X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=4ea010728574e04c80f0112a388c610185845a46;hp=b6029e0c71f4dcd3506092a0695b22a0c0446d4c;hb=48246468f2874c9e5e985baf224e202433d53fd3;hpb=c52da3b806b74ba5ab5249784d39da8fec3c7465 diff --git a/src/search.cpp b/src/search.cpp index b6029e0c..4ea01072 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -172,12 +172,16 @@ 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(0xA); + 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), @@ -277,7 +281,7 @@ 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); @@ -798,7 +802,6 @@ namespace { if (stopSearch) { - //FIXME: Implement fail-low emergency measures if (!PonderSearch) break; else @@ -1132,12 +1135,38 @@ namespace { moveIsCheck = pos.move_is_check(move, ci); captureOrPromotion = pos.move_is_capture_or_promotion(move); - movesSearched[moveCount++] = ss[ply].currentMove = move; - // Decide the new search depth 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. + if ( depth >= 4 * OnePly + && move == ttMove + && 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) + { + Depth d = Max(Min(depth / 2, depth - 4 * OnePly), OnePly); + Value excValue = search(pos, ss, ttValue - SingleReplyMargin, d, 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 pos.do_move(move, st, ci, moveIsCheck); @@ -1251,7 +1280,7 @@ 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); @@ -1293,8 +1322,12 @@ 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 - tte = TT.retrieve(pos.get_key()); + tte = TT.retrieve(posKey); ttMove = (tte ? tte->move() : MOVE_NONE); if (tte && ok_to_use_TT(tte, depth, beta, ply)) @@ -1391,77 +1424,59 @@ namespace { // 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. + // 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)); + if (move == excludedMove) + continue; + singleReply = (isCheck && mp.number_of_evasions() == 1); moveIsCheck = pos.move_is_check(move, ci); captureOrPromotion = pos.move_is_capture_or_promotion(move); - movesSearched[moveCount++] = ss[ply].currentMove = move; - // Decide the new search depth 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. + if ( depth >= 4 * OnePly + && !excludedMove // do not allow recursive single-reply search + && move == ttMove + && 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) + { + Depth d = Max(Min(depth / 2, depth - 4 * OnePly), OnePly); + Value excValue = search(pos, ss, ttValue - SingleReplyMargin, d, 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 = (depth >= 8 * OnePly) ? OnePly : ext + OnePly / 2; + } + } + newDepth = depth - OnePly + ext; + // Update current move + movesSearched[moveCount++] = ss[ply].currentMove = move; + // Futility pruning if ( useFutilityPruning && !dangerous && !captureOrPromotion && move != ttMove) { - //std::cout << std::endl; - //for (int d = 2; d < 14; d++) - // std::cout << d << ", " << 64*(1+bitScanReverse32(d*d)) << std::endl; - - //std::cout << std::endl; -/* - 64*(1+bitScanReverse32(d*d)) - - 2 -> 256 - 256 - 3 -> 288 - 320 - 4 -> 512 - 384 - 5 -> 544 - 384 - 6 -> 592 - 448 - 7 -> 624 - 448 - 8 -> 672 - 512 - 9 -> 704 - 512 - 10 -> 832 - 512 - 11 -> 864 - 512 - 12 -> 928 - 576 - 13 -> 960 - 576 - - 300 + 2*(1 << (3*d/4)) - - 2 -> 256 - 304 - 3 -> 288 - 308 - 4 -> 512 - 316 - 5 -> 544 - 316 - 6 -> 592 - 332 - 7 -> 624 - 364 - 8 -> 672 - 428 - 9 -> 704 - 428 - 10 -> 832 - 556 - 11 -> 864 - 812 - 12 -> 928 - 1324 - 13 -> 960 - 1324 - - - 3 + (1 << (3*int(depth)/8)) - - 1 * onePly - > moveCount >= 4 - 2 * onePly - > moveCount >= 5 - 3 * onePly - > moveCount >= 7 - 4 * onePly - > moveCount >= 11 - 5 * onePly - > moveCount >= 11 - 6 * onePly - > moveCount >= 19 - 7 * onePly - > moveCount >= 35 -*/ // History pruning. See ok_to_prune() definition if ( moveCount >= MCLimit && ok_to_prune(pos, move, ss[ply].threatMove, depth) @@ -1473,8 +1488,7 @@ namespace { { if (futilityValue == VALUE_NONE) futilityValue = evaluate(pos, ei, threadID) - + 64*(1+bitScanReverse32(int(depth) * int(depth))) - + 4*IncrementalFutilityMargin; + + 64*(2+bitScanReverse32(int(depth) * int(depth))); futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin; @@ -1541,7 +1555,7 @@ namespace { // 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. @@ -1549,7 +1563,7 @@ 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); @@ -1559,7 +1573,7 @@ namespace { 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, move); + TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move); } assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -2104,7 +2118,7 @@ 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();