace { && (PvNode || ss->staticEval + 256 >= beta)) { Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2); - ss->skipNullMove = true; + ss->skipEarlyPruning = true; search(pos, ss, alpha, beta, d / 2, true); - ss->skipNullMove = false; + ss->skipEarlyPruning = false; - tte = TT.probe(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; + tte = TT.probe(posKey, ttHit); + ttMove = ttHit ? tte->move() : MOVE_NONE; } moves_loop: // When in check and at SpNode search starts from here @@ -698,12 +783,15 @@ moves_loop: // When in check and at SpNode search starts from here Signals.firstRootMove = (moveCount == 1); if (thisThread == Threads.main() && Time::now() - SearchTime > 3000) - sync_cout << "info depth " << depth - << " currmove " << UCI::format_move(move, pos.is_chess960()) + sync_cout << "info depth " << depth / ONE_PLY + << " currmove " << UCI::move(move, pos.is_chess960()) << " currmovenumber " << moveCount + PVIdx << sync_endl; } - ext = DEPTH_ZERO; + if (PvNode) + (ss+1)->pv = NULL; + + extension = DEPTH_ZERO; captureOrPromotion = pos.capture_or_promotion(move); givesCheck = type_of(move) == NORMAL && !ci.dcCandidates @@ -716,7 +804,7 @@ moves_loop: // When in check and at SpNode search starts from here // Step 12. Extend checks if (givesCheck && pos.see_sign(move) >= VALUE_ZERO) - ext = ONE_PLY; + extension = ONE_PLY; // 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 @@ -725,29 +813,27 @@ moves_loop: // When in check and at SpNode search starts from here // ttValue minus a margin then we extend the ttMove. if ( singularExtensionNode && move == ttMove - && !ext + && !extension && pos.legal(move, ci.pinned)) { - Value rBeta = ttValue - int(2 * depth); + Value rBeta = ttValue - 2 * depth / ONE_PLY; ss->excludedMove = move; - ss->skipNullMove = true; + ss->skipEarlyPruning = true; value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); - ss->skipNullMove = false; + ss->skipEarlyPruning = false; ss->excludedMove = MOVE_NONE; if (value < rBeta) - ext = ONE_PLY; + extension = ONE_PLY; } // Update the current move (this must be done after singular extension search) - newDepth = depth - ONE_PLY + ext; + newDepth = depth - ONE_PLY + extension; - // Step 13. Pruning at shallow depth (exclude PV nodes) - if ( !PvNode - && !captureOrPromotion + // Step 13. Pruning at shallow depth + if ( !captureOrPromotion && !inCheck && !dangerous - /* && move != ttMove Already implicit in the next condition */ && bestValue > VALUE_MATED_IN_MAX_PLY) { // Move count based pruning @@ -802,7 +888,6 @@ moves_loop: // When in check and at SpNode search starts from here continue; } - pvMove = PvNode && moveCount == 1; ss->currentMove = move; if (!SpNode && !captureOrPromotion && quietCount < 64) quietsSearched[quietCount++] = move; @@ -813,16 +898,15 @@ moves_loop: // When in check and at SpNode search starts from here // Step 15. Reduced depth search (LMR). If the move fails high it will be // re-searched at full depth. if ( depth >= 3 * ONE_PLY - && !pvMove + && moveCount > 1 && !captureOrPromotion - && move != ttMove && move != ss->killers[0] && move != ss->killers[1]) { ss->reduction = reduction(improving, depth, moveCount); if ( (!PvNode && cutNode) - || History[pos.piece_on(to_sq(move))][to_sq(move)] < 0) + || History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO) ss->reduction += ONE_PLY; if (move == countermoves[0] || move == countermoves[1]) @@ -832,7 +916,7 @@ moves_loop: // When in check and at SpNode search starts from here if ( ss->reduction && type_of(move) == NORMAL && type_of(pos.piece_on(to_sq(move))) != PAWN - && pos.see(make_move(to_sq(move), from_sq(move))) < 0) + && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO) ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY); Depth d = std::max(newDepth - ss->reduction, ONE_PLY); @@ -852,7 +936,7 @@ moves_loop: // When in check and at SpNode search starts from here ss->reduction = DEPTH_ZERO; } else - doFullDepthSearch = !pvMove; + doFullDepthSearch = !PvNode || moveCount > 1; // Step 16. Full depth search, when LMR is skipped or fails high if (doFullDepthSearch) @@ -869,11 +953,17 @@ moves_loop: // When in check and at SpNode search starts from here // For PV nodes only, do a full PV search on the first move or after a fail // high (in the latter case search only if value < beta), otherwise let the // parent node fail low with value <= alpha and to try another move. - if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta)))) + if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta)))) + { + (ss+1)->pv = pv; + (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); + } + // Step 