From: Lucas Braesch Date: Sat, 14 Dec 2013 11:27:29 +0000 (+0800) Subject: Remove threat move stuff X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=f5727deee3823accf791984836f45db78e3a53e5 Remove threat move stuff A great simplification that shows no regression and it seems even a bit scalable. Tested with fixed number of games: Short TC ELO: 0.60 +-2.1 (95%) LOS: 71.1% Total: 39554 W: 7477 L: 7409 D: 24668 Long TC ELO: 2.97 +-2.0 (95%) LOS: 99.8% Total: 36424 W: 5894 L: 5583 D: 24947 bench: 8184352 --- diff --git a/src/search.cpp b/src/search.cpp index cf791334..713bd10f 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -94,8 +94,6 @@ namespace { void id_loop(Position& pos); Value value_to_tt(Value v, int ply); Value value_from_tt(Value v, int ply); - bool allows(const Position& pos, Move first, Move second); - bool refutes(const Position& pos, Move first, Move second); string uci_pv(const Position& pos, int depth, Value alpha, Value beta); struct Skill { @@ -490,7 +488,7 @@ namespace { const TTEntry *tte; SplitPoint* splitPoint; Key posKey; - Move ttMove, move, excludedMove, bestMove, threatMove; + Move ttMove, move, excludedMove, bestMove; Depth ext, newDepth, predictedDepth; Value bestValue, value, ttValue, eval, nullValue, futilityValue; bool inCheck, givesCheck, pvMove, singularExtensionNode, improving; @@ -505,7 +503,6 @@ namespace { { splitPoint = ss->splitPoint; bestMove = splitPoint->bestMove; - threatMove = splitPoint->threatMove; bestValue = splitPoint->bestValue; tte = NULL; ttMove = excludedMove = MOVE_NONE; @@ -518,7 +515,7 @@ namespace { moveCount = quietCount = 0; bestValue = -VALUE_INFINITE; - ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; + ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE; ss->ply = (ss-1)->ply + 1; (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; @@ -694,22 +691,6 @@ namespace { if (v >= beta) return nullValue; } - else - { - // 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). - threatMove = (ss+1)->currentMove; - - if ( depth < 5 * ONE_PLY - && (ss-1)->reduction - && threatMove != MOVE_NONE - && allows(pos, (ss-1)->currentMove, threatMove)) - return alpha; - } } // Step 9. ProbCut (skipped when in check) @@ -864,8 +845,7 @@ moves_loop: // When in check and at SpNode search starts from here { // Move count based pruning if ( depth < 16 * ONE_PLY - && moveCount >= FutilityMoveCounts[improving][depth] - && (!threatMove || !refutes(pos, move, threatMove))) + && moveCount >= FutilityMoveCounts[improving][depth] ) { if (SpNode) splitPoint->mutex.lock(); @@ -1053,7 +1033,7 @@ moves_loop: // When in check and at SpNode search starts from here assert(bestValue < beta); thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove, - depth, threatMove, moveCount, &mp, NT, cutNode); + depth, moveCount, &mp, NT, cutNode); if (bestValue >= beta) break; } @@ -1341,99 +1321,6 @@ moves_loop: // When in check and at SpNode search starts from here } - // allows() tests whether the 'first' move at previous ply somehow makes the - // 'second' move possible e.g. if the moving piece is the same in both moves. - // Normally the second move is the threat (the best move returned from a null - // search that fails low). - - bool allows(const Position& pos, Move first, Move second) { - - assert(is_ok(first)); - assert(is_ok(second)); - assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move()); - assert(type_of(first) == CASTLING || color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move()); - - Square m1from = from_sq(first); - Square m2from = from_sq(second); - Square m1to = to_sq(first); - Square m2to = to_sq(second); - - // The piece is the same or second's destination was vacated by the first move. - // We exclude the trivial case where a sliding piece does in two moves what - // it could do in one move: eg. Ra1a2, Ra2a3. - if ( m2to == m1from - || (m1to == m2from && !aligned(m1from, m2from, m2to))) - return