LimitsType Limits;
RootMoveVector RootMoves;
Position RootPos;
- Time::point SearchTime;
StateStackPtr SetupStates;
}
// Different node types, used as template parameter
enum NodeType { Root, PV, NonPV };
- // Dynamic razoring margin based on depth
- inline Value razor_margin(Depth d) { return Value(512 + 32 * d); }
+ // Razoring and futility margin based on depth
+ Value razor_margin(Depth d) { return Value(512 + 32 * d); }
+ Value futility_margin(Depth d) { return Value(200 * d); }
- // Futility lookup tables (initialized at startup) and their access functions
- int FutilityMoveCounts[2][16]; // [improving][depth]
+ // Futility and reductions lookup tables, initialized at startup
+ int FutilityMoveCounts[2][16]; // [improving][depth]
+ Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- inline Value futility_margin(Depth d) {
- return Value(200 * d);
+ 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)];
}
- // Reduction lookup tables (initialized at startup) and their access function
- int8_t Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
+ // Skill struct is used to implement strength limiting
+ struct Skill {
+ Skill(int l) : level(l) {}
+ bool enabled() const { return level < 20; }
+ bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
+ Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); }
+ Move pick_best(size_t multiPV);
- template <bool PvNode> inline Depth reduction(bool i, Depth d, int mn) {
- return (Depth) Reductions[PvNode][i][std::min(int(d), 63)][std::min(mn, 63)];
- }
+ int level;
+ Move best = MOVE_NONE;
+ };
+
+ // 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];
+ };
size_t PVIdx;
- TimeManager TimeMgr;
+ EasyMoveManager EasyMove;
double BestMoveChanges;
Value DrawValue[COLOR_NB];
HistoryStats History;
- GainsStats Gains;
- MovesStats Countermoves, Followupmoves;
+ CounterMovesHistoryStats CounterMovesHistory;
+ MovesStats Countermoves;
template <NodeType NT, bool SpNode>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
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);
- string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta);
-
- struct Skill {
- Skill(int l, size_t rootSize) : level(l),
- candidates(l < 20 ? std::min(4, (int)rootSize) : 0),
- best(MOVE_NONE) {}
- ~Skill() {
- if (candidates) // Swap best PV line with the sub-optimal one
- std::swap(RootMoves[0], *std::find(RootMoves.begin(),
- RootMoves.end(), best ? best : pick_move()));
- }
-
- size_t candidates_size() const { return candidates; }
- bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
- Move pick_move();
-
- int level;
- size_t candidates;
- Move best;
- };
} // namespace
void Search::init() {
- // Init reductions array
- for (int d = 1; d < 64; ++d)
- for (int mc = 1; mc < 64; ++mc)
- {
- double pvRed = 0.00 + log(double(d)) * log(double(mc)) / 3.00;
- double nonPVRed = 0.33 + log(double(d)) * log(double(mc)) / 2.25;
+ const double K[][2] = {{ 0.83, 2.25 }, { 0.50, 3.00 }};
- Reductions[1][1][d][mc] = int8_t( pvRed >= 1.0 ? pvRed + 0.5: 0);
- Reductions[0][1][d][mc] = int8_t(nonPVRed >= 1.0 ? nonPVRed + 0.5: 0);
+ for (int pv = 0; pv <= 1; ++pv)
+ for (int imp = 0; imp <= 1; ++imp)
+ for (int d = 1; d < 64; ++d)
+ for (int mc = 1; mc < 64; ++mc)
+ {
+ double r = K[pv][0] + log(d) * log(mc) / K[pv][1];
- Reductions[1][0][d][mc] = Reductions[1][1][d][mc];
- Reductions[0][0][d][mc] = Reductions[0][1][d][mc];
+ if (r >= 1.5)
+ Reductions[pv][imp][d][mc] = int(r) * ONE_PLY;
- // Increase reduction when eval is not improving
- if (Reductions[0][0][d][mc] >= 2)
- Reductions[0][0][d][mc] += 1;
- }
+ // Increase reduction when eval is not improving
+ if (!pv && !imp && Reductions[pv][imp][d][mc] >= 2 * ONE_PLY)
+ Reductions[pv][imp][d][mc] += ONE_PLY;
+ }
- // Init futility move count array
for (int d = 0; d < 16; ++d)
{
FutilityMoveCounts[0][d] = int(2.4 + 0.773 * pow(d + 0.00, 1.8));
}
+/// Search::reset() clears all search memory, to obtain reproducible search results
+
+void Search::reset () {
