const bool FakeSplit = false;
// Different node types, used as template parameter
- enum NodeType { Root, PV, NonPV, SplitPointPV, SplitPointNonPV };
+ enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
// RootMove struct is used for moves at the root of the tree. For each root
// move, we store a score, a node count, and a PV (really a refutation
// Node counters, used only by thread[0] but try to keep in different cache
// lines (64 bytes each) from the heavy multi-thread read accessed variables.
- bool SendSearchedNodes;
int NodesSincePoll;
int NodesBetweenPolls = 30000;
bool connected_moves(const Position& pos, Move m1, Move m2);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
- bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
+ bool can_return_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);
// MovePickerExt template class extends MovePicker and allows to choose at compile
// time the proper moves source according to the type of node. In the default case
// we simply create and use a standard MovePicker object.
- template<NodeType> struct MovePickerExt : public MovePicker {
+ template<bool SpNode> struct MovePickerExt : public MovePicker {
MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
: MovePicker(p, ttm, d, h, ss, b) {}
};
// In case of a SpNode we use split point's shared MovePicker object as moves source
- template<> struct MovePickerExt<SplitPointNonPV> : public MovePicker {
+ template<> struct MovePickerExt<true> : public MovePicker {
MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
: MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
MovePicker* mp;
};
- template<> struct MovePickerExt<SplitPointPV> : public MovePickerExt<SplitPointNonPV> {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
- : MovePickerExt<SplitPointNonPV>(p, ttm, d, h, ss, b) {}
- };
-
// Overload operator<<() to make it easier to print moves in a coordinate
// notation compatible with UCI protocol.
std::ostream& operator<<(std::ostream& os, Move m) {
bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
- static Book book;
+ static Book book; // Define static to initialize the PRNG only once
// Initialize global search-related variables
- StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
+ StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = false;
NodesSincePoll = 0;
current_search_time(get_system_time());
Limits = limits;
read_evaluation_uci_options(pos.side_to_move());
Threads.read_uci_options();
- // If needed allocate pawn and material hash tables and adjust TT size
- Threads.init_hash_tables();
+ // Set a new TT size if changed
TT.set_size(Options["Hash"].value<int>());
if (Options["Clear Hash"].value<bool>())
Rml.bestMoveChanges = 0;
- // MultiPV iteration loop
- for (MultiPVIteration = 0; MultiPVIteration < Min(MultiPV, (int)Rml.size()); MultiPVIteration++)
+ // MultiPV iteration loop. At depth 1 perform at least 2 iterations to
+ // get a score of the second best move for easy move detection.
+ int e = Min(Max(MultiPV, 2 * int(depth == 1)), (int)Rml.size());
+ for (MultiPVIteration = 0; MultiPVIteration < e; MultiPVIteration++)
{
// Calculate dynamic aspiration window based on previous iterations
if (depth >= 5 && abs(Rml[MultiPVIteration].prevScore) < VALUE_KNOWN_WIN)
// Start with a small aspiration window and, in case of fail high/low,
// research with bigger window until not failing high/low anymore.
do {
- // Search starting from ss+1 to allow calling update_gains()
+ // Search starting from ss+1 to allow referencing (ss-1). This is
+ // needed by update_gains() and ss copy when splitting at Root.
value = search<Root>(pos, ss+1, alpha, beta, depth * ONE_PLY);
// It is critical that sorting is done with a stable algorithm
// Send full PV info to GUI if we are going to leave the loop or
// if we have a fail high/low and we are deep in the search.
if ((value > alpha && value < beta) || current_search_time() > 2000)
- for (int i = 0; i < Min(UCIMultiPV, MultiPVIteration); i++)
- {
+ for (int i = 0; i < Min(UCIMultiPV, MultiPVIteration + 1); i++)
cout << "info"
<< depth_to_uci(depth * ONE_PLY)
<< (i == MultiPVIteration ? score_to_uci(Rml[i].score, alpha, beta) :
<< speed_to_uci(pos.nodes_searched())
<< pv_to_uci(&Rml[i].pv[0], i + 1, pos.is_chess960())
<< endl;
- }
// In case of failing high/low increase aspiration window and research,
// otherwise exit the fail high/low loop.
