X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=4a993b017542cd84b6cd159f4a5f64e0feee9dd4;hp=1610c206dd7580fd7f1d0db2e22e3f97bfc52819;hb=23ecf3d5c6ffbcfbe45acd2afcf503929474a4db;hpb=bf5ce1c214f8f8e3f98e5e3ac43db0dd28617e35 diff --git a/src/search.cpp b/src/search.cpp index 1610c206..4a993b01 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1,8 +1,6 @@ /* 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) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file) Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -227,6 +225,8 @@ void MainThread::search() { Time.init(Limits, us, rootPos.game_ply()); TT.new_search(); + Eval::verify_NNUE(); + if (rootMoves.empty()) { rootMoves.emplace_back(MOVE_NONE); @@ -263,10 +263,10 @@ void MainThread::search() { Thread* bestThread = this; - if (int(Options["MultiPV"]) == 1 && - !Limits.depth && - !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) && - rootMoves[0].pv[0] != MOVE_NONE) + if ( int(Options["MultiPV"]) == 1 + && !Limits.depth + && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) + && rootMoves[0].pv[0] != MOVE_NONE) bestThread = Threads.get_best_thread(); bestPreviousScore = bestThread->rootMoves[0].score; @@ -596,7 +596,7 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; - Value bestValue, value, ttValue, eval, maxValue; + Value bestValue, value, ttValue, eval, maxValue, probcutBeta; bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularQuietLMR; @@ -670,7 +670,11 @@ namespace { ttPv = PvNode || (ttHit && tte->is_pv()); formerPv = ttPv && !PvNode; - if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !priorCapture && is_ok((ss-1)->currentMove)) + if ( ttPv + && depth > 12 + && ss->ply - 1 < MAX_LPH + && !priorCapture + && 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 @@ -812,7 +816,7 @@ namespace { // Step 8. Futility pruning: child node (~50 Elo) if ( !PvNode - && depth < 6 + && depth < 8 && eval - futility_margin(depth, improving) >= beta && eval < VALUE_KNOWN_WIN) // Do not return unproven wins return eval; @@ -867,23 +871,33 @@ namespace { } } + probcutBeta = beta + 176 - 49 * improving; + // 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 > 4 - && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY) + && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY + && !( ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE + && ttValue < probcutBeta)) { - Value raisedBeta = beta + 176 - 49 * improving; - assert(raisedBeta < VALUE_INFINITE); - MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory); + if ( ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE + && ttValue >= probcutBeta + && ttMove + && pos.capture_or_promotion(ttMove)) + return probcutBeta; + + assert(probcutBeta < VALUE_INFINITE); + MovePicker mp(pos, ttMove, probcutBeta - ss->staticEval, &captureHistory); int probCutCount = 0; while ( (move = mp.next_move()) != MOVE_NONE - && probCutCount < 2 + 2 * cutNode - && !( move == ttMove - && tte->depth() >= depth - 4 - && ttValue < raisedBeta)) + && probCutCount < 2 + 2 * cutNode) if (move != excludedMove && pos.legal(move)) { assert(pos.capture_or_promotion(move)); @@ -901,16 +915,24 @@ namespace { pos.do_move(move, st); // Perform a preliminary qsearch to verify that the move holds - value = -qsearch(pos, ss+1, -raisedBeta, -raisedBeta+1); + value = -qsearch(pos, ss+1, -probcutBeta, -probcutBeta+1); // If the qsearch held, perform the regular search - if (value >= raisedBeta) - value = -search(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4, !cutNode); + if (value >= probcutBeta) + value = -search(pos, ss+1, -probcutBeta, -probcutBeta+1, depth - 4, !cutNode); pos.undo_move(move); - if (value >= raisedBeta) + if (value >= probcutBeta) + { + if ( !(ttHit + && tte->depth() >= depth - 3 + && ttValue != VALUE_NONE)) + tte->save(posKey, value_to_tt(value, ss->ply), ttPv, + BOUND_LOWER, + depth - 3, move, ss->staticEval); return value; + } } } @@ -964,6 +986,10 @@ moves_loop: // When in check, search starts from here thisThread->rootMoves.begin() + thisThread->pvLast, move)) continue; + // Check for legality + if (!rootNode && !pos.legal(move)) + continue; + ss->moveCount = ++moveCount; if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000) @@ -1002,7 +1028,7 @@ moves_loop: // When in check, search starts from here continue; // Futility pruning: parent node (~5 Elo) - if ( lmrDepth < 6 + if ( lmrDepth < 8 && !ss->inCheck && ss->staticEval + 284 + 188 * lmrDepth <= alpha && (*contHist[0])[movedPiece][to_sq(move)] @@ -1045,7 +1071,7 @@ moves_loop: // When in check, search starts from here // 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 - // result is lower than ttValue minus a margin then we will extend the ttMove. + // result is lower than ttValue minus a margin, then we will extend the ttMove. if ( depth >= 6 && move == ttMove && !rootNode @@ -1121,13 +1147,6 @@ moves_loop: // When in check, search starts from here // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); - // Check for legality just before making the move - if (!rootNode && !pos.legal(move)) - { - ss->moveCount = --moveCount; - continue; - } - // Update the current move (this must be done after singular extension search) ss->currentMove = move; ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] @@ -1151,6 +1170,13 @@ moves_loop: // When in check, search starts from here { Depth r = reduction(improving, depth, moveCount); + // Decrease reduction at non-check cut nodes for second move at low depths + if ( cutNode + && depth <= 10 + && moveCount <= 2 + && !ss->inCheck) + r--; + // Decrease reduction if the ttHit running average is large if (thisThread->ttHitAverage > 473 * TtHitAverageResolution * TtHitAverageWindow / 1024) r--;