namespace Search {
- volatile SignalsType Signals;
+ SignalsType Signals;
LimitsType Limits;
- RootMoveVector RootMoves;
- Position RootPos;
- TimePoint SearchTime;
StateStackPtr SetupStates;
}
enum NodeType { Root, PV, NonPV };
// Razoring and futility margin based on depth
- inline Value razor_margin(Depth d) { return Value(512 + 32 * d); }
- inline Value futility_margin(Depth d) { return Value(200 * d); }
+ const int razor_margin[4] = { 483, 570, 603, 554 };
+ Value futility_margin(Depth d) { return Value(200 * d); }
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- template <bool PvNode> inline Depth reduction(bool i, Depth d, int mn) {
+ template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)];
}
Move best = MOVE_NONE;
};
- size_t PVIdx;
- TimeManager TimeMgr;
+ // EasyMoveManager struct is used to detect a so called 'easy move'; when PV is
+ // stable across multiple search iterations we can fast return the best move.
+ struct EasyMoveManager {
+
+ void clear() {
+ stableCnt = 0;
+ expectedPosKey = 0;
+ pv[0] = pv[1] = pv[2] = MOVE_NONE;
+ }
+
+ Move get(Key key) const {
+ return expectedPosKey == key ? pv[2] : MOVE_NONE;
+ }
+
+ void update(Position& pos, const std::vector<Move>& newPv) {
+
+ assert(newPv.size() >= 3);
+
+ // Keep track of how many times in a row 3rd ply remains stable
+ stableCnt = (newPv[2] == pv[2]) ? stableCnt + 1 : 0;
+
+ if (!std::equal(newPv.begin(), newPv.begin() + 3, pv))
+ {
+ std::copy(newPv.begin(), newPv.begin() + 3, pv);
+
+ StateInfo st[2];
+ pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0], CheckInfo(pos)));
+ pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1], CheckInfo(pos)));
+ expectedPosKey = pos.key();
+ pos.undo_move(newPv[1]);
+ pos.undo_move(newPv[0]);
+ }
+ }
+
+ int stableCnt;
+ Key expectedPosKey;
+ Move pv[3];
+ };
+
+ EasyMoveManager EasyMove;
double BestMoveChanges;
Value DrawValue[COLOR_NB];
- HistoryStats History;
- GainsStats Gains;
- MovesStats Countermoves, Followupmoves;
+ CounterMovesHistoryStats CounterMovesHistory;
- template <NodeType NT, bool SpNode>
+ template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- void id_loop(Position& pos);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
void update_pv(Move* pv, Move move, Move* childPv);
void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt);
+ void check_time();
} // namespace
void Search::init() {
- const double K[][2] = {{ 0.83, 2.25 }, { 0.50, 3.00 }};
+ const double K[][2] = {{ 0.799, 2.281 }, { 0.484, 3.023 }};
for (int pv = 0; pv <= 1; ++pv)
for (int imp = 0; imp <= 1; ++imp)
}
+/// Search::clear() resets to zero search state, to obtain reproducible results
+
+void Search::clear() {
+
+ TT.clear();
+ CounterMovesHistory.clear();
+
+ for (Thread* th : Threads)
+ {
+ th->history.clear();
+ th->counterMoves.clear();
+ }
+}
+
+
/// Search::perft() is our utility to verify move generation. All the leaf nodes
/// up to the given depth are generated and counted and the sum returned.
template<bool Root>
return nodes;
}
-template uint64_t Search::perft<true>(Position& pos, Depth depth);
+template uint64_t Search::perft<true>(Position&, Depth);
-/// Search::think() is the external interface to Stockfish's search, and is
-/// called by the main thread when the program receives the UCI 'go' command. It
-/// searches from RootPos and at the end prints the "bestmove" to output.
+/// MainThread::search() is called by the main thread when the program receives
+/// the UCI 'go' command. It searches from root position and at the end prints
+/// the "bestmove" to output.
-void Search::think() {
+void MainThread::search() {
- TimeMgr.init(Limits, RootPos.side_to_move(), RootPos.game_ply());
+ Color us = rootPos.side_to_move();
+ Time.init(Limits, us, rootPos.game_ply());
int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
- DrawValue[ RootPos.side_to_move()] = VALUE_DRAW - Value(contempt);
- DrawValue[~RootPos.side_to_move()] = VALUE_DRAW + Value(contempt);
+ DrawValue[ us] = VALUE_DRAW - Value(contempt);
+ DrawValue[~us] = VALUE_DRAW + Value(contempt);
TB::Hits = 0;
TB::RootInTB = false;
TB::ProbeDepth = DEPTH_ZERO;
}
- if (RootMoves.empty())
+ if (rootMoves.empty())
{
- RootMoves.push_back(RootMove(MOVE_NONE));
+ rootMoves.push_back(RootMove(MOVE_NONE));
sync_cout << "info depth 0 score "
- << UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
+ << UCI::value(rootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
}
else
{
- if (TB::Cardinality >=
RootPos.count<ALL_PIECES>(WHITE)
- +
RootPos.count<ALL_PIECES>(BLACK))
+ if (TB::Cardinality >=
rootPos.count<ALL_PIECES>(WHITE)
+ +
rootPos.count<ALL_PIECES>(BLACK))
{
// If the current root position is in the tablebases then RootMoves
// contains only moves that preserve the draw or win.
- TB::RootInTB = Tablebases::root_probe(RootPos, RootMoves, TB::Score);
+ TB::RootInTB = Tablebases::root_probe(rootPos, rootMoves, TB::Score);
if (TB::RootInTB)
TB::Cardinality = 0; // Do not probe tablebases during the search
else // If DTZ tables are missing, use WDL tables as a fallback
{
// Filter out moves that do not preserve a draw or win
- TB::RootInTB = Tablebases::root_probe_wdl(RootPos, RootMoves, TB::Score);
+ TB::RootInTB = Tablebases::root_probe_wdl(rootPos, rootMoves, TB::Score);
// Only probe during search if winning
if (TB::Score <= VALUE_DRAW)
if (TB::RootInTB)
{
- TB::Hits = RootMoves.size();
+ TB::Hits = rootMoves.size();
if (!TB::UseRule50)
TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
}
for (Thread* th : Threads)
+ {
th->maxPly = 0;
+ th->rootDepth = DEPTH_ZERO;
+ if (th != this)
+ {
+ th->rootPos = Position(rootPos, th);
+ th->rootMoves = rootMoves;
+ th->start_searching();
+ }
+ }
- Threads.timer->run = true;
- Threads.timer->notify_one(); // Wake up the recurring timer
-
- id_loop(RootPos); // Let's start searching !
