X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=5426ce489ab851ade016e01d648a98f100de67f9;hp=aea07fdae7fdf93df1cc60b3981ea8bf99810f27;hb=9eedc0a46346bddb8b29c47a84fe6fe8f80d14af;hpb=b39a24ecca28620239818ca393a46a47f9d42824 diff --git a/src/search.cpp b/src/search.cpp index aea07fda..5426ce48 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -70,7 +70,6 @@ namespace { int active_threads() const { return ActiveThreads; } void set_active_threads(int newActiveThreads) { ActiveThreads = newActiveThreads; } - void set_stop_request(int threadID) { threads[threadID].stopRequest = true; } void incrementNodeCounter(int threadID) { threads[threadID].nodes++; } void incrementBetaCounter(Color us, Depth d, int threadID) { threads[threadID].betaCutOffs[us] += unsigned(d); } void print_current_line(SearchStack ss[], int ply, int threadID); @@ -85,7 +84,7 @@ namespace { void wake_sleeping_threads(); void put_threads_to_sleep(); void idle_loop(int threadID, SplitPoint* waitSp); - bool split(const Position& pos, SearchStack* ss, int ply, Value* alpha, Value* beta, Value* bestValue, + bool split(const Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue, const Value futilityValue, Depth depth, int* moves, MovePicker* mp, int master, bool pvNode); private: @@ -443,9 +442,6 @@ bool think(const Position& pos, bool infinite, bool ponder, int side_to_move, // Wake up sleeping threads TM.wake_sleeping_threads(); - for (int i = 1; i < TM.active_threads(); i++) - assert(TM.thread_is_available(i, 0)); - // Set thinking time int myTime = time[side_to_move]; int myIncrement = increment[side_to_move]; @@ -1211,7 +1207,7 @@ namespace { && TM.available_thread_exists(threadID) && !AbortSearch && !TM.thread_should_stop(threadID) - && TM.split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE, + && TM.split(pos, ss, ply, &alpha, beta, &bestValue, VALUE_NONE, depth, &moveCount, &mp, threadID, true)) break; } @@ -1271,29 +1267,30 @@ namespace { if (depth < OnePly) return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID); - // Initialize, and make an early exit in case of an aborted search, - // an instant draw, maximum ply reached, etc. + // Step 1. Initialize node and poll + // Polling can abort search. init_node(ss, ply, threadID); - // After init_node() that calls poll() + // Step 2. Check for aborted search and immediate draw if (AbortSearch || TM.thread_should_stop(threadID)) return Value(0); if (pos.is_draw() || ply >= PLY_MAX - 1) return VALUE_DRAW; - // Mate distance pruning + // Step 3. Mate distance pruning if (value_mated_in(ply) >= beta) return beta; if (value_mate_in(ply + 1) < beta) return beta - 1; + // Step 4. Transposition table lookup + // 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 exsists. Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key(); - // Transposition table lookup tte = TT.retrieve(posKey); ttMove = (tte ? tte->move() : MOVE_NONE); @@ -1303,9 +1300,9 @@ namespace { return value_from_tt(tte->value(), ply); } + // Step 5. Evaluate the position statically isCheck = pos.is_check(); - // Evaluate the position statically if (!isCheck) { if (tte && (tte->type() & VALUE_TYPE_EVAL)) @@ -1319,16 +1316,34 @@ namespace { update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval); } - // Static null move pruning. We're betting that the opponent doesn't have - // a move that will reduce the score by more than FutilityMargins[int(depth)] - // if we do a null move. + // Step 6. Razoring + if ( !value_is_mate(beta) + && !isCheck + && depth < RazorDepth + && staticValue < beta - (0x200 + 16 * depth) + && ss[ply - 1].currentMove != MOVE_NULL + && ttMove == MOVE_NONE + && !pos.has_pawn_on_7th(pos.side_to_move())) + { + Value rbeta = beta - (0x200 + 16 * depth); + Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID); + if (v < rbeta) + return v; //FIXME: Logically should be: return (v + 0x200 + 16 * depth); + } + + // Step 7. Static null move pruning + // We're betting that the opponent doesn't have a move that will reduce + // the score by more than fuility_margin(depth) if we do a null move. if ( !isCheck && allowNullmove && depth < RazorDepth && staticValue - futility_margin(depth, 0) >= beta) return staticValue - futility_margin(depth, 0); - // Null move search + // Step 8. Null move search with verification search + // When we jump directly to qsearch() we do a null move only if static value is + // at least beta. Otherwise we do a null move if static value is not more than + // NullMoveMargin under beta. if ( allowNullmove && depth > OnePly && !isCheck @@ -1377,36 +1392,23 @@ namespace { return beta - 1; } } - // Null move search not allowed, try razoring - else if ( !value_is_mate(beta) - && !isCheck - && depth < RazorDepth - && staticValue < beta - (NullMoveMargin + 16 * depth) - && ss[ply - 1].currentMove != MOVE_NULL - && ttMove == MOVE_NONE - && !pos.has_pawn_on_7th(pos.side_to_move())) - { - Value rbeta = beta - (NullMoveMargin + 16 * depth); - Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID); - if (v < rbeta) - return v; - } - // Go with internal iterative deepening if we don't have a TT move + // Step 9. Internal iterative deepening if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly && !isCheck && ss[ply].eval >= beta - IIDMargin) { - search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID); + search(pos, ss, beta, depth/2, ply, false, threadID); ttMove = ss[ply].pv[ply]; tte = TT.retrieve(posKey); } - // Initialize a MovePicker object for the current position, and prepare - // to search all moves. + // Step 10. Loop through moves + // Loop through all legal moves until no moves remain or a beta cutoff occurs + + // Initialize a MovePicker object for the current position MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]); CheckInfo ci(pos); - // Loop through all legal moves until no moves remain or a beta cutoff occurs while ( bestValue < beta && (move = mp.get_next_move()) != MOVE_NONE && !TM.thread_should_stop(threadID)) @@ -1420,7 +1422,7 @@ namespace { singleEvasion = (isCheck && mp.number_of_evasions() == 1); captureOrPromotion = pos.move_is_capture_or_promotion(move); - // Decide the new search depth + // Step 11. Decide the new search depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous); // Singular extension search. We extend the TT move if its value is much better than @@ -1447,10 +1449,10 @@ namespace { newDepth = depth - OnePly + ext; - // Update current move + // Update current move (this must be done after singular extension search) movesSearched[moveCount++] = ss[ply].currentMove = move; - // Futility pruning + // Step 12. Futility pruning if ( !isCheck && !dangerous && !captureOrPromotion @@ -1476,10 +1478,10 @@ namespace { } } - // Make and search the move + // Step 13. Make the move pos.do_move(move, st, ci, moveIsCheck); - // Try to reduce non-pv search depth by one ply if move seems not problematic, + // Step 14. Reduced search // if the move fails high will be re-searched at full depth. bool doFullDepthSearch = true; @@ -1497,16 +1499,19 @@ namespace { } } - if (doFullDepthSearch) // Go with full depth non-pv search + // Step 15. Full depth search + if (doFullDepthSearch) { ss[ply].reduction = Depth(0); value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID); } + + // Step 16. Undo move pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // New best move? + // Step 17. Check for new best move if (value > bestValue) { bestValue = value; @@ -1517,7 +1522,7 @@ namespace { ss[ply].mateKiller = move; } - // Split? + // Step 18. Check for split if ( TM.active_threads() > 1 && bestValue < beta && depth >= MinimumSplitDepth @@ -1525,16 +1530,19 @@ namespace { && TM.available_thread_exists(threadID) && !AbortSearch && !TM.thread_should_stop(threadID) - && TM.split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, //FIXME: SMP & futilityValue + && TM.split(pos, ss, ply, NULL, beta, &bestValue, futilityValue, //FIXME: SMP & futilityValue depth, &moveCount, &mp, threadID, false)) break; } - // All legal moves have been searched. A special case: If there were + // Step 19. Check for mate and stalemate + // All legal moves have been searched and if there were // no legal moves, it must be mate or stalemate. + // If one move was excluded return fail low. if (!moveCount) return excludedMove ? beta - 1 : (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW); + // Step 20. Update tables // If the search is not aborted, update the transposition table, // history counters, and killer moves. if (AbortSearch || TM.thread_should_stop(threadID)) @@ -1839,7 +1847,7 @@ namespace { if (ss[sp->ply].reduction) { value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID); - doFullDepthSearch = (value >= sp->beta); + doFullDepthSearch = (value >= sp->beta && !TM.thread_should_stop(threadID)); } } @@ -1852,12 +1860,6 @@ namespace { assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - if (TM.thread_should_stop(threadID)) - { - lock_grab(&(sp->lock)); - break; - } - // New best move? if (value > sp->bestValue) // Less then 2% of cases { @@ -1867,12 +1869,8 @@ namespace { sp->bestValue = value; if (sp->bestValue >= sp->beta) { + sp->stopRequest = true; sp_update_pv(sp->parentSstack, ss, sp->ply); - for (int i = 0; i < TM.active_threads(); i++) - if (i != threadID && (i == sp->master || sp->slaves[i])) - TM.set_stop_request(i); - - sp->finished = true; } } lock_release(&(sp->lock)); @@ -1881,15 +1879,6 @@ namespace { /* Here we have the lock still grabbed */ - // If this is the master thread and we have been asked to stop because of - // a beta cutoff higher up in the tree, stop all slave threads. Note that - // thread_should_stop(threadID) does not imply that 'stop' flag is set, so - // do this explicitly now, under lock protection. - if (sp->master == threadID && TM.thread_should_stop(threadID)) - for (int i = 0; i < TM.active_threads(); i++) - if (sp->slaves[i] || i == threadID) - TM.set_stop_request(i); - sp->cpus--; sp->slaves[threadID] = 0; @@ -1955,7 +1944,7 @@ namespace { { Value localAlpha = sp->alpha; value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID); - doFullDepthSearch = (value > localAlpha); + doFullDepthSearch = (value > localAlpha && !TM.thread_should_stop(threadID)); } } @@ -1965,27 +1954,19 @@ namespace { ss[sp->ply].reduction = Depth(0); value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID); - if (value > localAlpha && value < sp->beta) + if (value > localAlpha && value < sp->beta && !TM.thread_should_stop(threadID)) { // If another thread has failed high then sp->alpha has been increased // to be higher or equal then beta, if so, avoid to start a PV search. localAlpha = sp->alpha; if (localAlpha < sp->beta) value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID); - else - assert(TM.thread_should_stop(threadID)); - } + } } pos.undo_move(move); assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - if (TM.thread_should_stop(threadID)) - { - lock_grab(&(sp->lock)); - break; - } - // New best move? if (value > sp->bestValue) // Less then 2% of cases { @@ -1997,13 +1978,7 @@ namespace { { // Ask threads to stop before to modify sp->alpha if (value >= sp->beta) - { - for (int i = 0; i < TM.active_threads(); i++) - if (i != threadID && (i == sp->master || sp->slaves[i])) - TM.set_stop_request(i); - - sp->finished = true; - } + sp->stopRequest = true; sp->alpha = value; @@ -2018,15 +1993,6 @@ namespace { /* Here we have the