X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=a4bf172a99e7442f50109bc8d9b82dfa51c063b0;hp=70052bbc195df4e3b89c4da3a19f33ebdf99befb;hb=356147d99ae6783d79861c32f128a98685024c58;hpb=74e2fa97b7ce49722b908f35988f3c75dee9bf36 diff --git a/src/search.cpp b/src/search.cpp index 70052bbc..a4bf172a 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -61,7 +61,7 @@ using namespace Search; namespace { - // Different node types, used as template parameter + // Different node types, used as a template parameter enum NodeType { Root, PV, NonPV }; // Razoring and futility margin based on depth @@ -76,7 +76,7 @@ namespace { return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)]; } - // Skill struct is used to implement strength limiting + // Skill structure is used to implement strength limit struct Skill { Skill(int l) : level(l) {} bool enabled() const { return level < 20; } @@ -88,8 +88,8 @@ namespace { Move best = MOVE_NONE; }; - // EasyMoveManager struct is used to detect a so called 'easy move'; when PV is - // stable across multiple search iterations we can fast return the best move. + // EasyMoveManager structure is used to detect an 'easy move'. When the PV is + // stable across multiple search iterations, we can quickly return the best move. struct EasyMoveManager { void clear() { @@ -106,7 +106,7 @@ namespace { assert(newPv.size() >= 3); - // Keep track of how many times in a row 3rd ply remains stable + // Keep track of how many times in a row the 3rd ply remains stable stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0; if (!std::equal(newPv.begin(), newPv.begin() + 3, pv)) @@ -129,7 +129,7 @@ namespace { EasyMoveManager EasyMove; Value DrawValue[COLOR_NB]; - CounterMovesHistoryStats CounterMovesHistory; + CounterMoveHistoryStats CounterMoveHistory; template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode); @@ -175,12 +175,12 @@ void Search::init() { } -/// Search::clear() resets to zero search state, to obtain reproducible results +/// Search::clear() resets search state to zero, to obtain reproducible results void Search::clear() { TT.clear(); - CounterMovesHistory.clear(); + CounterMoveHistory.clear(); for (Thread* th : Threads) { @@ -188,12 +188,12 @@ void Search::clear() { th->counterMoves.clear(); } - Threads.main()->previousMoveScore = VALUE_INFINITE; + Threads.main()->previousScore = VALUE_INFINITE; } /// Search::perft() is our utility to verify move generation. All the leaf nodes -/// up to the given depth are generated and counted and the sum returned. +/// up to the given depth are generated and counted, and the sum is returned. template uint64_t Search::perft(Position& pos, Depth depth) { @@ -223,8 +223,7 @@ template uint64_t Search::perft(Position&, Depth); /// MainThread::search() is called by the main thread when the program receives -/// the UCI 'go' command. It searches from root position and at the end prints -/// the "bestmove" to output. +/// the UCI 'go' command. It searches from the root position and outputs the "bestmove". void MainThread::search() { @@ -260,8 +259,8 @@ void MainThread::search() { if (TB::Cardinality >= rootPos.count(WHITE) + rootPos.count(BLACK)) { - // If the current root position is in the tablebases then RootMoves - // contains only moves that preserve the draw or win. + // If the current root position is in the tablebases, then RootMoves + // contains only moves that preserve the draw or the win. TB::RootInTB = Tablebases::root_probe(rootPos, rootMoves, TB::Score); if (TB::RootInTB) @@ -269,7 +268,7 @@ void MainThread::search() { else // If DTZ tables are missing, use WDL tables as a fallback { - // Filter out moves that do not preserve a draw or win + // Filter out moves that do not preserve the draw or the win. TB::RootInTB = Tablebases::root_probe_wdl(rootPos, rootMoves, TB::Score); // Only probe during search if winning @@ -304,7 +303,7 @@ void MainThread::search() { } // When playing in 'nodes as time' mode, subtract the searched nodes from - // the available ones before to exit. + // the available ones before exiting. if (Limits.npmsec) Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); @@ -339,7 +338,7 @@ void MainThread::search() { bestThread = th; } - previousMoveScore = bestThread->rootMoves[0].score; + previousScore = bestThread->rootMoves[0].score; // Send new PV when needed if (bestThread != this) @@ -356,7 +355,7 @@ void MainThread::search() { // Thread::search() is the main iterative deepening loop. It calls search() // repeatedly with increasing depth