-
- Threads.timer->run = false;
+ Thread::search(); // Let's start searching!
}
+ // When playing in 'nodes as time' mode, subtract the searched nodes from
+ // the available ones before to exit.
+ if (Limits.npmsec)
+ Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
+
// When we reach the maximum depth, we can arrive here without a raise of
// Signals.stop. However, if we are pondering or in an infinite search,
// the UCI protocol states that we shouldn't print the best move before the
if (!Signals.stop && (Limits.ponder || Limits.infinite))
{
Signals.stopOnPonderhit = true;
- RootPos.this_thread()->wait_for(Signals.stop);
+ wait(Signals.stop);
}
- sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960());
+ // Stop the threads if not already stopped
+ Signals.stop = true;
+
+ // Wait until all threads have finished
+ for (Thread* th : Threads)
+ if (th != this)
+ th->wait_for_search_finished();
+
+ // Check if there are threads with a better score than main thread.
+ Thread* bestThread = this;
+ if (Options["MultiPV"] == 1 && !Skill(Options["Skill Level"]).enabled())
+ for (Thread* th : Threads)
+ if ( th->completedDepth > bestThread->completedDepth
+ && th->rootMoves[0].score > bestThread->rootMoves[0].score)
+ bestThread = th;
+
+ // Send new PV when needed.
+ // FIXME: Breaks multiPV, and skill levels
+ if (bestThread != this)
+ sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
+
+ sync_cout << "bestmove " << UCI::move(bestThread->rootMoves[0].pv[0], rootPos.is_chess960());
- if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos))
- std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960());
+ if (bestThread->rootMoves[0].pv.size() > 1 || bestThread->rootMoves[0].extract_ponder_from_tt(rootPos))
+ std::cout << " ponder " << UCI::move(bestThread->rootMoves[0].pv[1], rootPos.is_chess960());
std::cout << sync_endl;
}
-namespace {
+// Thread::search() is the main iterative deepening loop. It calls search()
+// repeatedly with increasing depth until the allocated thinking time has been
+// consumed, user stops the search, or the maximum search depth is reached.
- // id_loop() is the main iterative deepening loop. It calls search() repeatedly
- // with increasing depth until the allocated thinking time has been consumed,
- // user stops the search, or the maximum search depth is reached.
+void Thread::search() {
- void id_loop(Position& pos) {
+ Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
+ Value bestValue, alpha, beta, delta;
+ Move easyMove = MOVE_NONE;
+ bool isMainThread = (this == Threads.main());
- Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
- Depth depth;
- Value bestValue, alpha, beta, delta;
+ std::memset(ss-2, 0, 5 * sizeof(Stack));
- std::memset(ss-2, 0, 5 * sizeof(Stack));
+ bestValue = delta = alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
+ completedDepth = DEPTH_ZERO;
- depth = DEPTH_ZERO;
- BestMoveChanges = 0;
- bestValue = delta = alpha = -VALUE_INFINITE;
- beta = VALUE_INFINITE;
+ if (isMainThread)
+ {
+ easyMove = EasyMove.get(rootPos.key());
+ EasyMove.clear();
+ BestMoveChanges = 0;
+ TT.new_search();
+ }
- TT.new_search();
- History.clear();
- Gains.clear();
- Countermoves.clear();
- Followupmoves.clear();
+ size_t multiPV = Options["MultiPV"];
+ Skill skill(Options["Skill Level"]);
- size_t multiPV = Options["MultiPV"];
- Skill skill(Options["Skill Level"]);
+ // When playing with strength handicap enable MultiPV search that we will
+ // use behind the scenes to retrieve a set of possible moves.
+ if (skill.enabled())
+ multiPV = std::max(multiPV, (size_t)4);
- // When playing with strength handicap enable MultiPV search that we will
- // use behind the scenes to retrieve a set of possible moves.
- if (skill.enabled())
- multiPV = std::max(multiPV, (size_t)4);
+ multiPV = std::min(multiPV, rootMoves.size());
- multiPV = std::min(multiPV, RootMoves.size());
+ // Iterative deepening loop until requested to stop or target depth reached
+ while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= Limits.depth))
+ {
+ // Set up the new depth for the helper threads
+ if (!isMainThread)
+ rootDepth = std::min(DEPTH_MAX - ONE_PLY, Threads.main()->rootDepth + Depth(int(2.2 * log(1 + this->idx))));
- // Iterative deepening loop until requested to stop or target depth reached
- while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
- {
- // Age out PV variability metric
- BestMoveChanges *= 0.5;
+ // Age out PV variability metric
+ if (isMainThread)
+ BestMoveChanges *= 0.5;
- // Save the last iteration's scores before first PV line is searched and
- // all the move scores except the (new) PV are set to -VALUE_INFINITE.
- for (RootMove& rm : RootMoves)
- rm.previousScore = rm.score;
+ // Save the last iteration's scores before first PV line is searched and
+ // all the move scores except the (new) PV are set to -VALUE_INFINITE.
+ for (RootMove& rm : rootMoves)
+ rm.previousScore = rm.score;
- // MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
- {
- // Reset aspiration window starting size
- if (depth >= 5 * ONE_PLY)
- {
- delta = Value(16);
- alpha = std::max(RootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
- beta = std::min(RootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
- }
+ // MultiPV loop. We perform a full root search for each PV line
+ for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
+ {
+ // Reset aspiration window starting size
+ if (rootDepth >= 5 * ONE_PLY)
+ {
+ delta = Value(18);
+ alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
+ beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
+ }
- // Start with a small aspiration window and, in the case of a fail
- // high/low, re-search with a bigger window until we're not failing
- // high/low anymore.
- while (true)
- {
- bestValue = search<Root, false>(pos, ss, alpha, beta, depth, false);
-
- // Bring the best move to the front. It is critical that sorting
- // is done with a stable algorithm because all the values but the
- // first and eventually the new best one are set to -VALUE_INFINITE
- // and we want to keep the same order for all the moves except the
- // new PV that goes to the front. Note that in case of MultiPV
- // search the already searched PV lines are preserved.
- std::stable_sort(RootMoves.begin() + PVIdx, RootMoves.end());
-
- // Write PV back to transposition table in case the relevant
- // entries have been overwritten during the search.
