X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=993fa853f47ce51d95c167ae3c951f70fce4f27b;hp=b0bcc57a44ee05f8f71fe2205d187f25622613fb;hb=b7ecdaada7e2690dd286c41d3a73463f06fb088f;hpb=13f70d0392ca3ce7f1c8e34dd0a10c3537d2fbab diff --git a/src/search.cpp b/src/search.cpp index b0bcc57a..993fa853 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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2020 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 @@ -79,7 +79,7 @@ namespace { } constexpr int futility_move_count(bool improving, Depth depth) { - return (5 + depth * depth) * (1 + improving) / 2 - 1; + return (4 + depth * depth) / (2 - improving); } // History and stats update bonus, based on depth @@ -156,7 +156,7 @@ namespace { Value value_from_tt(Value v, int ply, int r50c); void update_pv(Move* pv, Move move, Move* childPv); void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus); - void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus); + void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth); void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq, Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth); @@ -290,13 +290,13 @@ void MainThread::search() { votes[th->rootMoves[0].pv[0]] += (th->rootMoves[0].score - minScore + 14) * int(th->completedDepth); - if (bestThread->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY) + if (bestThread->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY) { // Make sure we pick the shortest mate if (th->rootMoves[0].score > bestThread->rootMoves[0].score) bestThread = th; } - else if ( th->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY + else if ( th->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY || votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]]) bestThread = th; } @@ -365,7 +365,7 @@ void Thread::search() { // for match (TC 60+0.6) results spanning a wide range of k values. PRNG rng(now()); double floatLevel = Options["UCI_LimitStrength"] ? - clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) : + Utility::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) : double(Options["Skill Level"]); int intLevel = int(floatLevel) + ((floatLevel - int(floatLevel)) * 1024 > rng.rand() % 1024 ? 1 : 0); @@ -393,6 +393,8 @@ void Thread::search() { contempt = (us == WHITE ? make_score(ct, ct / 2) : -make_score(ct, ct / 2)); + int searchAgainCounter = 0; + // Iterative deepening loop until requested to stop or the target depth is reached while ( ++rootDepth < MAX_PLY && !Threads.stop @@ -410,6 +412,9 @@ void Thread::search() { size_t pvFirst = 0; pvLast = 0; + if (!Threads.increaseDepth) + searchAgainCounter++; + // MultiPV loop. We perform a full root search for each PV line for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx) { @@ -428,7 +433,7 @@ void Thread::search() { if (rootDepth >= 4) { Value previousScore = rootMoves[pvIdx].previousScore; - delta = Value(21 + abs(previousScore) / 256); + delta = Value(21); alpha = std::max(previousScore - delta,-VALUE_INFINITE); beta = std::min(previousScore + delta, VALUE_INFINITE); @@ -445,7 +450,7 @@ void Thread::search() { int failedHighCnt = 0; while (true) { - Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt); + Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter); bestValue = ::search(rootPos, ss, alpha, beta, adjustedDepth, false); // Bring the best move to the front. It is critical that sorting @@ -533,7 +538,7 @@ void Thread::search() { { double fallingEval = (332 + 6 * (mainThread->previousScore - bestValue) + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0; - fallingEval = clamp(fallingEval, 0.5, 1.5); + fallingEval = Utility::clamp(fallingEval, 0.5, 1.5); // If the bestMove is stable over several iterations, reduce time accordingly timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.94 : 0.91; @@ -558,6 +563,12 @@ void Thread::search() { else Threads.stop = true; } + else if ( Threads.increaseDepth + && !mainThread->ponder + && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6) + Threads.increaseDepth = false; + else + Threads.increaseDepth = true; } mainThread->iterValue[iterIdx] = bestValue; @@ -684,6 +695,10 @@ namespace { ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; ttPv = PvNode || (ttHit && tte->is_pv()); + + if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove)) + thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5); + // thisThread->ttHitAverage can be used to approximate the running average of ttHit thisThread->ttHitAverage = (ttHitAverageWindow - 1) * thisThread->ttHitAverage / ttHitAverageWindow + ttHitAverageResolution * ttHit; @@ -702,7 +717,7 @@ namespace { if (ttValue >= beta) { if (!pos.capture_or_promotion(ttMove)) - update_quiet_stats(pos, ss, ttMove, stat_bonus(depth)); + update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth); // Extra penalty for early quiet moves of the previous ply if ((ss-1)->moveCount <= 2 && !priorCapture) @@ -716,7 +731,9 @@ namespace { update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } - return ttValue; + + if (pos.rule50_count() < 90) + return ttValue; } // Step 5. Tablebases probe @@ -742,9 +759,10 @@ namespace { int drawScore = TB::UseRule50 ? 