until the allocated thinking time has been -// consumed, user stops the search, or the maximum search depth is reached. +// consumed, the user stops the search, or the maximum search depth is reached. void Thread::search() { @@ -390,11 +389,11 @@ void Thread::search() { multiPV = std::min(multiPV, rootMoves.size()); - // Iterative deepening loop until requested to stop or target depth reached + // Iterative deepening loop until requested to stop or the target depth is reached. while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= Limits.depth)) { - // Set up the new depth for the helper threads skipping in average each - // 2nd ply (using a half density map similar to a Hadamard matrix). + // Set up the new depths for the helper threads skipping on average every + // 2nd ply (using a half-density map similar to a Hadamard matrix). if (!mainThread) { int d = rootDepth + rootPos.game_ply(); @@ -452,14 +451,14 @@ void Thread::search() { // search the already searched PV lines are preserved. std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end()); - // Write PV back to transposition table in case the relevant + // Write PV back to the transposition table in case the relevant // entries have been overwritten during the search. for (size_t i = 0; i <= PVIdx; ++i) rootMoves[i].insert_pv_in_tt(rootPos); - // If search has been stopped break immediately. Sorting and + // If search has been stopped, break immediately. Sorting and // writing PV back to TT is safe because RootMoves is still - // valid, although it refers to previous iteration. + // valid, although it refers to the previous iteration. if (Signals.stop) break; @@ -536,16 +535,21 @@ void Thread::search() { if (rootDepth > 4 * ONE_PLY && multiPV == 1) Time.pv_instability(mainThread->bestMoveChanges); - // Stop the search if only one legal move is available or all - // of the available time has been used or we matched an easyMove + // Stop the search if only one legal move is available, or if all + // of the available time has been used, or if we matched an easyMove // from the previous search and just did a fast verification. + const bool F[] = { !mainThread->failedLow, + bestValue >= mainThread->previousScore }; + + int improvingFactor = 640 - 160*F[0] - 126*F[1] - 124*F[0]*F[1]; + + bool doEasyMove = rootMoves[0].pv[0] == easyMove + && mainThread->bestMoveChanges < 0.03 + && Time.elapsed() > Time.available() * 25 / 206; + if ( rootMoves.size() == 1 - || Time.elapsed() > Time.available() * ( 640 - 160 * !mainThread->failedLow - - 126 * (bestValue >= mainThread->previousMoveScore) - - 124 * (bestValue >= mainThread->previousMoveScore && !mainThread->failedLow))/640 - || ( mainThread->easyMovePlayed = ( rootMoves[0].pv[0] == easyMove - && mainThread->bestMoveChanges < 0.03 - && Time.elapsed() > Time.available() * 25/206))) + || Time.elapsed() > Time.available() * improvingFactor / 640 + || (mainThread->easyMovePlayed = doEasyMove)) { // If we are allowed to ponder do not stop the search now but // keep pondering until the GUI sends "ponderhit" or "stop". @@ -610,7 +614,7 @@ namespace { bestValue = -VALUE_INFINITE; ss->ply = (ss-1)->ply + 1; - // Check for available remaining time + // Check for the available remaining time if (thisThread->resetCalls.load(std::memory_order_relaxed)) { thisThread->resetCalls = false; @@ -853,7 +857,7 @@ moves_loop: // When in check search starts from here Square prevSq = to_sq((ss-1)->currentMove); Move cm = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq]; - const CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq]; + const CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq]; MovePicker mp(pos, ttMove, depth, thisThread->history, cmh, cm, ss); CheckInfo ci(pos); @@ -1000,15 +1004,15 @@ moves_loop: // When in check search starts from here && cmh[pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO)) r += ONE_PLY; - // Decrease reduction for moves with a good history and - // increase reduction for moves with a bad history - int rDecrease = ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] - + cmh[pos.piece_on(to_sq(move))][to_sq(move)]) / 14980; - r = std::max(DEPTH_ZERO, r - rDecrease * ONE_PLY); + // Decrease/increase reduction for moves with a good/bad history + int rHist = ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] + + cmh[pos.piece_on(to_sq(move))][to_sq(move)]) / 14980; + r = std::max(DEPTH_ZERO, r - rHist * ONE_PLY); - // Decrease reduction for moves that escape a capture. Filter out castling - // moves