- for (size_t i = 0; i <= PVIdx; ++i)
- RootMoves[i].insert_pv_in_tt(pos);
-
- // If search has been stopped break immediately. Sorting and
- // writing PV back to TT is safe because RootMoves is still
- // valid, although it refers to previous iteration.
- if (Signals.stop)
- break;
-
- // When failing high/low give some update (without cluttering
- // the UI) before a re-search.
- if ( multiPV == 1
- && (bestValue <= alpha || bestValue >= beta)
- && now() - SearchTime > 3000)
- sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl;
-
- // In case of failing low/high increase aspiration window and
- // re-search, otherwise exit the loop.
- if (bestValue <= alpha)
- {
- beta = (alpha + beta) / 2;
- alpha = std::max(bestValue - delta, -VALUE_INFINITE);
-
- Signals.failedLowAtRoot = true;
- Signals.stopOnPonderhit = false;
- }
- else if (bestValue >= beta)
- {
- alpha = (alpha + beta) / 2;
- beta = std::min(bestValue + delta, VALUE_INFINITE);
- }
- else
- break;
-
- delta += delta / 2;
-
- assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
- }
+ // Start with a small aspiration window and, in the case of a fail
+ // high/low, re-search with a bigger window until we're not failing
+ // high/low anymore.
+ while (true)
+ {
+ bestValue = ::search<Root>(rootPos, ss, alpha, beta, rootDepth, false);
+
+ // Bring the best move to the front. It is critical that sorting
+ // is done with a stable algorithm because all the values but the
+ // first and eventually the new best one are set to -VALUE_INFINITE
+ // and we want to keep the same order for all the moves except the
+ // new PV that goes to the front. Note that in case of MultiPV
+ // search the already searched PV lines are preserved.
+ std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end());
+
+ // Write PV back to transposition table in case the relevant
+ // entries have been overwritten during the search.
+ for (size_t i = 0; i <= PVIdx; ++i)
+ rootMoves[i].insert_pv_in_tt(rootPos);
+
+ // If search has been stopped break immediately. Sorting and
+ // writing PV back to TT is safe because RootMoves is still
+ // valid, although it refers to previous iteration.
+ if (Signals.stop)
+ break;
- // Sort the PV lines searched so far and update the GUI
- std::stable_sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
+ // When failing high/low give some update (without cluttering
+ // the UI) before a re-search.
+ if ( isMainThread
+ && multiPV == 1
+ && (bestValue <= alpha || bestValue >= beta)
+ && Time.elapsed() > 3000)
+ sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
+
+ // In case of failing low/high increase aspiration window and
+ // re-search, otherwise exit the loop.
+ if (bestValue <= alpha)
+ {
+ beta = (alpha + beta) / 2;
+ alpha = std::max(bestValue - delta, -VALUE_INFINITE);
- if (Signals.stop)
- sync_cout << "info nodes " << RootPos.nodes_searched()
- << " time " << now() - SearchTime << sync_endl;
+ if (isMainThread)
+ {
+ Signals.failedLowAtRoot = true;
+ Signals.stopOnPonderhit = false;
+ }
+ }
+ else if (bestValue >= beta)
+ {
+ alpha = (alpha + beta) / 2;
+ beta = std::min(bestValue + delta, VALUE_INFINITE);
+ }
+ else
+ break;
- else if (PVIdx + 1 == multiPV || now() - SearchTime > 3000)
- sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl;
- }
+ delta += delta / 4 + 5;
- // If skill level is enabled and time is up, pick a sub-optimal best move
- if (skill.enabled() && skill.time_to_pick(depth))
- skill.pick_best(multiPV);
+ assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ }
- // Have we found a "mate in x"?
- if ( Limits.mate
- && bestValue >= VALUE_MATE_IN_MAX_PLY
- && VALUE_MATE - bestValue <= 2 * Limits.mate)
- Signals.stop = true;
+ // Sort the PV lines searched so far and update the GUI
+ std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1);
- // Do we have time for the next iteration? Can we stop searching now?
- if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit)
- {
- // Take some extra time if the best move has changed
- if (depth > 4 * ONE_PLY && multiPV == 1)
- TimeMgr.pv_instability(BestMoveChanges);
-
- // Stop the search if only one legal move is available or all
- // of the available time has been used.
- if ( RootMoves.size() == 1
- || now() - SearchTime > TimeMgr.available_time())
- {
- // If we are allowed to ponder do not stop the search now but
- // keep pondering until the GUI sends "ponderhit" or "stop".
- if (Limits.ponder)
- Signals.stopOnPonderhit = true;
- else
- Signals.stop = true;
- }
- }
- }
+ if (!isMainThread)
+ break;
+
+ if (Signals.stop)
+ sync_cout << "info nodes " << Threads.nodes_searched()
+ << " time " << Time.elapsed() << sync_endl;
+
+ else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000)
+ sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
+ }
+
+ if (!Signals.stop)
+ completedDepth = rootDepth;
+
+ if (!isMainThread)
+ continue;
+
+ // If skill level is enabled and time is up, pick a sub-optimal best move
+ if (skill.enabled() && skill.time_to_pick(rootDepth))
+ skill.pick_best(multiPV);
+
+ // Have we found a "mate in x"?
+ if ( Limits.mate
+ && bestValue >= VALUE_MATE_IN_MAX_PLY
+ && VALUE_MATE - bestValue <= 2 * Limits.mate)
+ Signals.stop = true;
+
+ // Do we have time for the next iteration? Can we stop searching now?
+ if (Limits.use_time_management())
+ {
+ if (!Signals.stop && !Signals.stopOnPonderhit)
+ {
+ // Take some extra time if the best move has changed
+ if (rootDepth > 4 * ONE_PLY && multiPV == 1)
+ Time.pv_instability(BestMoveChanges);
+
+ // Stop the search if only one legal move is available or all
+ // of the available time has been used or we matched an easyMove
+ // from the previous search and just did a fast verification.
+ if ( rootMoves.size() == 1
+ || Time.elapsed() > Time.available()
+ || ( rootMoves[0].pv[0] == easyMove
+ && BestMoveChanges < 0.03
+ && Time.elapsed() > Time.available() / 10))
+ {
+ // If we are allowed to ponder do not stop the search now but
+ // keep pondering until the GUI sends "ponderhit" or "stop".