+
+ TT.clear();
+ History.clear();
+ CounterMovesHistory.clear();
+ 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>
CheckInfo ci(pos);
const bool leaf = (depth == 2 * ONE_PLY);
- for (MoveList<LEGAL> it(pos); *it; ++it)
+ for (const auto& m : MoveList<LEGAL>(pos))
{
if (Root && depth <= ONE_PLY)
cnt = 1, nodes++;
else
{
- pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
+ pos.do_move(m, st, pos.gives_check(m, ci));
cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
nodes += cnt;
- pos.undo_move(*it);
+ pos.undo_move(m);
}
if (Root)
- sync_cout << UCI::move(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
+ sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl;
}
return nodes;
}
void Search::think() {
- TimeMgr.init(Limits, RootPos.side_to_move(), RootPos.game_ply());
+ Color us = RootPos.side_to_move();
+ Time.init(Limits, us, RootPos.game_ply(), now());
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;
if (RootMoves.empty())
{
- RootMoves.push_back(MOVE_NONE);
+ RootMoves.push_back(RootMove(MOVE_NONE));
sync_cout << "info depth 0 score "
<< UCI::value(RootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
}
}
- for (size_t i = 0; i < Threads.size(); ++i)
- Threads[i]->maxPly = 0;
+ for (Thread* th : Threads)
+ {
+ th->maxPly = 0;
+ th->notify_one(); // Wake up all the threads
+ }
Threads.timer->run = true;
- Threads.timer->notify_one(); // Wake up the recurring timer
+ Threads.timer->notify_one(); // Start the recurring timer
id_loop(RootPos); // Let's start searching !
Threads.timer->run = false;
}
+ // 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] - RootPos.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
Depth depth;
Value bestValue, alpha, beta, delta;
+ Move easyMove = EasyMove.get(pos.key());
+ EasyMove.clear();
+
std::memset(ss-2, 0, 5 * sizeof(Stack));
depth = DEPTH_ZERO;
beta = VALUE_INFINITE;
TT.new_search();
- History.clear();
- Gains.clear();
- Countermoves.clear();
- Followupmoves.clear();
size_t multiPV = Options["MultiPV"];
- Skill skill(Options["Skill Level"], RootMoves.size());
+ 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);
- // Do we have to play with skill handicap? In this case enable MultiPV search
- // that we will use behind the scenes to retrieve a set of possible moves.
- multiPV = std::max(multiPV, skill.candidates_size());
+ multiPV = std::min(multiPV, RootMoves.size());
// Iterative deepening loop until requested to stop or target depth reached
while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
// 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 (size_t i = 0; i < RootMoves.size(); ++i)
- RootMoves[i].previousScore = RootMoves[i].score;
+ for (RootMove& rm : RootMoves)
+ rm.previousScore = rm.score;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
+ for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
{
// Reset aspiration window starting size
if (depth >= 5 * ONE_PLY)
// the UI) before a re-search.
if ( multiPV == 1
&& (bestValue <= alpha || bestValue >= beta)
- && Time::now() - SearchTime > 3000)
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ && Time.elapsed() > 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 (Signals.stop)
sync_cout << "info nodes " << RootPos.nodes_searched()
- << " time " << Time::now() - SearchTime << sync_endl;
+ << " time " << Time.elapsed() << sync_endl;
- else if ( PVIdx + 1 == std::min(multiPV, RootMoves.size())
- || Time::now() - SearchTime > 3000)
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ else if (PVIdx + 1 == multiPV || Time.elapsed() > 3000)
+ sync_cout << UCI::pv(pos, depth, alpha, beta) << sync_endl;
}
- // If skill levels are enabled and time is up, pick a sub-optimal best move
- if (skill.candidates_size() && skill.time_to_pick(depth))
- skill.pick_move();
+ // 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);
// Have we found a "mate in x"?
if ( Limits.mate
Signals.stop = true;
// Do we have time for the next iteration? Can we stop searching now?