1 : 0; - value = wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1 - : wdl > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1 - : VALUE_DRAW + 2 * wdl * drawScore; + // use the range VALUE_MATE_IN_MAX_PLY to VALUE_TB_WIN_IN_MAX_PLY to score + value = wdl < -drawScore ? VALUE_MATED_IN_MAX_PLY + ss->ply + 1 + : wdl > drawScore ? VALUE_MATE_IN_MAX_PLY - ss->ply - 1 + : VALUE_DRAW + 2 * wdl * drawScore; Bound b = wdl < -drawScore ? BOUND_UPPER : wdl > drawScore ? BOUND_LOWER : BOUND_EXACT; @@ -801,21 +819,21 @@ namespace { ss->staticEval = eval = evaluate(pos) + bonus; } else - ss->staticEval = eval = -(ss-1)->staticEval + 2 * Eval::Tempo; + ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo; tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); } - // Step 7. Razoring (~2 Elo) + // Step 7. Razoring (~1 Elo) if ( !rootNode // The required rootNode PV handling is not available in qsearch - && depth < 2 + && depth == 1 && eval <= alpha - RazorMargin) return qsearch(pos, ss, alpha, beta); - improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval >= (ss-4)->staticEval - || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval >= (ss-2)->staticEval; + improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval > (ss-4)->staticEval + || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval > (ss-2)->staticEval; - // Step 8. Futility pruning: child node (~30 Elo) + // Step 8. Futility pruning: child node (~50 Elo) if ( !PvNode && depth < 6 && eval - futility_margin(depth, improving) >= beta @@ -825,10 +843,10 @@ namespace { // Step 9. Null move search with verification search (~40 Elo) if ( !PvNode && (ss-1)->currentMove != MOVE_NULL - && (ss-1)->statScore < 23405 + && (ss-1)->statScore < 23397 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 32 * depth + 317 - improving * 30 + && ss->staticEval >= beta - 32 * depth - 30 * improving + 120 * ttPv + 292 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) @@ -850,7 +868,7 @@ namespace { if (nullValue >= beta) { // Do not return unproven mate scores - if (nullValue >= VALUE_MATE_IN_MAX_PLY) + if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY) nullValue = beta; if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 13)) @@ -877,7 +895,7 @@ namespace { // much above beta, we can (almost) safely prune the previous move. if ( !PvNode && depth >= 5 - && abs(beta) < VALUE_MATE_IN_MAX_PLY) + && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY) { Value raisedBeta = std::min(beta + 189 - 45 * improving, VALUE_INFINITE); MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory); @@ -915,7 +933,7 @@ namespace { } } - // Step 11. Internal iterative deepening (~2 Elo) + // Step 11. Internal iterative deepening (~1 Elo) if (depth >= 7 && !ttMove) { search(pos, ss, alpha, beta, depth - 7, cutNode); @@ -934,14 +952,17 @@ moves_loop: // When in check, search starts from here Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]; MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, + &thisThread->lowPlyHistory, &thisThread->captureHistory, contHist, countermove, - ss->killers); + ss->killers, + depth > 12 ? ss->ply : MAX_PLY); value = bestValue; singularLMR = moveCountPruning = false; ttCapture = ttMove && pos.capture_or_promotion(ttMove); + bool formerPv = ttPv && !PvNode; // Mark this node as being searched ThreadHolding th(thisThread, posKey, ss->ply); @@ -980,10 +1001,10 @@ moves_loop: // When in check, search starts from here // Calculate new depth for this move newDepth = depth - 1; - // Step 13. Pruning at shallow depth (~170 Elo) + // Step 13. Pruning at shallow depth (~200 Elo) if ( !rootNode && pos.non_pawn_material(us) - && bestValue > VALUE_MATED_IN_MAX_PLY) + && bestValue > VALUE_TB_LOSS_IN_MAX_PLY) { // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold moveCountPruning = moveCount >= futility_move_count(improving, depth); @@ -1000,23 +1021,26 @@ moves_loop: // When in check, search starts from here && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) continue; - // Futility pruning: parent node (~2 Elo) + // Futility pruning: parent node (~5 Elo) if ( lmrDepth < 6 && !inCheck - && ss->staticEval + 255 + 