+ if (Limits.ponder)
+ Signals.stopOnPonderhit = true;
+ else
+ Signals.stop = true;
+ }
+ }
- // If skill level is enabled, swap best PV line with the sub-optimal one
- if (skill.enabled())
- std::swap(RootMoves[0], *std::find(RootMoves.begin(),
- RootMoves.end(), skill.best_move(multiPV)));
+ if (rootMoves[0].pv.size() >= 3)
+ EasyMove.update(rootPos, rootMoves[0].pv);
+ else
+ EasyMove.clear();
+ }
}
+ if (!isMainThread)
+ return;
+
+ // Clear any candidate easy move that wasn't stable for the last search
+ // iterations; the second condition prevents consecutive fast moves.
+ if (EasyMove.stableCnt < 6 || Time.elapsed() < Time.available())
+ EasyMove.clear();
+
+ // If skill level is enabled, swap best PV line with the sub-optimal one
+ if (skill.enabled())
+ std::swap(rootMoves[0], *std::find(rootMoves.begin(),
+ rootMoves.end(), skill.best_move(multiPV)));
+}
+
+
+namespace {
- // search<>() is the main search function for both PV and non-PV nodes and for
- // normal and SplitPoint nodes. When called just after a split point the search
- // is simpler because we have already probed the hash table, done a null move
- // search, and searched the first move before splitting, so we don't have to
- // repeat all this work again. We also don't need to store anything to the hash
- // table here: This is taken care of after we return from the split point.
+ // search<>() is the main search function for both PV and non-PV nodes
- template <NodeType NT, bool SpNode>
+ template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
const bool RootNode = NT == Root;
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
- assert(depth > DEPTH_ZERO);
+ assert(DEPTH_ZERO < depth && depth < DEPTH_MAX);
Move pv[MAX_PLY+1], quietsSearched[64];
StateInfo st;
TTEntry* tte;
- SplitPoint* splitPoint;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth, predictedDepth;
Value bestValue, value, ttValue, eval, nullValue, futilityValue;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
- bool captureOrPromotion, dangerous, doFullDepthSearch;
+ bool captureOrPromotion, doFullDepthSearch;
int moveCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
inCheck = pos.checkers();
+ moveCount = quietCount = ss->moveCount = 0;
+ bestValue = -VALUE_INFINITE;
+ ss->ply = (ss-1)->ply + 1;
- if (SpNode)
+ // Check for available remaining time
+ if (thisThread->resetCalls.load(std::memory_order_relaxed))
{
- splitPoint = ss->splitPoint;
- bestMove = splitPoint->bestMove;
- bestValue = splitPoint->bestValue;
- tte = nullptr;
- ttHit = false;
- ttMove = excludedMove = MOVE_NONE;
- ttValue = VALUE_NONE;
-
- assert(splitPoint->bestValue > -VALUE_INFINITE && splitPoint->moveCount > 0);
-
- goto moves_loop;
+ thisThread->resetCalls = false;
+ thisThread->callsCnt = 0;
}
+ if (++thisThread->callsCnt > 4096)
+ {
+ for (Thread* th : Threads)
+ th->resetCalls = true;
- moveCount = quietCount = 0;
- bestValue = -VALUE_INFINITE;
- ss->ply = (ss-1)->ply + 1;
+ check_time();
+ }
// Used to send selDepth info to GUI
if (PvNode && thisThread->maxPly < ss->ply)
if (!RootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop || pos.is_draw() || ss->ply >= MAX_PLY)
- return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
+ if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY)
+ return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos)
+ : DrawValue[pos.side_to_move()];
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
(ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
- // 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.
+ // 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.
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.exclusion_key() : pos.key();
tte = TT.probe(posKey, ttHit);
- ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE;
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ss->ttMove = ttMove = RootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
+ : ttHit ? tte->move() : MOVE_NONE;
- // At non-PV nodes we check for a fail high/low. We don't probe at PV nodes
+ // At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& ttHit
&& tte->depth() >= depth
- && ttValue != VALUE_NONE // Only in case of TT access race
+ && ttValue != VALUE_NONE // Possible in case of TT access race
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
: (tte->bound() & BOUND_UPPER)))
{
ss->currentMove = ttMove; // Can be MOVE_NONE
- // If ttMove is quiet, update killers, history, counter move and followup move on TT hit
- if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove) && !inCheck)
+ // If ttMove is quiet, update killers, history, counter move on TT hit
+ if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove))
update_stats(pos, ss, ttMove, depth, nullptr, 0);
return ttValue;
}
}
- // Step 5. Evaluate the position statically and update parent's gain statistics
+ // Step 5. Evaluate the position statically
if (inCheck)
{
ss->staticEval = eval = VALUE_NONE;
else
{
eval = ss->staticEval =
- (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
+ (ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
+ : -(ss-1)->staticEval + 2 * Eval::Tempo;
- tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation());
+ tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
+ ss->staticEval, TT.generation());
}
if (ss->skipEarlyPruning)
goto moves_loop;
- if ( !pos.captured_piece_type()
- && ss->staticEval != VALUE_NONE
- && (ss-1)->staticEval != VALUE_NONE
- && (move = (ss-1)->currentMove) != MOVE_NULL
- && move != MOVE_NONE
- && type_of(move) == NORMAL)
- {
- Square to = to_sq(move);
- Gains.update(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
- }
-
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && eval + razor_margin(depth) <= alpha
- && ttMove == MOVE_NONE
- && !pos.pawn_on_7th(pos.side_to_move()))
+ && eval + razor_margin[depth] <= alpha
+ && ttMove == MOVE_NONE)
{
if ( depth <= ONE_PLY
- && eval + razor_margin(3 * ONE_PLY) <= alpha)
+ && eval + razor_margin[3 * ONE_PLY] <= alpha)
return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
- Value ralpha = alpha - razor_margin(depth);
+ Value ralpha = alpha - razor_margin[depth];
Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
if (v <= ralpha)
return v;
pos.do_null_move(st);
(ss+1)->skipEarlyPruning = true;
nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
- : - search<NonPV, false>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
+ : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
(ss+1)->skipEarlyPruning = false;
pos.undo_null_move();
// Do verification search at high depths
ss->skipEarlyPruning = true;
Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
- : search<NonPV, false>(pos, ss, beta-1, beta, depth-R, false);
+ : search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
ss->skipEarlyPruning = false;
if (v >= beta)
// Step 9. ProbCut (skipped when in check)
// If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
- // and a reduced search returns a value much above beta, we can (almost) safely
- // prune the previous move.