template <NodeType NT>
Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
- const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV);
- const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV);
- const bool RootNode = (NT == Root);
+ const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
+ const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
+ const bool RootNode = (NT == Root || NT == SplitPointRoot);
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
Depth ext, newDepth;
ValueType vt;
Value bestValue, value, oldAlpha;
- Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
+ Value refinedValue, nullValue, futilityBase, futilityValue;
bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous;
int moveCount = 0, playedMoveCount = 0;
Thread& thread = Threads[pos.thread()];
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
tte = TT.probe(posKey);
- ttMove = tte ? tte->move() : MOVE_NONE;
+ ttMove = RootNode ? Rml[MultiPVIteration].pv[0] : tte ? tte->move() : MOVE_NONE;
// At PV nodes we check for exact scores, while at non-PV nodes we check for
// a fail high/low. Biggest advantage at probing at PV nodes is to have a
// smooth experience in analysis mode. We don't probe at Root nodes otherwise
// we should also update RootMoveList to avoid bogus output.
if (!RootNode && tte && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
- : ok_to_use_TT(tte, depth, beta, ss->ply)))
+ : can_return_tt(tte, depth, beta, ss->ply)))
{
TT.refresh(tte);
- ss->bestMove = ttMove; // Can be MOVE_NONE
- return value_from_tt(tte->value(), ss->ply);
+ ss->bestMove = move = ttMove; // Can be MOVE_NONE
+ value = value_from_tt(tte->value(), ss->ply);
+
+ if ( value >= beta
+ && move
+ && !pos.move_is_capture_or_promotion(move)
+ && move != ss->killers[0])
+ {
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
+ }
+ return value;
}
// Step 5. Evaluate the position statically and update parent's gain statistics
split_point_start: // At split points actual search starts from here
// Initialize a MovePicker object for the current position
- MovePickerExt<NT> mp(pos, RootNode ? Rml[MultiPVIteration].pv[0] : ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
+ MovePickerExt<SpNode> mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
CheckInfo ci(pos);
ss->bestMove = MOVE_NONE;
futilityBase = ss->eval + ss->evalMargin;
// At root obey the "searchmoves" option and skip moves not listed in Root Move List.
// Also in MultiPV mode we skip moves which already have got an exact score
- // in previous MultiPV Iteration.
+ // in previous MultiPV Iteration. Finally any illegal move is skipped here.
if (RootNode && !Rml.find(move, MultiPVIteration))
continue;
// Save the current node count before the move is searched
nodes = pos.nodes_searched();
- // If it's time to send nodes info, do it here where we have the
- // correct accumulated node counts searched by each thread.
- if (SendSearchedNodes)
- {
- SendSearchedNodes = false;
- cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
- }
-
// For long searches send current move info to GUI
- if (current_search_time() > 2000)
+ if (pos.thread() == 0 && current_search_time() > 2000)
cout << "info" << depth_to_uci(depth)
- << " currmove " << move << " currmovenumber " << moveCount + MultiPVIteration << endl;
+ << " currmove " << move
+ << " currmovenumber " << moveCount + MultiPVIteration << endl;
}
- // At Root and at first iteration do a PV search on all the moves to score root moves
- isPvMove = (PvNode && moveCount <= ((RootNode && depth <= ONE_PLY) ? MAX_MOVES : 1));
+ isPvMove = (PvNode && moveCount == 1);
givesCheck = pos.move_gives_check(move, ci);
captureOrPromotion = pos.move_is_capture_or_promotion(move);
// We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
// but fixing this made program slightly weaker.
Depth predictedDepth = newDepth - reduction<PvNode>(depth, moveCount);
- futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_on(move_from(move)), move_to(move));
+ futilityValue = futilityBase + futility_margin(predictedDepth, moveCount)
+ + H.gain(pos.piece_on(move_from(move)), move_to(move));
- if (futilityValueScaled < beta)
+ if (futilityValue < beta)
{
if (SpNode)
{
lock_grab(&(sp->lock));
- if (futilityValueScaled > sp->bestValue)
- sp->bestValue = bestValue = futilityValueScaled;
+ if (futilityValue > sp->bestValue)
+ sp->bestValue = bestValue = futilityValue;
}
- else if (futilityValueScaled > bestValue)
- bestValue = futilityValueScaled;
+ else if (futilityValue > bestValue)
+ bestValue = futilityValue;
continue;
}
alpha = sp->alpha;
}
- if (value > bestValue)
+ // Finished searching the move. If StopRequest is true, the search
+ // 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 && !StopRequest)
{
- bestValue = value;
- ss->bestMove = move;
-
- if ( !RootNode
- && PvNode
- && value > alpha
- && value < beta) // We want always alpha < beta
- alpha = value;
-
- if (SpNode && !thread.cutoff_occurred())
- {
- sp->bestValue = value;
- sp->ss->bestMove = move;
- sp->alpha = alpha;
- sp->is_betaCutoff = (value >= beta);
- }
- }
-
- if (RootNode)
- {
- // Finished searching the move. If StopRequest is true, the search
- // 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 break out of the loop without updating the best
- // move and/or PV.
