X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=7eb04308b4c3bbd6c72247a6d920927ffc91b9e5;hp=d073b7da31a2e14056bee54e2c4d45dbfd8b0ba7;hb=5bec768d42fc8ce34b4dc0574ef9f4e61bfd8853;hpb=b50921fd5c3e1753adecfea77557ad1afece7641 diff --git a/src/search.cpp b/src/search.cpp index d073b7da..7eb04308 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -119,7 +119,6 @@ namespace { inline Move get_move_pv(int moveNum, int i) const; inline int64_t get_move_cumulative_nodes(int moveNum) const; inline int move_count() const; - Move scan_for_easy_move() const; inline void sort(); void sort_multipv(int n); @@ -172,10 +171,17 @@ namespace { const bool PruneDefendingMoves = false; const bool PruneBlockingMoves = false; + // If the TT move is at least SingleReplyMargin better then the + // remaining ones we will extend it. + const Value SingleReplyMargin = Value(0x64); + // Margins for futility pruning in the quiescence search, and at frontier // and near frontier nodes. const Value FutilityMarginQS = Value(0x80); + // Each move futility margin is decreased + const Value IncrementalFutilityMargin = Value(0x8); + // Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270), // 4 ply 4.5 ply 5 ply 5.5 ply 6 ply 6.5 ply @@ -274,7 +280,7 @@ namespace { Value id_loop(const Position& pos, Move searchMoves[]); Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value alpha, Value beta); Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); - Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID); + Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE); Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); void sp_search(SplitPoint* sp, int threadID); void sp_search_pv(SplitPoint* sp, int threadID); @@ -310,7 +316,7 @@ namespace { Value *alpha, Value *beta, Value *bestValue, const Value futilityValue, const Value approximateValue, Depth depth, int *moves, - MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode); + MovePicker *mp, int master, bool pvNode); void wake_sleeping_threads(); #if !defined(_MSC_VER) @@ -326,6 +332,37 @@ namespace { //// Functions //// + +/// perft() is our utility to verify move generation is bug free. All the +/// legal moves up to given depth are generated and counted and the sum returned. + +int perft(Position& pos, Depth depth) +{ + Move move; + int sum = 0; + MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H); + + // If we are at the last ply we don't need to do and undo + // the moves, just to count them. + if (depth <= OnePly) // Replace with '<' to test also qsearch + { + while (mp.get_next_move()) sum++; + return sum; + } + + // Loop through all legal moves + CheckInfo ci(pos); + while ((move = mp.get_next_move()) != MOVE_NONE) + { + StateInfo st; + pos.do_move(move, st, ci, pos.move_is_check(move, ci)); + sum += perft(pos, depth - OnePly); + pos.undo_move(move); + } + return sum; +} + + /// think() is the external interface to Stockfish's search, and is called when /// the program receives the UCI 'go' command. It initializes various /// search-related global variables, and calls root_search(). It returns false @@ -447,7 +484,7 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, if (movesToGo == 1) { MaxSearchTime = myTime / 2; - AbsoluteMaxSearchTime = + AbsoluteMaxSearchTime = (myTime > 3000)? (myTime - 500) : ((myTime * 3) / 4); } else { MaxSearchTime = myTime / Min(movesToGo, 20); @@ -489,23 +526,36 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, << " moves to go: " << movesToGo << std::endl; - // We're ready to start thinking. Call the iterative deepening loop function - // - // FIXME we really need to cleanup all this LSN ugliness - if (!loseOnTime) + // LSN filtering. Used only for developing purpose. Disabled by default. + if ( UseLSNFiltering + && loseOnTime) { - Value v = id_loop(pos, searchMoves); - loseOnTime = ( UseLSNFiltering - && myTime < LSNTime - && myIncrement == 0 - && v < -LSNValue); + // Step 2. If after last move we decided to lose on time, do it