X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=31b6967c17ff008b97e6c939731a523232d92c17;hp=25383aae9d2504801f05e8e82aff4245d3990f61;hb=d7022031130ef84b801e087c1804d0cf05bc369b;hpb=108f0da4d7f993732aa2e854b8f3fa8ca6d3b46c diff --git a/src/search.cpp b/src/search.cpp index 25383aae..31b6967c 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -92,7 +92,7 @@ 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 +107,7 @@ 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); @@ -317,7 +317,7 @@ void Thread::search() { multiPV = std::min(multiPV, rootMoves.size()); - int ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns + int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns // In analysis mode, adjust contempt in accordance with user preference if (Limits.infinite || Options["UCI_AnalyseMode"]) @@ -379,7 +379,7 @@ void Thread::search() { 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 +390,7 @@ 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 @@ -517,7 +517,7 @@ 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) { + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { // Use quiescence search when needed if (depth < ONE_PLY) @@ -547,6 +547,7 @@ 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; @@ -577,6 +578,17 @@ namespace { beta = std::min(mate_in(ss->ply+1), beta); if (alpha >= beta) return alpha; + + // Check if there exists a move which draws by repetition, or an alternative + // earlier move to this position. + if ( pos.rule50_count() >= 3 + && alpha < VALUE_DRAW + && pos.has_game_cycle(ss->ply)) + { + alpha = VALUE_DRAW; + if (alpha >= beta) + return alpha; + } } assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -628,7 +640,7 @@ 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 +694,12 @@ 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 +722,7 @@ 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 +733,10 @@ 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 +745,13 @@ 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->nmp_min_ply || us != thisThread->nmp_color)) { assert(eval - beta >= 0); @@ -750,7 +763,7 @@ 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 +773,30 @@ namespace { if (nullValue >= VALUE_MATE_IN_MAX_PLY) nullValue = beta; - if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply)) + if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_min_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; + thisThread->nmp_min_ply = ss->ply + 3 * (depth-R) / 4 - 1; + thisThread->nmp_color = us; - Value v = search(pos, ss, beta-1, beta, depth-R, false, true); + Value v = search(pos, ss, beta-1, beta, depth-R, false); - thisThread->nmp_odd = thisThread->nmp_ply = 0; + thisThread->nmp_min_ply = 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 +819,7 @@ 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 +828,12 @@ 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, d, cutNode); tte = TT.probe(posKey, ttHit); ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; @@ -835,7 +845,11 @@ 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; @@ -894,7 +908,7 @@ 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 +924,7 @@ 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 @@ -978,53 +992,53 @@ moves_loop: // When in check, search starts from here { Depth r = reduction(improving, depth, moveCount); - if (captureOrPromotion) + if (captureOrPromotion) // (~5 Elo) r -= r ? ONE_PLY : DEPTH_ZERO; else { - // Decrease reduction if opponent's move count is high + // Decrease reduction if opponent's move count is high (~5 Elo) if ((ss-1)->moveCount > 15) r -= ONE_PLY; - // Decrease reduction for exact PV nodes + // Decrease reduction for exact PV nodes (~0 Elo) if (pvExact) r -= ONE_PLY; - // Increase reduction if ttMove is a capture + // Increase reduction if ttMove is a capture (~0 Elo) if (ttCapture) r += ONE_PLY; - // Increase reduction for cut nodes + // Increase reduction for cut nodes (~5 Elo) if (cutNode) r += 2 * ONE_PLY; // 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(). + // hence break make_move(). (~5 Elo) else if ( type_of(move) == NORMAL && !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)] - 4000; - // Decrease/increase reduction by comparing opponent's stat score + // Decrease/increase reduction by comparing opponent's stat score (~10 Elo) if (ss->statScore >= 0 && (ss-1)->statScore < 0) r -= ONE_PLY; else if ((ss-1)->statScore >= 0 && ss->statScore < 0) r += ONE_PLY; - // Decrease/increase reduction for moves with a good/bad history + // Decrease/increase reduction for moves with a good/bad history (~30 Elo) r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY); } 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 +1047,7 @@ 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 +1057,7 @@ 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 +1118,7 @@ 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; } } @@ -1151,7 +1165,7 @@ moves_loop: // When in check, search starts from here 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 +1289,9 @@ 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) @@ -1632,9 +1648,9 @@ bool RootMove::extract_ponder_from_tt(Position& pos) { void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) { RootInTB = false; - UseRule50 = Options["Syzygy50MoveRule"]; - ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY; - Cardinality = Options["SyzygyProbeLimit"]; + UseRule50 = bool(Options["Syzygy50MoveRule"]); + ProbeDepth = int(Options["SyzygyProbeDepth"]) * ONE_PLY; + Cardinality = int(Options["SyzygyProbeLimit"]); bool dtz_available = true; // Tables with fewer pieces than SyzygyProbeLimit are searched with