+ // and a reduced search returns a value much above beta, we can (almost)
+ // safely prune the previous move.
if ( !PvNode
&& depth >= 5 * ONE_PLY
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
assert((ss-1)->currentMove != MOVE_NONE);
assert((ss-1)->currentMove != MOVE_NULL);
- MovePicker mp(pos, ttMove, History, pos.captured_piece_type());
+ MovePicker mp(pos, ttMove, thisThread->history, PieceValue[MG][pos.captured_piece_type()]);
CheckInfo ci(pos);
- while ((move = mp.next_move<false>()) != MOVE_NONE)
+ while ((move = mp.next_move()) != MOVE_NONE)
if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
pos.do_move(move, st, pos.gives_check(move, ci));
- value = -search<NonPV, false>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
return value;
&& !ttMove
&& (PvNode || ss->staticEval + 256 >= beta))
{
- Depth d = 2 * (depth - 2 * ONE_PLY) - (PvNode ? DEPTH_ZERO : depth / 2);
+ Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
ss->skipEarlyPruning = true;
- search<PvNode ? PV : NonPV, false>(pos, ss, alpha, beta, d / 2, true);
+ search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d, true);
ss->skipEarlyPruning = false;
tte = TT.probe(posKey, ttHit);
ttMove = ttHit ? tte->move() : MOVE_NONE;
}
-moves_loop: // When in check and at SpNode search starts from here
-
- Square prevMoveSq = to_sq((ss-1)->currentMove);
- Move countermoves[] = { Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].first,
- Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq].second };
+moves_loop: // When in check search starts from here
- Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
- Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
- Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+ Square prevSq = to_sq((ss-1)->currentMove);
+ Move cm = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
+ const CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
- MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
+ MovePicker mp(pos, ttMove, depth, thisThread->history, cmh, cm, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
||(ss-2)->staticEval == VALUE_NONE;
singularExtensionNode = !RootNode
- && !SpNode
&& depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
/* && ttValue != VALUE_NONE Already implicit in the next condition */
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
- while ((move = mp.next_move<SpNode>()) != MOVE_NONE)
+ while ((move = mp.next_move()) != MOVE_NONE)
{
assert(is_ok(move));
// At root obey the "searchmoves" option and skip moves not listed in Root
// Move List. As a consequence any illegal move is also skipped. In MultiPV
// mode we also skip PV moves which have been already searched.
- if (RootNode && !std::count(RootMoves.begin() + PVIdx, RootMoves.end(), move))
+ if (RootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
+ thisThread->rootMoves.end(), move))
continue;
- if (SpNode)
- {
- // Shared counter cannot be decremented later if the move turns out to be illegal
- if (!pos.legal(move, ci.pinned))
- continue;
+ ss->moveCount = ++moveCount;
- moveCount = ++splitPoint->moveCount;
- splitPoint->spinlock.release();
- }
- else
- ++moveCount;
-
- if (RootNode)
+ if (RootNode && thisThread == Threads.main())
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main() && now() - SearchTime > 3000)
+ if (Time.elapsed() > 3000)
sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << UCI::move(move, pos.is_chess960())
- << " currmovenumber " << moveCount + PVIdx << sync_endl;
+ << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl;
}
if (PvNode)
captureOrPromotion = pos.capture_or_promotion(move);
givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
- ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+ ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
: pos.gives_check(move, ci);
- dangerous = givesCheck
- || type_of(move) != NORMAL
- || pos.advanced_pawn_push(move);
-
// Step 12. Extend checks
if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
extension = ONE_PLY;
Value rBeta = ttValue - 2 * depth / ONE_PLY;
ss->excludedMove = move;
ss->skipEarlyPruning = true;
- value = search<NonPV, false>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
ss->skipEarlyPruning = false;
ss->excludedMove = MOVE_NONE;
if ( !RootNode
&& !captureOrPromotion
&& !inCheck
- && !dangerous
+ && !givesCheck
+ && !pos.advanced_pawn_push(move)
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
if ( depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[improving][depth])
- {
- if (SpNode)
- splitPoint->spinlock.acquire();
+ continue;
+ // History based pruning
+ if ( depth <= 4 * ONE_PLY
+ && move != ss->killers[0]
+ && thisThread->history[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO
+ && cmh[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO)
continue;
- }
predictedDepth = newDepth - reduction<PvNode>(improving, depth, moveCount);
// Futility pruning: parent node
if (predictedDepth < 7 * ONE_PLY)
{
- futilityValue = ss->staticEval + futility_margin(predictedDepth)
- + 128 + Gains[pos.moved_piece(move)][to_sq(move)];
+ futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256;
if (futilityValue <= alpha)
{
bestValue = std::max(bestValue, futilityValue);
-
- if (SpNode)
- {
- splitPoint->spinlock.acquire();
- if (bestValue > splitPoint->bestValue)
- splitPoint->bestValue = bestValue;
- }
continue;
}
}
// Prune moves with negative SEE at low depths
if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
- {
- if (SpNode)
- splitPoint->spinlock.acquire();
-
continue;
- }
}
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
- if (!RootNode && !SpNode && !pos.legal(move, ci.pinned))
+ if (!RootNode && !pos.legal(move, ci.pinned))
{
- moveCount--;
+ ss->moveCount = --moveCount;
continue;
}
ss->currentMove = move;
- if (!SpNode && !captureOrPromotion && quietCount < 64)
- quietsSearched[quietCount++] = move;
// Step 14. Make the move
pos.do_move(move, st, givesCheck);
{
ss->reduction = reduction<PvNode>(improving, depth, moveCount);
+ // Increase reduction for cut nodes and moves with a bad history
if ( (!PvNode && cutNode)
- || History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO)
+ || ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO
+ && cmh[pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO))
ss->reduction += ONE_PLY;
- if (move == countermoves[0] || move == countermoves[1])
+ // Decrease reduction for moves with a good history
+ if ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO
+ && cmh[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO)
ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
// Decrease reduction for moves that escape a capture
ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
- if (SpNode)
- alpha = splitPoint->alpha;
- value = -search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, d, true);
-
- // Re-search at intermediate depth if reduction is very high
- if (value > alpha && ss->reduction >= 4 * ONE_PLY)
- {
- Depth d2 = std::max(newDepth - 2 * ONE_PLY, ONE_PLY);
- value = -search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, d2, true);
- }
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
// Step 16. Full depth search, when LMR is skipped or fails high
if (doFullDepthSearch)
- {
- if (SpNode)
- alpha = splitPoint->alpha;
-
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
: -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
- }
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
// For PV nodes only, do a full PV search on the first move or after a fail
// high (in the latter case search only if value < beta), otherwise let the
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
: -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<PV, false>(pos, ss+1, -beta, -alpha, newDepth, false);
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
}
// Step 17. Undo move
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// Step 18. Check for new best move
- if (SpNode)
- {
- splitPoint->spinlock.acquire();
- bestValue = splitPoint->bestValue;
- alpha = splitPoint->alpha;
- }
-
- // Finished searching the move. If a stop or a cutoff occurred, the return
- // value of the search cannot be trusted, and we return immediately without
+ // Finished searching the move. If a stop occurred, the return value of
+ // the search cannot be trusted, and we return immediately without
// updating best move, PV and TT.
