X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=7249a113862f87ebe8cd6563f0bb3fa08e937ddb;hp=ed15902d4838c5800b53fc32a98ae0140e890dce;hb=1322ab97c737fe761bd6ae8786f852851b8f019f;hpb=02fe05cd0db6491c82e1d3c0522fe824432113e5 diff --git a/src/search.cpp b/src/search.cpp index ed15902d..7249a113 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -89,8 +89,8 @@ namespace { void idle_loop(int threadID, SplitPoint* sp); template - bool split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, - Depth depth, bool mateThreat, int* moves, MovePicker* mp, int master, bool pvNode); + void split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, + Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, bool pvNode); private: friend void poll(); @@ -98,7 +98,6 @@ namespace { int ActiveThreads; volatile bool AllThreadsShouldExit, AllThreadsShouldSleep; Thread threads[MAX_THREADS]; - SplitPoint SplitPointStack[MAX_THREADS][ACTIVE_SPLIT_POINTS_MAX]; Lock MPLock, WaitLock; @@ -122,7 +121,7 @@ namespace { // RootMove::operator<() is the comparison function used when // sorting the moves. A move m1 is considered to be better // than a move m2 if it has a higher score, or if the moves - // have equal score but m1 has the higher node count. + // have equal score but m1 has the higher beta cut-off count. bool operator<(const RootMove& m) const { return score != m.score ? score < m.score : theirBeta <= m.theirBeta; @@ -188,7 +187,7 @@ namespace { const Depth IIDDepth[2] = { 8 * OnePly /* non-PV */, 5 * OnePly /* PV */}; // At Non-PV nodes we do an internal iterative deepening search - // when the static evaluation is at most IIDMargin below beta. + // when the static evaluation is bigger then beta - IIDMargin. const Value IIDMargin = Value(0x100); // Step 11. Decide the new search depth @@ -214,7 +213,7 @@ namespace { int32_t FutilityMarginsMatrix[16][64]; // [depth][moveNumber] int FutilityMoveCountArray[32]; // [depth] - inline Value futility_margin(Depth d, int mn) { return Value(d < 7 * OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); } + inline Value futility_margin(Depth d, int mn) { return Value(d < 7 * OnePly ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE); } inline int futility_move_count(Depth d) { return d < 16 * OnePly ? FutilityMoveCountArray[d] : 512; } // Step 14. Reduced search @@ -234,12 +233,6 @@ namespace { // better than the second best move. const Value EasyMoveMargin = Value(0x200); - // Last seconds noise filtering (LSN) - const bool UseLSNFiltering = true; - const int LSNTime = 4000; // In milliseconds - const Value LSNValue = value_from_centipawns(200); - bool loseOnTime = false; - /// Global variables @@ -282,13 +275,13 @@ namespace { /// Local functions Value id_loop(const Position& pos, Move searchMoves[]); - Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr); + Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr); template - Value search(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE); + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); template - Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID); + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply); template void sp_search(SplitPoint* sp, int threadID); @@ -296,27 +289,26 @@ namespace { template Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous); - void init_node(SearchStack ss[], int ply, int threadID); - void update_pv(SearchStack ss[], int ply); - void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply); bool connected_moves(const Position& pos, Move m1, Move m2); bool value_is_mate(Value value); - bool move_is_killer(Move m, const SearchStack& ss); - bool ok_to_do_nullmove(const Position& pos); - bool ok_to_prune(const Position& pos, Move m, Move threat); + Value value_to_tt(Value v, int ply); + Value value_from_tt(Value v, int ply); + bool move_is_killer(Move m, SearchStack* ss); bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply); + bool connected_threat(const Position& pos, Move m, Move threat); Value refine_eval(const TTEntry* tte, Value defaultEval, int ply); void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); - void update_killers(Move m, SearchStack& ss); + void update_killers(Move m, SearchStack* ss); void update_gains(const Position& pos, Move move, Value before, Value after); int current_search_time(); + std::string value_to_uci(Value v); int nps(); void poll(); void ponderhit(); void wait_for_stop_or_ponderhit(); - void init_ss_array(SearchStack ss[]); - void print_pv_info(const Position& pos, SearchStack ss[], Value alpha, Value beta, Value value); + void init_ss_array(SearchStack* ss, int size); + void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value); #if !defined(_MSC_VER) void *init_thread(void *threadID); @@ -339,6 +331,50 @@ void exit_threads() { TM.exit_threads(); } int64_t nodes_searched() { return TM.nodes_searched(); } +/// init_search() is called during startup. It initializes various lookup tables + +void init_search() { + + int d; // depth (OnePly == 2) + int hd; // half depth (OnePly == 1) + int mc; // moveCount + + // Init reductions array + for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++) + { + double pvRed = 0.33 + log(double(hd)) * log(double(mc)) / 4.5; + double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25; + ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0); + ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0); + } + + // Init futility margins array + for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++) + FutilityMarginsMatrix[d][mc] = 112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45; + + // Init futility move count array + for (d = 0; d < 32; d++) + FutilityMoveCountArray[d] = 3 + (1 << (3 * d / 8)); +} + + +// SearchStack::init() initializes a search stack entry. +// Called at the beginning of search() when starting to examine a new node. +void SearchStack::init() { + + currentMove = threatMove = bestMove = MOVE_NONE; + reduction = Depth(0); +} + +// SearchStack::initKillers() initializes killers for a search stack entry +void SearchStack::initKillers() { + + mateKiller = MOVE_NONE; + for (int i = 0; i < KILLER_MAX; i++) + killers[i] = MOVE_NONE; +} + + /// perft() is our utility to verify move generation is bug free. All the legal /// moves up to given depth are generated and counted and the sum returned. @@ -374,9 +410,8 @@ int perft(Position& pos, Depth depth) /// search-related global variables, and calls root_search(). It returns false /// when a quit command is received during the search. -bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, - int time[], int increment[], int movesToGo, int maxDepth, - int maxNodes, int maxTime, Move searchMoves[]) { +bool think(const Position& pos, bool infinite, bool ponder, int time[], int increment[], + int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) { // Initialize global search variables StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false; @@ -408,10 +443,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, } } - // Reset loseOnTime flag at the beginning of a new game - if (button_was_pressed("New Game")) - loseOnTime = false; - // Read UCI option values TT.set_size(get_option_value_int("Hash")); if (button_was_pressed("Clear Hash")) @@ -453,8 +484,8 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, TM.wake_sleeping_threads(); // Set thinking time - int myTime = time[side_to_move]; - int myIncrement = increment[side_to_move]; + int myTime = time[pos.side_to_move()]; + int