X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=997cfd3b6a32c20ecbbb493dbb1e1cba8f87f536;hp=897121fdc63570925ca02515c135fd8dd4e47bc1;hb=745160572f9ffcc55317fcfedc47653eb95494aa;hpb=82f7d507eaf83e27a33bf0b433be08d23320b6fe diff --git a/src/search.cpp b/src/search.cpp index 897121fd..997cfd3b 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -71,16 +71,6 @@ namespace { return Value((175 - 50 * improving) * d / ONE_PLY); } - // Margin for pruning capturing moves: almost linear in depth - constexpr int CapturePruneMargin[] = { 0, - 1 * PawnValueEg * 1055 / 1000, - 2 * PawnValueEg * 1042 / 1000, - 3 * PawnValueEg * 963 / 1000, - 4 * PawnValueEg * 1038 / 1000, - 5 * PawnValueEg * 950 / 1000, - 6 * PawnValueEg * 930 / 1000 - }; - // Futility and reductions lookup tables, initialized at startup int FutilityMoveCounts[2][16]; // [improving][depth] int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] @@ -92,7 +82,7 @@ namespace { // 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; + return d > 17 ? 0 : 32 * d * d + 64 * d - 64; } // Skill structure is used to implement strength limit @@ -107,7 +97,7 @@ namespace { }; template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO); @@ -296,6 +286,7 @@ void Thread::search() { MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); double timeReduction = 1.0; Color us = rootPos.side_to_move(); + bool failedLow; std::memset(ss-4, 0, 7 * sizeof(Stack)); for (int i = 4; i > 0; i--) @@ -305,7 +296,7 @@ void Thread::search() { beta = VALUE_INFINITE; if (mainThread) - mainThread->bestMoveChanges = 0, mainThread->failedLow = false; + mainThread->bestMoveChanges = 0, failedLow = false; size_t multiPV = Options["MultiPV"]; Skill skill(Options["Skill Level"]); @@ -346,24 +337,24 @@ void Thread::search() { // Age out PV variability metric if (mainThread) - mainThread->bestMoveChanges *= 0.517, mainThread->failedLow = false; + mainThread->bestMoveChanges *= 0.517, failedLow = false; // Save the last iteration's scores before first PV line is searched and // all the move scores except the (new) PV are set to -VALUE_INFINITE. for (RootMove& rm : rootMoves) rm.previousScore = rm.score; - size_t PVFirst = 0; - PVLast = 0; + size_t pvFirst = 0; + pvLast = 0; // MultiPV loop. We perform a full root search for each PV line - for (PVIdx = 0; PVIdx < multiPV && !Threads.stop; ++PVIdx) + for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx) { - if (PVIdx == PVLast) + if (pvIdx == pvLast) { - PVFirst = PVLast; - for (PVLast++; PVLast < rootMoves.size(); PVLast++) - if (rootMoves[PVLast].TBRank != rootMoves[PVFirst].TBRank) + pvFirst = pvLast; + for (pvLast++; pvLast < rootMoves.size(); pvLast++) + if (rootMoves[pvLast].tbRank != rootMoves[pvFirst].tbRank) break; } @@ -373,13 +364,13 @@ void Thread::search() { // Reset aspiration window starting size if (rootDepth >= 5 * ONE_PLY) { - Value previousScore = rootMoves[PVIdx].previousScore; + Value previousScore = rootMoves[pvIdx].previousScore; delta = Value(18); alpha = std::max(previousScore - delta,-VALUE_INFINITE); beta = std::min(previousScore + delta, VALUE_INFINITE); // Adjust contempt based on root move's previousScore (dynamic contempt) - int dct = ct + int(std::round(48 * atan(float(previousScore) / 128))); + int dct = ct + 88 * previousScore / (abs(previousScore) + 200); contempt = (us == WHITE ? make_score(dct, dct / 2) : -make_score(dct, dct / 2)); @@ -390,7 +381,7 @@ void Thread::search() { // high/low anymore. while (true) { - bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false, false); + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); // Bring the best move to the front. It is critical that sorting // is done with a stable algorithm because all the values but the @@ -398,7 +389,7 @@ void Thread::search() { // and we want to keep the same order for all the moves except the // new PV that goes to the front. Note that in case of MultiPV // search the already searched PV lines are preserved. - std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.begin() + PVLast); + std::stable_sort(rootMoves.begin() + pvIdx, rootMoves.begin() + pvLast); // If search has been stopped, we break immediately. Sorting is // safe because RootMoves is still valid, although it refers to @@ -423,7 +414,7 @@ void Thread::search() { if (mainThread) { - mainThread->failedLow = true; + failedLow = true; Threads.stopOnPonderhit = false; } } @@ -438,10 +429,10 @@ void Thread::search() { } // Sort the PV lines searched so far and update the GUI - std::stable_sort(rootMoves.begin() + PVFirst, rootMoves.begin() + PVIdx + 1); + std::stable_sort(rootMoves.begin() + pvFirst, rootMoves.begin() + pvIdx + 1); if ( mainThread - && (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000)) + && (Threads.stop || pvIdx + 1 == multiPV || Time.elapsed() > 3000)) sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl; } @@ -471,7 +462,7 @@ void Thread::search() { && !Threads.stop && !Threads.stopOnPonderhit) { - const int F[] = { mainThread->failedLow, + const int F[] = { failedLow, bestValue - mainThread->previousScore }; int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1])); @@ -517,15 +508,27 @@ 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, bool skipEarlyPruning) { - - // Use quiescence search when needed - if (depth < ONE_PLY) - return qsearch(pos, ss, alpha, beta); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { constexpr bool PvNode = NT == PV; const bool rootNode = PvNode && ss->ply == 0; + // Check if we have an upcoming move which draws by repetition, or + // if the opponent had an alternative move earlier to this position. + if ( pos.rule50_count() >= 3 + && alpha < VALUE_DRAW + && !rootNode + && pos.has_game_cycle(ss->ply)) + { + alpha = VALUE_DRAW; + if (alpha >= beta) + return alpha; + } + + // Dive into quiescence search when the depth reaches zero + if (depth < ONE_PLY) + return qsearch(pos, ss, alpha, beta); + assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); @@ -547,6 +550,7 @@ namespace { // Step 1. Initialize node Thread* thisThread = pos.this_thread(); inCheck = pos.checkers(); + Color us = pos.side_to_move(); moveCount = captureCount = quietCount = ss->moveCount = 0; bestValue = -VALUE_INFINITE; maxValue = VALUE_INFINITE; @@ -601,7 +605,7 @@ namespace { posKey = pos.key() ^ Key(excludedMove << 16); // Isn't a very good hash tte = TT.probe(posKey, ttHit); ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; - ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] + ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; // At non-PV nodes we check for an early TT cutoff @@ -628,7 +632,7 @@ namespace { else if (!pos.capture_or_promotion(ttMove)) { int penalty = -stat_bonus(depth); - thisThread->mainHistory[pos.side_to_move()][from_to(ttMove)] << penalty; + thisThread->mainHistory[us][from_to(ttMove)] << penalty; update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } @@ -682,12 +686,12 @@ namespace { } } - // Step 6. Evaluate the position statically + // Step 6. Static evaluation of the position if (inCheck) { ss->staticEval = eval = VALUE_NONE; improving = false; - goto moves_loop; + goto moves_loop; // Skip early pruning when in check } else if (ttHit) { @@ -710,13 +714,7 @@ namespace { ss->staticEval, TT.generation()); } - improving = ss->staticEval >= (ss-2)->staticEval - ||(ss-2)->staticEval == VALUE_NONE; - - if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move())) - goto moves_loop; - - // Step 7. Razoring (skipped when in check, ~2 Elo) + // Step 7. Razoring (~2 Elo) if ( !PvNode && depth < 3 * ONE_PLY && eval <= alpha - RazorMargin[depth / ONE_PLY]) @@ -727,7 +725,10 @@ namespace { return v; } - // Step 8. Futility pruning: child node (skipped when in check, ~30 Elo) + improving = ss->staticEval >= (ss-2)->staticEval + || (ss-2)->staticEval == VALUE_NONE; + + // Step 8. Futility pruning: child node (~30 Elo) if ( !rootNode && depth < 7 * ONE_PLY && eval - futility_margin(depth, improving) >= beta @@ -736,9 +737,13 @@ namespace { // Step 9. Null move search with verification search (~40 Elo) if ( !PvNode + && (ss-1)->currentMove != MOVE_NULL + && (ss-1)->statScore < 22500 && eval >= beta && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225 - && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd)) + && !excludedMove + && pos.non_pawn_material(us) + && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) { assert(eval - beta >= 0); @@ -750,7 +755,7 @@ namespace { pos.do_null_move(st); - Value nullValue = -search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); + Value nullValue = -search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); pos.undo_null_move(); @@ -760,32 +765,32 @@ namespace { if (nullValue >= VALUE_MATE_IN_MAX_PLY) nullValue = beta; - if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply)) + if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 12 * ONE_PLY)) return nullValue; - // Do verification search at high depths. Disable null move pruning - // for side to move for the first part of the remaining