now! + while (SearchStartTime + myTime + 1000 > get_system_time()) + ; // wait here } - else + + // We're ready to start thinking. Call the iterative deepening loop function + Value v = id_loop(pos, searchMoves); + + // LSN filtering. Used only for developing purpose. Disabled by default. + if (UseLSNFiltering) { - loseOnTime = false; // reset for next match - while (SearchStartTime + myTime + 1000 > get_system_time()) - ; // wait here - id_loop(pos, searchMoves); // to fail gracefully + // Step 1. If this is sudden death game and our position is hopeless, + // decide to lose on time. + if ( !loseOnTime // If we already lost on time, go to step 3. + && myTime < LSNTime + && myIncrement == 0 + && movesToGo == 0 + && v < -LSNValue) + { + loseOnTime = true; + } + else if (loseOnTime) + { + // Step 3. Now after stepping over the time limit, reset flag for next match. + loseOnTime = false; + } } if (UseLogFile) @@ -647,7 +697,11 @@ namespace { IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0)); Iteration = 1; - Move EasyMove = rml.scan_for_easy_move(); + // Is one move significantly better than others after initial scoring ? + Move EasyMove = MOVE_NONE; + if ( rml.move_count() == 1 + || rml.get_move_score(0) > rml.get_move_score(1) + EasyMoveMargin) + EasyMove = rml.get_move(0); // Iterative deepening loop while (Iteration < PLY_MAX) @@ -764,7 +818,6 @@ namespace { if (stopSearch) { - //FIXME: Implement fail-low emergency measures if (!PonderSearch) break; else @@ -831,7 +884,7 @@ namespace { Value oldAlpha = alpha; Value value; - Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move()); + CheckInfo ci(pos); // Loop through all the moves in the root move list for (int i = 0; i < rml.move_count() && !AbortSearch; i++) @@ -867,13 +920,14 @@ namespace { << " currmovenumber " << i + 1 << std::endl; // Decide search depth for this move + bool moveIsCheck = pos.move_is_check(move); bool captureOrPromotion = pos.move_is_capture_or_promotion(move); bool dangerous; - ext = extension(pos, move, true, captureOrPromotion, pos.move_is_check(move), false, false, &dangerous); + ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous); newDepth = (Iteration - 2) * OnePly + ext + InitialDepth; // Make the move, and search it - pos.do_move(move, st, dcCandidates); + pos.do_move(move, st, ci, moveIsCheck); if (i < MultiPV) { @@ -976,7 +1030,7 @@ namespace { std::cout << std::endl; if (UseLogFile) - LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, + LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ((value >= beta)? VALUE_TYPE_LOWER : ((value <= alpha)? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT)), ss[0].pv) @@ -1031,6 +1085,17 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); + Move movesSearched[256]; + EvalInfo ei; + StateInfo st; + const TTEntry* tte; + Move ttMove, move; + Depth ext, newDepth; + Value oldAlpha, value; + bool isCheck, mateThreat, singleReply, moveIsCheck, captureOrPromotion, dangerous; + int moveCount = 0; + Value bestValue = -VALUE_INFINITE; + if (depth < OnePly) return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID); @@ -1045,41 +1110,46 @@ namespace { if (pos.is_draw()) return VALUE_DRAW; - EvalInfo ei; - if (ply >= PLY_MAX - 1) return pos.is_check() ? quick_evaluate(pos) : evaluate(pos, ei, threadID); // Mate distance pruning - Value oldAlpha = alpha; + oldAlpha = alpha; alpha = Max(value_mated_in(ply), alpha); beta = Min(value_mate_in(ply+1), beta); if (alpha >= beta) return alpha; // Transposition table lookup. At PV nodes, we don't use the TT for - // pruning, but only for move ordering. - const TTEntry* tte = TT.retrieve(pos.get_key()); - Move ttMove = (tte ? tte->move() : MOVE_NONE); + // pruning, but only for move ordering. This is to avoid problems in + // the following areas: + // + // * Repetition draw detection + // * Fifty move rule detection + // * Searching for a mate + // * Printing of full PV line + // + tte = TT.retrieve(pos.get_key()); + ttMove = (tte ? tte->move() : MOVE_NONE); // Go with internal iterative deepening if we don't have a TT move if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly) { search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID); ttMove = ss[ply].pv[ply]; + tte = TT.retrieve(pos.get_key()); + + // Following assert could fail, for instance when we have + // moveCount == 0 we return without saving a TT entry. + /* assert(tte); */ } // Initialize a MovePicker object for the current position, and prepare // to search all moves - Move move, movesSearched[256]; - int moveCount = 0; - Value value, bestValue = -VALUE_INFINITE; - Color us = pos.side_to_move(); - bool isCheck = pos.is_check(); - bool mateThreat = pos.has_mate_threat(opposite_color(us)); - + isCheck = pos.is_check(); + mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); + CheckInfo ci(pos); MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]); - Bitboard dcCandidates = mp.discovered_check_candidates(); // Loop through all legal moves until no moves remain or a beta cutoff // occurs. @@ -1089,20 +1159,46 @@ namespace { { assert(move_is_ok(move)); - bool singleReply = (isCheck && mp.number_of_evasions() == 1); - bool moveIsCheck = pos.move_is_check(move, dcCandidates); - bool captureOrPromotion = pos.move_is_capture_or_promotion(move); - - movesSearched[moveCount++] = ss[ply].currentMove = move; + singleReply = (isCheck && mp.number_of_evasions() == 1); + moveIsCheck = pos.move_is_check(move, ci); + captureOrPromotion = pos.move_is_capture_or_promotion(move); // Decide the new search depth - bool dangerous; - Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous); - Depth newDepth = depth - OnePly + ext; + ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous); + + // We want to extend the TT move if it is much better then remaining ones. + // To verify this we do a reduced search on all the other moves but the ttMove, + // if result is lower then TT value minus a margin then we assume ttMove is the + // only one playable. It is a kind of relaxed single reply extension. + // Note that could be ttMove != tte->move() due to IID, so we always use tte->move() + // to avoid aliases when we probe tte->depth() and tte->type() + if ( depth >= 8 * OnePly + && tte + && move == tte->move() + && ext < OnePly + && is_lower_bound(tte->type()) + && tte->depth() >= depth - 3 * OnePly) + { + Value ttValue = value_from_tt(tte->value(), ply); + + if (abs(ttValue) < VALUE_KNOWN_WIN) + { + Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, ttMove); + + // If search result is well below the foreseen score of the ttMove then we + // assume ttMove is the only one realistically playable and we extend it. + if (excValue < ttValue - SingleReplyMargin) + ext = OnePly; + } + } + + newDepth = depth - OnePly + ext; + + // Update current move + movesSearched[moveCount++] = ss[ply].currentMove = move; // Make and search the move - StateInfo st; - pos.do_move(move, st, dcCandidates); + pos.do_move(move, st, ci, moveIsCheck); if (moveCount == 1) // The first move in list is the PV value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID); @@ -1175,8 +1271,8 @@ namespace { && idle_thread_exists(threadID) && !AbortSearch && !thread_should_stop(threadID) - && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, VALUE_NONE, depth, - &moveCount, &mp, dcCandidates, threadID, true)) + && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, VALUE_NONE, + depth, &moveCount, &mp, threadID, true)) break; } @@ -1196,13 +1292,13 @@ namespace { else if (bestValue >= beta) { BetaCounter.add(pos.side_to_move(), depth, threadID); - Move m = ss[ply].pv[ply]; - if (!pos.move_is_capture_or_promotion(m)) + move = ss[ply].pv[ply]; + if (!pos.move_is_capture_or_promotion(move)) { - update_history(pos, m, depth, movesSearched, moveCount); - update_killers(m, ss[ply]); + update_history(pos, move, depth, movesSearched, moveCount); + update_killers(move, ss[ply]); } - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m); + TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move); } else TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]); @@ -1214,12 +1310,24 @@ namespace { // search() is the search function for zero-width nodes. Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, - int ply, bool allowNullmove, int threadID) { + int ply, bool allowNullmove, int threadID, Move excludedMove) { assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); + Move movesSearched[256]; + EvalInfo ei; + StateInfo st; + const TTEntry* tte; + Move ttMove, move; + Depth ext, newDepth; + Value approximateEval, nullValue, value, futilityValue, futilityValueScaled; + bool isCheck, useFutilityPruning, singleReply, moveIsCheck, captureOrPromotion, dangerous; + bool mateThreat = false; + int moveCount = 0; + Value bestValue = -VALUE_INFINITE; + if (depth < OnePly) return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); @@ -1234,8 +1342,6 @@ namespace { if (pos.is_draw()) return VALUE_DRAW; - EvalInfo ei; - if (ply >= PLY_MAX - 1) return pos.is_check() ? quick_evaluate(pos) : evaluate(pos, ei, threadID); @@ -1246,9 +1352,13 @@ namespace { if (value_mate_in(ply + 1) < beta) return beta - 1; + // We don't want the score of a partial search to overwrite a previous full search + // TT value, so we use a different position key in case of an excluded move exsists. + Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); + // Transposition table lookup - const TTEntry* tte = TT.retrieve(pos.get_key()); - Move ttMove = (tte ? tte->move() : MOVE_NONE); + tte = TT.retrieve(posKey); + ttMove = (tte ? tte->move() : MOVE_NONE); if (tte && ok_to_use_TT(tte, depth, beta, ply)) { @@ -1256,9 +1366,8 @@ namespace { return value_from_tt(tte->value(), ply); } - Value approximateEval = quick_evaluate(pos); - bool mateThreat = false; - bool isCheck = pos.is_check(); + approximateEval = quick_evaluate(pos); + isCheck = pos.is_check(); // Null move search if ( allowNullmove @@ -1270,11 +1379,16 @@ namespace { { ss[ply].currentMove = MOVE_NULL; - StateInfo st; pos.do_null_move(st); - int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction - Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID); + // Null move dynamic reduction based on depth + int R = (depth >= 5 * OnePly ? 4 : 3); + + // Null move dynamic reduction based on value + if (approximateEval - beta > PawnValueMidgame) + R++; + + nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID); pos.undo_null_move(); @@ -1312,8 +1426,9 @@ namespace { && ttMove == MOVE_NONE && !pos.has_pawn_on_7th(pos.side_to_move())) { - Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); - if (v < beta - RazorMargins[int(depth) - 2]) + Value rbeta = beta - RazorMargins[int(depth) - 2]; + Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID); + if (v < rbeta) return v; } @@ -1323,50 +1438,80 @@ namespace { { search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID); ttMove = ss[ply].pv[ply]; + tte = TT.retrieve(pos.get_key()); } // Initialize a MovePicker object for the current position, and prepare // to search all moves. MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]); - - Move move, movesSearched[256]; - int moveCount = 0; - Value value, bestValue = -VALUE_INFINITE; - Bitboard dcCandidates = mp.discovered_check_candidates(); - Value futilityValue = VALUE_NONE; - bool useFutilityPruning = depth < SelectiveDepth - && !isCheck; + CheckInfo ci(pos); + futilityValue = VALUE_NONE; + useFutilityPruning = depth < SelectiveDepth && !isCheck; // Avoid calling evaluate() if we already have the score in TT if (tte && (tte->type() & VALUE_TYPE_EVAL)) futilityValue = value_from_tt(tte->value(), ply) + FutilityMargins[int(depth) - 2]; - // Loop through all legal moves until no moves remain or a beta cutoff - // occurs. + // Move count pruning limit + const int MCLimit = 3 + (1 << (3*int(depth)/8)); + + // Loop through all legal moves until no moves remain or a beta cutoff