- if (Limits.use_time_management() && !Signals.stop && !Signals.stopOnPonderhit)
+ if (Limits.use_time_management())
{
- // 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
- || Time::now() - SearchTime > TimeMgr.available_time())
+ if (!Signals.stop && !Signals.stopOnPonderhit)
{
- // 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;
+ // Take some extra time if the best move has changed
+ if (depth > 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 (RootMoves[0].pv.size() >= 3)
+ EasyMove.update(pos, RootMoves[0].pv);
+ else
+ EasyMove.clear();
}
}
+
+ // 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)));
}
splitPoint = ss->splitPoint;
bestMove = splitPoint->bestMove;
bestValue = splitPoint->bestValue;
- tte = NULL;
+ tte = nullptr;
ttHit = false;
ttMove = excludedMove = MOVE_NONE;
ttValue = VALUE_NONE;
goto moves_loop;
}
- moveCount = quietCount = 0;
+ moveCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
ss->ply = (ss-1)->ply + 1;
ss->ttMove = ttMove = RootNode ? RootMoves[PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE;
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_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 a fail high/low. We don't prune at PV nodes
if ( !PvNode
&& ttHit
&& tte->depth() >= depth
{
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)
- update_stats(pos, ss, ttMove, depth, NULL, 0);
+ // 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;
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()))
+ && ttMove == MOVE_NONE)
{
if ( depth <= ONE_PLY
&& eval + razor_margin(3 * ONE_PLY) <= alpha)
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, History, CounterMovesHistory, PieceValue[MG][pos.captured_piece_type()]);
CheckInfo ci(pos);
while ((move = mp.next_move<false>()) != MOVE_NONE)
if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
- pos.do_move(move, st, ci, pos.gives_check(move, ci));
+ pos.do_move(move, st, pos.gives_check(move, ci));
value = -search<NonPV, false>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
&& !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, false>(pos, ss, alpha, beta, d, true);
ss->skipEarlyPruning = false;
tte = TT.probe(posKey, ttHit);
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 };
-
- Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
- Move followupmoves[] = { Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].first,
- Followupmoves[pos.piece_on(prevOwnMoveSq)][prevOwnMoveSq].second };
+ Move countermove = Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq];
- MovePicker mp(pos, ttMove, depth, History, countermoves, followupmoves, ss);
+ MovePicker mp(pos, ttMove, depth, History, CounterMovesHistory, countermove, ss);
CheckInfo ci(pos);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
if (!pos.legal(move, ci.pinned))
continue;
- moveCount = ++splitPoint->moveCount;
- splitPoint->mutex.unlock();
+ ss->moveCount = moveCount = ++splitPoint->moveCount;
+ splitPoint->spinlock.release();
}
else
- ++moveCount;
+ ss->moveCount = ++moveCount;
if (RootNode)
{
Signals.firstRootMove = (moveCount == 1);
- if (thisThread == Threads.main() && Time::now() - SearchTime > 3000)
+ if (thisThread == Threads.main() && Time.elapsed() > 3000)
sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << UCI::move(move, pos.is_chess960())
<< " currmovenumber " << moveCount + PVIdx << sync_endl;
}
if (PvNode)
- (ss+1)->pv = NULL;
+ (ss+1)->pv = nullptr;
extension = DEPTH_ZERO;
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
&& moveCount >= FutilityMoveCounts[improving][depth])
{
if (SpNode)
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
continue;
}
// 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)
{
if (SpNode)
{
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
if (bestValue > splitPoint->bestValue)
splitPoint->bestValue = bestValue;
}
if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
{
if (SpNode)
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
continue;
}
}
// Speculative prefetch as early as possible
- prefetch((char*)TT.first_entry(pos.key_after(move)));
+ prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
if (!RootNode && !SpNode && !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, ci, givesCheck);
+ pos.do_move(move, st, givesCheck);
// Step 15. Reduced depth search (LMR). If the move fails high it will be
// re-searched at full depth.