- if (Signals.stop || thisThread->cutoff_occurred())
+ if (Signals.stop.load(std::memory_order_relaxed))
return VALUE_ZERO;
if (RootNode)
{
- RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move);
+ RootMove& rm = *std::find(thisThread->rootMoves.begin(),
+ thisThread->rootMoves.end(), move);
// PV move or new best move ?
if (moveCount == 1 || value > alpha)
// We record how often the best move has been changed in each
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
- if (moveCount > 1)
+ if (moveCount > 1 && thisThread == Threads.main())
++BestMoveChanges;
}
else
if (value > bestValue)
{
- bestValue = SpNode ? splitPoint->bestValue = value : value;
+ bestValue = value;
if (value > alpha)
{
- bestMove = SpNode ? splitPoint->bestMove = move : move;
+ // If there is an easy move for this position, clear it if unstable
+ if ( PvNode
+ && thisThread == Threads.main()
+ && EasyMove.get(pos.key())
+ && (move != EasyMove.get(pos.key()) || moveCount > 1))
+ EasyMove.clear();
+
+ bestMove = move;
if (PvNode && !RootNode) // Update pv even in fail-high case
- update_pv(SpNode ? splitPoint->ss->pv : ss->pv, move, (ss+1)->pv);
+ update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
- alpha = SpNode ? splitPoint->alpha = value : value;
+ alpha = value;
else
{
assert(value >= beta); // Fail high
-
- if (SpNode)
- splitPoint->cutoff = true;
-
break;
}
}
}
- // Step 19. Check for splitting the search
- if ( !SpNode
- && Threads.size() >= 2
- && depth >= Threads.minimumSplitDepth
- && ( !thisThread->activeSplitPoint
- || !thisThread->activeSplitPoint->allSlavesSearching
- || ( Threads.size() > MAX_SLAVES_PER_SPLITPOINT
- && thisThread->activeSplitPoint->slavesMask.count() == MAX_SLAVES_PER_SPLITPOINT))
- && thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)
- {
- assert(bestValue > -VALUE_INFINITE && bestValue < beta);
-
- thisThread->split(pos, ss, alpha, beta, &bestValue, &bestMove,
- depth, moveCount, &mp, NT, cutNode);
-
- if (Signals.stop || thisThread->cutoff_occurred())
- return VALUE_ZERO;
-
- if (bestValue >= beta)
- break;
- }
+ if (!captureOrPromotion && move != bestMove && quietCount < 64)
+ quietsSearched[quietCount++] = move;
}
- if (SpNode)
- return bestValue;
-
- // Following condition would detect a stop or a cutoff set only after move
- // loop has been completed. But in this case bestValue is valid because we
- // have fully searched our subtree, and we can anyhow save the result in TT.
+ // Following condition would detect a stop only after move loop has been
+ // completed. But in this case bestValue is valid because we have fully
+ // searched our subtree, and we can anyhow save the result in TT.
/*
- if (Signals.stop || thisThread->cutoff_occurred())
+ if (Signals.stop)
return VALUE_DRAW;
*/
bestValue = excludedMove ? alpha
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
- // Quiet best move: update killers, history, countermoves and followupmoves
- else if (bestValue >= beta && !pos.capture_or_promotion(bestMove) && !inCheck)
- update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount - 1);
+ // Quiet best move: update killers, history and countermoves
+ else if (bestMove && !pos.capture_or_promotion(bestMove))
+ update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount);
+
+ // Bonus for prior countermove that caused the fail low
+ else if ( depth >= 3 * ONE_PLY
+ && !bestMove
+ && !inCheck
+ && !pos.captured_piece_type()
+ && is_ok((ss - 1)->currentMove)
+ && is_ok((ss - 2)->currentMove))
+ {
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);
+ Square prevPrevSq = to_sq((ss - 2)->currentMove);
+ CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
+ prevCmh.update(pos.piece_on(prevSq), prevSq, bonus);
+ }
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
// Check for an instant draw or if the maximum ply has been reached
if (pos.is_draw() || ss->ply >= MAX_PLY)
- return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : DrawValue[pos.side_to_move()];
+ return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos)
+ : DrawValue[pos.side_to_move()];
assert(0 <= ss->ply && ss->ply < MAX_PLY);
}
else
ss->staticEval = bestValue =
- (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval + 2 * Eval::Tempo;
+ (ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
+ : -(ss-1)->staticEval + 2 * Eval::Tempo;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
// be generated.
- MovePicker mp(pos, ttMove, depth, History, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, pos.this_thread()->history, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ((move = mp.next_move<false>()) != MOVE_NONE)
+ while ((move = mp.next_move()) != MOVE_NONE)
{
assert(is_ok(move));
givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
- ? ci.checkSq[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
+ ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
: pos.gives_check(move, ci);
// Futility pruning
// Detect non-capture evasions that are candidates to be pruned
evasionPrunable = InCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY
- && !pos.capture(move)
- && !pos.can_castle(pos.side_to_move());
+ && !pos.capture(move);
// Don't search moves with negative SEE values
if ( (!InCheck || evasionPrunable)
if (PvNode) // Update pv even in fail-high case
update_pv(ss->pv, move, (ss+1)->pv);
- if (PvNode && value < beta) // Update alpha here! Always alpha < beta
+ if (PvNode && value < beta) // Update alpha here!
{
alpha = value;
bestMove = move;
*pv = MOVE_NONE;
}
- // update_stats() updates killers, history, countermoves and followupmoves stats after a fail-high
- // of a quiet move.
