X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=085d124ee66b994819a1e8e71e20bf99eb3532cd;hp=785cf0efb8ec7ec055f369ec3566c88f9dd87ccf;hb=db097921bc0f631d770c3437569f105579823471;hpb=5436d98fc54600ead011304274250e8b5de35c6a diff --git a/src/search.cpp b/src/search.cpp index 785cf0ef..085d124e 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -62,10 +62,6 @@ namespace { // Different node types, used as template parameter enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; - // Lookup table to check if a Piece is a slider and its access function - const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; - inline bool piece_is_slider(Piece p) { return Slidings[p]; } - // Dynamic razoring margin based on depth inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } @@ -96,15 +92,15 @@ namespace { template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); void id_loop(Position& pos); - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta); - bool connected_moves(const Position& pos, Move m1, Move m2); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool connected_threat(const Position& pos, Move m, Move threat); + bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta); + bool allows_move(const Position& pos, Move first, Move second); + bool prevents_move(const Position& pos, Move first, Move second); string uci_pv(const Position& pos, int depth, Value alpha, Value beta); struct Skill { @@ -192,7 +188,7 @@ void Search::think() { { RootMoves.push_back(MOVE_NONE); sync_cout << "info depth 0 score " - << score_to_uci(RootPos.in_check() ? -VALUE_MATE : VALUE_DRAW) + << score_to_uci(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW) << sync_endl; goto finalize; @@ -212,7 +208,7 @@ void Search::think() { if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"]) { int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns - cf = cf * MaterialTable::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase + cf = cf * Material::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase DrawValue[ RootColor] = VALUE_DRAW - Value(cf); DrawValue[~RootColor] = VALUE_DRAW + Value(cf); } @@ -222,7 +218,7 @@ void Search::think() { if (Options["Use Search Log"]) { Log log(Options["Search Log Filename"]); - log << "\nSearching: " << RootPos.to_fen() + log << "\nSearching: " << RootPos.fen() << "\ninfinite: " << Limits.infinite << " ponder: " << Limits.ponder << " time: " << Limits.time[RootColor] @@ -394,8 +390,9 @@ namespace { } // Sort the PV lines searched so far and update the GUI - sort(RootMoves.begin(), RootMoves.begin() + PVIdx); - sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; + sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1); + if (PVIdx + 1 == PVSize || Time::now() - SearchTime > 3000) + sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl; } // Do we need to pick now the sub-optimal best move ? @@ -488,13 +485,14 @@ namespace { Value bestValue, value, ttValue; Value eval, nullValue, futilityValue; bool inCheck, givesCheck, pvMove, singularExtensionNode; - bool captureOrPromotion, dangerous, doFullDepthSearch; + bool captureOrPromotion, dangerous, doFullDepthSearch, threatExtension; int moveCount, playedMoveCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); moveCount = playedMoveCount = 0; - inCheck = pos.in_check(); + threatExtension = false; + inCheck = pos.checkers(); if (SpNode) { @@ -524,7 +522,7 @@ namespace { if (!RootNode) { // Step 2. Check for aborted search and immediate draw - if (Signals.stop || (PvNode?pos.is_draw():pos.is_draw()) || ss->ply > MAX_PLY) + if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) return DrawValue[pos.side_to_move()]; // Step 3. Mate distance pruning. Even if we mate at the next move our score @@ -553,13 +551,13 @@ namespace { // smooth experience in analysis mode. We don't probe at Root nodes otherwise // we should also update RootMoveList to avoid bogus output. if ( !RootNode - && tte && tte->depth() >= depth + && tte + && tte->depth() >= depth + && ttValue != VALUE_NONE // Only in case of TT access race && ( PvNode ? tte->type() == BOUND_EXACT : ttValue >= beta ? (tte->type() & BOUND_LOWER) : (tte->type() & BOUND_UPPER))) { - assert(ttValue != VALUE_NONE); // Due to depth > DEPTH_NONE - TT.refresh(tte); ss->currentMove = ttMove; // Can be MOVE_NONE @@ -577,25 +575,17 @@ namespace { // Step 5. Evaluate the position statically and update parent's gain statistics if (inCheck) ss->staticEval = ss->evalMargin = eval = VALUE_NONE; - - else if (tte) - { - assert(tte->static_value() != VALUE_NONE); - assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE); - - ss->staticEval = eval = tte->static_value(); - ss->evalMargin = tte->static_value_margin(); - - // Can ttValue be used as a better position evaluation? - if ( ((tte->type() & BOUND_LOWER) && ttValue > eval) - || ((tte->type() & BOUND_UPPER) && ttValue < eval)) - eval = ttValue; - } else { eval = ss->staticEval = evaluate(pos, ss->evalMargin); - TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, - ss->staticEval, ss->evalMargin); + + // Can ttValue be used as a better position evaluation? + if (tte && ttValue != VALUE_NONE) + { + if ( ((tte->type() & BOUND_LOWER) && ttValue > eval) + || ((tte->type() & BOUND_UPPER) && ttValue < eval)) + eval = ttValue; + } } // Update gain for the parent non-capture move given the static position @@ -620,7 +610,7 @@ namespace { && !pos.pawn_on_7th(pos.side_to_move())) { Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); + Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -659,7 +649,7 @@ namespace { pos.do_null_move(st); (ss+1)->skipNullMove = true; - nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) : - search(pos, ss+1, -beta, -alpha, depth-R); (ss+1)->skipNullMove = false; pos.do_null_move(st); @@ -686,16 +676,15 @@ namespace { // The null move failed low, which means that we may be faced with // some kind of threat. If the previous move was reduced, check if // the move that refuted the null move was somehow connected to the - // move which was reduced. If a connection is found, return a fail - // low score (which will cause the reduced move to fail high in the - // parent node, which will trigger a re-search with full depth). + // move which was reduced. If a connection is found extend moves that + // defend against threat. threatMove = (ss+1)->currentMove; if ( depth < 5 * ONE_PLY && (ss-1)->reduction && threatMove != MOVE_NONE - && connected_moves(pos, (ss-1)->currentMove, threatMove)) - return beta - 1; + && allows_move(pos, (ss-1)->currentMove, threatMove)) + threatExtension = true; } } @@ -791,7 +780,7 @@ split_point_start: // At split points actual search starts from here { Signals.firstRootMove = (moveCount == 1); - if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000) + if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 3000) sync_cout << "info depth " << depth / ONE_PLY << " currmove " << move_to_uci(move, pos.is_chess960()) << " currmovenumber " << moveCount + PVIdx << sync_endl; @@ -813,6 +802,9 @@ split_point_start: // At split points actual search starts from here if (PvNode && dangerous) ext = ONE_PLY; + else if (threatExtension && prevents_move(pos, move, threatMove)) + ext = ONE_PLY; + else if (givesCheck && pos.see_sign(move) >= 0) ext = ONE_PLY / 2; @@ -855,7 +847,7 @@ split_point_start: // At split points actual search starts from here // Move count based pruning if ( depth < 16 * ONE_PLY && moveCount >= FutilityMoveCounts[depth] - && (!threatMove || !connected_threat(pos, move, threatMove))) + && (!threatMove || !prevents_move(pos, move, threatMove))) { if (SpNode) sp->mutex.lock(); @@ -890,7 +882,7 @@ split_point_start: // At split points actual search starts from here } // Check for legality only before to do the move - if (!pos.pl_move_is_legal(move, ci.pinned)) + if (!RootNode && !SpNode && !pos.pl_move_is_legal(move, ci.pinned)) { moveCount--; continue; @@ -929,7 +921,9 @@ split_point_start: // At split points actual search starts from here if (doFullDepthSearch) { alpha = SpNode ? sp->alpha : alpha; - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + 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); } @@ -937,9 +931,10 @@ split_point_start: // At split points actual search starts from here // high, in the latter case search only if value < beta, otherwise let the // parent node to fail low with value <= alpha and to try another move. if (PvNode && (pvMove || (value > alpha && (RootNode || value < beta)))) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + 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); - // Step 17. Undo move pos.undo_move(move); @@ -998,8 +993,10 @@ split_point_start: // At split points actual search starts from here alpha = value; // Update alpha here! Always alpha < beta if (SpNode) sp->alpha = value; } - else // Fail high + else { + assert(value >= beta); // Fail high + if (SpNode) sp->cutoff = true; break; } @@ -1009,12 +1006,14 @@ split_point_start: // At split points actual search starts from here // Step 19. Check for splitting the search if ( !SpNode && depth >= Threads.min_split_depth() - && bestValue < beta && Threads.available_slave_exists(thisThread)) { + assert(bestValue < beta); + bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove, depth, threatMove, moveCount, mp, NT); - break; + if (bestValue >= beta) + break; } } @@ -1042,8 +1041,7 @@ split_point_start: // At split points actual search starts from here if (bestValue >= beta) // Failed high { - TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, - bestMove, ss->staticEval, ss->evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, bestMove); if (!pos.is_capture_or_promotion(bestMove) && !inCheck) { @@ -1068,7 +1066,7 @@ split_point_start: // At split points actual search starts from here else // Failed low or PV search TT.store(posKey, value_to_tt(bestValue, ss->ply), PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, - depth, bestMove, ss->staticEval, ss->evalMargin); + depth, bestMove); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1080,12 +1078,13 @@ split_point_start: // At split points actual search starts from here // search function when the remaining depth is zero (or, to be more precise, // less than ONE_PLY). - template + template Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { const bool PvNode = (NT == PV); assert(NT == PV || NT == NonPV); + assert(InCheck == !!pos.checkers()); assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(depth <= DEPTH_ZERO); @@ -1094,16 +1093,20 @@ split_point_start: // At split points actual search starts from here const TTEntry* tte; Key posKey; Move ttMove, move, bestMove; - Value bestValue, value, ttValue, futilityValue, futilityBase; - bool inCheck, givesCheck, enoughMaterial, evasionPrunable; + Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; + bool givesCheck, enoughMaterial, evasionPrunable, fromNull; Depth ttDepth; - inCheck = pos.in_check(); + // To flag BOUND_EXACT a node with eval above alpha and no available moves + if (PvNode) + oldAlpha = alpha; + ss->currentMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; + fromNull = (ss-1)->currentMove == MOVE_NULL; // Check for an instant draw or maximum ply reached - if (pos.is_draw() || ss->ply > MAX_PLY) + if (pos.is_draw() || ss->ply > MAX_PLY) return DrawValue[pos.side_to_move()]; // Transposition table lookup. At PV nodes, we don't use the TT for @@ -1116,21 +1119,21 @@ split_point_start: // At split points actual search starts from here // Decide whether or not to include checks, this fixes also the type of // TT entry depth that we are going to use. Note that in qsearch we use // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. - ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS + ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS; - if ( tte && tte->depth() >= ttDepth + if ( tte + && tte->depth() >= ttDepth + && ttValue != VALUE_NONE // Only in case of TT access race && ( PvNode ? tte->type() == BOUND_EXACT : ttValue >= beta ? (tte->type() & BOUND_LOWER) : (tte->type() & BOUND_UPPER))) { - assert(ttValue != VALUE_NONE); // Due to ttDepth > DEPTH_NONE - ss->currentMove = ttMove; // Can be MOVE_NONE return ttValue; } // Evaluate the position statically - if (inCheck) + if (InCheck) { ss->staticEval = ss->evalMargin = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; @@ -1138,12 +1141,11 @@ split_point_start: // At split points actual search starts from here } else { - if (tte) + if (fromNull) { - assert(tte->static_value() != VALUE_NONE); - - ss->staticEval = bestValue = tte->static_value(); - ss->evalMargin = tte->static_value_margin(); + // Approximated score. Real one is slightly higher due to tempo + ss->staticEval = bestValue = -(ss-1)->staticEval; + ss->evalMargin = VALUE_ZERO; } else ss->staticEval = bestValue = evaluate(pos, ss->evalMargin); @@ -1152,8 +1154,7 @@ split_point_start: // At split points actual search starts from here if (bestValue >= beta) { if (!tte) - TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, - DEPTH_NONE, MOVE_NONE, ss->staticEval, ss->evalMargin); + TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER, DEPTH_NONE, MOVE_NONE); return bestValue; } @@ -1181,7 +1182,8 @@ split_point_start: // At split points actual search starts from here // Futility pruning if ( !PvNode - && !inCheck + && !InCheck + && !fromNull && !givesCheck && move != ttMove && enoughMaterial @@ -1194,9 +1196,7 @@ split_point_start: // At split points actual search starts from here if (futilityValue < beta) { - if (futilityValue > bestValue) - bestValue = futilityValue; - + bestValue = std::max(bestValue, futilityValue); continue; } @@ -1204,19 +1204,22 @@ split_point_start: // At split points actual search starts from here if ( futilityBase < beta && depth < DEPTH_ZERO && pos.see(move) <= 0) + { + bestValue = std::max(bestValue, futilityBase); continue; + } } // Detect non-capture evasions that are candidate to be pruned evasionPrunable = !PvNode - && inCheck + && InCheck && bestValue > VALUE_MATED_IN_MAX_PLY && !pos.is_capture(move) && !pos.can_castle(pos.side_to_move()); // Don't search moves with negative SEE values if ( !PvNode - && (!inCheck || evasionPrunable) + && (!InCheck || evasionPrunable) && move != ttMove && type_of(move) != PROMOTION && pos.see_sign(move) < 0) @@ -1224,7 +1227,7 @@ split_point_start: // At split points actual search starts from here // Don't search useless checks if ( !PvNode - && !inCheck + && !InCheck && givesCheck && move != ttMove && !pos.is_capture_or_promotion(move) @@ -1240,7 +1243,8 @@ split_point_start: // At split points actual search starts from here // Make and search the move pos.do_move(move, st, ci, givesCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY); + value = givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY) + : -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1259,9 +1263,7 @@ split_point_start: // At split points actual search starts from here } else // Fail high { - TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, - ttDepth, move, ss->staticEval, ss->evalMargin); - + TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER, ttDepth, move); return value; } } @@ -1270,12 +1272,12 @@ split_point_start: // At split points actual search starts from here // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (inCheck && bestValue == -VALUE_INFINITE) + if (InCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root TT.store(posKey, value_to_tt(bestValue, ss->ply), - PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER, - ttDepth, bestMove, ss->staticEval, ss->evalMargin); + PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + ttDepth, bestMove); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1283,40 +1285,56 @@ split_point_start: // At split points actual search starts from here } - // check_is_dangerous() tests if a checking move can be pruned in qsearch(). - // bestValue is updated only when returning false because in that case move - // will be pruned. + // value_to_tt() adjusts a mate score from "plies to mate from the root" to + // "plies to mate from the current position". Non-mate scores are unchanged. + // The function is called before storing a value to the transposition table. + + Value value_to_tt(Value v, int ply) { + + assert(v != VALUE_NONE); + + return v >= VALUE_MATE_IN_MAX_PLY ? v + ply + : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; + } + + + // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score + // from the transposition table (where refers to the plies to mate/be mated + // from current position) to "plies to mate/be mated from the root". + + Value value_from_tt(Value v, int ply) { + + return v == VALUE_NONE ? VALUE_NONE + : v >= VALUE_MATE_IN_MAX_PLY ? v - ply + : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v; + } + + + // check_is_dangerous() tests if a checking move can be pruned in qsearch() - bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta) + bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta) { - Bitboard b, occ, oldAtt, newAtt, kingAtt; - Square from, to, ksq; - Piece pc; - Color them; - - from = from_sq(move); - to = to_sq(move); - them = ~pos.side_to_move(); - ksq = pos.king_square(them); - kingAtt = pos.attacks_from(ksq); - pc = pos.piece_moved(move); - - occ = pos.pieces() ^ from ^ ksq; - oldAtt = pos.attacks_from(pc, from, occ); - newAtt = pos.attacks_from(pc, to, occ); - - // Rule 1. Checks which give opponent's king at most one escape square are dangerous - b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to); - - if (!more_than_one(b)) + Piece pc = pos.piece_moved(move); + Square from = from_sq(move); + Square to = to_sq(move); + Color them = ~pos.side_to_move(); + Square ksq = pos.king_square(them); + Bitboard enemies = pos.pieces(them); + Bitboard kingAtt = pos.attacks_from(ksq); + Bitboard occ = pos.pieces() ^ from ^ ksq; + Bitboard oldAtt = pos.attacks_from(pc, from, occ); + Bitboard newAtt = pos.attacks_from(pc, to, occ); + + // Checks which give opponent's king at most one escape square are dangerous + if (!more_than_one(kingAtt & ~(enemies | newAtt | to))) return true; - // Rule 2. Queen contact check is very dangerous + // Queen contact check is very dangerous if (type_of(pc) == QUEEN && (kingAtt & to)) return true; - // Rule 3. Creating new double threats with checks - b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq); + // Creating new double threats with checks is dangerous + Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt; while (b) { // Note that here we generate illegal "double move"! @@ -1328,113 +1346,93 @@ split_point_start: // At split points actual search starts from here } - // connected_moves() tests whether two moves are 'connected' in the sense - // that the first move somehow made the second move possible (for instance - // if the moving piece is the same in both moves). The first move is assumed - // to be the move that was made to reach the current position, while the - // second move is assumed to be a move from the current position. + // allows_move() tests whether the move at previous ply (first) somehow makes a + // second move possible, for instance if the moving piece is the same in both + // moves. Normally the second move is the threat move (the best move returned + // from a null search that fails low). - bool connected_moves(const Position& pos, Move m1, Move m2) { + bool allows_move(const Position& pos, Move first, Move second) { - Square f1, t1, f2, t2; - Piece p1, p2; - Square ksq; + assert(is_ok(first)); + assert(is_ok(second)); + assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move()); + assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move()); - assert(is_ok(m1)); - assert(is_ok(m2)); + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); - // Case 1: The moving piece is the same in both moves - f2 = from_sq(m2); - t1 = to_sq(m1); - if (f2 == t1) + // The piece is the same or second's destination was vacated by the first move + if (m1to == m2from || m2to == m1from) return true; - // Case 2: The destination square for m2 was vacated by m1 - t2 = to_sq(m2); - f1 = from_sq(m1); - if (t2 == f1) - return true; - - // Case 3: Moving through the vacated square - p2 = pos.piece_on(f2); - if (piece_is_slider(p2) && (between_bb(f2, t2) & f1)) + // Second one moves through the square vacated by first one + if (between_bb(m2from, m2to) & m1from) return true; - // Case 4: The destination square for m2 is defended by the moving piece in m1 - p1 = pos.piece_on(t1); - if (pos.attacks_from(p1, t1) & t2) + // Second's destination is defended by the first move's piece + Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from); + if (m1att & m2to) return true; - // Case 5: Discovered check, checking piece is the piece moved in m1 - ksq = pos.king_square(pos.side_to_move()); - if ( piece_is_slider(p1) - && (between_bb(t1, ksq) & f2) - && (pos.attacks_from(p1, t1, pos.pieces() ^ f2) & ksq)) + // Second move gives a discovered check through the first's checking piece + if (m1att & pos.king_square(pos.side_to_move())) + { + assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from); return true; + } return false; } - // value_to_tt() adjusts a mate score from "plies to mate from the root" to - // "plies to mate from the current position". Non-mate scores are unchanged. - // The function is called before storing a value to the transposition table. + // prevents_move() tests whether a move (first) is able to defend against an + // opponent's move (second). In this case will not be pruned. Normally the + // second move is the threat move (the best move returned from a null search + // that fails low). - Value value_to_tt(Value v, int ply) { + bool prevents_move(const Position& pos, Move first, Move second) { - assert(v != VALUE_NONE); + assert(is_ok(first)); + assert(is_ok(second)); + assert(!pos.is_capture_or_promotion(first)); + assert(!pos.is_passed_pawn_push(first)); - return v >= VALUE_MATE_IN_MAX_PLY ? v + ply - : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v; - } - - - // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score - // from the transposition table (where refers to the plies to mate/be mated - // from current position) to "plies to mate/be mated from the root". + Square m1from = from_sq(first); + Square m2from = from_sq(second); + Square m1to = to_sq(first); + Square m2to = to_sq(second); - Value value_from_tt(Value v, int ply) { - - return v == VALUE_NONE ? VALUE_NONE - : v >= VALUE_MATE_IN_MAX_PLY ? v - ply - : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v; - } - - - // connected_threat() tests whether it is safe to forward prune a move or if - // is somehow connected to the threat move returned by null search. - - bool connected_threat(const Position& pos, Move m, Move threat) { + // Don't prune moves of the threatened piece + if (m1from == m2to) + return true; - assert(is_ok(m)); - assert(is_ok(threat)); - assert(!pos.is_capture_or_promotion(m)); - assert(!pos.is_passed_pawn_push(m)); + // If the threatened piece has value less than or equal to the value