X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=44347f79f8b85ec1aee88b579c65c6f9d9b48908;hp=cfa737dbd6773bf72cd460a19eb71f9b143232e1;hb=5c4002aa827653a125130a0d01d0bb96dd2b8bae;hpb=76f1807baa90eb69f66001d25df2a28533f9406f diff --git a/src/search.cpp b/src/search.cpp index cfa737db..44347f79 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -67,10 +67,10 @@ namespace { } // Reductions lookup table, initialized at startup - int Reductions[64]; // [depth or moveNumber] + int Reductions[MAX_MOVES]; // [depth or moveNumber] template Depth reduction(bool i, Depth d, int mn) { - int r = Reductions[std::min(d / ONE_PLY, 63)] * Reductions[std::min(mn, 63)] / 1024; + int r = Reductions[d / ONE_PLY] * Reductions[mn] / 1024; return ((r + 512) / 1024 + (!i && r > 1024) - PvNode) * ONE_PLY; } @@ -84,11 +84,10 @@ namespace { return d > 17 ? 0 : 29 * d * d + 138 * d - 134; } - // Add a small random component to draw evaluations to keep search dynamic - // and to avoid 3fold-blindness. + // Add a small random component to draw evaluations to avoid 3fold-blindness Value value_draw(Depth depth, Thread* thisThread) { - return depth < 4 ? VALUE_DRAW - : VALUE_DRAW + Value(2 * (thisThread->nodes.load(std::memory_order_relaxed) % 2) - 1); + return depth < 4 * ONE_PLY ? VALUE_DRAW + : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1); } // Skill structure is used to implement strength limit @@ -148,7 +147,7 @@ namespace { void Search::init() { - for (int i = 1; i < 64; ++i) + for (int i = 1; i < MAX_MOVES; ++i) Reductions[i] = int(1024 * std::log(i) / std::sqrt(1.95)); } @@ -162,12 +161,12 @@ void Search::clear() { Time.availableNodes = 0; TT.clear(); Threads.clear(); - Tablebases::init(Options["SyzygyPath"]); // Free up mapped files + Tablebases::init(Options["SyzygyPath"]); // Free mapped files } -/// MainThread::search() is called by the main thread when the program receives -/// the UCI 'go' command. It searches from the root position and outputs the "bestmove". +/// MainThread::search() is started when the program receives the UCI 'go' +/// command. It searches from the root position and outputs the "bestmove". void MainThread::search() { @@ -192,8 +191,11 @@ void MainThread::search() { else { for (Thread* th : Threads) + { + th->bestMoveChanges = 0; if (th != this) th->start_searching(); + } Thread::search(); // Let's start searching! } @@ -221,8 +223,9 @@ void MainThread::search() { if (Limits.npmsec) Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); - // Check if there are threads with a better score than main thread Thread* bestThread = this; + + // Check if there are threads with a better score than main thread if ( Options["MultiPV"] == 1 && !Limits.depth && !Skill(Options["Skill Level"]).enabled() @@ -273,9 +276,9 @@ void MainThread::search() { void Thread::search() { - // To allow access to (ss-5) up to (ss+2), the stack must be oversized. + // To allow access to (ss-7) up to (ss+2), the stack must be oversized. // The former is needed to allow update_continuation_histories(ss-1, ...), - // which accesses its argument at ss-4, also near the root. + // which accesses its argument at ss-6, also near the root. // The latter is needed for statScores and killer initialization. Stack stack[MAX_PLY+10], *ss = stack+7; Move pv[MAX_PLY+1]; @@ -283,7 +286,7 @@ void Thread::search() { Move lastBestMove = MOVE_NONE; Depth lastBestMoveDepth = DEPTH_ZERO; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); - double timeReduction = 1.0; + double timeReduction = 1, totBestMoveChanges = 0; Color us = rootPos.side_to_move(); std::memset(ss-7, 0, 10 * sizeof(Stack)); @@ -294,9 +297,6 @@ void Thread::search() { bestValue = delta = alpha = -VALUE_INFINITE; beta = VALUE_INFINITE; - if (mainThread) - mainThread->bestMoveChanges = 0; - size_t multiPV = Options["MultiPV"]; Skill skill(Options["Skill Level"]); @@ -317,7 +317,7 @@ void Thread::search() { : Options["Analysis Contempt"] == "Black" && us == WHITE ? -ct : ct; - // In evaluate.cpp the evaluation is from the white point of view + // Evaluation