ss->reduction = reduction<PvNode>(improving, depth, moveCount);
if ( (!PvNode && cutNode)
- || History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO)
+ || ( History[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO
+ && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq]
+ [pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO))
ss->reduction += ONE_PLY;
- if (move == countermoves[0] || move == countermoves[1])
+ if ( History[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO
+ && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq]
+ [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
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);
- }
-
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
}
// Step 18. Check for new best move
if (SpNode)
{
- splitPoint->mutex.lock();
+ splitPoint->spinlock.acquire();
bestValue = splitPoint->bestValue;
alpha = splitPoint->alpha;
}
if (value > alpha)
{
+ // If there is an easy move for this position, clear it if unstable
+ if ( PvNode
+ && EasyMove.get(pos.key())
+ && (move != EasyMove.get(pos.key()) || moveCount > 1))
+ EasyMove.clear();
+
bestMove = SpNode ? splitPoint->bestMove = move : move;
if (PvNode && !RootNode) // Update pv even in fail-high case
}
}
+ if (!SpNode && !captureOrPromotion && move != bestMove && quietCount < 64)
+ quietsSearched[quietCount++] = move;
+
// Step 19. Check for splitting the search
if ( !SpNode
&& Threads.size() >= 2
&& depth >= Threads.minimumSplitDepth
&& ( !thisThread->activeSplitPoint
- || !thisThread->activeSplitPoint->allSlavesSearching)
+ || !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);
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);
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
// 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, History, CounterMovesHistory, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
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)
continue;
// Speculative prefetch as early as possible
- prefetch((char*)TT.first_entry(pos.key_after(move)));
+ prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
if (!pos.legal(move, ci.pinned))
ss->currentMove = move;
// Make and search the move
- pos.do_move(move, st, ci, givesCheck);
+ pos.do_move(move, st, givesCheck);
value = givesCheck ? -qsearch<NT, true>(pos, ss+1, -beta, -alpha, depth - ONE_PLY)
: -qsearch<NT, false>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(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 history and
+ // countermoves stats for a quiet best move.
+
+ 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));
+
+ Square prevSq = to_sq((ss-1)->currentMove);
+ HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+
History.update(pos.moved_piece(move), to_sq(move), bonus);
- for (int i = 0; i < quietsCnt; ++i)
+
+ if (is_ok((ss-1)->currentMove))
{
- Move m = quiets[i];
- History.update(pos.moved_piece(m), to_sq(m), -bonus);
+ 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);
+ 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 PV move in previous ply when it gets refuted
+ if (is_ok((ss-2)->currentMove) && (ss-1)->moveCount == 1 && !pos.captured_piece_type())
{
- Square prevOwnMoveSq = to_sq((ss-2)->currentMove);
- Followupmoves.update(pos.piece_on(prevOwnMoveSq), prevOwnMoveSq, move);
+ Square prevPrevSq = to_sq((ss-2)->currentMove);
+ HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
+ ttMoveCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1);
}
}
- // When playing with a strength handicap, choose best move among the first 'candidates'
- // RootMoves using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
+ // When playing with strength handicap, choose best move among a set of RootMoves
+ // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- Move Skill::pick_move() {
+ 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(Time::now());
+ static PRNG rng(now());
// RootMoves are already sorted by score in descending order
- int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg);
+ int variance = std::min(RootMoves[0].score - RootMoves[multiPV - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
int maxScore = -VALUE_INFINITE;
- best = MOVE_NONE;
// Choose best move. For each move score we add two terms both dependent on
- // weakness. One deterministic and bigger for weaker moves, and one random,
+ // 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 < candidates; ++i)
+ for (size_t i = 0; i < multiPV; ++i)
{
- int score = RootMoves[i].score;
-
- // Don't allow crazy blunders even at very low skills
- if (i > 0 && RootMoves[i - 1].score > score + 2 * PawnValueMg)
- break;
-
// This is our magic formula
- score += ( weakness * int(RootMoves[0].score - score)
- + variance * (rng.rand<unsigned>() % weakness)) / 128;
+ int push = ( weakness * int(RootMoves[0].score - RootMoves[i].score)
+ + variance * (rng.rand<unsigned>() % weakness)) / 128;
- if (score > maxScore)
+ if (RootMoves[i].score + push > maxScore)
{
- maxScore = score;
+ maxScore = RootMoves[i].score + push;
best = RootMoves[i].pv[0];
}
}
return best;
}
+} // namespace
- // uci_pv() formats PV information according to the UCI protocol. UCI
- // requires that all (if any) unsearched PV lines are sent using a previous
- // search score.