- void update_stats(const Position& pos, Stack* ss, Move move, Depth depth, Move* quiets, int quietsCnt) {
+ // update_stats() updates killers, history, countermove and countermove
+ // history when a new quiet best move is found.
+
+ void update_stats(const Position& pos, Stack* ss, Move move,
+ Depth depth, Move* quiets, int quietsCnt) {
if (ss->killers[0] != move)
{
ss->killers[0] = move;
}
- // Increase history value of the cut-off move and decrease all the other
- // played quiet moves.
- Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
- History.update(pos.moved_piece(move), to_sq(move), bonus);
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);
- for (int i = 0; i < quietsCnt; ++i)
+ Square prevSq = to_sq((ss-1)->currentMove);
+ CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+ Thread* thisThread = pos.this_thread();
+
+ thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
+
+ if (is_ok((ss-1)->currentMove))
{
- Move m = quiets[i];
- History.update(pos.moved_piece(m), to_sq(m), -bonus);
+ thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
+ cmh.update(pos.moved_piece(move), to_sq(move), bonus);
}
- if (is_ok((ss-1)->currentMove))
+ // Decrease all the other played quiet moves
+ for (int i = 0; i < quietsCnt; ++i)
{
- Square prevMoveSq = to_sq((ss-1)->currentMove);
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, move);
+ thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+
+ if (is_ok((ss-1)->currentMove))
+ cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
- if (is_ok((ss-2)->currentMove) && (ss-1)->currentMove == (ss-1)->ttMove)
+ // Extra penalty for a quiet TT move in previous ply when it gets refuted
+ if ( (ss-1)->moveCount == 1
+ && !pos.captured_piece_type()
+ && is_ok((ss-2)->currentMove))
{
- Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
- Followupmoves.update(pos.piece_on(prevOwnMoveSq), prevOwnMoveSq, move);
+ Square prevPrevSq = to_sq((ss-2)->currentMove);
+ CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
+ prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);
}
}
Move Skill::pick_best(size_t multiPV) {
- // PRNG sequence should be non-deterministic, so we seed it with the time at init
- static PRNG rng(now());
+ const Search::RootMoveVector& rootMoves = Threads.main()->rootMoves;
+ static PRNG rng(now()); // PRNG sequence should be non-deterministic
// RootMoves are already sorted by score in descending order
- int variance = std::min(RootMoves[0].score - RootMoves[multiPV - 1].score, PawnValueMg);
+ Value topScore = rootMoves[0].score;
+ int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
int maxScore = -VALUE_INFINITE;
- // Choose best move. For each move score we add two terms both dependent on
+ // Choose best move. For each move score we add two terms, both dependent on
// weakness. One deterministic and bigger for weaker levels, and one random,
// then we choose the move with the resulting highest score.
for (size_t i = 0; i < multiPV; ++i)
{
// This is our magic formula
- int push = ( weakness * int(RootMoves[0].score - RootMoves[i].score)
- + variance * (rng.rand<unsigned>() % weakness)) / 128;
+ int push = ( weakness * int(topScore - rootMoves[i].score)
+ + delta * (rng.rand<unsigned>() % weakness)) / 128;
- if (RootMoves[i].score + push > maxScore)
+ if (rootMoves[i].score + push > maxScore)
{
- maxScore = RootMoves[i].score + push;
- best = RootMoves[i].pv[0];
+ maxScore = rootMoves[i].score + push;
+ best = rootMoves[i].pv[0];
}
}
+
return best;
}
+
+ // check_time() is used to print debug info and, more importantly, to detect
+ // when we are out of available time and thus stop the search.
+
+ void check_time() {
+
+ static TimePoint lastInfoTime = now();
+
+ int elapsed = Time.elapsed();
+ TimePoint tick = Limits.startTime + elapsed;
+
+ if (tick - lastInfoTime >= 1000)
+ {
+ lastInfoTime = tick;
+ dbg_print();
+ }
+
+ // An engine may not stop pondering until told so by the GUI
+ if (Limits.ponder)
+ return;
+
+ if (Limits.use_time_management())
+ {
+ bool stillAtFirstMove = Signals.firstRootMove.load(std::memory_order_relaxed)
+ && !Signals.failedLowAtRoot.load(std::memory_order_relaxed)
+ && elapsed > Time.available() * 3 / 4;
+
+ if (stillAtFirstMove || elapsed > Time.maximum() - 10)
+ Signals.stop = true;
+ }
+ else if (Limits.movetime && elapsed >= Limits.movetime)
+ Signals.stop = true;
+
+ else if (Limits.nodes && Threads.nodes_searched() >= Limits.nodes)
+ Signals.stop = true;
+ }
+
} // namespace
string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
std::stringstream ss;
- TimePoint elapsed = now() - SearchTime + 1;
- size_t multiPV = std::min((size_t)Options["MultiPV"], RootMoves.size());
- int selDepth = 0;
-
- for (Thread* th : Threads)
- if (th->maxPly > selDepth)
- selDepth = th->maxPly;
+ int elapsed = Time.elapsed() + 1;
+ const Search::RootMoveVector& rootMoves = pos.this_thread()->rootMoves;
+ size_t PVIdx = pos.this_thread()->PVIdx;
+ size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
+ uint64_t nodes_searched = Threads.nodes_searched();
for (size_t i = 0; i < multiPV; ++i)
{
continue;
Depth d = updated ? depth : depth - ONE_PLY;
- Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore;
+ Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
v = tb ? TB::Score : v;
ss << "info"
<< " depth " << d / ONE_PLY
- << " seldepth " << selDepth
+ << " seldepth " << pos.this_thread()->maxPly
<< " multipv " << i + 1
<< " score " << UCI::value(v);
if (!tb && i == PVIdx)
ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
- ss << " nodes " << pos.nodes_searched()
- << " nps " << pos.nodes_searched() * 1000 / elapsed;
+ ss << " nodes " << nodes_searched
+ << " nps " << nodes_searched * 1000 / elapsed;
if (elapsed > 1000) // Earlier makes little sense
ss << " hashfull " << TT.hashfull();
<< " time " << elapsed
<< " pv";
- for (Move m : RootMoves[i].pv)
+ for (Move m : rootMoves[i].pv)
ss << " " << UCI::move(m, pos.is_chess960());
}
TTEntry* tte = TT.probe(pos.key(), ttHit);
if (!ttHit || tte->move() != m) // Don't overwrite correct entries
- tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, m, VALUE_NONE, TT.generation());
+ tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE,
+ m, VALUE_NONE, TT.generation());
pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos)));
}
}
-/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move before
-/// exiting the search, for instance in case we stop the search during a fail high at
-/// root. We try hard to have a ponder move to return to the GUI, otherwise in case of
-/// 'ponder on' we have nothing to think on.