17. Undo move pos.undo_move(move); @@ -898,15 +988,20 @@ moves_loop: // When in check and at SpNode search starts from here RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); // PV move or new best move ? - if (pvMove || value > alpha) + if (moveCount == 1 || value > alpha) { rm.score = value; - rm.extract_pv_from_tt(pos); + rm.pv.resize(1); + + assert((ss+1)->pv); + + for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m) + rm.pv.push_back(*m); // We record how often the best move has been changed in each // iteration. This information is used for time management: When // the best move changes frequently, we allocate some more time. - if (!pvMove) + if (moveCount > 1) ++BestMoveChanges; } else @@ -924,6 +1019,9 @@ moves_loop: // When in check and at SpNode search starts from here { bestMove = SpNode ? splitPoint->bestMove = move : move; + if (PvNode && !RootNode) // Update pv even in fail-high case + update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv); + if (PvNode && value < beta) // Update alpha! Always alpha < beta alpha = SpNode ? splitPoint->alpha = value : value; else @@ -982,10 +1080,10 @@ moves_loop: // When in check and at SpNode search starts from here else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck) update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1); - TT.store(posKey, value_to_tt(bestValue, ss->ply), - bestValue >= beta ? BOUND_LOWER : - PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval); + 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); @@ -1008,17 +1106,21 @@ moves_loop: // When in check and at SpNode search starts from here assert(PvNode || (alpha == beta - 1)); assert(depth <= DEPTH_ZERO); + Move pv[MAX_PLY+1]; StateInfo st; - const TTEntry* tte; + TTEntry* tte; Key posKey; Move ttMove, move, bestMove; Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; - bool givesCheck, evasionPrunable; + bool ttHit, givesCheck, evasionPrunable; Depth ttDepth; - // To flag BOUND_EXACT a node with eval above alpha and no available moves if (PvNode) - oldAlpha = alpha; + { + oldAlpha = alpha; // To flag BOUND_EXACT when eval above alpha and no available moves + (ss+1)->pv = pv; + ss->pv[0] = MOVE_NONE; + } ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; @@ -1037,16 +1139,16 @@ moves_loop: // When in check and at SpNode search starts from here // Transposition table lookup posKey = pos.key(); - tte = TT.probe(posKey); - ttMove = tte ? tte->move() : MOVE_NONE; - ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE; + tte = TT.probe(posKey, ttHit); + ttMove = ttHit ? tte->move() : MOVE_NONE; + ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - if ( tte + if ( !PvNode + && ttHit && tte->depth() >= ttDepth && ttValue != VALUE_NONE // Only in case of TT access race - && ( PvNode ? tte->bound() == BOUND_EXACT - : ttValue >= beta ? (tte->bound() & BOUND_LOWER) - : (tte->bound() & BOUND_UPPER))) + && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) + : (tte->bound() & BOUND_UPPER))) { ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; @@ -1060,10 +1162,10 @@ moves_loop: // When in check and at SpNode search starts from here } else { - if (tte) + if (ttHit) { // Never assume anything on values stored in TT - if ((ss->staticEval = bestValue = tte->eval_value()) == VALUE_NONE) + if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE) ss->staticEval = bestValue = evaluate(pos); // Can ttValue be used as a better position evaluation? @@ -1078,9 +1180,9 @@ moves_loop: // When in check and at SpNode search starts from here // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { - if (!tte) - TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, - DEPTH_NONE, MOVE_NONE, ss->staticEval); + if (!ttHit) + tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, + DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation()); return bestValue; } @@ -1108,10 +1210,8 @@ moves_loop: // When in check and at SpNode search starts from here : pos.gives_check(move, ci); // Futility pruning - if ( !PvNode - && !InCheck + if ( !InCheck && !givesCheck - && move != ttMove && futilityBase > -VALUE_KNOWN_WIN && !pos.advanced_pawn_push(move)) { @@ -1119,13 +1219,13 @@ moves_loop: // When in check and at SpNode search starts from here futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))]; - if (futilityValue < beta) + if (futilityValue <= alpha) { bestValue = std::max(bestValue, futilityValue); continue; } - if (futilityBase < beta && pos.see(move) <= VALUE_ZERO) + if (futilityBase <= alpha && pos.see(move) <= VALUE_ZERO) { bestValue = std::max(bestValue, futilityBase); continue; @@ -1139,9 +1239,7 @@ moves_loop: // When in check and at SpNode search starts from here && !pos.can_castle(pos.side_to_move()); // Don't search moves with negative SEE values - if ( !PvNode - && (!InCheck || evasionPrunable) - && move != ttMove + if ( (!InCheck || evasionPrunable) && type_of(move) != PROMOTION && pos.see_sign(move) < VALUE_ZERO) continue; @@ -1170,6 +1268,9 @@ moves_loop: // When in check and at SpNode search starts from here if (value > alpha) { + if (PvNode) // Update pv even in fail-high case + update_pv(ss->pv, move, (ss+1)->pv); + if (PvNode && value < beta) // Update alpha here! Always alpha < beta { alpha = value; @@ -1177,8 +1278,8 @@ moves_loop: // When in check and at SpNode search starts from here } else // Fail high { - TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, - ttDepth, move, ss->staticEval); + tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, + ttDepth, move, ss->staticEval, TT.generation()); return value; } @@ -1191,9 +1292,9 @@ moves_loop: // When in check and at SpNode search starts from here if (InCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root - TT.store(posKey, value_to_tt(bestValue, ss->ply), - PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, - ttDepth, bestMove, ss->staticEval); + tte->save(posKey, value_to_tt(bestValue, ss->ply), + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove, ss->staticEval, TT.generation()); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1226,6 +1327,15 @@ moves_loop: // When in check and at SpNode search starts from here } + // update_pv() adds current move and appends child pv[] + + void update_pv(Move* pv, Move move, Move* childPv) { + + for (*pv++ = move; childPv && *childPv != MOVE_NONE; ) + *pv++ = *childPv++; + *pv = MOVE_NONE; + } + // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high // of a quiet move. @@ -1239,7 +1349,7 @@ moves_loop: // When in check and at SpNode search starts from here // Increase history value of the cut-off move and decrease all the other // played quiet moves. - Value bonus = Value(4 * int(depth) * int(depth)); + Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY)); History.update(pos.moved_piece(move), to_sq(move), bonus); for (int i = 0; i < quietsCnt; ++i) { @@ -1266,16 +1376,13 @@ moves_loop: // When in check and at SpNode search starts from here Move Skill::pick_move() { - static RKISS rk; - - // PRNG sequence should be not deterministic - for (int i = Time::now() % 50; i > 0; --i) - rk.rand(); + // PRNG sequence should be non-deterministic, so we seed it with the time at init + static PRNG rng(Time::now()); // RootMoves are already sorted by score in descending order int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg); int weakness = 120 - 2 * level; - int max_s = -VALUE_INFINITE; + int maxScore = -VALUE_INFINITE; best = MOVE_NONE; // Choose best move. For each move score we add two terms both dependent on @@ -1283,19 +1390,19 @@ moves_loop: // When in check and at SpNode search starts from here // then we choose the move with the resulting highest score. for (size_t i = 0; i < candidates; ++i) { - int s = RootMoves[i].score; + int score = RootMoves[i].score; // Don't allow crazy blunders even at very low skills - if (i > 0 && RootMoves[i - 1].score > s + 2 * PawnValueMg) + if (i > 0 && RootMoves[i - 1].score > score + 2 * PawnValueMg) break; // This is our magic formula - s += ( weakness * int(RootMoves[0].score - s) - + variance * (rk.rand() % weakness)) / 128; + score += ( weakness * int(RootMoves[0].score - score) + + variance * (rng.rand() % weakness)) / 128; - if (s > max_s) + if (score > maxScore) { - max_s = s; + maxScore = score; best = RootMoves[i].pv[0]; } } @@ -1307,7 +1414,7 @@ moves_loop: // When in check and at SpNode search starts from here // requires that all (if any) unsearched PV lines are sent using a previous // search score. - string uci_pv(const Position& pos, int depth, Value alpha, Value beta) { + string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta) { std::stringstream ss; Time::point elapsed = Time::now() - SearchTime + 1; @@ -1322,26 +1429,34 @@ moves_loop: // When in check and at SpNode search starts from here { bool updated = (i <= PVIdx); - if (depth == 1 && !updated) + if (depth == ONE_PLY && !updated) continue; - int d = updated ? depth : depth - 1; - Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore; + Depth d = updated ? depth : depth - ONE_PLY; + Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore; + + bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; + v = tb ? TB::Score : v; if (ss.rdbuf()->in_avail()) // Not at first line ss << "\n"; - ss << "info depth " << d + ss << "info depth " << d / ONE_PLY << " seldepth " << selDepth << " multipv " << i + 1 - << " score " << (i == PVIdx ? UCI::format_value(v, alpha, beta) : UCI::format_value(v)) - << " nodes " << pos.nodes_searched() + << " score " << UCI::value(v); + + if (!tb && i == PVIdx) + ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); + + ss << " nodes " << pos.nodes_searched() << " nps " << pos.nodes_searched() * 1000 / elapsed + << " tbhits " << TB::Hits << " time " << elapsed << " pv"; - for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; ++j) - ss << " " << UCI::format_move(RootMoves[i].pv[j], pos.is_chess960()); + for (size_t j = 0; j < RootMoves[i].pv.size(); ++j) + ss << " " << UCI::move(RootMoves[i].pv[j], pos.is_chess960()); } return ss.str(); @@ -1350,66 +1465,53 @@ moves_loop: // When in check and at SpNode search starts from here } // namespace -/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table. -/// We also consider both failing high nodes and BOUND_EXACT nodes here to -/// ensure that we have a ponder move even when we fail high at root. This -/// results in a long PV to print that is important for position analysis. +/// RootMove::insert_pv_in_tt() is called at the end of a search iteration, and +/// inserts the PV back into the TT. This makes sure the old PV moves are searched +/// first, even if the old TT entries have been overwritten. -void RootMove::extract_pv_from_tt(Position& pos) { +void RootMove::insert_pv_in_tt(Position& pos) { StateInfo state[MAX_PLY], *st = state; - const TTEntry* tte; - int ply = 1; // At root ply is 1... - Move m = pv[0]; // ...instead pv[] array starts from 0 - Value expectedScore = score; - - pv.clear(); - - do { - pv.push_back(m); + size_t idx = 0; - assert(MoveList(pos).contains(pv[ply - 1])); + for ( ; idx < pv.size(); ++idx) + { + bool ttHit; + TTEntry* tte = TT.probe(pos.key(), ttHit); - pos.do_move(pv[ply++ - 1], *st++); - tte = TT.probe(pos.key()); - expectedScore = -expectedScore; + if (!ttHit || tte->move() != pv[idx]) // Don't overwrite correct entries + tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE, TT.generation()); - } while ( tte - && expectedScore == value_from_tt(tte->value(), ply) - && pos.pseudo_legal(m = tte->move()) // Local copy, TT could change - && pos.legal(m, pos.pinned_pieces(pos.side_to_move())) - && ply < MAX_PLY - && (!pos.is_draw() || ply <= 2)); + assert(MoveList(pos).contains(pv[idx])); - pv.push_back(MOVE_NONE); // Must be zero-terminating + pos.do_move(pv[idx], *st++); + } - while (--ply) pos.undo_move(pv[ply - 1]); + while (idx) pos.undo_move(pv[--idx]); } -/// RootMove::insert_pv_in_tt() is called at the end of a search iteration, and -/// inserts the PV back into the TT. This makes sure the old PV moves are searched -/// first, even if the old TT entries have been overwritten. - -void RootMove::insert_pv_in_tt(Position& pos) { - - StateInfo state[MAX_PLY], *st = state; - const TTEntry* tte; - int idx = 0; // Ply starts from 1, we need to start from 0 - - do { - tte = TT.probe(pos.key()); +/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move before +/// exiting the search, for instance in case we stop the search during a fail high at +/// root. We try hard to have a ponder move to return to the GUI, otherwise in case of +/// 'ponder on' we have nothing to think on. - if (!tte || tte->move() != pv[idx]) // Don't overwrite correct entries - TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE); - - assert(MoveList(pos).contains(pv[idx])); +Move RootMove::extract_ponder_from_tt(Position& pos) +{ + StateInfo st; + bool found; - pos.do_move(pv[idx++], *st++); + assert(pv.size() == 1); - } while (pv[idx] != MOVE_NONE); + pos.do_move(pv[0], st); + TTEntry* tte = TT.probe(pos.key(), found); + Move m = found ? tte->move() : MOVE_NONE; + if (!MoveList(pos).contains(m)) + m = MOVE_NONE; - while (idx) pos.undo_move(pv[--idx]); + pos.undo_move(pv[0]); + pv.push_back(m); + return m; } @@ -1549,7 +1651,11 @@ void check_time() { dbg_print(); } - if (Limits.use_time_management() && !Limits.ponder) + // An engine may not stop pondering until told so by the GUI + if (Limits.ponder) + return; + + if (Limits.use_time_management()) { bool stillAtFirstMove = Signals.firstRootMove && !Signals.failedLowAtRoot @@ -1566,7 +1672,7 @@ void check_time() { { Threads.mutex.lock(); - int nodes = RootPos.nodes_searched(); + int64_t nodes = RootPos.nodes_searched(); // Loop across all split points and sum accumulated SplitPoint nodes plus // all the currently active positions nodes.