X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=4d1a6af784d1e41217df9b29c3676c20a55dc6cd;hp=abb5116d2cfe3114bfdd74f7c7c48c3161033c5d;hb=cedbd3332a4a1574e701bda098a9df1153e299c6;hpb=1b6b711c444362d442f8362d356f668f676ec5cb diff --git a/src/search.cpp b/src/search.cpp index abb5116d..4d1a6af7 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -55,6 +55,9 @@ namespace { // Set to true to force running with one thread. Used for debugging const bool FakeSplit = false; + // This is the minimum interval in msec between two check_time() calls + const int TimerResolution = 5; + // Different node types, used as template parameter enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV }; @@ -62,28 +65,9 @@ namespace { 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]; } - // Maximum depth for razoring - const Depth RazorDepth = 4 * ONE_PLY; - // Dynamic razoring margin based on depth inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); } - // Maximum depth for use of dynamic threat detection when null move fails low - const Depth ThreatDepth = 5 * ONE_PLY; - - // Minimum depth for use of internal iterative deepening - const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY }; - - // At Non-PV nodes we do an internal iterative deepening search - // when the static evaluation is bigger then beta - IIDMargin. - const Value IIDMargin = Value(256); - - // Minimum depth for use of singular extension - const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY }; - - // Futility margin for quiescence search - const Value FutilityMarginQS = Value(128); - // Futility lookup tables (initialized at startup) and their access functions Value FutilityMargins[16][64]; // [depth][moveNumber] int FutilityMoveCounts[32]; // [depth] @@ -94,11 +78,6 @@ namespace { : 2 * VALUE_INFINITE; } - inline int futility_move_count(Depth d) { - - return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES; - } - // Reduction lookup tables (initialized at startup) and their access function int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] @@ -107,14 +86,6 @@ namespace { return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)]; } - // Easy move margin. An easy move candidate must be at least this much better - // than the second best move. - const Value EasyMoveMargin = Value(0x150); - - // This is the minimum interval in msec between two check_time() calls - const int TimerResolution = 5; - - size_t MultiPV, UCIMultiPV, PVIdx; TimeManager TimeMgr; int BestMoveChanges; @@ -122,7 +93,6 @@ namespace { bool SkillLevelEnabled, Chess960; History H; - template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); @@ -229,6 +199,8 @@ void Search::think() { Position& pos = RootPosition; Chess960 = pos.is_chess960(); Eval::RootColor = pos.side_to_move(); + Eval::ValueDraw[ Eval::RootColor] = VALUE_DRAW - Eval::ContemptFactor; + Eval::ValueDraw[~Eval::RootColor] = VALUE_DRAW + Eval::ContemptFactor; TimeMgr.init(Limits, pos.startpos_ply_counter(), pos.side_to_move()); TT.new_search(); H.clear(); @@ -469,7 +441,7 @@ namespace { && ( (bestMoveNeverChanged && pos.captured_piece_type()) || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100)) { - Value rBeta = bestValue - EasyMoveMargin; + Value rBeta = bestValue - 2 * PawnValueMg; (ss+1)->excludedMove = RootMoves[0].pv[0]; (ss+1)->skipNullMove = true; Value v = search(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY); @@ -528,7 +500,7 @@ namespace { Key posKey; Move ttMove, move, excludedMove, bestMove, threatMove; Depth ext, newDepth; - Value bestValue, value, oldAlpha, ttValue; + Value bestValue, value, ttValue; Value refinedValue, nullValue, futilityValue; bool pvMove, inCheck, singularExtensionNode, givesCheck; bool captureOrPromotion, dangerous, doFullDepthSearch; @@ -537,7 +509,6 @@ namespace { // Step 1. Initialize node Thread* thisThread = pos.this_thread(); moveCount = playedMoveCount = 0; - oldAlpha = alpha; inCheck = pos.in_check(); if (SpNode) @@ -569,7 +540,7 @@ namespace { { // Step 2. Check for aborted search and immediate draw if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY) - return VALUE_DRAW; + return Eval::ValueDraw[pos.side_to_move()]; // Step 3. Mate distance pruning. Even if we mate at the next move our score // would be at best mate_in(ss->ply+1), but if alpha is already bigger because @@ -644,7 +615,7 @@ namespace { // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode - && depth < RazorDepth + && depth < 4 * ONE_PLY && !inCheck && refinedValue + razor_margin(depth) < beta && ttMove == MOVE_NONE @@ -664,12 +635,12 @@ namespace { // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode && !ss->skipNullMove - && depth < RazorDepth + && depth < 4 * ONE_PLY && !inCheck - && refinedValue - futility_margin(depth, 0) >= beta + && refinedValue - FutilityMargins[depth][0] >= beta && abs(beta) < VALUE_MATE_IN_MAX_PLY && pos.non_pawn_material(pos.side_to_move())) - return refinedValue - futility_margin(depth, 0); + return refinedValue - FutilityMargins[depth][0]; // Step 8. Null move search with verification search (is omitted in PV nodes) if ( !PvNode @@ -723,7 +694,7 @@ namespace { // parent node, which will trigger a re-search with full depth). threatMove = (ss+1)->currentMove; - if ( depth < ThreatDepth + if ( depth < 5 * ONE_PLY && (ss-1)->reduction && threatMove != MOVE_NONE && connected_moves(pos, (ss-1)->currentMove, threatMove)) @@ -736,7 +707,7 @@ namespace { // and a reduced search returns a value much above beta, we can (almost) safely // prune the previous move. if ( !PvNode - && depth >= RazorDepth + ONE_PLY + && depth >= 5 * ONE_PLY && !inCheck && !ss->skipNullMove && excludedMove == MOVE_NONE @@ -765,9 +736,9 @@ namespace { } // Step 10. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] + if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY) && ttMove == MOVE_NONE - && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta))) + && (PvNode || (!inCheck && ss->eval + Value(256) >= beta))) { Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2); @@ -786,7 +757,7 @@ split_point_start: // At split points actual search starts from here value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc singularExtensionNode = !RootNode && !SpNode - && depth >= SingularExtensionDepth[PvNode] + && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY) && ttMove != MOVE_NONE && !excludedMove // Recursive singular search is not allowed && (tte->type() & BOUND_LOWER) @@ -794,10 +765,7 @@ split_point_start: // At split points actual search starts from here // Step 11. Loop through moves // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs - while ( bestValue < beta - && (move = mp.next_move()) != MOVE_NONE - && !thisThread->cutoff_occurred() - && !Signals.stop) + while ((move = mp.next_move()) != MOVE_NONE) { assert(is_ok(move)); @@ -863,7 +831,7 @@ split_point_start: // At split points actual search starts from here ss->excludedMove = MOVE_NONE; if (value < rBeta) - ext = ONE_PLY; + ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY; } // Update current move (this must be done after singular extension search) @@ -878,7 +846,8 @@ split_point_start: // At split points actual search starts from here && (bestValue > VALUE_MATED_IN_MAX_PLY || bestValue == -VALUE_INFINITE)) { // Move count based pruning - if ( moveCount >= futility_move_count(depth) + if ( depth < 16 * ONE_PLY + && moveCount >= FutilityMoveCounts[depth] && (!threatMove || !connected_threat(pos, move, threatMove))) { if (SpNode) @@ -981,7 +950,10 @@ split_point_start: // At split points actual search starts from here // was aborted because the user interrupted the search or because we // ran out of time. In this case, the return value of the search cannot // be trusted, and we don't update the best move and/or PV. - if (RootNode && !Signals.stop) + if (Signals.stop || thisThread->cutoff_occurred()) + return bestValue; + + if (RootNode) { RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move); @@ -1007,37 +979,41 @@ split_point_start: // At split points actual search starts from here if (value > bestValue) { bestValue = value; - bestMove = move; - - if ( PvNode - && value > alpha - && value < beta) // We want always alpha < beta - { - alpha = bestValue; // Update alpha here! - } + if (SpNode) sp->bestValue = value; - if (SpNode && !thisThread->cutoff_occurred()) + if (value > alpha) { - sp->bestValue = bestValue; - sp->bestMove = bestMove; - sp->alpha = alpha; + bestMove = move; + if (SpNode) sp->bestMove = move; - if (bestValue >= beta) - sp->cutoff = true; + if (PvNode && value < beta) + { + alpha = value; // Update alpha here! Always alpha < beta + if (SpNode) sp->alpha = alpha; + } + else // Fail high + { + if (SpNode) sp->cutoff = true; + break; + } } } - // Step 19. Check for split + // Step 19. Check for splitting the search if ( !SpNode && depth >= Threads.min_split_depth() && bestValue < beta - && Threads.available_slave_exists(thisThread) - && !Signals.stop - && !thisThread->cutoff_occurred()) + && Threads.available_slave_exists(thisThread)) + { bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove, depth, threatMove, moveCount, mp, NT); + break; + } } + if (SpNode) + return bestValue; + // Step 20. Check for mate and stalemate // All legal moves have been searched and if there are no legal moves, it // must be mate or stalemate. Note that we can have a false positive in @@ -1045,7 +1021,7 @@ split_point_start: // At split points actual search starts from here // harmless because return value is discarded anyhow in the parent nodes. // If we are in a singular extension search then return a fail low score. // A split node has at least one move, the one tried before to be splitted. - if (!SpNode && !moveCount) + if (!moveCount) return excludedMove ? alpha : inCheck ? mated_in(ss->ply) : VALUE_DRAW; // If we have pruned all the moves without searching return a fail-low score @@ -1056,20 +1032,12 @@ split_point_start: // At split points actual search starts from here bestValue = alpha; } - // Step 21. Update tables - // Update transposition table entry, killers and history - if (!SpNode && !Signals.stop && !thisThread->cutoff_occurred()) + if (bestValue >= beta) // Failed high { - Move ttm = bestValue <= oldAlpha ? MOVE_NONE : bestMove; - Bound bt = bestValue <= oldAlpha ? BOUND_UPPER - : bestValue >= beta ? BOUND_LOWER : BOUND_EXACT; - - TT.store(posKey, value_to_tt(bestValue, ss->ply), bt, depth, ttm, ss->eval, ss->evalMargin); + TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth, + bestMove, ss->eval, ss->evalMargin); - // Update killers and history for non capture cut-off moves - if ( bestValue >= beta - && !pos.is_capture_or_promotion(bestMove) - && !inCheck) + if (!pos.is_capture_or_promotion(bestMove) && !inCheck) { if (bestMove != ss->killers[0]) { @@ -1089,6 +1057,10 @@ 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->eval, ss->evalMargin); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1124,7 +1096,7 @@ split_point_start: // At split points actual search starts from here // Check for an instant draw or maximum ply reached if (pos.is_draw() || ss->ply > MAX_PLY) - return VALUE_DRAW; + return Eval::ValueDraw[pos.side_to_move()]; // 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 @@ -1175,7 +1147,7 @@ split_point_start: // At split points actual search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = ss->eval + evalMargin + FutilityMarginQS; + futilityBase = ss->eval + evalMargin + Value(128); enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg; } @@ -1513,7 +1485,7 @@ split_point_start: // At split points actual search starts from here int s = RootMoves[i].score; // Don't allow crazy blunders even at very low skills - if (i > 0 && RootMoves[i-1].score > s + EasyMoveMargin) + if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg) break; // This is our magic formula