X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=2a2e32f943fae435ef69719364504b7b2f58fedc;hp=ed1cdc7faa0187184d3a1ac14df6a2b7ab269d2e;hb=c172af1b6181b39288870689f912143c04a4040a;hpb=ee9f650242899373136a76d9549db7f2858c1b06 diff --git a/src/search.cpp b/src/search.cpp index ed1cdc7f..2a2e32f9 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -106,6 +106,9 @@ namespace { const bool UseIIDAtPVNodes = true; const bool UseIIDAtNonPVNodes = false; + // Use null move driven internal iterative deepening? + bool UseNullDrivenIID = true; + // Internal iterative deepening margin. At Non-PV moves, when // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search // when the static evaluation is at most IIDMargin below beta. @@ -188,7 +191,7 @@ namespace { // Time managment variables int SearchStartTime; int MaxNodes, MaxDepth; - int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime, TimeAdvantage; + int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime; Move BestRootMove, PonderMove, EasyMove; int RootMoveNumber; bool InfiniteSearch; @@ -245,7 +248,7 @@ namespace { void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply); bool connected_moves(const Position &pos, Move m1, Move m2); bool move_is_killer(Move m, const SearchStack& ss); - Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* extendable); + Depth extension(const Position &pos, Move m, bool pvNode, bool check, bool singleReply, bool mateThreat, bool* dangerous); bool ok_to_do_nullmove(const Position &pos); bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); @@ -427,8 +430,6 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, int myIncrement = increment[side_to_move]; int oppTime = time[1 - side_to_move]; - TimeAdvantage = myTime - oppTime; - if (!movesToGo) // Sudden death time control { if (myIncrement) @@ -436,7 +437,7 @@ void think(const Position &pos, bool infinite, bool ponder, int side_to_move, MaxSearchTime = myTime / 30 + myIncrement; AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100); } else { // Blitz game without increment - MaxSearchTime = myTime / 40; + MaxSearchTime = myTime / 30; AbsoluteMaxSearchTime = myTime / 8; } } @@ -680,10 +681,6 @@ namespace { ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2) + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3); - // If we need some more and we are in time advantage take it - if (ExtraSearchTime > 0 && TimeAdvantage > 2 * MaxSearchTime) - ExtraSearchTime += MaxSearchTime / 2; - // Try to guess if the current iteration is the last one or the last two LastIterations = (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*58) / 128); @@ -778,8 +775,8 @@ namespace { << " currmovenumber " << i + 1 << std::endl; // Decide search depth for this move - bool dummy; - ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dummy); + bool dangerous; + ext = extension(pos, move, true, pos.move_is_check(move), false, false, &dangerous); newDepth = (Iteration - 2) * OnePly + ext + InitialDepth; // Make the move, and search it @@ -953,8 +950,7 @@ namespace { Value value, bestValue = -VALUE_INFINITE; Bitboard dcCandidates = mp.discovered_check_candidates(); bool isCheck = pos.is_check(); - bool mateThreat = MateThreatExtension[1] > Depth(0) - && pos.has_mate_threat(opposite_color(pos.side_to_move())); + bool mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); // Loop through all legal moves until no moves remain or a beta cutoff // occurs. @@ -967,7 +963,6 @@ namespace { bool singleReply = (isCheck && mp.number_of_moves() == 1); bool moveIsCheck = pos.move_is_check(move, dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); movesSearched[moveCount++] = ss[ply].currentMove = move; @@ -979,8 +974,8 @@ namespace { ss[ply].currentMoveCaptureValue = Value(0); // Decide the new search depth - bool extendable; - Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &extendable); + bool dangerous; + Depth ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Make and search the move @@ -994,11 +989,10 @@ namespace { // 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. if ( depth >= 2*OnePly - && !extendable && moveCount >= LMRPVMoves + && !dangerous && !moveIsCapture && !move_promotion(move) - && !moveIsPassedPawnPush && !move_is_castle(move) && !move_is_killer(move, ss[ply])) { @@ -1133,12 +1127,13 @@ namespace { if (tte && ok_to_use_TT(tte, depth, beta, ply)) { - ss[ply].currentMove = ttMove; // can be MOVE_NONE ? + ss[ply].currentMove = ttMove; // can be MOVE_NONE return value_from_tt(tte->value(), ply); } Value approximateEval = quick_evaluate(pos); bool mateThreat = false; + bool nullDrivenIID = false; bool isCheck = pos.is_check(); // Null move search @@ -1152,7 +1147,21 @@ namespace { UndoInfo u; pos.do_null_move(u); int R = (depth > 7 ? 4 : 3); + Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID); + + // Check for a null capture artifact, if the value without the null capture + // is above beta then there is a good possibility that this is a cut-node. + // We will do an IID later to find a ttMove. + if ( UseNullDrivenIID + && nullValue < beta + && depth > 6 * OnePly + && ttMove == MOVE_NONE + && ss[ply + 1].currentMove != MOVE_NONE + && pos.move_is_capture(ss[ply + 1].currentMove) + && pos.see(ss[ply + 1].currentMove) * PawnValueMidgame + nullValue > beta - IIDMargin) + nullDrivenIID = true; + pos.undo_null_move(u); if (nullValue >= beta) @@ -1172,8 +1181,10 @@ namespace { // low score (which will cause the reduced move to fail high in the // parent node, which will trigger a re-search with full depth). if (nullValue == value_mated_in(ply + 2)) + { mateThreat = true; - + nullDrivenIID = false; + } ss[ply].threatMove = ss[ply + 1].currentMove; if ( depth < ThreatDepth && ss[ply - 1].reduction @@ -1197,6 +1208,19 @@ namespace { search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID); ttMove = ss[ply].pv[ply]; } + else if (nullDrivenIID) + { + // The null move failed low due to a suspicious capture. Perhaps we + // are facing a null capture artifact due to the side to move change + // and this is a cut-node. So it's a good time to search for a ttMove. + Move tm = ss[ply].threatMove; + + assert(tm != MOVE_NONE); + + search(pos, ss, beta, Min(depth/2, depth-3*OnePly), ply, false, threadID); + ttMove = ss[ply].pv[ply]; + ss[ply].threatMove = tm; + } // Initialize a MovePicker object for the current position, and prepare // to search all moves: @@ -1222,20 +1246,18 @@ namespace { bool singleReply = (isCheck && mp.number_of_moves() == 1); bool moveIsCheck = pos.move_is_check(move, dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); movesSearched[moveCount++] = ss[ply].currentMove = move; // Decide the new search depth - bool extendable; - Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &extendable); + bool dangerous; + Depth ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat, &dangerous); Depth newDepth = depth - OnePly + ext; // Futility pruning if ( useFutilityPruning - && !extendable + && !dangerous && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move)) { if ( moveCount >= 2 + int(depth) @@ -1263,12 +1285,11 @@ namespace { // 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. - if ( depth >= 2*OnePly - && !extendable - && moveCount >= LMRNonPVMoves + if ( depth >= 2*OnePly + && moveCount >= LMRNonPVMoves + && !dangerous && !moveIsCapture && !move_promotion(move) - && !moveIsPassedPawnPush && !move_is_castle(move) && !move_is_killer(move, ss[ply])) { @@ -1401,20 +1422,17 @@ namespace { { assert(move_is_ok(move)); - bool moveIsCheck = pos.move_is_check(move, dcCandidates); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); - moveCount++; ss[ply].currentMove = move; // Futility pruning if ( UseQSearchFutilityPruning + && enoughMaterial && !isCheck - && !moveIsCheck - && !move_promotion(move) - && !moveIsPassedPawnPush && !pvNode - && enoughMaterial) + && !move_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)), @@ -1509,7 +1527,6 @@ namespace { bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); lock_grab(&(sp->lock)); int moveCount = ++sp->moves; @@ -1518,15 +1535,14 @@ namespace { ss[sp->ply].currentMove = move; // Decide the new search depth. - bool extendable; - Depth ext = extension(pos, move, false, moveIsCheck, false, false, &extendable); + bool dangerous; + Depth ext = extension(pos, move, false, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Prune? if ( useFutilityPruning - && !extendable + && !dangerous && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && moveCount >= 2 + int(sp->depth) && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth)) @@ -1538,10 +1554,9 @@ namespace { // 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. - if ( !extendable + if ( !dangerous && moveCount >= LMRNonPVMoves && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && !move_is_castle(move) && !move_is_killer(move, ss[sp->ply])) @@ -1622,7 +1637,6 @@ namespace { { bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates); bool moveIsCapture = pos.move_is_capture(move); - bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move); assert(move_is_ok(move)); @@ -1636,8 +1650,8 @@ namespace { ss[sp->ply].currentMove = move; // Decide the new search depth. - bool extendable; - Depth ext = extension(pos, move, true, moveIsCheck, false, false, &extendable); + bool dangerous; + Depth ext = extension(pos, move, true, moveIsCheck, false, false, &dangerous); Depth newDepth = sp->depth - OnePly + ext; // Make and search the move. @@ -1646,10 +1660,9 @@ namespace { // 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. - if ( !extendable + if ( !dangerous && moveCount >= LMRPVMoves && !moveIsCapture - && !moveIsPassedPawnPush && !move_promotion(move) && !move_is_castle(move) && !move_is_killer(move, ss[sp->ply])) @@ -2053,13 +2066,16 @@ namespace { // extension() decides whether a move should be searched with normal depth, // or with extended depth. Certain classes of moves (checking moves, in - // particular) are searched with bigger depth than ordinary moves. + // particular) are searched with bigger depth than ordinary moves and in + // any case are marked as 'dangerous'. Note that also if a move is not + // extended, as example because the corresponding UCI option is set to zero, + // the move is marked as 'dangerous' so, at least, we avoid to prune it. - Depth extension(const Position &pos, Move m, bool pvNode, - bool check, bool singleReply, bool mateThreat, bool* extendable) { + Depth extension(const Position &pos, Move m, bool pvNode, bool check, + bool singleReply, bool mateThreat, bool* dangerous) { Depth result = Depth(0); - *extendable = check || singleReply || mateThreat; + *dangerous = check || singleReply || mateThreat; if (check) result += CheckExtension[pvNode]; @@ -2073,12 +2089,12 @@ namespace { if (pos.move_is_pawn_push_to_7th(m)) { result += PawnPushTo7thExtension[pvNode]; - *extendable = true; + *dangerous = true; } if (pos.move_is_passed_pawn_push(m)) { result += PassedPawnExtension[pvNode]; - *extendable = true; + *dangerous = true; } if ( pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame @@ -2087,7 +2103,7 @@ namespace { && !move_promotion(m)) { result += PawnEndgameExtension[pvNode]; - *extendable = true; + *dangerous = true; } if ( pvNode @@ -2096,7 +2112,7 @@ namespace { && pos.see(m) >= 0) { result += OnePly/2; - *extendable = true; + *dangerous = true; } return Min(result, OnePly);