search tree. - thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4; - thisThread->nmp_odd = ss->ply % 2; + assert(!thisThread->nmpMinPly); // Recursive verification is not allowed - Value v = search(pos, ss, beta-1, beta, depth-R, false, true); + // Do verification search at high depths, with null move pruning disabled + // for us, until ply exceeds nmpMinPly. + thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4; + thisThread->nmpColor = us; - thisThread->nmp_odd = thisThread->nmp_ply = 0; + Value v = search(pos, ss, beta-1, beta, depth-R, false); + + thisThread->nmpMinPly = 0; if (v >= beta) return nullValue; } } - // Step 10. ProbCut (skipped when in check, ~10 Elo) + // Step 10. ProbCut (~10 Elo) // If we have a good enough capture and a reduced search returns a value // much above beta, we can (almost) safely prune the previous move. if ( !PvNode && depth >= 5 * ONE_PLY && abs(beta) < VALUE_MATE_IN_MAX_PLY) { - assert(is_ok((ss-1)->currentMove)); - Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE); MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory); int probCutCount = 0; @@ -808,7 +813,7 @@ namespace { // If the qsearch held perform the regular search if (value >= rbeta) - value = -search(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false); + value = -search(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode); pos.undo_move(move); @@ -817,13 +822,11 @@ namespace { } } - // Step 11. Internal iterative deepening (skipped when in check, ~2 Elo) - if ( depth >= 6 * ONE_PLY - && !ttMove - && (PvNode || ss->staticEval + 128 >= beta)) + // Step 11. Internal iterative deepening (~2 Elo) + if ( depth >= 8 * ONE_PLY + && !ttMove) { - Depth d = 3 * depth / 4 - 2 * ONE_PLY; - search(pos, ss, alpha, beta, d, cutNode, true); + search(pos, ss, alpha, beta, depth - 7 * ONE_PLY, cutNode); tte = TT.probe(posKey, ttHit); ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; @@ -835,7 +838,11 @@ moves_loop: // When in check, search starts from here 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, &thisThread->mainHistory, &thisThread->captureHistory, contHist, countermove, ss->killers); + MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, + &thisThread->captureHistory, + contHist, + countermove, + ss->killers); value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc skipQuiets = false; @@ -855,8 +862,8 @@ moves_loop: // When in check, search starts from here // Move List. As a consequence any illegal move is also skipped. In MultiPV // mode we also skip PV moves which have been already searched and those // of lower "TB rank" if we are in a TB root position. - if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx, - thisThread->rootMoves.begin() + thisThread->PVLast, move)) + if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->pvIdx, + thisThread->rootMoves.begin() + thisThread->pvLast, move)) continue; ss->moveCount = ++moveCount; @@ -864,7 +871,7 @@ moves_loop: // When in check, search starts from here if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000) sync_cout << "info depth " << depth / ONE_PLY << " currmove " << UCI::move(move, pos.is_chess960()) - << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl; + << " currmovenumber " << moveCount + thisThread->pvIdx << sync_endl; if (PvNode) (ss+1)->pv = nullptr; @@ -894,7 +901,7 @@ moves_loop: // When in check, search starts from here { Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); ss->excludedMove = move; - value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode, true); + value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); ss->excludedMove = MOVE_NONE; if (value < rBeta) @@ -910,7 +917,7 @@ moves_loop: // When in check, search starts from here // Step 14. Pruning at shallow depth (~170 Elo) if ( !rootNode - && pos.non_pawn_material(pos.side_to_move()) + && pos.non_pawn_material(us) && bestValue > VALUE_MATED_IN_MAX_PLY) { if ( !captureOrPromotion @@ -940,13 +947,11 @@ moves_loop: // When in check, search starts from here continue; // Prune moves with negative SEE (~10 Elo) - if ( lmrDepth < 8 - && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth))) + if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth))) continue; } - else if ( depth < 7 * ONE_PLY // (~20 Elo) - && !extension - && !pos.see_ge(move, -Value(CapturePruneMargin[depth / ONE_PLY]))) + else if ( !extension // (~20 Elo) + && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) continue; } @@ -979,7 +984,13 @@ moves_loop: // When in check, search