occurs while ( bestValue < beta && (move = mp.get_next_move()) != MOVE_NONE && !thread_should_stop(threadID)) { assert(move_is_ok(move)); - bool singleReply = (isCheck && mp.number_of_evasions() == 1); - bool moveIsCheck = pos.move_is_check(move, dcCandidates); - bool captureOrPromotion = pos.move_is_capture_or_promotion(move); + if (move == excludedMove) + continue; - movesSearched[moveCount++] = ss[ply].currentMove = move; + singleReply = (isCheck && mp.number_of_evasions() == 1); + moveIsCheck = pos.move_is_check(move, ci); + captureOrPromotion = pos.move_is_capture_or_promotion(move); // Decide the new search depth - bool dangerous; - Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous); - Depth newDepth = depth - OnePly + ext; + ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleReply, mateThreat, &dangerous); + + // We want to extend the TT move if it is much better then remaining ones. + // To verify this we do a reduced search on all the other moves but the ttMove, + // if result is lower then TT value minus a margin then we assume ttMove is the + // only one playable. It is a kind of relaxed single reply extension. + // Note that could be ttMove != tte->move() due to IID, so we always use tte->move() + // to avoid aliases when we probe tte->depth() and tte->type() + if ( depth >= 8 * OnePly + && tte + && move == tte->move() + && !excludedMove // Do not allow recursive single-reply search + && ext < OnePly + && is_lower_bound(tte->type()) + && tte->depth() >= depth - 3 * OnePly) + { + Value ttValue = value_from_tt(tte->value(), ply); + + if (abs(ttValue) < VALUE_KNOWN_WIN) + { + Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, ttMove); + + // If search result is well below the foreseen score of the ttMove then we + // assume ttMove is the only one realistically playable and we extend it. + if (excValue < ttValue - SingleReplyMargin) + ext = OnePly; + } + } + + newDepth = depth - OnePly + ext; + + // Update current move + movesSearched[moveCount++] = ss[ply].currentMove = move; // Futility pruning if ( useFutilityPruning && !dangerous - && !captureOrPromotion) + && !captureOrPromotion + && move != ttMove) { // History pruning. See ok_to_prune() definition - if ( moveCount >= 2 + int(depth) + if ( moveCount >= MCLimit && ok_to_prune(pos, move, ss[ply].threatMove, depth) && bestValue > value_mated_in(PLY_MAX)) continue; @@ -1376,20 +1521,21 @@ namespace { { if (futilityValue == VALUE_NONE) futilityValue = evaluate(pos, ei, threadID) - + FutilityMargins[int(depth) - 2]; + + 64*(2+bitScanReverse32(int(depth) * int(depth))); + + futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin; - if (futilityValue < beta) + if (futilityValueScaled < beta) { - if (futilityValue > bestValue) - bestValue = futilityValue; + if (futilityValueScaled > bestValue) + bestValue = futilityValueScaled; continue; } } } // Make and search the move - StateInfo st; - pos.do_move(move, st, dcCandidates); + pos.do_move(move, st, ci, moveIsCheck); // Try to reduce non-pv search depth by one ply if move seems not problematic, // if the move fails high will be re-searched at full depth. @@ -1434,15 +1580,15 @@ namespace { && idle_thread_exists(threadID) && !AbortSearch && !thread_should_stop(threadID) - && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, approximateEval, depth, &moveCount, - &mp, dcCandidates, threadID, false)) + && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, approximateEval, + depth, &moveCount, &mp, threadID, false)) break; } // All legal moves have been searched. A special case: If there were // no legal moves, it must be mate or stalemate. if (moveCount == 0) - return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); + return excludedMove ? beta - 1 : (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); // If the search is not aborted, update the transposition table, // history counters, and killer moves. @@ -1450,17 +1596,17 @@ namespace { return bestValue; if (bestValue < beta) - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE); + TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE); else { BetaCounter.add(pos.side_to_move(), depth, threadID); - Move m = ss[ply].pv[ply]; - if (!pos.move_is_capture_or_promotion(m)) + move = ss[ply].pv[ply]; + if (!pos.move_is_capture_or_promotion(move)) { - update_history(pos, m, depth, movesSearched, moveCount); - update_killers(m, ss[ply]); + update_history(pos, move, depth, movesSearched, moveCount); + update_killers(move, ss[ply]); } - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m); + TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move); } assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1482,6 +1628,15 @@ namespace { assert(ply >= 0 && ply < PLY_MAX); assert(threadID >= 0 && threadID < ActiveThreads); + EvalInfo ei; + StateInfo st; + Move ttMove, move; + Value staticValue, bestValue, value, futilityValue; + bool isCheck, enoughMaterial, moveIsCheck; + const TTEntry* tte = NULL; + int moveCount = 0; + bool pvNode = (beta - alpha != 1); + // Initialize, and make an early exit in case of an aborted search, // an instant draw, maximum ply reached, etc. init_node(ss, ply, threadID); @@ -1494,8 +1649,6 @@ namespace { return VALUE_DRAW; // Transposition table lookup, only when not in PV - TTEntry* tte = NULL; - bool pvNode = (beta - alpha != 1); if (!pvNode) { tte = TT.retrieve(pos.get_key()); @@ -1506,12 +1659,10 @@ namespace { return value_from_tt(tte->value(), ply); } } - Move ttMove = (tte ? tte->move() : MOVE_NONE); + ttMove = (tte ? tte->move() : MOVE_NONE); // Evaluate the position statically - EvalInfo ei; - Value staticValue; - bool isCheck = pos.is_check(); + isCheck = pos.is_check(); ei.futilityMargin = Value(0); // Manually initialize futilityMargin if (isCheck) @@ -1532,7 +1683,7 @@ namespace { // Initialize "stand pat score", and return it immediately if it is // at least beta. - Value bestValue = staticValue; + bestValue = staticValue; if (bestValue >= beta) { @@ -1550,11 +1701,8 @@ namespace { // to search the moves. Because the depth is <= 0 here, only captures, // queen promotions and checks (only if depth == 0) will be generated. MovePicker mp = MovePicker(pos, ttMove, depth, H); - Move move; - int moveCount = 0; - Bitboard dcCandidates = mp.discovered_check_candidates(); - Color us = pos.side_to_move(); - bool enoughMaterial = pos.non_pawn_material(us) > RookValueMidgame; + CheckInfo ci(pos); + enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; // Loop through the moves until no moves remain or a beta cutoff // occurs. @@ -1566,20 +1714,23 @@ namespace { moveCount++; ss[ply].currentMove = move; + moveIsCheck = pos.move_is_check(move, ci); + // Futility pruning if ( enoughMaterial && !isCheck && !pvNode + && !moveIsCheck + && move != ttMove && !move_is_promotion(move) - && !pos.move_is_check(move, dcCandidates) && !pos.move_is_passed_pawn_push(move)) { - Value futilityValue = staticValue - + Max(pos.midgame_value_of_piece_on(move_to(move)), - pos.endgame_value_of_piece_on(move_to(move))) - + (move_is_ep(move) ? PawnValueEndgame : Value(0)) - + FutilityMarginQS - + ei.futilityMargin; + futilityValue = staticValue + + Max(pos.midgame_value_of_piece_on(move_to(move)), + pos.endgame_value_of_piece_on(move_to(move))) + + (move_is_ep(move) ? PawnValueEndgame : Value(0)) + + FutilityMarginQS + + ei.futilityMargin; if (futilityValue < alpha) { @@ -1596,10 +1747,9 @@ namespace { && pos.see_sign(move) < 0) continue; - // Make and search the move. - StateInfo st; - pos.do_move(move, st, dcCandidates); - Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID); + // Make and search the move + pos.do_move(move, st, ci, moveIsCheck); + value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1624,7 +1774,7 @@ namespace { assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); // Update transposition table - Move m = ss[ply].pv[ply]; + move = ss[ply].pv[ply]; if (!pvNode) { // If bestValue isn't changed it