X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=756b2d5769fb6f44b854cad829f9e1b1242746ef;hp=c9526ec3c683e38a013089dfcd98bb661f3f2c0e;hb=ae5d2c38e1b9f6a990c29d31a37d6555d197f939;hpb=3f1eb85a1ceb1b408f8f51cb82064b69e095399d diff --git a/src/search.cpp b/src/search.cpp index c9526ec3..756b2d57 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) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2019 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 @@ -85,10 +85,10 @@ namespace { return d > 17 ? 0 : 29 * d * d + 138 * d - 134; } - // Add a small random component to draw evaluations to keep search dynamic + // Add a small random component to draw evaluations to keep search dynamic // and to avoid 3fold-blindness. Value value_draw(Depth depth, Thread* thisThread) { - return depth < 4 ? VALUE_DRAW + return depth < 4 ? VALUE_DRAW : VALUE_DRAW + Value(2 * (thisThread->nodes.load(std::memory_order_relaxed) % 2) - 1); } @@ -187,6 +187,7 @@ void Search::clear() { Time.availableNodes = 0; TT.clear(); Threads.clear(); + Tablebases::init(Options["SyzygyPath"]); // Free up mapped files } @@ -253,7 +254,7 @@ void MainThread::search() { && !Skill(Options["Skill Level"]).enabled() && rootMoves[0].pv[0] != MOVE_NONE) { - std::map votes; + std::map votes; Value minScore = this->rootMoves[0].score; // Find out minimum score and reset votes for moves which can be voted @@ -264,12 +265,13 @@ void MainThread::search() { } // Vote according to score and depth + auto square = [](int64_t x) { return x * x; }; for (Thread* th : Threads) - votes[th->rootMoves[0].pv[0]] += int(th->rootMoves[0].score - minScore) - + int(th->completedDepth); + votes[th->rootMoves[0].pv[0]] += 200 + (square(th->rootMoves[0].score - minScore + 1) + * int64_t(th->completedDepth)); // Select best thread - int bestVote = votes[this->rootMoves[0].pv[0]]; + int64_t bestVote = votes[this->rootMoves[0].pv[0]]; for (Thread* th : Threads) { if (votes[th->rootMoves[0].pv[0]] > bestVote) @@ -302,6 +304,7 @@ void MainThread::search() { void Thread::search() { Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2) + Move pv[MAX_PLY+1]; Value bestValue, alpha, beta, delta; Move lastBestMove = MOVE_NONE; Depth lastBestMoveDepth = DEPTH_ZERO; @@ -313,6 +316,7 @@ void Thread::search() { std::memset(ss-4, 0, 7 * sizeof(Stack)); for (int i = 4; i > 0; i--) (ss-i)->continuationHistory = &this->continuationHistory[NO_PIECE][0]; // Use as sentinel + ss->pv = pv; bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; @@ -447,7 +451,7 @@ void Thread::search() { { beta = std::min(bestValue + delta, VALUE_INFINITE); if (mainThread) - ++failedHighCnt; + ++failedHighCnt; } else break; @@ -491,10 +495,8 @@ void Thread::search() { && !Threads.stop && !Threads.stopOnPonderhit) { - const int F[] = { failedLow, - bestValue - mainThread->previousScore }; - - int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1])); + double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0; + fallingEval = std::max(0.5, std::min(1.5, fallingEval)); // If the bestMove is stable over several iterations, reduce time accordingly timeReduction = 1.0; @@ -508,7 +510,7 @@ void Thread::search() { // Stop the search if we have only one legal move, or if available time elapsed if ( rootMoves.size() == 1 - || Time.elapsed() > Time.optimum() * bestMoveInstability * improvingFactor / 581) + || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval) { // If we are allowed to ponder do not stop the search now but // keep pondering until the GUI sends "ponderhit" or "stop". @@ -598,7 +600,7 @@ namespace { if ( Threads.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) - return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) + return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) : value_draw(depth, pos.this_thread()); // Step 3. Mate distance pruning. Even if we mate at the next move our score @@ -654,9 +656,11 @@ namespace { if (!pos.capture_or_promotion(ttMove)) update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted + if ( (ss-1)->moveCount == 1 + || ((ss-1)->currentMove == (ss-1)->killers[0] && (ss-1)->killers[0])) + if (!pos.captured_piece()) + update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); } // Penalty for a quiet ttMove that fails low else if (!pos.capture_or_promotion(ttMove)) @@ -682,6 +686,10 @@ namespace { TB::ProbeState err; TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err); + // Force check of time on the next occasion + if (thisThread == Threads.main()) + static_cast(thisThread)->callsCnt = 0; + if (err != TB::ProbeState::FAIL) { thisThread->tbHits.fetch_add(1, std::memory_order_relaxed); @@ -753,15 +761,16 @@ namespace { } // Step 7. Razoring (~2 Elo) - if ( depth < 2 * ONE_PLY - && eval <= alpha - RazorMargin) + if ( !rootNode // The required rootNode PV handling is not available in qsearch + && depth < 2 * ONE_PLY + && eval <= alpha - RazorMargin) return qsearch(pos, ss, alpha, beta); improving = ss->staticEval >= (ss-2)->staticEval || (ss-2)->staticEval == VALUE_NONE; // Step 8. Futility pruning: child node (~30 Elo) - if ( !rootNode + if ( !PvNode && depth < 7 * ONE_PLY && eval - futility_margin(depth, improving) >= beta && eval < VALUE_KNOWN_WIN) // Do not return unproven wins @@ -823,8 +832,8 @@ namespace { && depth >= 5 * ONE_PLY && abs(beta) < VALUE_MATE_IN_MAX_PLY) { - Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE); - MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory); + Value raisedBeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE); + MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory); int probCutCount = 0; while ( (move = mp.next_move()) != MOVE_NONE @@ -841,15 +850,15 @@ namespace { pos.do_move(move, st); // Perform a preliminary qsearch to verify that the move holds - value = -qsearch(pos, ss+1, -rbeta, -rbeta+1); + value = -qsearch(pos, ss+1, -raisedBeta, -raisedBeta+1); // If the qsearch held perform the regular search - if (value >= rbeta) - value = -search(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode); + if (value >= raisedBeta) + value = -search(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4 * ONE_PLY, !cutNode); pos.undo_move(move); - if (value >= rbeta) + if (value >= raisedBeta) return value; } } @@ -925,24 +934,28 @@ moves_loop: // When in check, search starts from here if ( depth >= 8 * ONE_PLY && move == ttMove && !rootNode - && !excludedMove // Recursive singular search is not allowed + && !excludedMove // Avoid recursive singular search && ttValue != VALUE_NONE && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3 * ONE_PLY && pos.legal(move)) { - Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); + Value reducedBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); ss->excludedMove = move; - value = search(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode); + value = search(pos, ss, reducedBeta - 1, reducedBeta, depth / 2, cutNode); ss->excludedMove = MOVE_NONE; - if (value < rBeta) + if (value < reducedBeta) extension = ONE_PLY; } else if ( givesCheck // Check extension (~2 Elo) && pos.see_ge(move)) extension = ONE_PLY; + // Extension if castling + else if (type_of(move) == CASTLING) + extension = ONE_PLY; + // Calculate new depth for this move newDepth = depth - ONE_PLY + extension; @@ -953,7 +966,7 @@ moves_loop: // When in check, search starts from here { if ( !captureOrPromotion && !givesCheck - && (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= Value(5000))) + && !pos.advanced_pawn_push(move)) { // Move count based pruning (~30 Elo) if (moveCountPruning) @@ -966,7 +979,7 @@ moves_loop: // When in check, search starts from here int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY; // Countermoves based pruning (~20 Elo) - if ( lmrDepth < 3 + ((ss-1)->statScore > 0) + if ( lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1) && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) continue; @@ -1178,9 +1191,12 @@ moves_loop: // When in check, search starts from here 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)); + // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted + if ( (ss-1)->moveCount == 1 + || ((ss-1)->currentMove == (ss-1)->killers[0] && (ss-1)->killers[0])) + if (!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 || PvNode) @@ -1386,21 +1402,15 @@ moves_loop: // When in check, search starts from here if (value > alpha) { + bestMove = move; + if (PvNode) // Update pv even in fail-high case update_pv(ss->pv, move, (ss+1)->pv); if (PvNode && value < beta) // Update alpha here! - { alpha = value; - bestMove = move; - } - else // Fail high - { - tte->save(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, - ttDepth, move, ss->staticEval); - - return value; - } + else + break; // Fail high } } } @@ -1411,7 +1421,8 @@ moves_loop: // When in check, search starts from here return mated_in(ss->ply); // Plies to mate from the root tte->save(posKey, value_to_tt(bestValue, ss->ply), - PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + bestValue >= beta ? BOUND_LOWER : + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, ttDepth, bestMove, ss->staticEval); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);