starts from here Depth r = reduction(improving, depth, moveCount); if (captureOrPromotion) // (~5 Elo) + { + // Increase reduction by comparing opponent's stat score + if ((ss-1)->statScore >= 0) + r += ONE_PLY; + r -= r ? ONE_PLY : DEPTH_ZERO; + } else { // Decrease reduction if opponent's move count is high (~5 Elo) @@ -1005,7 +1016,7 @@ moves_loop: // When in check, search starts from here && !pos.see_ge(make_move(to_sq(move), from_sq(move)))) r -= 2 * ONE_PLY; - ss->statScore = thisThread->mainHistory[~pos.side_to_move()][from_to(move)] + ss->statScore = thisThread->mainHistory[us][from_to(move)] + (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)] @@ -1024,7 +1035,7 @@ 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, false); + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); doFullDepthSearch = (value > alpha && d != newDepth); } @@ -1033,7 +1044,7 @@ moves_loop: // When in check, search starts from here // Step 17. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); // For PV nodes only, do a full PV search on the first move or after a fail // high (in the latter case search only if value < beta), otherwise let the @@ -1043,7 +1054,7 @@ moves_loop: // When in check, search starts from here (ss+1)->pv = pv; (ss+1)->pv[0] = MOVE_NONE; - value = -search(pos, ss+1, -beta, -alpha, newDepth, false, false); + value = -search(pos, ss+1, -beta, -alpha, newDepth, false); } // Step 18. Undo move @@ -1104,7 +1115,7 @@ moves_loop: // When in check, search starts from here else { assert(value >= beta); // Fail high - ss->statScore = std::max(ss->statScore, 0); + ss->statScore = 0; break; } } @@ -1142,16 +1153,17 @@ moves_loop: // When in check, search starts from here { // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); + update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, + stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO))); else - update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth)); + update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY)); // 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)); } // Bonus for prior countermove that caused the fail low - else if ( depth >= 3 * ONE_PLY + else if ( (depth >= 3 * ONE_PLY || PvNode) && !pos.captured_piece() && is_ok((ss-1)->currentMove)) update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); @@ -1275,7 +1287,9 @@ 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, &pos.this_thread()->mainHistory, &pos.this_thread()->captureHistory, to_sq((ss-1)->currentMove)); + MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory, + &pos.this_thread()->captureHistory, + 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) @@ -1552,14 +1566,14 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { std::stringstream ss; TimePoint elapsed = Time.elapsed() + 1; const RootMoves& rootMoves = pos.this_thread()->rootMoves; - size_t PVIdx = pos.this_thread()->PVIdx; + size_t pvIdx = pos.this_thread()->pvIdx; size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size()); uint64_t nodesSearched = Threads.nodes_searched(); uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0); for (size_t i = 0; i < multiPV; ++i) { - bool updated = (i <= PVIdx && rootMoves[i].score != -VALUE_INFINITE); + bool updated = (i <= pvIdx && rootMoves[i].score != -VALUE_INFINITE); if (depth == ONE_PLY && !updated) continue; @@ -1568,7 +1582,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore; bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; - v = tb ? rootMoves[i].TBScore : v; + v = tb ? rootMoves[i].tbScore : v; if (ss.rdbuf()->in_avail()) // Not at first line ss << "\n"; @@ -1579,7 +1593,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { << " multipv " << i + 1 << " score " << UCI::value(v); - if (!tb && i == PVIdx) + if (!tb && i == pvIdx) ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : ""); ss << " nodes " << nodesSearched @@ -1662,16 +1676,16 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) { { // Sort moves according to TB rank std::sort(rootMoves.begin(), rootMoves.end(), - [](const RootMove &a, const RootMove &b) { return a.TBRank > b.TBRank; } ); + [](const RootMove &a, const RootMove &b) { return a.tbRank > b.tbRank; } ); // Probe during search only if DTZ is not available and we are winning - if (dtz_available || rootMoves[0].TBScore <= VALUE_DRAW) + if (dtz_available || rootMoves[0].tbScore <= VALUE_DRAW) Cardinality = 0; } else { // Assign the same rank to all moves for (auto& m : rootMoves) - m.TBRank = 0; + m.tbRank = 0; } }