- if (StopRequest)
- break;
-
// Remember searched nodes counts for this move
RootMove* rm = Rml.find(move);
rm->nodes += pos.nodes_searched() - nodes;
// the best move changes frequently, we allocate some more time.
if (!isPvMove && MultiPV == 1)
Rml.bestMoveChanges++;
-
- // Update alpha.
- if (value > alpha)
- alpha = value;
}
else
// All other moves but the PV are set to the lowest value, this
} // RootNode
+ if (value > bestValue)
+ {
+ bestValue = value;
+ ss->bestMove = move;
+
+ if ( PvNode
+ && value > alpha
+ && value < beta) // We want always alpha < beta
+ alpha = value;
+
+ if (SpNode && !thread.cutoff_occurred())
+ {
+ sp->bestValue = value;
+ sp->ss->bestMove = move;
+ sp->alpha = alpha;
+ sp->is_betaCutoff = (value >= beta);
+ }
+ }
+
// Step 19. Check for split
- if ( !RootNode
- && !SpNode
+ if ( !SpNode
&& depth >= Threads.min_split_depth()
&& bestValue < beta
&& Threads.available_slave_exists(pos.thread())
&& !StopRequest
&& !thread.cutoff_occurred())
- Threads.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
- threatMove, moveCount, &mp, PvNode);
+ bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, depth,
+ threatMove, moveCount, &mp, NT);
}
// Step 20. Check for mate and stalemate
bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
const TTEntry* tte;
Depth ttDepth;
+ ValueType vt;
Value oldAlpha = alpha;
ss->bestMove = ss->currentMove = MOVE_NONE;
tte = TT.probe(pos.get_key());
ttMove = (tte ? tte->move() : MOVE_NONE);
- if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ss->ply))
+ if (!PvNode && tte && can_return_tt(tte, ttDepth, beta, ss->ply))
{
ss->bestMove = ttMove; // Can be MOVE_NONE
return value_from_tt(tte->value(), ss->ply);
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ( alpha < beta
+ while ( bestValue < beta
&& (move = mp.get_next_move()) != MOVE_NONE)
{
assert(move_is_ok(move));
+ piece_value_endgame(pos.piece_on(move_to(move)))
+ (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
- if (futilityValue < alpha)
+ if (futilityValue < beta)
{
if (futilityValue > bestValue)
bestValue = futilityValue;
+
continue;
}
if (value > bestValue)
{
bestValue = value;
- if (value > alpha)
- {
+ ss->bestMove = move;
+
+ if ( PvNode
+ && value > alpha
+ && value < beta) // We want always alpha < beta
alpha = value;
- ss->bestMove = move;
- }
}
}
return value_mated_in(ss->ply);
// Update transposition table
- ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
- TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
+ move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
+ vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
+ : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
+
+ TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, move, ss->eval, evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
Piece p1, p2;
Square ksq;
- assert(m1 && move_is_ok(m1));
- assert(m2 && move_is_ok(m2));
+ assert(move_is_ok(m1));
+ assert(move_is_ok(m2));
// Case 1: The moving piece is the same in both moves
f2 = move_from(m2);
bool connected_threat(const Position& pos, Move m, Move threat) {
assert(move_is_ok(m));
- assert(threat && move_is_ok(threat));
+ assert(move_is_ok(threat));
assert(!pos.move_is_capture_or_promotion(m));
assert(!pos.move_is_passed_pawn_push(m));
}
- // ok_to_use_TT() returns true if a transposition table score
- // can be used at a given point in search.
+ // can_return_tt() returns true if a transposition table score
+ // can be used to cut-off at a given point in search.
- bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
+ bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply) {
Value v = value_from_tt(tte->value(), ply);
dbg_print_mean();
dbg_print_hit_rate();
-
- // Send info on searched nodes as soon as we return to root
- SendSearchedNodes = true;
}
// Should we stop the search?
} // namespace
-// ThreadsManager::idle_loop() is where the threads are parked when they have no work
-// to do. The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
-// object for which the current thread is the master.
+// Little helper used by idle_loop() to check that all the slave threads of a
+// split point have finished searching.
+
+static bool all_slaves_finished(SplitPoint* sp) {
+
+ for (int i = 0; i < Threads.size(); i++)
+ if (sp->is_slave[i])
+ return false;
+
+ return true;
+}
-void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
- assert(threadID >= 0 && threadID < MAX_THREADS);
+// Thread::idle_loop() is where the thread is parked when it has no work to do.
+// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
+// for which the thread is the master.