lock still grabbed */ - // If this is the master thread and we have been asked to stop because of - // a beta cutoff higher up in the tree, stop all slave threads. Note that - // thread_should_stop(threadID) does not imply that 'stop' flag is set, so - // do this explicitly now, under lock protection. - if (sp->master == threadID && TM.thread_should_stop(threadID)) - for (int i = 0; i < TM.active_threads(); i++) - if (sp->slaves[i] || i == threadID) - TM.set_stop_request(i); - sp->cpus--; sp->slaves[threadID] = 0; @@ -2627,34 +2593,40 @@ namespace { { // Slave threads can exit as soon as AllThreadsShouldExit raises, // master should exit as last one. - if (AllThreadsShouldExit && !waitSp) + if (AllThreadsShouldExit) { + assert(!waitSp); threads[threadID].state = THREAD_TERMINATED; return; } // If we are not thinking, wait for a condition to be signaled // instead of wasting CPU time polling for work. - while ( threadID != 0 - && !AllThreadsShouldExit - && (AllThreadsShouldSleep || threadID >= ActiveThreads)) + while (AllThreadsShouldSleep || threadID >= ActiveThreads) { + assert(!waitSp); + assert(threadID != 0); threads[threadID].state = THREAD_SLEEPING; #if !defined(_MSC_VER) pthread_mutex_lock(&WaitLock); - pthread_cond_wait(&WaitCond, &WaitLock); + if (AllThreadsShouldSleep || threadID >= ActiveThreads) + pthread_cond_wait(&WaitCond, &WaitLock); pthread_mutex_unlock(&WaitLock); #else WaitForSingleObject(SitIdleEvent[threadID], INFINITE); #endif - // State is already changed by wake_sleeping_threads() - assert(threads[threadID].state == THREAD_AVAILABLE || threadID >= ActiveThreads); } + // If thread has just woken up, mark it as available + if (threads[threadID].state == THREAD_SLEEPING) + threads[threadID].state = THREAD_AVAILABLE; + // If this thread has been assigned work, launch a search if (threads[threadID].state == THREAD_WORKISWAITING) { + assert(!AllThreadsShouldExit && !AllThreadsShouldSleep); + threads[threadID].state = THREAD_SEARCHING; if (threads[threadID].splitPoint->pvNode) @@ -2664,21 +2636,14 @@ namespace { assert(threads[threadID].state == THREAD_SEARCHING); - // If this is a slave thread reset to available, instead - // if it is a master thread and all slaves have finished - // then leave as is to avoid booking by another master, - // we will leave idle loop shortly anyhow. - if ( !AllThreadsShouldExit - && (!waitSp || waitSp->cpus > 0)) - threads[threadID].state = THREAD_AVAILABLE; + threads[threadID].state = THREAD_AVAILABLE; } // If this thread is the master of a split point and all threads have // finished their work at this split point, return from the idle loop. if (waitSp != NULL && waitSp->cpus == 0) { - assert( threads[threadID].state == THREAD_AVAILABLE - || threads[threadID].state == THREAD_SEARCHING); + assert(threads[threadID].state == THREAD_AVAILABLE); threads[threadID].state = THREAD_SEARCHING; return; @@ -2705,7 +2670,7 @@ namespace { lock_init(&IOLock, NULL); // Initialize SplitPointStack locks - for (int i = 0; i < MAX_THREADS; i++) + for (i = 0; i < MAX_THREADS; i++) for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++) { SplitPointStack[i][j].parent = NULL; @@ -2769,8 +2734,7 @@ namespace { // Wait for thread termination for (int i = 1; i < MAX_THREADS; i++) - while (threads[i].state != THREAD_TERMINATED) - threads[i].stopRequest = true; + while (threads[i].state != THREAD_TERMINATED); // Now we can safely destroy the locks for (int i = 0; i < MAX_THREADS; i++) @@ -2779,10 +2743,9 @@ namespace { } - // thread_should_stop() checks whether the thread with a given threadID has - // been asked to stop, directly or indirectly. This can happen if a beta - // cutoff has occurred in the thread's currently active split point, or in - // some ancestor of the current split point. + // thread_should_stop() checks