myIncrement = increment[pos.side_to_move()]; if (UseTimeManagement) { if (!movesToGo) // Sudden death time control @@ -511,36 +542,8 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, << " increment: " << myIncrement << " moves to go: " << movesToGo << endl; - // LSN filtering. Used only for developing purposes, disabled by default - if ( UseLSNFiltering - && loseOnTime) - { - // Step 2. If after last move we decided to lose on time, do it now! - while (SearchStartTime + myTime + 1000 > get_system_time()) - /* wait here */; - } - // We're ready to start thinking. Call the iterative deepening loop function - Value v = id_loop(pos, searchMoves); - - if (UseLSNFiltering) - { - // Step 1. If this is sudden death game and our position is hopeless, - // decide to lose on time. - if ( !loseOnTime // If we already lost on time, go to step 3. - && myTime < LSNTime - && myIncrement == 0 - && movesToGo == 0 - && v < -LSNValue) - { - loseOnTime = true; - } - else if (loseOnTime) - { - // Step 3. Now after stepping over the time limit, reset flag for next match. - loseOnTime = false; - } - } + id_loop(pos, searchMoves); if (UseLogFile) LogFile.close(); @@ -551,51 +554,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, } -/// init_search() is called during startup. It initializes various lookup tables - -void init_search() { - - // Init our reduction lookup tables - for (int i = 1; i < 64; i++) // i == depth (OnePly = 1) - for (int j = 1; j < 64; j++) // j == moveNumber - { - double pvRed = log(double(i)) * log(double(j)) / 3.0; - double nonPVRed = log(double(i)) * log(double(j)) / 1.5; - ReductionMatrix[PV][i][j] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0); - ReductionMatrix[NonPV][i][j] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0); - } - - // Init futility margins array - for (int i = 0; i < 16; i++) // i == depth (OnePly = 2) - for (int j = 0; j < 64; j++) // j == moveNumber - { - // FIXME: test using log instead of BSR - FutilityMarginsMatrix[i][j] = (i < 2 ? 0 : 112 * bitScanReverse32(i * i / 2)) - 8 * j + 45; - } - - // Init futility move count array - for (int i = 0; i < 32; i++) // i == depth (OnePly = 2) - FutilityMoveCountArray[i] = 3 + (1 << (3 * i / 8)); -} - - -// SearchStack::init() initializes a search stack. Used at the beginning of a -// new search from the root. -void SearchStack::init(int ply) { - - pv[ply] = pv[ply + 1] = MOVE_NONE; - currentMove = threatMove = MOVE_NONE; - reduction = Depth(0); - eval = VALUE_NONE; -} - -void SearchStack::initKillers() { - - mateKiller = MOVE_NONE; - for (int i = 0; i < KILLER_MAX; i++) - killers[i] = MOVE_NONE; -} - namespace { // id_loop() is the main iterative deepening loop. It calls root_search @@ -605,8 +563,9 @@ namespace { Value id_loop(const Position& pos, Move searchMoves[]) { - Position p(pos); + Position p(pos, pos.thread()); SearchStack ss[PLY_MAX_PLUS_2]; + Move pv[PLY_MAX_PLUS_2]; Move EasyMove = MOVE_NONE; Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; @@ -626,7 +585,7 @@ namespace { // so to output information also for iteration 1. cout << "info depth " << 1 << "\ninfo depth " << 1 - << " score " << value_to_string(rml.get_move_score(0)) + << " score " << value_to_uci(rml.get_move_score(0)) << " time " << current_search_time() << " nodes " << TM.nodes_searched() << " nps " << nps() @@ -635,7 +594,8 @@ namespace { // Initialize TT.new_search(); H.clear(); - init_ss_array(ss); + init_ss_array(ss, PLY_MAX_PLUS_2); + pv[0] = pv[1] = MOVE_NONE; ValueByIteration[1] = rml.get_move_score(0); Iteration = 1; @@ -667,11 +627,11 @@ namespace { } // Search to the current depth, rml is updated and sorted, alpha and beta could change - value = root_search(p, ss, rml, &alpha, &beta); + value = root_search(p, ss, pv, rml, &alpha, &beta); // Write PV to transposition table, in case the relevant entries have // been overwritten during the search. - TT.insert_pv(p, ss[0].pv); + TT.insert_pv(p, pv); if (AbortSearch) break; // Value cannot be trusted. Break out immediately! @@ -680,7 +640,7 @@ namespace { ValueByIteration[Iteration] = value; // Drop the easy move if differs from the new best move - if (ss[0].pv[0] != EasyMove) + if (pv[0] != EasyMove) EasyMove = MOVE_NONE; if (UseTimeManagement) @@ -702,7 +662,7 @@ namespace { // Stop search early if one move seems to be much better than the others int64_t nodes = TM.nodes_searched(); if ( Iteration >= 8 - && EasyMove == ss[0].pv[0] + && EasyMove == pv[0] && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 && current_search_time() > MaxSearchTime / 16) ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100 @@ -741,22 +701,21 @@ namespace { // Print final search statistics cout << "info nodes " << TM.nodes_searched() << " nps " << nps() - << " time " << current_search_time() - << " hashfull " << TT.full() << endl; + << " time " << current_search_time() << endl; // Print the best move and the ponder move to the standard output - if (ss[0].pv[0] == MOVE_NONE) + if (pv[0] == MOVE_NONE) { - ss[0].pv[0] = rml.get_move(0); - ss[0].pv[1] = MOVE_NONE; + pv[0] = rml.get_move(0); + pv[1] = MOVE_NONE; } - assert(ss[0].pv[0] != MOVE_NONE); + assert(pv[0] != MOVE_NONE); - cout << "bestmove " << ss[0].pv[0]; + cout << "bestmove " << pv[0]; - if (ss[0].pv[1] != MOVE_NONE) - cout << " ponder " << ss[0].pv[1]; + if (pv[1] != MOVE_NONE) + cout << " ponder " << pv[1]; cout << endl; @@ -770,12 +729,12 @@ namespace { LogFile << "\nNodes: " << TM.nodes_searched() << "\nNodes/second: " << nps() - << "\nBest move: " << move_to_san(p, ss[0].pv[0]); + << "\nBest move: " << move_to_san(p, pv[0]); StateInfo st; - p.do_move(ss[0].pv[0], st); + p.do_move(pv[0], st); LogFile << "\nPonder move: " - << move_to_san(p, ss[0].pv[1]) // Works also with MOVE_NONE + << move_to_san(p, pv[1]) // Works also with MOVE_NONE << endl; } return rml.get_move_score(0); @@ -787,7 +746,7 @@ namespace { // scheme, prints some information to the standard output and handles // the fail low/high loops. - Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value* alphaPtr, Value* betaPtr) { + Value root_search(Position& pos, SearchStack* ss, Move* pv, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) { EvalInfo ei; StateInfo st; @@ -804,17 +763,14 @@ namespace { beta = *betaPtr; isCheck = pos.is_check(); - // Step 1. Initialize node and poll (omitted at root, but I can see no good reason for this, FIXME) - // Step 2. Check for aborted search (omitted at root, because we do not initialize root node) + // Step 1. Initialize node and poll (omitted at root, init_ss_array() has already initialized root node) + // Step 2. Check for aborted search (omitted at root) // Step 3. Mate distance pruning (omitted at root) // Step 4. Transposition table lookup (omitted at root) // Step 5. Evaluate the position statically // At root we do this only to get reference value for child nodes - if (!isCheck) - ss[0].eval = evaluate(pos, ei, 0); - else - ss[0].eval = VALUE_NONE; // HACK because we do not initialize root node + ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ei); // Step 6. Razoring (omitted at root) // Step 7. Static null move pruning (omitted at root) @@ -843,7 +799,7 @@ namespace { // Pick the next root move, and print the move and the move number to // the standard output. - move = ss[0].currentMove = rml.get_move(i); + move = ss->currentMove = rml.get_move(i); if (current_search_time() >= 1000) cout << "info currmove " << move @@ -879,7 +835,7 @@ namespace { alpha = -VALUE_INFINITE; // Full depth PV search, done