means it is still the static evaluation of @@ -1635,12 +1785,12 @@ namespace { if (bestValue < beta) TT.store(pos.get_key(), value_to_tt(bestValue, ply), type, d, MOVE_NONE); else - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, m); + TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move); } // Update killers only for good check moves - if (alpha >= beta && !pos.move_is_capture_or_promotion(m)) - update_killers(m, ss[ply]); + if (alpha >= beta && !pos.move_is_capture_or_promotion(move)) + update_killers(move, ss[ply]); return bestValue; } @@ -1660,6 +1810,7 @@ namespace { assert(ActiveThreads > 1); Position pos = Position(sp->pos); + CheckInfo ci(pos); SearchStack* ss = sp->sstack[threadID]; Value value; Move move; @@ -1673,7 +1824,7 @@ namespace { { assert(move_is_ok(move)); - bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); + bool moveIsCheck = pos.move_is_check(move, ci); bool captureOrPromotion = pos.move_is_capture_or_promotion(move); lock_grab(&(sp->lock)); @@ -1724,7 +1875,7 @@ namespace { // Make and search the move. StateInfo st; - pos.do_move(move, st, sp->dcCandidates); + pos.do_move(move, st, ci, moveIsCheck); // Try to reduce non-pv search depth by one ply if move seems not problematic, // if the move fails high will be re-searched at full depth. @@ -1803,6 +1954,7 @@ namespace { assert(ActiveThreads > 1); Position pos = Position(sp->pos); + CheckInfo ci(pos); SearchStack* ss = sp->sstack[threadID]; Value value; Move move; @@ -1811,7 +1963,7 @@ namespace { && !thread_should_stop(threadID) && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE) { - bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); + bool moveIsCheck = pos.move_is_check(move, ci); bool captureOrPromotion = pos.move_is_capture_or_promotion(move); assert(move_is_ok(move)); @@ -1829,7 +1981,7 @@ namespace { // Make and search the move. StateInfo st; - pos.do_move(move, st, sp->dcCandidates); + pos.do_move(move, st, ci, moveIsCheck); // Try to reduce non-pv search depth by one ply if move seems not problematic, // if the move fails high will be re-searched at full depth. @@ -1999,7 +2151,7 @@ namespace { moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0); pos.undo_move(moves[count].move); moves[count].pv[0] = moves[count].move; - moves[count].pv[1] = MOVE_NONE; // FIXME + moves[count].pv[1] = MOVE_NONE; count++; } sort(); @@ -2050,28 +2202,6 @@ namespace { } - // RootMoveList::scan_for_easy_move() is called at the end of the first - // iteration, and is used to detect an "easy move", i.e. a move which appears - // to be much bester than all the rest. If an easy move is found, the move - // is returned, otherwise the function returns MOVE_NONE. It is very - // important that this function is called at the right moment: The code - // assumes that the first iteration has been completed and the moves have - // been sorted. This is done in RootMoveList c'tor. - - Move RootMoveList::scan_for_easy_move() const { - - assert(count); - - if (count == 1) - return get_move(0); - - // moves are sorted so just consider the best and the second one - if (get_move_score(0) > get_move_score(1) + EasyMoveMargin) - return get_move(0); - - return MOVE_NONE; - } - // RootMoveList::sort() sorts the root move list at the beginning of a new // iteration. @@ -2773,7 +2903,7 @@ namespace { bool split(const Position& p, SearchStack* sstck, int ply, Value* alpha, Value* beta, Value* bestValue, const Value futilityValue, const Value approximateEval, Depth depth, int* moves, - MovePicker* mp, Bitboard dcCandidates, int master, bool pvNode) { + MovePicker* mp, int master, bool pvNode) { assert(p.is_ok()); assert(sstck != NULL); @@ -2810,7 +2940,6 @@ namespace { splitPoint->alpha = pvNode? *alpha : (*beta - 1); splitPoint->beta = *beta; splitPoint->pvNode = pvNode; - splitPoint->dcCandidates = dcCandidates; splitPoint->bestValue = *bestValue; splitPoint->futilityValue = futilityValue; splitPoint->approximateEval = approximateEval;