X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=b75870ff5021968f66d0e0a0aa02271a310cec00;hp=b916264a790e03f1544ec5a9f7578fa2f16059ea;hb=5254a6040c59cf7d3b9faa847168ccbd628c0574;hpb=e70da0d2eb20cffee505c4e7ef61399de7d3fa16 diff --git a/src/search.cpp b/src/search.cpp index b916264a..b75870ff 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) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2017 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 @@ -75,6 +75,12 @@ namespace { return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY; } + // History and stats update bonus, based on depth + Value stat_bonus(Depth depth) { + int d = depth / ONE_PLY ; + return Value(d * d + 2 * d - 2); + } + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} @@ -159,10 +165,10 @@ namespace { Value DrawValue[COLOR_NB]; template - Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning); template - Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); @@ -208,9 +214,8 @@ void Search::clear() { for (Thread* th : Threads) { - th->history.clear(); th->counterMoves.clear(); - th->fromTo.clear(); + th->history.clear(); th->counterMoveHistory.clear(); th->resetCalls = true; } @@ -309,9 +314,13 @@ void MainThread::search() { && rootMoves[0].pv[0] != MOVE_NONE) { for (Thread* th : Threads) - if ( th->completedDepth > bestThread->completedDepth - && th->rootMoves[0].score > bestThread->rootMoves[0].score) + { + Depth depthDiff = th->completedDepth - bestThread->completedDepth; + Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score; + + if (scoreDiff > 0 && depthDiff >= 0) bestThread = th; + } } previousScore = bestThread->rootMoves[0].score; @@ -404,7 +413,7 @@ void Thread::search() { // high/low anymore. while (true) { - bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false); + bestValue = ::search(rootPos, ss, alpha, beta, rootDepth, false, 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 @@ -538,7 +547,7 @@ 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) { + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) { const bool PvNode = NT == PV; const bool rootNode = PvNode && (ss-1)->ply == 0; @@ -594,7 +603,7 @@ namespace { if (!rootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY) + if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -614,8 +623,8 @@ namespace { ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; ss->counterMoves = nullptr; - (ss+1)->skipEarlyPruning = false; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; + Square prevSq = to_sq((ss-1)->currentMove); // Step 4. Transposition table lookup. We don't want the score of a partial // search to overwrite a previous full search TT value, so we use a different @@ -635,23 +644,24 @@ namespace { && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) { - // If ttMove is quiet, update killers, history, counter move on TT hit - if (ttValue >= beta && ttMove) + // If ttMove is quiet, update move sorting heuristics on TT hit + if (ttMove) { - int d = depth / ONE_PLY; - - if (!pos.capture_or_promotion(ttMove)) + if (ttValue >= beta) { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, ttMove, nullptr, 0, bonus); - } + if (!pos.capture_or_promotion(ttMove)) + update_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()) + // Extra penalty for a quiet TT move in previous ply when it gets refuted + if ((ss-1)->moveCount == 1 && !pos.captured_piece()) + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + } + // Penalty for a quiet ttMove that fails low + else if (ttValue < alpha && !pos.capture_or_promotion(ttMove)) { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); + Value penalty = -stat_bonus(depth + ONE_PLY); + thisThread->history.update(pos.side_to_move(), ttMove, penalty); + update_cm_stats(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty); } } return ttValue; @@ -660,10 +670,10 @@ namespace { // Step 4a. Tablebase probe if (!rootNode && TB::Cardinality) { - int piecesCnt = pos.count(WHITE) + pos.count(BLACK); + int piecesCount = pos.count(WHITE) + pos.count(BLACK); - if ( piecesCnt <= TB::Cardinality - && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth) + if ( piecesCount <= TB::Cardinality + && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth) && pos.rule50_count() == 0 && !pos.can_castle(ANY_CASTLING)) { @@ -717,7 +727,7 @@ namespace { ss->staticEval, TT.generation()); } - if (ss->skipEarlyPruning) + if (skipEarlyPruning) goto moves_loop; // Step 6. Razoring (skipped when in check) @@ -727,10 +737,10 @@ namespace { && eval + razor_margin[depth / ONE_PLY] <= alpha) { if (depth <= ONE_PLY) - return qsearch(pos, ss, alpha, beta, DEPTH_ZERO); + return qsearch(pos, ss, alpha, alpha+1); Value ralpha = alpha - razor_margin[depth / ONE_PLY]; - Value v = qsearch(pos, ss, ralpha, ralpha+1, DEPTH_ZERO); + Value v = qsearch(pos, ss, ralpha, ralpha+1); if (v <= ralpha) return v; } @@ -758,10 +768,8 @@ namespace { Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY; pos.do_null_move(st); - (ss+1)->skipEarlyPruning = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode); - (ss+1)->skipEarlyPruning = false; + nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -beta+1) + : - search(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true); pos.undo_null_move(); if (nullValue >= beta) @@ -774,10 +782,8 @@ namespace { return nullValue; // Do verification search at high depths - ss->skipEarlyPruning = true; - Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta, DEPTH_ZERO) - : search(pos, ss, beta-1, beta, depth-R, false); - ss->skipEarlyPruning = false; + Value v = depth-R < ONE_PLY ? qsearch(pos, ss, beta-1, beta) + : search(pos, ss, beta-1, beta, depth-R, false, true); if (v >= beta) return nullValue; @@ -806,7 +812,7 @@ namespace { ss->currentMove = move; ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)]; pos.do_move(move, st); - value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode); + value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false); pos.undo_move(move); if (value >= rbeta) return value; @@ -819,9 +825,7 @@ namespace { && (PvNode || ss->staticEval + 256 >= beta)) { Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY; - ss->skipEarlyPruning = true; - search(pos, ss, alpha, beta, d, cutNode); - ss->skipEarlyPruning = false; + search(pos, ss, alpha, beta, d, cutNode, true); tte = TT.probe(posKey, ttHit); ttMove = ttHit ? tte->move() : MOVE_NONE; @@ -884,7 +888,8 @@ moves_loop: // When in check search starts from here moveCountPruning = depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY]; - // Step 12. Extend checks + // Step 12. Extensions + // Extend checks if ( givesCheck && !moveCountPruning && pos.see_ge(move, VALUE_ZERO)) @@ -903,16 +908,14 @@ moves_loop: // When in check search starts from here Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY; ss->excludedMove = move; - ss->skipEarlyPruning = true; - value = search(pos, ss, rBeta - 1, rBeta, d, cutNode); - ss->skipEarlyPruning = false; + value = search(pos, ss, rBeta - 1, rBeta, d, cutNode, true); ss->excludedMove = MOVE_NONE; if (value < rBeta) extension = ONE_PLY; } - // Update the current move (this must be done after singular extension search) + // Calculate new depth for this move newDepth = depth - ONE_PLY + extension; // Step 13. Pruning at shallow depth @@ -948,16 +951,10 @@ moves_loop: // When in check search starts from here && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth))) continue; } - else if (depth < 7 * ONE_PLY && !extension) - { - Value v = -Value(399 + 35 * depth / ONE_PLY * depth / ONE_PLY); - - if (PvNode) - v += beta - alpha - 1; - - if (!pos.see_ge(move, v)) + else if ( depth < 7 * ONE_PLY + && !extension + && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) continue; - } } // Speculative prefetch as early as possible @@ -970,6 +967,7 @@ moves_loop: // When in check search starts from here continue; } + // Update the current move (this must be done after singular extension search) ss->currentMove = move; ss->counterMoves = &thisThread->counterMoveHistory[moved_piece][to_sq(move)]; @@ -996,16 +994,14 @@ moves_loop: // When in check search starts from here // castling moves, because they are coded as "king captures rook" and // hence break make_move(). else if ( type_of(move) == NORMAL - && type_of(pos.piece_on(to_sq(move))) != PAWN && !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO)) r -= 2 * ONE_PLY; - ss->history = thisThread->history[moved_piece][to_sq(move)] - + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO) - + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO) - + thisThread->fromTo.get(~pos.side_to_move(), move) - - 8000; // Correction factor + ss->history = (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO) + + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO) + + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO) + + thisThread->history.get(~pos.side_to_move(), move) + - 4000; // Correction factor // Decrease/increase reduction by comparing opponent's stat score if (ss->history > VALUE_ZERO && (ss-1)->history < VALUE_ZERO) @@ -1020,7 +1016,7 @@ moves_loop: // When in check search starts from here Depth d = std::max(newDepth - r, ONE_PLY); - value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + value = -search(pos, ss+1, -(alpha+1), -alpha, d, true, false); doFullDepthSearch = (value > alpha && d != newDepth); } @@ -1030,9 +1026,9 @@ moves_loop: // When in check search starts from here // Step 16. Full depth search when LMR is skipped or fails high if (doFullDepthSearch) value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode); + givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha) + : -qsearch(pos, ss+1, -(alpha+1), -alpha) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false); // 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 @@ -1043,9 +1039,9 @@ moves_loop: // When in check search starts from here (ss+1)->pv[0] = MOVE_NONE; value = newDepth < ONE_PLY ? - givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth, false); + givesCheck ? -qsearch(pos, ss+1, -beta, -alpha) + : -qsearch(pos, ss+1, -beta, -alpha) + : - search(pos, ss+1, -beta, -alpha, newDepth, false, false); } // Step 17. Undo move @@ -1095,13 +1091,6 @@ moves_loop: // When in check search starts from here if (value > alpha) { - // If there is an easy move for this position, clear it if unstable - if ( PvNode - && thisThread == Threads.main() - && EasyMove.get(pos.key()) - && (move != EasyMove.get(pos.key()) || moveCount > 1)) - EasyMove.clear(); - bestMove = move; if (PvNode && !rootNode) // Update pv even in fail-high case @@ -1141,33 +1130,20 @@ moves_loop: // When in check search starts from here : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()]; else if (bestMove) { - int d = depth / ONE_PLY; - // Quiet best move: update killers, history and countermoves + // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - { - Value bonus = Value(d * d + 2 * d - 2); - update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus); - } + update_stats(pos, ss, bestMove, quietsSearched, quietCount, 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()) - { - Value penalty = Value(d * d + 4 * d + 1); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty); - } + update_cm_stats(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 && !pos.captured_piece() && is_ok((ss-1)->currentMove)) - { - int d = depth / ONE_PLY; - Value bonus = Value(d * d + 2 * d - 2); - Square prevSq = to_sq((ss-1)->currentMove); - update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus); - } + update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); tte->save(posKey, value_to_tt(bestValue, ss->ply), bestValue >= beta ? BOUND_LOWER : @@ -1181,8 +1157,7 @@ moves_loop: // When in check search starts from here // qsearch() is the quiescence search function, which is called by the main - // search function when the remaining depth is zero (or, to be more precise, - // less than ONE_PLY). + // search function with depth zero, or recursively with depth less than ONE_PLY. template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { @@ -1215,7 +1190,7 @@ moves_loop: // When in check search starts from here ss->ply = (ss-1)->ply + 1; // Check for an instant draw or if the maximum ply has been reached - if (pos.is_draw() || ss->ply >= MAX_PLY) + if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()]; @@ -1442,8 +1417,7 @@ moves_loop: // When in check search starts from here } - // update_stats() updates killers, history, countermove and countermove plus - // follow-up move history when a new quiet best move is found. + // update_stats() updates move sorting heuristics when a new quiet best move is found void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus) { @@ -1456,8 +1430,7 @@ moves_loop: // When in check search starts from here Color c = pos.side_to_move(); Thread* thisThread = pos.this_thread(); - thisThread->fromTo.update(c, move, bonus); - thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); + thisThread->history.update(c, move, bonus); update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus); if ((ss-1)->counterMoves) @@ -1469,8 +1442,7 @@ moves_loop: // When in check search starts from here // Decrease all the other played quiet moves for (int i = 0; i < quietsCnt; ++i) { - thisThread->fromTo.update(c, quiets[i], -bonus); - thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); + thisThread->history.update(c, quiets[i], -bonus); update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); } }