true; - - // Second one moves through the square vacated by first one - if (between_bb(m2from, m2to) & m1from) - return true; - - // Second's destination is defended by the first move's piece - Bitboard m1att = attacks_bb(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from); - if (m1att & m2to) - return true; - - // 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; - } - - - // refutes() tests whether a 'first' move is able to defend against a 'second' - // opponent's move. In this case will not be pruned. Normally the second move - // is the threat (the best move returned from a null search that fails low). - - bool refutes(const Position& pos, Move first, Move second) { - - assert(is_ok(first)); - assert(is_ok(second)); - - Square m1from = from_sq(first); - Square m2from = from_sq(second); - Square m1to = to_sq(first); - Square m2to = to_sq(second); - - // Don't prune moves of the threatened piece - if (m1from == m2to) - return true; - - // If the threatened piece has a value less than or equal to the value of - // the threat piece, don't prune moves which defend it. - if ( pos.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 pc = pos.piece_on(m1from); - - // Does the moved piece attack the square 'm2to' ? - if (attacks_bb(pc, m1to, occ) & m2to) - return true; - - // Scan for possible X-ray attackers behind the moved piece - Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(pc), QUEEN, ROOK)) - | (attacks_bb(m2to, occ) & pos.pieces(color_of(pc), QUEEN, BISHOP)); - - // Verify attackers are triggered by our move and not already existing - if (unlikely(xray) && (xray & ~pos.attacks_from(m2to))) - return true; - } - - // 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; - } - - // When playing with a strength handicap, choose best move among the MultiPV // set using a statistical rule dependent on 'level'. Idea by Heinz van Saanen. diff --git a/src/thread.cpp b/src/thread.cpp index 7966499d..eb991f65 100644 --- a/src/thread.cpp +++ b/src/thread.cpp @@ -260,7 +260,7 @@ Thread* ThreadPool::available_slave(const Thread* master) const { template void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Value* bestValue, - Move* bestMove, Depth depth, Move threatMove, int moveCount, + Move* bestMove, Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode) { assert(pos.pos_is_ok()); @@ -279,7 +279,6 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu sp.depth = depth; sp.bestValue = *bestValue; sp.bestMove = *bestMove; - sp.threatMove = threatMove; sp.alpha = alpha; sp.beta = beta; sp.nodeType = nodeType; @@ -350,8 +349,8 @@ void Thread::split(Position& pos, const Stack* ss, Value alpha, Value beta, Valu } // Explicit template instantiations -template void Thread::split(Position&, const Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int, bool); -template void Thread::split< true>(Position&, const Stack*, Value, Value, Value*, Move*, Depth, Move, int, MovePicker*, int, bool); +template void Thread::split(Position&, const Stack*, Value, Value, Value*, Move*, Depth, int, MovePicker*, int, bool); +template void Thread::split< true>(Position&, const Stack*, Value, Value, Value*, Move*, Depth, int, MovePicker*, int, bool); // wait_for_think_finished() waits for main thread to go to sleep then returns diff --git a/src/thread.h b/src/thread.h index dc8418dc..8169407e 100644 --- a/src/thread.h +++ b/src/thread.h @@ -67,7 +67,6 @@ struct SplitPoint { Depth depth; Value beta; int nodeType; - Move threatMove; bool cutNode; // Const pointers to shared data @@ -118,7 +117,7 @@ struct Thread : public ThreadBase { template void split(Position& pos, const Search::Stack* ss, Value alpha, Value beta, Value* bestValue, Move* bestMove, - Depth depth, Move threatMove, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode); + Depth depth, int moveCount, MovePicker* movePicker, int nodeType, bool cutNode); SplitPoint splitPoints[MAX_SPLITPOINTS_PER_THREAD]; Material::Table materialTable;