182 * lmrDepth <= alpha) + && ss->staticEval + 235 + 172 * lmrDepth <= alpha + && (*contHist[0])[movedPiece][to_sq(move)] + + (*contHist[1])[movedPiece][to_sq(move)] + + (*contHist[3])[movedPiece][to_sq(move)] < 27400) continue; - // Prune moves with negative SEE (~10 Elo) + // Prune moves with negative SEE (~20 Elo) if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) continue; } - else if (!pos.see_ge(move, Value(-194) * depth)) // (~20 Elo) - continue; + else if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo) + continue; } - // Step 14. Extensions (~70 Elo) + // Step 14. Extensions (~75 Elo) - // Singular extension search (~60 Elo). If all moves but one fail low on a + // Singular extension search (~70 Elo). 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 is singular and should be extended. To verify this we do // a reduced search on all the other moves but the ttMove and if the @@ -1031,10 +1055,10 @@ moves_loop: // When in check, search starts from here && tte->depth() >= depth - 3 && pos.legal(move)) { - Value singularBeta = ttValue - 2 * depth; - Depth halfDepth = depth / 2; + Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2; + Depth singularDepth = (depth - 1 + 3 * formerPv) / 2; ss->excludedMove = move; - value = search(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode); + value = search(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode); ss->excludedMove = MOVE_NONE; if (value < singularBeta) @@ -1095,7 +1119,7 @@ moves_loop: // When in check, search starts from here // Step 15. Make the move pos.do_move(move, st, givesCheck); - // Step 16. Reduced depth search (LMR). If the move fails high it will be + // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be // re-searched at full depth. if ( depth >= 3 && moveCount > 1 + 2 * rootNode @@ -1116,34 +1140,37 @@ moves_loop: // When in check, search starts from here if (th.marked()) r++; - // Decrease reduction if position is or has been on the PV + // Decrease reduction if position is or has been on the PV (~10 Elo) if (ttPv) r -= 2; - // Decrease reduction if opponent's move count is high (~10 Elo) + if (moveCountPruning && !formerPv) + r++; + + // Decrease reduction if opponent's move count is high (~5 Elo) if ((ss-1)->moveCount > 14) r--; - // Decrease reduction if ttMove has been singularly extended + // Decrease reduction if ttMove has been singularly extended (~3 Elo) if (singularLMR) - r -= 2; + r -= 1 + formerPv; if (!captureOrPromotion) { - // Increase reduction if ttMove is a capture (~0 Elo) + // Increase reduction if ttMove is a capture (~5 Elo) if (ttCapture) r++; - // Increase reduction for cut nodes (~5 Elo) + // Increase reduction for cut nodes (~10 Elo) if (cutNode) r += 2; // 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(). (~5 Elo) + // hence break make_move(). (~2 Elo) else if ( type_of(move) == NORMAL && !pos.see_ge(reverse_move(move))) - r -= 2; + r -= 2 + ttPv; ss->statScore = thisThread->mainHistory[us][from_to(move)] + (*contHist[0])[movedPiece][to_sq(move)] @@ -1151,13 +1178,6 @@ moves_loop: // When in check, search starts from here + (*contHist[3])[movedPiece][to_sq(move)] - 4926; - // Reset statScore to zero if negative and most stats shows >= 0 - if ( ss->statScore < 0 - && (*contHist[0])[movedPiece][to_sq(move)] >= 0 - && (*contHist[1])[movedPiece][to_sq(move)] >= 0 - && thisThread->mainHistory[us][from_to(move)] >= 0) - ss->statScore = 0; - // Decrease/increase reduction by comparing opponent's stat score (~10 Elo) if (ss->statScore >= -102 && (ss-1)->statScore < -114) r--; @@ -1166,17 +1186,27 @@ moves_loop: // When in check, search starts from here r++; // Decrease/increase reduction for moves with a good/bad history (~30 Elo) - r -= ss->statScore / 16384; + r -= ss->statScore / 16434; } - Depth d = clamp(newDepth - r, 1, newDepth); + // Increase reduction for captures/promotions if late move and at low depth + else if (depth < 8 && moveCount > 2) + r++; + + Depth d = Utility::clamp(newDepth - r, 1, newDepth); value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); - doFullDepthSearch = (value > alpha && d != newDepth), didLMR = true; + doFullDepthSearch = value > alpha && d != newDepth; + + didLMR = true; } else - doFullDepthSearch = !PvNode || moveCount > 1, didLMR = false; + { + doFullDepthSearch = !PvNode || moveCount > 1; + + didLMR = false; + } // Step 17. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) @@ -1311,7 +1341,7 @@ moves_loop: // When in check, search starts from here if (PvNode) bestValue = std::min(bestValue, maxValue); - if (!excludedMove) + if (!excludedMove && !