on first move or after a fail high - value = -search(pos, ss, -beta, -alpha, newDepth, 1, false, 0); + value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); } else { @@ -892,26 +848,40 @@ namespace { && !captureOrPromotion && !move_is_castle(move)) { - ss[0].reduction = reduction(depth, i - MultiPV + 2); - if (ss[0].reduction) + ss->reduction = reduction(depth, i - MultiPV + 2); + if (ss->reduction) { + assert(newDepth-ss->reduction >= OnePly); + // Reduced depth non-pv search using alpha as upperbound - value = -search(pos, ss, -(alpha+1), -alpha, newDepth-ss[0].reduction, 1, true, 0); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); doFullDepthSearch = (value > alpha); } + + // The move failed high, but if reduction is very big we could + // face a false positive, retry with a less aggressive reduction, + // if the move fails high again then go with full depth search. + if (doFullDepthSearch && ss->reduction > 2 * OnePly) + { + assert(newDepth - OnePly >= OnePly); + + ss->reduction = OnePly; + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1); + doFullDepthSearch = (value > alpha); + } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { // Full depth non-pv search using alpha as upperbound - ss[0].reduction = Depth(0); - value = -search(pos, ss, -(alpha+1), -alpha, newDepth, 1, true, 0); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, 1); // If we are above alpha then research at same depth but as PV // to get a correct score or eventually a fail high above beta. if (value > alpha) - value = -search(pos, ss, -beta, -alpha, newDepth, 1, false, 0); + value = -search(pos, ss+1, -beta, -alpha, newDepth, 1); } } @@ -925,12 +895,12 @@ namespace { // We are failing high and going to do a research. It's important to update // the score before research in case we run out of time while researching. rml.set_move_score(i, value); - update_pv(ss, 0); - TT.extract_pv(pos, ss[0].pv, PLY_MAX); - rml.set_move_pv(i, ss[0].pv); + ss->bestMove = move; + TT.extract_pv(pos, move, pv, PLY_MAX); + rml.set_move_pv(i, pv); // Print information to the standard output - print_pv_info(pos, ss, alpha, beta, value); + print_pv_info(pos, pv, alpha, beta, value); // Prepare for a research after a fail high, each time with a wider window *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE); @@ -965,9 +935,9 @@ namespace { // Update PV rml.set_move_score(i, value); - update_pv(ss, 0); - TT.extract_pv(pos, ss[0].pv, PLY_MAX); - rml.set_move_pv(i, ss[0].pv); + ss->bestMove = move; + TT.extract_pv(pos, move, pv, PLY_MAX); + rml.set_move_pv(i, pv); if (MultiPV == 1) { @@ -978,7 +948,7 @@ namespace { BestMoveChangesByIteration[Iteration]++; // Print information to the standard output - print_pv_info(pos, ss, alpha, beta, value); + print_pv_info(pos, pv, alpha, beta, value); // Raise alpha to setup proper non-pv search upper bound if (value > alpha) @@ -990,7 +960,7 @@ namespace { for (int j = 0; j < Min(MultiPV, rml.move_count()); j++) { cout << "info multipv " << j + 1 - << " score " << value_to_string(rml.get_move_score(j)) + << " score " << value_to_uci(rml.get_move_score(j)) << " depth " << (j <= i ? Iteration : Iteration - 1) << " time " << current_search_time() << " nodes " << TM.nodes_searched() @@ -1034,35 +1004,40 @@ namespace { // search<>() is the main search function for both PV and non-PV nodes template - Value search(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, - int ply, bool allowNullmove, int threadID, Move excludedMove) { + Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta > alpha && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); - assert(ply >= 0 && ply < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); + assert(ply > 0 && ply < PLY_MAX); + assert(pos.thread() >= 0 && pos.thread() < TM.active_threads()); Move movesSearched[256]; EvalInfo ei; StateInfo st; const TTEntry* tte; - Move ttMove, move; + Key posKey; + Move ttMove, move, excludedMove; Depth ext, newDepth; Value bestValue, value, oldAlpha; Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific - bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous; + bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous; bool mateThreat = false; int moveCount = 0; + int threadID = pos.thread(); refinedValue = bestValue = value = -VALUE_INFINITE; oldAlpha = alpha; - if (depth < OnePly) - return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID); + // Step 1. Initialize node and poll. Polling can abort search + TM.incrementNodeCounter(threadID); + ss->init(); + (ss+2)->initKillers(); - // Step 1. Initialize node and poll - // Polling can abort search. - init_node(ss, ply, threadID); + if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls) + { + NodesSincePoll = 0; + poll(); + } // Step 2. Check for aborted search and immediate draw if (AbortSearch || TM.thread_should_stop(threadID)) @@ -1081,7 +1056,8 @@ namespace { // 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 exists. - Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); + excludedMove = ss->excludedMove; + posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); tte = TT.retrieve(posKey); ttMove = (tte ? tte->move() : MOVE_NONE); @@ -1097,9 +1073,9 @@ namespace { if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) { // Refresh tte entry to avoid aging - TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove); + TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove, tte->static_value(), tte->king_danger()); - ss[ply].currentMove = ttMove; // Can be MOVE_NONE + ss->currentMove = ttMove; // Can be MOVE_NONE return value_from_tt(tte->value(), ply); } @@ -1108,27 +1084,36 @@ namespace { isCheck = pos.is_check(); if (!isCheck) { - if (tte && (tte->type() & VALUE_TYPE_EVAL)) - ss[ply].eval = value_from_tt(tte->value(), ply); + if (tte && tte->static_value() != VALUE_NONE) + { + ss->eval = tte->static_value(); + ei.kingDanger[pos.side_to_move()] = tte->king_danger(); + } else - ss[ply].eval = evaluate(pos, ei, threadID); + ss->eval = evaluate(pos, ei); - refinedValue = refine_eval(tte, ss[ply].eval, ply); // Enhance accuracy with TT value if possible - update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval); + refinedValue = refine_eval(tte, ss->eval, ply); // Enhance accuracy with TT value if possible + update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); } + else + ss->eval = VALUE_NONE; // Step 6. Razoring (is omitted in PV nodes) if ( !PvNode - && refinedValue < beta - razor_margin(depth) - && ttMove == MOVE_NONE - && ss[ply - 1].currentMove != MOVE_NULL && depth < RazorDepth && !isCheck + && refinedValue < beta - razor_margin(depth) + && ttMove == MOVE_NONE + && (ss-1)->currentMove != MOVE_NULL && !value_is_mate(beta) && !pos.has_pawn_on_7th(pos.side_to_move())) { + // Pass ss->eval to qsearch() and avoid an evaluate call + if (!tte || tte->static_value() == VALUE_NONE) + TT.store(posKey, ss->eval, VALUE_TYPE_EXACT, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); + Value rbeta = beta - razor_margin(depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID); + Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply); if (v < rbeta) // Logically we should return (v + razor_margin(depth)), but // surprisingly this did slightly weaker in tests. @@ -1139,12 +1124,12 @@ namespace { // We're betting that the opponent doesn't have a move that will reduce // the score by more than futility_margin(depth) if we do a null move. if ( !PvNode - && allowNullmove + && !ss->skipNullMove && depth < RazorDepth + && refinedValue >= beta + futility_margin(depth, 0) && !isCheck && !value_is_mate(beta) - && ok_to_do_nullmove(pos) - && refinedValue >= beta + futility_margin(depth, 0)) + && pos.non_pawn_material(pos.side_to_move())) return refinedValue - futility_margin(depth, 0); // Step 8. Null move search with verification search (is omitted in PV nodes) @@ -1152,14 +1137,14 @@ namespace { // at least beta. Otherwise we do a null move if static value is not more than // NullMoveMargin under beta. if ( !PvNode - && allowNullmove + && !ss->skipNullMove && depth > OnePly + && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0) && !isCheck && !value_is_mate(beta) - && ok_to_do_nullmove(pos) - && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0)) + && pos.non_pawn_material(pos.side_to_move())) { - ss[ply].currentMove = MOVE_NULL; + ss->currentMove = MOVE_NULL; // Null move dynamic reduction based on depth int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0); @@ -1169,9 +1154,11 @@ namespace { R++; pos.do_null_move(st); + (ss+1)->skipNullMove = true; - nullValue = -search(pos, ss, -beta, -alpha, depth-R*OnePly, ply+1, false, threadID); - + nullValue = depth-R*OnePly < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, depth-R*OnePly, ply+1); + (ss+1)->skipNullMove = false; pos.undo_null_move(); if (nullValue >= beta) @@ -1183,11 +1170,16 @@ namespace { if (depth < 6 * OnePly) return nullValue; - // Do zugzwang verification search - Value v = search(pos, ss, alpha, beta, depth-5*OnePly, ply, false, threadID); + // Do verification search at high depths + ss->skipNullMove = true; + Value v = search(pos, ss, alpha, beta, depth-R*OnePly, ply); + ss->skipNullMove = false; + if (v >= beta) return nullValue; - } else { + } + 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 @@ -1197,22 +1189,26 @@ namespace { if (nullValue == value_mated_in(ply + 2)) mateThreat = true; - ss[ply].threatMove = ss[ply + 1].currentMove; + ss->threatMove = (ss+1)->currentMove; if ( depth < ThreatDepth - && ss[ply - 1].reduction - && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove)) + && (ss-1)->reduction + && connected_moves(pos, (ss-1)->currentMove, ss->threatMove)) return beta - 1; } } // Step 9. Internal iterative deepening - if ( depth >= IIDDepth[PvNode] - && ttMove == MOVE_NONE - && (PvNode || (!isCheck && ss[ply].eval >= beta - IIDMargin))) + if ( depth >= IIDDepth[PvNode] + && ttMove == MOVE_NONE + && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin))) { Depth d = (PvNode ? depth - 2 * OnePly : depth / 2); - search(pos, ss, alpha, beta, d, ply, false, threadID); - ttMove = ss[ply].pv[ply]; + + ss->skipNullMove = true; + search(pos, ss, alpha, beta, d, ply); + ss->skipNullMove = false; + + ttMove = ss->bestMove; tte = TT.retrieve(posKey); } @@ -1221,8 +1217,14 @@ namespace { mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move())); // Initialize a MovePicker object for the current position - MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply], (PvNode ? -VALUE_INFINITE : beta)); + MovePicker mp = MovePicker(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta)); CheckInfo ci(pos); + singleEvasion = isCheck && mp.number_of_evasions() == 1; + singularExtensionNode = depth >= SingularExtensionDepth[PvNode] + && tte && tte->move() + && !excludedMove // Do not allow recursive singular extension search + && is_lower_bound(tte->type()) + && tte->depth() >= depth - 3 * OnePly; // Step 10. Loop through moves // Loop through all legal moves until no moves remain or a beta cutoff occurs @@ -1235,32 +1237,31 @@ namespace { if (move == excludedMove) continue; - singleEvasion = (isCheck && mp.number_of_evasions() == 1); moveIsCheck = pos.move_is_check(move, ci); captureOrPromotion = pos.move_is_capture_or_promotion(move); // Step 11. Decide the new search depth ext = extension(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous); - // Singular extension search. We extend the TT move if its value is much better than - // its siblings. To verify this we do a reduced search on all the other moves but the - // ttMove, if result is lower then ttValue minus a margin then we extend ttMove. - if ( depth >= SingularExtensionDepth[PvNode] - && tte + // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s), + // and just one fails high on (alpha, beta), then that move is singular and should be extended. + // To verify this we do a reduced search on all the other moves but the ttMove, if result is + // lower then ttValue minus a margin then we extend ttMove. + if ( singularExtensionNode && move == tte->move() - && !excludedMove // Do not allow recursive singular extension search - && ext < OnePly - && is_lower_bound(tte->type()) - && tte->depth() >= depth - 3 * OnePly) + && ext < OnePly) { Value ttValue = value_from_tt(tte->value(), ply); if (abs(ttValue) < VALUE_KNOWN_WIN) { Value b = ttValue - SingularExtensionMargin; - Value v = search(pos, ss, b - 1, b, depth / 2, ply, false, threadID, move); - - if (v < ttValue - SingularExtensionMargin) + ss->excludedMove = move; + ss->skipNullMove = true; + Value v = search(pos, ss, b - 1, b, depth / 2, ply); + ss->skipNullMove = false; + ss->excludedMove = MOVE_NONE; + if (v < b) ext = OnePly; } } @@ -1268,25 +1269,27 @@ namespace { newDepth = depth - OnePly + ext; // Update current move (this must be done after singular extension search) - movesSearched[moveCount++] = ss[ply].currentMove = move; + movesSearched[moveCount++] = ss->currentMove = move; // Step 12. Futility pruning (is omitted in PV nodes) if ( !PvNode + && !captureOrPromotion && !isCheck && !dangerous - && !captureOrPromotion - && !move_is_castle(move) - && move != ttMove) + && move != ttMove + && !move_is_castle(move)) { // Move count based pruning if ( moveCount >= futility_move_count(depth) - && ok_to_prune(pos, move, ss[ply].threatMove) + && !(ss->threatMove && connected_threat(pos, move, ss->threatMove)) && bestValue > value_mated_in(PLY_MAX)) continue; // Value based pruning - Depth predictedDepth = newDepth - reduction(depth, moveCount); // FIXME We illogically ignore reduction condition depth >= 3*OnePly - futilityValueScaled = ss[ply].eval + futility_margin(predictedDepth, moveCount) + // We illogically ignore reduction condition depth >= 3*OnePly for predicted depth, + // but fixing this made program slightly weaker. + Depth predictedDepth = newDepth - reduction(depth, moveCount); + futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount) + H.gain(pos.piece_on(move_from(move)), move_to(move)); if (futilityValueScaled < beta) @@ -1303,38 +1306,56 @@ namespace { // Step extra. pv search (only in PV nodes) // The first move in list is the expected PV if (PvNode && moveCount == 1) - value = -search(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); else { - // Step 14. Reduced search - // if the move fails high will be re-searched at full depth. + // Step 14. Reduced depth search + // If the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; if ( depth >= 3 * OnePly - && !dangerous && !captureOrPromotion + && !dangerous && !move_is_castle(move) - && !move_is_killer(move, ss[ply])) + && !move_is_killer(move, ss)) { - ss[ply].reduction = reduction(depth, moveCount); - if (ss[ply].reduction) + ss->reduction = reduction(depth, moveCount); + if (ss->reduction) { - value = -search(pos, ss, -(alpha+1), -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID); + Depth d = newDepth - ss->reduction; + value = d < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -(alpha+1), -alpha, d, ply+1); + doFullDepthSearch = (value > alpha); } + + // The move failed high, but if reduction is very big we could + // face a false positive, retry with a less aggressive reduction, + // if the move fails high again then go with full depth search. + if (doFullDepthSearch && ss->reduction > 2 * OnePly) + { + assert(newDepth - OnePly >= OnePly); + + ss->reduction = OnePly; + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, ply+1); + doFullDepthSearch = (value > alpha); + } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { - ss[ply].reduction = Depth(0); - value = -search(pos, ss, -(alpha+1), -alpha, newDepth, ply+1, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(alpha+1), -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1); // Step extra. pv search (only in PV nodes) // Search only for possible new PV nodes, if instead value >= beta then // parent node fails low with value <= alpha and tries another move. if (PvNode && value > alpha && value < beta) - value = -search(pos, ss, -beta, -alpha, newDepth, ply+1, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -beta, -alpha, Depth(0), ply+1) + : - search(pos, ss+1, -beta, -alpha, newDepth, ply+1); } } @@ -1352,24 +1373,23 @@ namespace { if (PvNode && value < beta) // This guarantees that always: alpha < beta alpha = value; - update_pv(ss, ply); - if (value == value_mate_in(ply + 1)) - ss[ply].mateKiller = move; + ss->mateKiller = move; + + ss->bestMove = move; } } // Step 18. Check for split - if ( TM.active_threads() > 1 + if ( depth >= MinimumSplitDepth + && TM.active_threads() > 1 && bestValue < beta - && depth >= MinimumSplitDepth - && Iteration <= 99 && TM.available_thread_exists(threadID) && !AbortSearch && !TM.thread_should_stop(threadID) - && TM.split(pos, ss, ply, &alpha, beta, &bestValue, depth, - mateThreat, &moveCount, &mp, threadID, PvNode)) - break; + && Iteration <= 99) + TM.split(pos, ss, ply, &alpha, beta, &bestValue, depth, + mateThreat, &moveCount, &mp, PvNode); } // Step 19. Check for mate and stalemate @@ -1385,22 +1405,20 @@ namespace { if (AbortSearch || TM.thread_should_stop(threadID)) return bestValue; - if (bestValue <= oldAlpha) - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE); + ValueType f = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); + move = (bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove); + TT.store(posKey, value_to_tt(bestValue, ply), f, depth, move, ss->eval, ei.kingDanger[pos.side_to_move()]); - else if (bestValue >= beta) + // Update killers and history only for non capture moves that fails high + if (bestValue >= beta) { TM.incrementBetaCounter(pos.side_to_move(), depth, threadID); - move = ss[ply].pv[ply]; - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move); if (!pos.move_is_capture_or_promotion(move)) { update_history(pos, move, depth, movesSearched, moveCount); - update_killers(move, ss[ply]); + update_killers(move, ss); } } - else - TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1413,33 +1431,27 @@ namespace { // less than OnePly). template - Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, - Depth depth, int ply, int threadID) { + Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) { assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE); assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE); assert(PvNode || alpha == beta - 1); assert(depth <= 0); - assert(ply >= 0 && ply < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); + assert(ply > 0 && ply < PLY_MAX); + assert(pos.thread() >= 0 && pos.thread() < TM.active_threads()); EvalInfo ei; StateInfo st; Move ttMove, move; - Value staticValue, bestValue, value, futilityBase, futilityValue; - bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable; - const TTEntry* tte = NULL; - int moveCount = 0; + Value bestValue, value, futilityValue, futilityBase; + bool isCheck, deepChecks, enoughMaterial, moveIsCheck, evasionPrunable; + const TTEntry* tte; Value oldAlpha = alpha; - // Initialize, and make an early exit in case of an aborted search, - // an instant draw, maximum ply reached, etc. - init_node(ss, ply, threadID); - - // After init_node() that calls poll() - if (AbortSearch || TM.thread_should_stop(threadID)) - return Value(0); + TM.incrementNodeCounter(pos.thread()); + ss->bestMove = ss->currentMove = MOVE_NONE; + // Check for an instant draw or maximum ply reached if (pos.is_draw() || ply >= PLY_MAX - 1) return VALUE_DRAW; @@ -1450,9 +1462,7 @@ namespace { if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply)) { - assert(tte->type() != VALUE_TYPE_EVAL); - - ss[ply].currentMove = ttMove; // Can be MOVE_NONE + ss->currentMove = ttMove; // Can be MOVE_NONE return value_from_tt(tte->value(), ply); } @@ -1460,36 +1470,43 @@ namespace { // Evaluate the position statically if (isCheck) - staticValue = -VALUE_INFINITE; - else if (tte && (tte->type() & VALUE_TYPE_EVAL)) - staticValue = value_from_tt(tte->value(), ply); - else - staticValue = evaluate(pos, ei, threadID); - - if (!isCheck) { - ss[ply].eval = staticValue; - update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval); + bestValue = futilityBase = -VALUE_INFINITE; + ss->eval = VALUE_NONE; + deepChecks = enoughMaterial = false; } + else + { + if (tte && tte->static_value() != VALUE_NONE) + { + ei.kingDanger[pos.side_to_move()] = tte->king_danger(); + bestValue = tte->static_value(); + } + else + bestValue = evaluate(pos, ei); - // Initialize "stand pat score", and return it immediately if it is - // at least beta. - bestValue = staticValue; + ss->eval = bestValue; + update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval); - if (bestValue >= beta) - { - // Store the score to avoid a future costly evaluation() call - if (!isCheck && !tte && ei.kingDanger[pos.side_to_move()] == 0) - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EV_LO, Depth(-127*OnePly), MOVE_NONE); + // Stand pat. Return immediately if static value is at least beta + if (bestValue >= beta) + { + if (!tte) + TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]); - return bestValue; - } + return bestValue; + } + + if (PvNode && bestValue > alpha) + alpha = bestValue; - if (bestValue > alpha) - alpha = bestValue; + // If we are near beta then try to get a cutoff pushing checks a bit further + deepChecks = (depth == -OnePly && bestValue >= beta - PawnValueMidgame / 8); - // If we are near beta then try to get a cutoff pushing checks a bit further - bool deepChecks = (depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8); + // Futility pruning parameters, not needed when in check + futilityBase = bestValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()]; + enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; + } // Initialize a MovePicker object for the current position, and prepare // to search the moves. Because the depth is <= 0 here, only captures, @@ -1497,8 +1514,6 @@ namespace { // and we are near beta) will be generated. MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H); CheckInfo ci(pos); - enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; - futilityBase = staticValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()]; // Loop through the moves until no moves remain or a beta cutoff occurs while ( alpha < beta @@ -1508,16 +1523,12 @@ namespace { moveIsCheck = pos.move_is_check(move, ci); - // Update current move - moveCount++; - ss[ply].currentMove = move; - // Futility pruning if ( !PvNode - && enoughMaterial && !isCheck && !moveIsCheck && move != ttMove + && enoughMaterial && !move_is_promotion(move) && !pos.move_is_passed_pawn_push(move)) { @@ -1548,9 +1559,12 @@ namespace { && pos.see_sign(move) < 0) continue; + // Update current move + ss->currentMove = move; + // Make and search the move pos.do_move(move, st, ci, moveIsCheck); - value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID); + value = -qsearch(pos, ss+1, -beta, -alpha, depth-OnePly, ply+1); pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); @@ -1562,36 +1576,25 @@ namespace { if (value > alpha) { alpha = value; - update_pv(ss, ply); + ss->bestMove = move; } } } // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (!moveCount && isCheck) // Mate! + if (isCheck && bestValue == -VALUE_INFINITE) return value_mated_in(ply); // Update transposition table Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1)); - if (bestValue <= oldAlpha) - { - // If bestValue isn't changed it means it is still the static evaluation - // of the node, so keep this info to avoid a future evaluation() call. - ValueType type = (bestValue == staticValue && !ei.kingDanger[pos.side_to_move()] ? VALUE_TYPE_EV_UP : VALUE_TYPE_UPPER); - TT.store(pos.get_key(), value_to_tt(bestValue, ply), type, d, MOVE_NONE); - } - else if (bestValue >= beta) - { - move = ss[ply].pv[ply]; - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move); + ValueType f = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT); + TT.store(pos.get_key(), value_to_tt(bestValue, ply), f, d, ss->bestMove, ss->eval, ei.kingDanger[pos.side_to_move()]); - // Update killers only for good checking moves - if (!pos.move_is_capture_or_promotion(move)) - update_killers(move, ss[ply]); - } - else - TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, d, ss[ply].pv[ply]); + // Update killers only for checking moves that fails high + if ( bestValue >= beta + && !pos.move_is_capture_or_promotion(ss->bestMove)) + update_killers(ss->bestMove, ss); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1622,9 +1625,9 @@ namespace { int moveCount; value = -VALUE_INFINITE; - Position pos(*sp->pos); + Position pos(*sp->pos, threadID); CheckInfo ci(pos); - SearchStack* ss = sp->sstack[threadID]; + SearchStack* ss = sp->sstack[threadID] + 1; isCheck = pos.is_check(); // Step 10. Loop through moves @@ -1635,7 +1638,7 @@ namespace { && (move = sp->mp->get_next_move()) != MOVE_NONE && !TM.thread_should_stop(threadID)) { - moveCount = ++sp->moves; + moveCount = ++sp->moveCount; lock_release(&(sp->lock)); assert(move_is_ok(move)); @@ -1648,18 +1651,18 @@ namespace { newDepth = sp->depth - OnePly + ext; // Update current move - ss[sp->ply].currentMove = move; + ss->currentMove = move; // Step 12. Futility pruning (is omitted in PV nodes) if ( !PvNode + && !captureOrPromotion && !isCheck && !dangerous - && !captureOrPromotion && !move_is_castle(move)) { // Move count based pruning if ( moveCount >= futility_move_count(sp->depth) - && ok_to_prune(pos, move, ss[sp->ply].threatMove) + && !(ss->threatMove && connected_threat(pos, move, ss->threatMove)) && sp->bestValue > value_mated_in(PLY_MAX)) { lock_grab(&(sp->lock)); @@ -1668,7 +1671,7 @@ namespace { // Value based pruning Depth predictedDepth = newDepth - reduction(sp->depth, moveCount); - futilityValueScaled = ss[sp->ply].eval + futility_margin(predictedDepth, moveCount) + futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount) + H.gain(pos.piece_on(move_from(move)), move_to(move)); if (futilityValueScaled < sp->beta) @@ -1685,32 +1688,53 @@ namespace { pos.do_move(move, st, ci, moveIsCheck); // Step 14. Reduced search - // if the move fails high will be re-searched at full depth. + // If the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; - if ( !dangerous - && !captureOrPromotion + if ( !captureOrPromotion + && !dangerous && !move_is_castle(move) - && !move_is_killer(move, ss[sp->ply])) + && !move_is_killer(move, ss)) { - ss[sp->ply].reduction = reduction(sp->depth, moveCount); - if (ss[sp->ply].reduction) + ss->reduction = reduction(sp->depth, moveCount); + if (ss->reduction) { Value localAlpha = sp->alpha; - value = -search(pos, ss, -(localAlpha+1), -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID); + Depth d = newDepth - ss->reduction; + value = d < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, d, sp->ply+1); + doFullDepthSearch = (value > localAlpha); } + + // The move failed high, but if reduction is very big we could + // face a false positive, retry with a less aggressive reduction, + // if the move fails high again then go with full depth search. + if (doFullDepthSearch && ss->reduction > 2 * OnePly) + { + assert(newDepth - OnePly >= OnePly); + + ss->reduction = OnePly; + Value localAlpha = sp->alpha; + value = -search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, sp->ply+1); + doFullDepthSearch = (value > localAlpha); + } + ss->reduction = Depth(0); // Restore original reduction } // Step 15. Full depth search if (doFullDepthSearch) { - ss[sp->ply].reduction = Depth(0); Value localAlpha = sp->alpha; - value = -search(pos, ss, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1, true, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, sp->ply+1); + // Step extra. pv search (only in PV nodes) + // Search only for possible new PV nodes, if instead value >= beta then + // parent node fails low with value <= alpha and tries another move. if (PvNode && value > localAlpha && value < sp->beta) - value = -search(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, false, threadID); + value = newDepth < OnePly ? -qsearch(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), sp->ply+1) + : - search(pos, ss+1, -sp->beta, -sp->alpha, newDepth, sp->ply+1); } // Step 16. Undo move @@ -1733,7 +1757,7 @@ namespace { if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta sp->alpha = value; - sp_update_pv(sp->parentSstack, ss, sp->ply); + sp->parentSstack->bestMove = ss->bestMove = move; } } } @@ -1745,69 +1769,6 @@ namespace { lock_release(&(sp->lock)); } - // init_node() is called at the beginning of all the search functions - // (search() qsearch(), and so on) and initializes the - // search stack object corresponding to the current node. Once every - // NodesBetweenPolls nodes, init_node() also calls poll(), which polls - // for user input and checks whether it is time to stop the search. - - void init_node(SearchStack ss[], int ply, int threadID) { - - assert(ply >= 0 && ply < PLY_MAX); - assert(threadID >= 0 && threadID < TM.active_threads()); - - TM.incrementNodeCounter(threadID); - - if (threadID == 0) - { - NodesSincePoll++; - if (NodesSincePoll >= NodesBetweenPolls) - { - poll(); - NodesSincePoll = 0; - } - } - ss[ply].init(ply); - ss[ply + 2].initKillers(); - } - - // update_pv() is called whenever a search returns a value > alpha. - // It updates the PV in the SearchStack object corresponding to the - // current node. - - void update_pv(SearchStack ss[], int ply) { - - assert(ply >= 0 && ply < PLY_MAX); - - int p; - - ss[ply].pv[ply] = ss[ply].currentMove; - - for (p = ply + 1; ss[ply + 1].pv[p] != MOVE_NONE; p++) - ss[ply].pv[p] = ss[ply + 1].pv[p]; - - ss[ply].pv[p] = MOVE_NONE; - } - - - // sp_update_pv() is a variant of update_pv for use at split points. The - // difference between the two functions is that sp_update_pv also updates - // the PV at the parent node. - - void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply) { - - assert(ply >= 0 && ply < PLY_MAX); - - int p; - - ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove; - - for (p = ply + 1; ss[ply + 1].pv[p] != MOVE_NONE; p++) - ss[ply].pv[p] = pss[ply].pv[p] = ss[ply + 1].pv[p]; - - ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE; - } - // connected_moves() tests whether two moves are 'connected' in the sense // that the first move somehow made the second move possible (for instance @@ -1865,8 +1826,8 @@ namespace { } - // value_is_mate() checks if the given value is a mate one - // eventually compensated for the ply. + // value_is_mate() checks if the given value is a mate one eventually + // compensated for the ply. bool value_is_mate(Value value) { @@ -1877,12 +1838,42 @@ namespace { } - // move_is_killer() checks if the given move is among the - // killer moves of that ply. + // value_to_tt() adjusts a mate score from "plies to mate from the root" to + // "plies to mate from the current ply". Non-mate scores are unchanged. + // The function is called before storing a value to the transposition table. - bool move_is_killer(Move m, const SearchStack& ss) { + Value value_to_tt(Value v, int ply) { - const Move* k = ss.killers; + if (v >= value_mate_in(PLY_MAX)) + return v + ply; + + if (v <= value_mated_in(PLY_MAX)) + return v - ply; + + return v; + } + + + // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from + // the transposition table to a mate score corrected for the current ply. + + Value value_from_tt(Value v, int ply) { + + if (v >= value_mate_in(PLY_MAX)) + return v - ply; + + if (v <= value_mated_in(PLY_MAX)) + return v + ply; + + return v; + } + + + // move_is_killer() checks if the given move is among the killer moves + + bool move_is_killer(Move m, SearchStack* ss) { + + const Move* k = ss->killers; for (int i = 0; i < KILLER_MAX; i++, k++) if (*k == m) return true; @@ -1908,7 +1899,7 @@ namespace { if (*dangerous) { - if (moveIsCheck) + if (moveIsCheck && pos.see_sign(m) >= 0) result += CheckExtension[PvNode]; if (singleEvasion) @@ -1957,38 +1948,19 @@ namespace { } - // ok_to_do_nullmove() looks at the current position and decides whether - // doing a 'null move' should be allowed. In order to avoid zugzwang - // problems, null moves are not allowed when the side to move has very - // little material left. Currently, the test is a bit too simple: Null - // moves are avoided only when the side to move has only pawns left. - // It's probably a good idea to avoid null moves in at least some more - // complicated endgames, e.g. KQ vs KR. FIXME - - bool ok_to_do_nullmove(const Position& pos) { - - return pos.non_pawn_material(pos.side_to_move()) != Value(0); - } - - - // ok_to_prune() tests whether it is safe to forward prune a move. Only - // non-tactical moves late in the move list close to the leaves are - // candidates for pruning. + // connected_threat() tests whether it is safe to forward prune a move or if + // is somehow coonected to the threat move returned by null search. - bool ok_to_prune(const Position& pos, Move m, Move threat) { + bool connected_threat(const Position& pos, Move m, Move threat) { assert(move_is_ok(m)); - assert(threat == MOVE_NONE || move_is_ok(threat)); + assert(threat && move_is_ok(threat)); assert(!pos.move_is_check(m)); assert(!pos.move_is_capture_or_promotion(m)); assert(!pos.move_is_passed_pawn_push(m)); Square mfrom, mto, tfrom, tto; - // Prune if there isn't any threat move - if (threat == MOVE_NONE) - return true; - mfrom = move_from(m); mto = move_to(m); tfrom = move_from(threat); @@ -1996,7 +1968,7 @@ namespace { // Case 1: Don't prune moves which move the threatened piece if (mfrom == tto) - return false; + return true; // Case 2: If the threatened piece has value less than or equal to the // value of the threatening piece, don't prune move which defend it. @@ -2004,16 +1976,16 @@ namespace { && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto) || pos.type_of_piece_on(tfrom) == KING) && pos.move_attacks_square(m, tto)) - return false; + 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)) && bit_is_set(squares_between(tfrom, tto), mto) && pos.see_sign(m) >= 0) - return false; + return true; - return true; + return false; } @@ -2076,15 +2048,15 @@ namespace { // update_killers() add a good move that produced a beta-cutoff // among the killer moves of that ply. - void update_killers(Move m, SearchStack& ss) { + void update_killers(Move m, SearchStack* ss) { - if (m == ss.killers[0]) + if (m == ss->killers[0]) return; for (int i = KILLER_MAX - 1; i > 0; i--) - ss.killers[i] = ss.killers[i - 1]; + ss->killers[i] = ss->killers[i - 1]; - ss.killers[0] = m; + ss->killers[0] = m; } @@ -2112,6 +2084,20 @@ namespace { } + // value_to_uci() converts a value to a string suitable for use with the UCI protocol + + std::string value_to_uci(Value v) { + + std::stringstream s; + + if (abs(v) < VALUE_MATE - PLY_MAX * OnePly) + s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to pawn = 100 + else + s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 ); + + return s.str(); + } + // nps() computes the current nodes/second count. int nps() { @@ -2175,7 +2161,7 @@ namespace { dbg_print_hit_rate(); cout << "info nodes " << TM.nodes_searched() << " nps " << nps() - << " time " << t << " hashfull " << TT.full() << endl; + << " time " << t << endl; } // Should we stop the search? @@ -2217,14 +2203,21 @@ namespace { } - // init_ss_array() does a fast reset of the first entries of a SearchStack array + // init_ss_array() does a fast reset of the first entries of a SearchStack + // array and of all the excludedMove and skipNullMove entries. - void init_ss_array(SearchStack ss[]) { + void init_ss_array(SearchStack* ss, int size) { - for (int i = 0; i < 3; i++) + for (int i = 0; i < size; i++, ss++) { - ss[i].init(i); - ss[i].initKillers(); + ss->excludedMove = MOVE_NONE; + ss->skipNullMove = false; + + if (i < 3) + { + ss->init(); + ss->initKillers(); + } } } @@ -2259,29 +2252,28 @@ namespace { // print_pv_info() prints to standard output and eventually to log file information on // the current PV line. It is called at each iteration or after a new pv is found. - void print_pv_info(const Position& pos, SearchStack ss[], Value alpha, Value beta, Value value) { + void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value) { cout << "info depth " << Iteration - << " score " << value_to_string(value) - << ((value >= beta) ? " lowerbound" : - ((value <= alpha)? " upperbound" : "")) + << " score " << value_to_uci(value) + << (value >= beta ? " lowerbound" : value <= alpha ? " upperbound" : "") << " time " << current_search_time() << " nodes " << TM.nodes_searched() << " nps " << nps() << " pv "; - for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++) - cout << ss[0].pv[j] << " "; + for (Move* m = pv; *m != MOVE_NONE; m++) + cout << *m << " "; cout << endl; if (UseLogFile) { - ValueType type = (value >= beta ? VALUE_TYPE_LOWER - : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT)); + ValueType t = value >= beta ? VALUE_TYPE_LOWER : + value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT; LogFile << pretty_pv(pos, current_search_time(), Iteration, - TM.nodes_searched(), value, type, ss[0].pv) << endl; + TM.nodes_searched(), value, t, pv) << endl; } } @@ -2451,13 +2443,10 @@ namespace { SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0); #endif - // Initialize SplitPointStack locks + // Initialize splitPoints[] locks for (i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++) - { - SplitPointStack[i][j].parent = NULL; - lock_init(&(SplitPointStack[i][j].lock), NULL); - } + for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) + lock_init(&(threads[i].splitPoints[j].lock), NULL); // Will be set just before program exits to properly end the threads AllThreadsShouldExit = false; @@ -2507,12 +2496,12 @@ namespace { // Wait for thread termination for (int i = 1; i < MAX_THREADS; i++) - while (threads[i].state != THREAD_TERMINATED); + while (threads[i].state != THREAD_TERMINATED) {} // Now we can safely destroy the locks for (int i = 0; i < MAX_THREADS; i++) - for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++) - lock_destroy(&(SplitPointStack[i][j].lock)); + for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++) + lock_destroy(&(threads[i].splitPoints[j].lock)); lock_destroy(&WaitLock); lock_destroy(&MPLock); @@ -2565,7 +2554,7 @@ namespace { // Apply the "helpful master" concept if possible. Use localActiveSplitPoints // that is known to be > 0, instead of threads[slave].activeSplitPoints that // could have been set to 0 by another thread leading to an out of bound access. - if (SplitPointStack[slave][localActiveSplitPoints - 1].slaves[master]) + if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master]) return true; return false; @@ -2589,80 +2578,77 @@ namespace { // split() does the actual work of distributing the work at a node between - // several threads at PV nodes. If it does not succeed in splitting the + // several available threads. If it does not succeed in splitting the // node (because no idle threads are available, or because we have no unused - // split point objects), the function immediately returns false. If - // splitting is possible, a SplitPoint object is initialized with all the - // data that must be copied to the helper threads (the current position and - // search stack, alpha, beta, the search depth, etc.), and we tell our - // helper threads that they have been assigned work. This will cause them - // to instantly leave their idle loops and call sp_search(). When all - // threads have returned from sp_search() then split() returns true. + // split point objects), the function immediately returns. If splitting is + // possible, a SplitPoint object is initialized with all the data that must be + // copied to the helper threads and we tell our helper threads that they have + // been assigned work. This will cause them to instantly leave their idle loops + // and call sp_search(). When all threads have returned from sp_search() then + // split() returns. template - bool ThreadsManager::split(const Position& p, SearchStack* sstck, int ply, Value* alpha, + void ThreadsManager::split(const Position& p, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, Depth depth, bool mateThreat, - int* moves, MovePicker* mp, int master, bool pvNode) { + int* moveCount, MovePicker* mp, bool pvNode) { assert(p.is_ok()); - assert(sstck != NULL); - assert(ply >= 0 && ply < PLY_MAX); + assert(ply > 0 && ply < PLY_MAX); assert(*bestValue >= -VALUE_INFINITE); assert(*bestValue <= *alpha); assert(*alpha < beta); assert(beta <= VALUE_INFINITE); assert(depth > Depth(0)); - assert(master >= 0 && master < ActiveThreads); + assert(p.thread() >= 0 && p.thread() < ActiveThreads); assert(ActiveThreads > 1); - SplitPoint* splitPoint; + int i, master = p.thread(); + Thread& masterThread = threads[master]; lock_grab(&MPLock); // If no other thread is available to help us, or if we have too many // active split points, don't split. if ( !available_thread_exists(master) - || threads[master].activeSplitPoints >= ACTIVE_SPLIT_POINTS_MAX) + || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS) { lock_release(&MPLock); - return false; + return; } // Pick the next available split point object from the split point stack - splitPoint = &SplitPointStack[master][threads[master].activeSplitPoints]; + SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++]; // Initialize the split point object - splitPoint->parent = threads[master].splitPoint; - splitPoint->stopRequest = false; - splitPoint->ply = ply; - splitPoint->depth = depth; - splitPoint->mateThreat = mateThreat; - splitPoint->alpha = *alpha; - splitPoint->beta = beta; - splitPoint->pvNode = pvNode; - splitPoint->bestValue = *bestValue; - splitPoint->master = master; - splitPoint->mp = mp; - splitPoint->moves = *moves; - splitPoint->pos = &p; - splitPoint->parentSstack = sstck; - for (int i = 0; i < ActiveThreads; i++) - splitPoint->slaves[i] = 0; - - threads[master].splitPoint = splitPoint; - threads[master].activeSplitPoints++; + splitPoint.parent = masterThread.splitPoint; + splitPoint.stopRequest = false; + splitPoint.ply = ply; + splitPoint.depth = depth; + splitPoint.mateThreat = mateThreat; + splitPoint.alpha = *alpha; + splitPoint.beta = beta; + splitPoint.pvNode = pvNode; + splitPoint.bestValue = *bestValue; + splitPoint.mp = mp; + splitPoint.moveCount = *moveCount; + splitPoint.pos = &p; + splitPoint.parentSstack = ss; + for (i = 0; i < ActiveThreads; i++) + splitPoint.slaves[i] = 0; + + masterThread.splitPoint = &splitPoint; // If we are here it means we are not available - assert(threads[master].state != THREAD_AVAILABLE); + assert(masterThread.state != THREAD_AVAILABLE); int workersCnt = 1; // At least the master is included // Allocate available threads setting state to THREAD_BOOKED - for (int i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++) + for (i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++) if (thread_is_available(i, master)) { threads[i].state = THREAD_BOOKED; - threads[i].splitPoint = splitPoint; - splitPoint->slaves[i] = 1; + threads[i].splitPoint = &splitPoint; + splitPoint.slaves[i] = 1; workersCnt++; } @@ -2673,10 +2659,10 @@ namespace { // Tell the threads that they have work to do. This will make them leave // their idle loop. But before copy search stack tail for each thread. - for (int i = 0; i < ActiveThreads; i++) - if (i == master || splitPoint->slaves[i]) + for (i = 0; i < ActiveThreads; i++) + if (i == master || splitPoint.slaves[i]) { - memcpy(splitPoint->sstack[i] + ply - 1, sstck + ply - 1, 4 * sizeof(SearchStack)); + memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack)); assert(i == master || threads[i].state == THREAD_BOOKED); @@ -2688,19 +2674,18 @@ namespace { // THREAD_WORKISWAITING. We send the split point as a second parameter to the // idle loop, which means that the main thread will return from the idle // loop when all threads have finished their work at this split point. - idle_loop(master, splitPoint); + idle_loop(master, &splitPoint); // We have returned from the idle loop, which means that all threads are // finished. Update alpha and bestValue, and return. lock_grab(&MPLock); - *alpha = splitPoint->alpha; - *bestValue = splitPoint->bestValue; - threads[master].activeSplitPoints--; - threads[master].splitPoint = splitPoint->parent; + *alpha = splitPoint.alpha; + *bestValue = splitPoint.bestValue; + masterThread.activeSplitPoints--; + masterThread.splitPoint = splitPoint.parent; lock_release(&MPLock); - return true; } @@ -2767,10 +2752,12 @@ namespace { continue; // Find a quick score for the move - init_ss_array(ss); + init_ss_array(ss, PLY_MAX_PLUS_2); + ss[0].eval = VALUE_NONE; + ss[0].currentMove = cur->move; pos.do_move(cur->move, st); moves[count].move = cur->move; - moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0); + moves[count].score = -qsearch(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1); moves[count].pv[0] = cur->move; moves[count].pv[1] = MOVE_NONE; pos.undo_move(cur->move);