whether the thread should stop its search. + // This can happen if a beta cutoff has occurred in the thread's currently + // active split point, or in some ancestor of the current split point. bool ThreadsManager::thread_should_stop(int threadID) const { @@ -2790,17 +2753,8 @@ namespace { SplitPoint* sp; - if (threads[threadID].stopRequest) - return true; - - if (ActiveThreads <= 2) - return false; - - for (sp = threads[threadID].splitPoint; sp != NULL; sp = sp->parent) - if (sp->finished) - return true; - - return false; + for (sp = threads[threadID].splitPoint; sp && !sp->stopRequest; sp = sp->parent); + return sp != NULL; } @@ -2871,15 +2825,17 @@ namespace { // splitPoint->cpus becomes 0), split() returns true. bool ThreadsManager::split(const Position& p, SearchStack* sstck, int ply, - Value* alpha, Value* beta, Value* bestValue, const Value futilityValue, + Value* alpha, const Value beta, Value* bestValue, const Value futilityValue, Depth depth, int* moves, MovePicker* mp, int master, bool pvNode) { assert(p.is_ok()); assert(sstck != NULL); assert(ply >= 0 && ply < PLY_MAX); - assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha); - assert(!pvNode || *alpha < *beta); - assert(*beta <= VALUE_INFINITE); + assert(*bestValue >= -VALUE_INFINITE); + assert( ( pvNode && *bestValue <= *alpha) + || (!pvNode && *bestValue < beta )); + assert(!pvNode || *alpha < beta); + assert(beta <= VALUE_INFINITE); assert(depth > Depth(0)); assert(master >= 0 && master < ActiveThreads); assert(ActiveThreads > 1); @@ -2898,16 +2854,15 @@ namespace { } // Pick the next available split point object from the split point stack - splitPoint = SplitPointStack[master] + threads[master].activeSplitPoints; - threads[master].activeSplitPoints++; + splitPoint = &SplitPointStack[master][threads[master].activeSplitPoints]; // Initialize the split point object splitPoint->parent = threads[master].splitPoint; - splitPoint->finished = false; + splitPoint->stopRequest = false; splitPoint->ply = ply; splitPoint->depth = depth; - splitPoint->alpha = pvNode ? *alpha : (*beta - 1); - splitPoint->beta = *beta; + splitPoint->alpha = pvNode ? *alpha : beta - 1; + splitPoint->beta = beta; splitPoint->pvNode = pvNode; splitPoint->bestValue = *bestValue; splitPoint->futilityValue = futilityValue; @@ -2921,6 +2876,7 @@ namespace { splitPoint->slaves[i] = 0; threads[master].splitPoint = splitPoint; + threads[master].activeSplitPoints++; // If we are here it means we are not available assert(threads[master].state != THREAD_AVAILABLE); @@ -2930,7 +2886,6 @@ namespace { if (thread_is_available(i, master)) { threads[i].state = THREAD_BOOKED; - threads[i].stopRequest = false; threads[i].splitPoint = splitPoint; splitPoint->slaves[i] = 1; splitPoint->cpus++; @@ -2968,9 +2923,7 @@ namespace { if (pvNode) *alpha = splitPoint->alpha; - *beta = splitPoint->beta; *bestValue = splitPoint->bestValue; - threads[master].stopRequest = false; threads[master].activeSplitPoints--; threads[master].splitPoint = splitPoint->parent; @@ -2993,12 +2946,8 @@ namespace { return; for (int i = 1; i < ActiveThreads; i++) - { assert(threads[i].state == THREAD_SLEEPING); - threads[i].state = THREAD_AVAILABLE; - } - #if !defined(_MSC_VER) pthread_mutex_lock(&WaitLock); pthread_cond_broadcast(&WaitCond); @@ -3022,14 +2971,11 @@ namespace { // This makes the threads to go to sleep AllThreadsShouldSleep = true; - // Wait for the threads to be all sleeping and reset flags - // to a known state. + // Reset flags to a known state. for (int i = 1; i < ActiveThreads; i++) { - while (threads[i].state != THREAD_SLEEPING); - - // These two flags can be in a random state - threads[i].stopRequest = threads[i].printCurrentLineRequest = false; + // This flag can be in a random state + threads[i].printCurrentLineRequest = false; } }