(rootNode && thisThread->pvIdx)) tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv, bestValue >= beta ? BOUND_LOWER : PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, @@ -1406,13 +1436,13 @@ moves_loop: // When in check, search starts from here else ss->staticEval = bestValue = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) - : -(ss-1)->staticEval + 2 * Eval::Tempo; + : -(ss-1)->staticEval + 2 * Tempo; // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) { if (!ttHit) - tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, BOUND_LOWER, + tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->staticEval); return bestValue; @@ -1473,7 +1503,7 @@ moves_loop: // When in check, search starts from here // Detect non-capture evasions that are candidates to be pruned evasionPrunable = inCheck && (depth != 0 || moveCount > 2) - && bestValue > VALUE_MATED_IN_MAX_PLY + && bestValue > VALUE_TB_LOSS_IN_MAX_PLY && !pos.capture(move); // Don't search moves with negative SEE values @@ -1539,28 +1569,47 @@ moves_loop: // When in check, search starts from here } - // value_to_tt() adjusts a mate score from "plies to mate from the root" to - // "plies to mate from the current position". Non-mate scores are unchanged. + // value_to_tt() adjusts a mate or TB score from "plies to mate from the root" to + // "plies to mate from the current position". standard scores are unchanged. // The function is called before storing a value in the transposition table. Value value_to_tt(Value v, int ply) { assert(v != VALUE_NONE); - return v >= VALUE_MATE_IN_MAX_PLY ? v + ply - : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; + return v >= VALUE_TB_WIN_IN_MAX_PLY ? v + ply + : v <= VALUE_TB_LOSS_IN_MAX_PLY ? v - ply : v; } - // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score + // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate or TB score // from the transposition table (which refers to the plies to mate/be mated - // from current position) to "plies to mate/be mated from the root". + // from current position) to "plies to mate/be mated (TB win/loss) from the root". + // However, for mate scores, to avoid potentially false mate scores related to the 50 moves rule, + // and the graph history interaction, return an optimal TB score instead. Value value_from_tt(Value v, int ply, int r50c) { - return v == VALUE_NONE ? VALUE_NONE - : v >= VALUE_MATE_IN_MAX_PLY ? VALUE_MATE - v > 99 - r50c ? VALUE_MATE_IN_MAX_PLY : v - ply - : v <= VALUE_MATED_IN_MAX_PLY ? VALUE_MATE + v > 99 - r50c ? VALUE_MATED_IN_MAX_PLY : v + ply : v; + if (v == VALUE_NONE) + return VALUE_NONE; + + if (v >= VALUE_TB_WIN_IN_MAX_PLY) // TB win or better + { + if (v >= VALUE_MATE_IN_MAX_PLY && VALUE_MATE - v > 99 - r50c) + return VALUE_MATE_IN_MAX_PLY - 1; // do not return a potentially false mate score + + return v - ply; + } + + if (v <= VALUE_TB_LOSS_IN_MAX_PLY) // TB loss or worse + { + if (v <= VALUE_MATED_IN_MAX_PLY && VALUE_MATE + v > 99 - r50c) + return VALUE_MATED_IN_MAX_PLY + 1; // do not return a potentially false mate score + + return v + ply; + } + + return v; } @@ -1592,7 +1641,7 @@ moves_loop: // When in check, search starts from here if (!pos.capture_or_promotion(bestMove)) { - update_quiet_stats(pos, ss, bestMove, bonus2); + update_quiet_stats(pos, ss, bestMove, bonus2, depth); // Decrease all the non-best quiet moves for (int i = 0; i < quietCount; ++i) @@ -1620,7 +1669,7 @@ moves_loop: // When in check, search starts from here // update_continuation_histories() updates histories of the move pairs formed - // by moves at ply -1, -2, and -4 with current move. + // by moves at ply -1, -2, -4, and -6 with current move. void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) { @@ -1632,7 +1681,7 @@ moves_loop: // When in check, search starts from here // update_quiet_stats() updates move sorting heuristics - void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus) { + void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth) { if (ss->killers[0] != move) { @@ -1653,6 +1702,9 @@ moves_loop: // When in check, search starts from here Square prevSq = to_sq((ss-1)->currentMove); thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move; } + + if (depth > 12 && ss->ply < MAX_LPH) + thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7); } // When playing with strength handicap, choose best move among a set of RootMoves @@ -1746,7 +1798,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) { Depth d = updated ? depth : depth - 1; Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore; - bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY; + bool tb = TB::RootInTB && abs(v) < VALUE_MATE_IN_MAX_PLY; v = tb ? rootMoves[i].tbScore : v; if (ss.rdbuf()->in_avail()) // Not at first line