of the + // threat piece, don't prune moves which defend it. + if ( pos.is_capture(second) + && ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)] + || type_of(pos.piece_on(m2from)) == KING)) + { + // Update occupancy as if the piece and the threat are moving + Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from; + Piece piece = pos.piece_on(m1from); - Square mfrom, mto, tfrom, tto; + // The moved piece attacks the square 'tto' ? + if (pos.attacks_from(piece, m1to, occ) & m2to) + return true; - mfrom = from_sq(m); - mto = to_sq(m); - tfrom = from_sq(threat); - tto = to_sq(threat); + // Scan for possible X-ray attackers behind the moved piece + Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, ROOK)) + | (attacks_bb(m2to, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP)); - // Case 1: Don't prune moves which move the threatened piece - if (mfrom == tto) - return true; - - // Case 2: If the threatened piece has value less than or equal to the - // value of the threatening piece, don't prune moves which defend it. - if ( pos.is_capture(threat) - && ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)] - || type_of(pos.piece_on(tfrom)) == KING) - && pos.move_attacks_square(m, tto)) - return true; + // Verify attackers are triggered by our move and not already existing + if (xray && (xray ^ (xray & pos.attacks_from(m2to)))) + return true; + } - // Case 3: If the moving piece in the threatened move is a slider, don't - // prune safe moves which block its ray. - if ( piece_is_slider(pos.piece_on(tfrom)) - && (between_bb(tfrom, tto) & mto) - && pos.see_sign(m) >= 0) + // Don't prune safe moves which block the threat path + if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0) return true; return false; @@ -1491,23 +1489,24 @@ split_point_start: // At split points actual search starts from here std::stringstream s; Time::point elaspsed = Time::now() - SearchTime + 1; + size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size()); int selDepth = 0; for (size_t i = 0; i < Threads.size(); i++) if (Threads[i].maxPly > selDepth) selDepth = Threads[i].maxPly; - for (size_t i = 0; i < std::min((size_t)Options["MultiPV"], RootMoves.size()); i++) + for (size_t i = 0; i < uciPVSize; i++) { bool updated = (i <= PVIdx); if (depth == 1 && !updated) continue; - int d = (updated ? depth : depth - 1); - Value v = (updated ? RootMoves[i].score : RootMoves[i].prevScore); + int d = updated ? depth : depth - 1; + Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore; - if (s.rdbuf()->in_avail()) + if (s.rdbuf()->in_avail()) // Not at first line s << "\n"; s << "info depth " << d @@ -1538,29 +1537,28 @@ void RootMove::extract_pv_from_tt(Position& pos) { StateInfo state[MAX_PLY_PLUS_2], *st = state; TTEntry* tte; - int ply = 1; + int ply = 0; Move m = pv[0]; - assert(m != MOVE_NONE && pos.is_pseudo_legal(m)); - pv.clear(); - pv.push_back(m); - pos.do_move(m, *st++); - - while ( (tte = TT.probe(pos.key())) != NULL - && (m = tte->move()) != MOVE_NONE // Local copy, TT entry could change - && pos.is_pseudo_legal(m) - && pos.pl_move_is_legal(m, pos.pinned_pieces()) - && ply < MAX_PLY - && (!pos.is_draw() || ply < 2)) - { + + do { pv.push_back(m); - pos.do_move(m, *st++); - ply++; - } - pv.push_back(MOVE_NONE); - do pos.undo_move(pv[--ply]); while (ply); + assert(MoveList(pos).contains(pv[ply])); + + pos.do_move(pv[ply++], *st++); + tte = TT.probe(pos.key()); + + } while ( tte + && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change + && pos.pl_move_is_legal(m, pos.pinned_pieces()) + && ply < MAX_PLY + && (!pos.is_draw() || ply < 2)); + + pv.push_back(MOVE_NONE); // Must be zero-terminating + + while (ply) pos.undo_move(pv[--ply]); } @@ -1572,27 +1570,21 @@ void RootMove::insert_pv_in_tt(Position& pos) { StateInfo state[MAX_PLY_PLUS_2], *st = state; TTEntry* tte; - Key k; - Value v, m = VALUE_NONE; int ply = 0; - assert(pv[ply] != MOVE_NONE && pos.is_pseudo_legal(pv[ply])); - do { - k = pos.key(); - tte = TT.probe(k); + tte = TT.probe(pos.key()); - // Don't overwrite existing correct entries - if (!tte || tte->move() != pv[ply]) - { - v = (pos.in_check() ? VALUE_NONE : evaluate(pos, m)); - TT.store(k, VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m); - } - pos.do_move(pv[ply], *st++); + if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries + TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply]); + + assert(MoveList(pos).contains(pv[ply])); + + pos.do_move(pv[ply++], *st++); - } while (pv[++ply] != MOVE_NONE); + } while (pv[ply] != MOVE_NONE); - do pos.undo_move(pv[--ply]); while (ply); + while (ply) pos.undo_move(pv[--ply]); }