score is from the white point of view contempt = (us == WHITE ? make_score(ct, ct / 2) : -make_score(ct, ct / 2)); @@ -328,7 +328,7 @@ void Thread::search() { { // Age out PV variability metric if (mainThread) - mainThread->bestMoveChanges *= 0.517; + totBestMoveChanges /= 2; // 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. @@ -459,7 +459,7 @@ void Thread::search() { && !Threads.stop && !mainThread->stopOnPonderhit) { - double fallingEval = (306 + 9 * (mainThread->previousScore - bestValue)) / 581.0; + double fallingEval = (314 + 9 * (mainThread->previousScore - bestValue)) / 581.0; fallingEval = clamp(fallingEval, 0.5, 1.5); // If the bestMove is stable over several iterations, reduce time accordingly @@ -467,7 +467,12 @@ void Thread::search() { double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction; // Use part of the gained time from a previous stable move for the current move - double bestMoveInstability = 1.0 + mainThread->bestMoveChanges; + for (Thread* th : Threads) + { + totBestMoveChanges += th->bestMoveChanges; + th->bestMoveChanges = 0; + } + double bestMoveInstability = 1 + totBestMoveChanges / Threads.size(); // Stop the search if we have only one legal move, or if available time elapsed if ( rootMoves.size() == 1 @@ -533,7 +538,7 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, maxValue, pureStaticEval; + Value bestValue, value, ttValue, eval, maxValue; bool ttHit, ttPv, inCheck, givesCheck, improving; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture; Piece movedPiece; @@ -579,8 +584,7 @@ namespace { assert(0 <= ss->ply && ss->ply < MAX_PLY); (ss+1)->ply = ss->ply + 1; - ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; - ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0]; + (ss+1)->excludedMove = bestMove = MOVE_NONE; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; Square prevSq = to_sq((ss-1)->currentMove); @@ -602,15 +606,6 @@ namespace { : ttHit ? tte->move() : MOVE_NONE; ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY); - // if position has been searched at higher depths and we are shuffling, return value_draw - if (pos.rule50_count() > 36 - && ss->ply > 36 - && depth < 3 * ONE_PLY - && ttHit - && tte->depth() > depth - && pos.count() > 0) - return VALUE_DRAW; - // At non-PV nodes we check for an early TT cutoff if ( !PvNode && ttHit @@ -627,9 +622,8 @@ namespace { if (!pos.capture_or_promotion(ttMove)) update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // 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]) - && !pos.captured_piece()) + // Extra penalty for early quiet moves of the previous ply + if ((ss-1)->moveCount <= 2 && !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 @@ -697,16 +691,16 @@ namespace { // Step 6. Static evaluation of the position if (inCheck) { - ss->staticEval = eval = pureStaticEval = VALUE_NONE; + ss->staticEval = eval = VALUE_NONE; improving = false; goto moves_loop; // Skip early pruning when in check } else if (ttHit) { // Never assume anything on values stored in TT - ss->staticEval = eval = pureStaticEval = tte->eval(); + ss->staticEval = eval = tte->eval(); if (eval == VALUE_NONE) - ss->staticEval = eval = pureStaticEval = evaluate(pos); + ss->staticEval = eval = evaluate(pos); // Can ttValue be used as a better position evaluation? if ( ttValue != VALUE_NONE @@ -719,13 +713,12 @@ namespace { { int bonus = -(ss-1)->statScore / 512; - pureStaticEval = evaluate(pos); - ss->staticEval = eval = pureStaticEval + bonus; + ss->staticEval = eval = evaluate(pos) + bonus; } else - ss->staticEval = eval = pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo; + ss->staticEval = eval = -(ss-1)->staticEval + 2 * Eval::Tempo; - tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval); + tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); } // Step 7. Razoring (~2 Elo) @@ -749,7 +742,7 @@ namespace { && (ss-1)->currentMove != MOVE_NULL && (ss-1)->statScore < 23200 && eval >= beta - && pureStaticEval >= beta - 36 * depth / ONE_PLY + 225 + && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) @@ -781,7 +774,7 @@ namespace { // 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->nmpMinPly = ss->ply + 3 * (depth-R) / (4 * ONE_PLY); thisThread->nmpColor = us; Value v = search(pos, ss, beta-1, beta, depth-R, false); @@ -832,8 +825,7 @@ namespace { } // Step 11. Internal iterative deepening (~2 Elo) - if ( depth >= 8 * ONE_PLY - && !ttMove) + if (depth >= 8 * ONE_PLY && !ttMove) { search(pos, ss, alpha, beta, depth - 7 * ONE_PLY, cutNode); @@ -847,6 +839,7 @@ moves_loop: // When in check, search starts from here const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, nullptr, (ss-4)->continuationHistory, nullptr, (ss-6)->continuationHistory }; + Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]; MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, @@ -854,8 +847,8 @@ moves_loop: // When in check, search starts from here contHist, countermove, ss->killers); - value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc + value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc moveCountPruning = false; ttCapture = ttMove && pos.capture_or_promotion(ttMove); @@ -908,8 +901,9 @@ moves_loop: // When in check, search starts from here && pos.legal(move)) { Value singularBeta = ttValue - 2 * depth / ONE_PLY; + Depth halfDepth = depth / (2 * ONE_PLY) * ONE_PLY; // ONE_PLY invariant ss->excludedMove = move; - value = search(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode); + value = search(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode); ss->excludedMove = MOVE_NONE; if (value < singularBeta) @@ -929,12 +923,21 @@ moves_loop: // When in check, search starts from here && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move))) extension = ONE_PLY; + // Castling extension + else if (type_of(move) == CASTLING) + extension = ONE_PLY; + // Shuffle extension - else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode) + else if ( PvNode + && pos.rule50_count() > 18 + && depth < 3 * ONE_PLY + && ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid too deep searches extension = ONE_PLY; - // Castling extension - else if (type_of(move) == CASTLING) + // Passed pawn extension + else if ( move == ss->killers[0] + && pos.advanced_pawn_push(move) + && pos.pawn_passed(us, to_sq(move))) extension = ONE_PLY; // Calculate new depth for this move @@ -946,7 +949,7 @@ moves_loop: // When in check, search starts from here && bestValue > VALUE_MATED_IN_MAX_PLY) { // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold - moveCountPruning = moveCount >= futility_move_count(improving,depth / ONE_PLY); + moveCountPruning = moveCount >= futility_move_count(improving, depth / ONE_PLY); if ( !captureOrPromotion && !givesCheck @@ -957,7 +960,8 @@ moves_loop: // When in check, search starts from here continue; // Reduced depth of the next LMR search - int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY; + int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO); + lmrDepth /= ONE_PLY; // Countermoves based pruning (~20 Elo) if ( lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1) @@ -1102,8 +1106,8 @@ moves_loop: // When in check, search starts from here // 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 (moveCount > 1 && thisThread == Threads.main()) - ++static_cast(thisThread)->bestMoveChanges; + if (moveCount > 1) + ++thisThread->bestMoveChanges; } else // All other moves but the PV are set to the lowest value: this @@ -1189,7 +1193,7 @@ moves_loop: // When in check, search starts from here tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv, bestValue >= beta ? BOUND_LOWER : PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, pureStaticEval); + depth, bestMove, ss->staticEval); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1228,8 +1232,7 @@ moves_loop: // When in check, search starts from here Thread* thisThread = pos.this_thread(); (ss+1)->ply = ss->ply + 1; - ss->currentMove = bestMove = MOVE_NONE; - ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0]; + bestMove = MOVE_NONE; inCheck = pos.checkers(); moveCount = 0;