+/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move
+/// before exiting the search, for instance in case we stop the search during a
+/// fail high at root. We try hard to have a ponder move to return to the GUI,
+/// otherwise in case of 'ponder on' we have nothing to think on.
bool RootMove::extract_ponder_from_tt(Position& pos)
{
return false;
}
-
-
-/// Thread::idle_loop() is where the thread is parked when it has no work to do
-
-void Thread::idle_loop() {
-
- // Pointer 'this_sp' is not null only if we are called from split(), and not
- // at the thread creation. This means we are the split point's master.
- SplitPoint* this_sp = activeSplitPoint;
-
- assert(!this_sp || (this_sp->master == this && searching));
-
- while (!exit)
- {
- // If this thread has been assigned work, launch a search
- while (searching)
- {
- Threads.spinlock.acquire();
-
- assert(activeSplitPoint);
-
- SplitPoint* sp = activeSplitPoint;
-
- Threads.spinlock.release();
-
- Stack stack[MAX_PLY+4], *ss = stack+2; // To allow referencing (ss-2) and (ss+2)
- Position pos(*sp->pos, this);
-
- std::memcpy(ss-2, sp->ss-2, 5 * sizeof(Stack));
- ss->splitPoint = sp;
-
- sp->spinlock.acquire();
-
- assert(activePosition == nullptr);
-
- activePosition = &pos;
-
- if (sp->nodeType == NonPV)
- search<NonPV, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
-
- else if (sp->nodeType == PV)
- search<PV, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
-
- else if (sp->nodeType == Root)
- search<Root, true>(pos, ss, sp->alpha, sp->beta, sp->depth, sp->cutNode);
-
- else
- assert(false);
-
- assert(searching);
-
- searching = false;
- activePosition = nullptr;
- sp->slavesMask.reset(idx);
- sp->allSlavesSearching = false;
- sp->nodes += pos.nodes_searched();
-
- // Wake up the master thread so to allow it to return from the idle
- // loop in case we are the last slave of the split point.
- if (this != sp->master && sp->slavesMask.none())
- {
- assert(!sp->master->searching);
-
- sp->master->notify_one();
- }
-
- // After releasing the lock we can't access any SplitPoint related data
- // in a safe way because it could have been released under our feet by
- // the sp master.
- sp->spinlock.release();
-
- // Try to late join to another split point if none of its slaves has
- // already finished.
- SplitPoint* bestSp = NULL;
- int minLevel = INT_MAX;
-
- for (Thread* th : Threads)
- {
- const size_t size = th->splitPointsSize; // Local copy
- sp = size ? &th->splitPoints[size - 1] : nullptr;
-
- if ( sp
- && sp->allSlavesSearching
- && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
- && can_join(sp))
- {
- assert(this != th);
- assert(!(this_sp && this_sp->slavesMask.none()));
- assert(Threads.size() > 2);
-
- // Prefer to join to SP with few parents to reduce the probability
- // that a cut-off occurs above us, and hence we waste our work.
- int level = 0;
- for (SplitPoint* p = th->activeSplitPoint; p; p = p->parentSplitPoint)
- level++;
-
- if (level < minLevel)
- {
- bestSp = sp;
- minLevel = level;
- }
- }
- }
-
- if (bestSp)
- {
- sp = bestSp;
-
- // Recheck the conditions under lock protection
- Threads.spinlock.acquire();
- sp->spinlock.acquire();
-
- if ( sp->allSlavesSearching
- && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT
- && can_join(sp))
- {
- sp->slavesMask.set(idx);
- activeSplitPoint = sp;
- searching = true;
- }
-
- sp->spinlock.release();
- Threads.spinlock.release();
- }
- }
-
- // Avoid races with notify_one() fired from last slave of the split point
- std::unique_lock<std::mutex> lk(mutex);
-
- // If we are master and all slaves have finished then exit idle_loop
- if (this_sp && this_sp->slavesMask.none())
- {
- assert(!searching);
- break;
- }
-
- // If we are not searching, wait for a condition to be signaled instead of
- // wasting CPU time polling for work.
- if (!searching && !exit)
- sleepCondition.wait(lk);
- }
-}
-
-
-/// check_time() is called by the timer thread when the timer triggers. It is
-/// used to print debug info and, more importantly, to detect when we are out of
-/// available time and thus stop the search.
-
-void check_time() {
-
- static TimePoint lastInfoTime = now();
- TimePoint elapsed = now() - SearchTime;
-
- if (now() - lastInfoTime >= 1000)
- {
- lastInfoTime = now();
- dbg_print();
- }
-
- // An engine may not stop pondering until told so by the GUI
- if (Limits.ponder)
- return;
-
- if (Limits.use_time_management())
- {
- bool stillAtFirstMove = Signals.firstRootMove
- && !Signals.failedLowAtRoot
- && elapsed > TimeMgr.available_time() * 75 / 100;
-
- if ( stillAtFirstMove
- || elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution)
- Signals.stop = true;
- }
- else if (Limits.movetime && elapsed >= Limits.movetime)
- Signals.stop = true;
-
- else if (Limits.nodes)
- {
- Threads.spinlock.acquire();
-
- int64_t nodes = RootPos.nodes_searched();
-
- // Loop across all split points and sum accumulated SplitPoint nodes plus
- // all the currently active positions nodes.
- for (Thread* th : Threads)
- for (size_t i = 0; i < th->splitPointsSize; ++i)
- {
- SplitPoint& sp = th->splitPoints[i];
-
- sp.spinlock.acquire();
-
- nodes += sp.nodes;
-
- for (size_t idx = 0; idx < Threads.size(); ++idx)
- if (sp.slavesMask.test(idx) && Threads[idx]->activePosition)
- nodes += Threads[idx]->activePosition->nodes_searched();
-
- sp.spinlock.release();
- }
-
- Threads.spinlock.release();
-
- if (nodes >= Limits.nodes)
- Signals.stop = true;
- }
-}
projects / stockfish / blobdiff