because are coded as "king captures rook" and break make_move(). - // Also use see() instead of see_sign() because destination square is empty. + // 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(). Also use see() instead of see_sign(), + // because the destination square is empty. if ( r && type_of(move) == NORMAL && type_of(pos.piece_on(to_sq(move))) != PAWN @@ -1024,7 +1028,7 @@ moves_loop: // When in check search starts from here else doFullDepthSearch = !PvNode || moveCount > 1; - // Step 16. Full depth search, when LMR is skipped or fails high + // 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) @@ -1033,7 +1037,7 @@ moves_loop: // When in check search starts from here // 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 - // parent node fail low with value <= alpha and to try another move. + // parent node fail low with value <= alpha and try another move. if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta)))) { (ss+1)->pv = pv; @@ -1050,7 +1054,7 @@ moves_loop: // When in check search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 18. Check for new best move + // Step 18. Check for a new best move // Finished searching the move. If a stop occurred, the return value of // the search cannot be trusted, and we return immediately without // updating best move, PV and TT. @@ -1118,7 +1122,7 @@ moves_loop: // When in check search starts from here quietsSearched[quietCount++] = move; } - // Following condition would detect a stop only after move loop has been + // The following condition would detect a stop only after move loop has been // completed. But in this case bestValue is valid because we have fully // searched our subtree, and we can anyhow save the result in TT. /* @@ -1128,7 +1132,7 @@ moves_loop: // When in check search starts from here // Step 20. Check for mate and stalemate // All legal moves have been searched and if there are no legal moves, it - // must be mate or stalemate. If we are in a singular extension search then + // must be a mate or a stalemate. If we are in a singular extension search then // return a fail low score. if (!moveCount) bestValue = excludedMove ? alpha @@ -1148,7 +1152,7 @@ moves_loop: // When in check search starts from here { Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); Square prevPrevSq = to_sq((ss - 2)->currentMove); - CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; + CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; prevCmh.update(pos.piece_on(prevSq), prevSq, bonus); } @@ -1334,7 +1338,7 @@ moves_loop: // When in check search starts from here assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Check for new best move + // Check for a new best move if (value > bestValue) { bestValue = value; @@ -1425,7 +1429,7 @@ moves_loop: // When in check search starts from here Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1); Square prevSq = to_sq((ss-1)->currentMove); - CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq]; + CounterMoveStats& cmh = CounterMoveHistory[pos.piece_on(prevSq)][prevSq]; Thread* thisThread = pos.this_thread(); thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus); @@ -1451,7 +1455,7 @@ moves_loop: // When in check search starts from here && is_ok((ss-2)->currentMove)) { Square prevPrevSq = to_sq((ss-2)->currentMove); - CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; + CounterMoveStats& prevCmh = CounterMoveHistory[pos.piece_on(prevPrevSq)][prevPrevSq]; prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY); } } @@ -1472,8 +1476,8 @@ moves_loop: // When in check search starts from here int maxScore = -VALUE_INFINITE; // Choose best move. For each move score we add two terms, both dependent on - // weakness. One deterministic and bigger for weaker levels, and one random, - // then we choose the move with the resulting highest score. + // weakness. One is deterministic and bigger for weaker levels, and one is + // random. Then we choose the move with the resulting highest score. for (size_t i = 0; i < multiPV; ++i) { // This is our magic formula @@ -1603,7 +1607,7 @@ void RootMove::insert_pv_in_tt(Position& pos) { /// RootMove::extract_ponder_from_tt() is called in case we have no ponder move -/// before exiting the search, for instance in case we stop the search during a +/// before exiting the search, for instance, in case we stop the search during a /// fail high at root. We try hard to have a ponder move to return to the GUI, /// otherwise in case of 'ponder on' we have nothing to think on.