- int i;
- bool allFinished;
+void Thread::idle_loop(SplitPoint* sp) {
while (true)
{
- // Slave threads can exit as soon as AllThreadsShouldExit raises,
- // master should exit as last one.
- if (allThreadsShouldExit)
- {
- assert(!sp);
- threads[threadID].state = Thread::TERMINATED;
- return;
- }
-
- // If we are not thinking, wait for a condition to be signaled
+ // If we are not searching, wait for a condition to be signaled
// instead of wasting CPU time polling for work.
- while ( threadID >= activeThreads
- || threads[threadID].state == Thread::INITIALIZING
- || (useSleepingThreads && threads[threadID].state == Thread::AVAILABLE))
+ while ( do_sleep
+ || do_terminate
+ || (Threads.use_sleeping_threads() && !is_searching))
{
- assert(!sp || useSleepingThreads);
- assert(threadID != 0 || useSleepingThreads);
+ assert((!sp && threadID) || Threads.use_sleeping_threads());
- if (threads[threadID].state == Thread::INITIALIZING)
- threads[threadID].state = Thread::AVAILABLE;
+ // Slave thread should exit as soon as do_terminate flag raises
+ if (do_terminate)
+ {
+ assert(!sp);
+ return;
+ }
// Grab the lock to avoid races with Thread::wake_up()
- lock_grab(&threads[threadID].sleepLock);
+ lock_grab(&sleepLock);
- // If we are master and all slaves have finished do not go to sleep
- for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
- allFinished = (i == activeThreads);
-
- if (allFinished || allThreadsShouldExit)
+ // If we are master and all slaves have finished don't go to sleep
+ if (sp && all_slaves_finished(sp))
{
- lock_release(&threads[threadID].sleepLock);
+ lock_release(&sleepLock);
break;
}
- // Do sleep here after retesting sleep conditions
- if (threadID >= activeThreads || threads[threadID].state == Thread::AVAILABLE)
- cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock);
+ // Do sleep after retesting sleep conditions under lock protection, in
+ // particular we need to avoid a deadlock in case a master thread has,
+ // in the meanwhile, allocated us and sent the wake_up() call before we
+ // had the chance to grab the lock.
+ if (do_sleep || !is_searching)
+ cond_wait(&sleepCond, &sleepLock);
- lock_release(&threads[threadID].sleepLock);
+ lock_release(&sleepLock);
}
// If this thread has been assigned work, launch a search
- if (threads[threadID].state == Thread::WORKISWAITING)
+ if (is_searching)
{
- assert(!allThreadsShouldExit);
-
- threads[threadID].state = Thread::SEARCHING;
+ assert(!do_terminate);
// Copy split point position and search stack and call search()
- // with SplitPoint template parameter set to true.
SearchStack ss[PLY_MAX_PLUS_2];
- SplitPoint* tsp = threads[threadID].splitPoint;
+ SplitPoint* tsp = splitPoint;
Position pos(*tsp->pos, threadID);
memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
(ss+1)->sp = tsp;
- if (tsp->pvNode)
+ if (tsp->nodeType == Root)
+ search<SplitPointRoot>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ else if (tsp->nodeType == PV)
search<SplitPointPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
- else
+ else if (tsp->nodeType == NonPV)
search<SplitPointNonPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ else
+ assert(false);
- assert(threads[threadID].state == Thread::SEARCHING);
+ assert(is_searching);
- threads[threadID].state = Thread::AVAILABLE;
+ is_searching = false;
// Wake up master thread so to allow it to return from the idle loop in
// case we are the last slave of the split point.
- if ( useSleepingThreads
+ if ( Threads.use_sleeping_threads()
&& threadID != tsp->master
- && threads[tsp->master].state == Thread::AVAILABLE)
- threads[tsp->master].wake_up();
+ && !Threads[tsp->master].is_searching)
+ Threads[tsp->master].wake_up();
}
// If this thread is the master of a split point and all slaves have
// finished their work at this split point, return from the idle loop.
- for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
- allFinished = (i == activeThreads);
-
- if (allFinished)
+ if (sp && all_slaves_finished(sp))
{
- // Because sp->slaves[] is reset under lock protection,
+ // Because sp->is_slave[] is reset under lock protection,
// be sure sp->lock has been released before to return.
lock_grab(&(sp->lock));
lock_release(&(sp->lock));
-
- // In helpful master concept a master can help only a sub-tree, and
- // because here is all finished is not possible master is booked.
- assert(threads[threadID].state == Thread::AVAILABLE);
-
- threads[threadID].state = Thread::SEARCHING;
return;
}
}
projects / stockfish / blobdiff