- string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta) {
+/// UCI::pv() formats PV information according to the UCI protocol. UCI requires
+/// that all (if any) unsearched PV lines are sent using a previous search score.
- std::stringstream ss;
- Time::point elapsed = Time::now() - SearchTime + 1;
- size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
- int selDepth = 0;
+string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
- for (size_t i = 0; i < Threads.size(); ++i)
- if (Threads[i]->maxPly > selDepth)
- selDepth = Threads[i]->maxPly;
+ std::stringstream ss;
+ int elapsed = Time.elapsed() + 1;
+ size_t multiPV = std::min((size_t)Options["MultiPV"], RootMoves.size());
+ int selDepth = 0;
- for (size_t i = 0; i < uciPVSize; ++i)
- {
- bool updated = (i <= PVIdx);
+ for (Thread* th : Threads)
+ if (th->maxPly > selDepth)
+ selDepth = th->maxPly;
- if (depth == ONE_PLY && !updated)
- continue;
+ for (size_t i = 0; i < multiPV; ++i)
+ {
+ bool updated = (i <= PVIdx);
- Depth d = updated ? depth : depth - ONE_PLY;
- Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore;
+ if (depth == ONE_PLY && !updated)
+ continue;
- bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
- v = tb ? TB::Score : v;
+ Depth d = updated ? depth : depth - ONE_PLY;
+ Value v = updated ? RootMoves[i].score : RootMoves[i].previousScore;
- if (ss.rdbuf()->in_avail()) // Not at first line
- ss << "\n";
+ bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
+ v = tb ? TB::Score : v;
- ss << "info depth " << d / ONE_PLY
- << " seldepth " << selDepth
- << " multipv " << i + 1
- << " score " << UCI::value(v);
+ if (ss.rdbuf()->in_avail()) // Not at first line
+ ss << "\n";
- if (!tb && i == PVIdx)
- ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
+ ss << "info"
+ << " depth " << d / ONE_PLY
+ << " seldepth " << selDepth
+ << " multipv " << i + 1
+ << " score " << UCI::value(v);
- ss << " nodes " << pos.nodes_searched()
- << " nps " << pos.nodes_searched() * 1000 / elapsed
- << " tbhits " << TB::Hits
- << " time " << elapsed
- << " pv";
+ if (!tb && i == PVIdx)
+ ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
- for (size_t j = 0; j < RootMoves[i].pv.size(); ++j)
- ss << " " << UCI::move(RootMoves[i].pv[j], pos.is_chess960());
- }
+ ss << " nodes " << pos.nodes_searched()
+ << " nps " << pos.nodes_searched() * 1000 / elapsed;
+
+ if (elapsed > 1000) // Earlier makes little sense
+ ss << " hashfull " << TT.hashfull();
+
+ ss << " tbhits " << TB::Hits
+ << " time " << elapsed
+ << " pv";
- return ss.str();
+ for (Move m : RootMoves[i].pv)
+ ss << " " << UCI::move(m, pos.is_chess960());
}
-} // namespace
+ return ss.str();
+}
/// RootMove::insert_pv_in_tt() is called at the end of a search iteration, and
void RootMove::insert_pv_in_tt(Position& pos) {
StateInfo state[MAX_PLY], *st = state;
- size_t idx = 0;
+ bool ttHit;
- for ( ; idx < pv.size(); ++idx)
+ for (Move m : pv)
{
- bool ttHit;
- TTEntry* tte = TT.probe(pos.key(), ttHit);
+ assert(MoveList<LEGAL>(pos).contains(m));
- if (!ttHit || tte->move() != pv[idx]) // Don't overwrite correct entries
- tte->save(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[idx], VALUE_NONE, TT.generation());
+ TTEntry* tte = TT.probe(pos.key(), ttHit);
- assert(MoveList<LEGAL>(pos).contains(pv[idx]));
+ 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());
- pos.do_move(pv[idx], *st++);
+ pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos)));
}
- while (idx) pos.undo_move(pv[--idx]);
+ for (size_t i = pv.size(); i > 0; )
+ pos.undo_move(pv[--i]);
}
/// 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.
-Move RootMove::extract_ponder_from_tt(Position& pos)
+bool RootMove::extract_ponder_from_tt(Position& pos)
{
StateInfo st;
- bool found;
+ bool ttHit;
assert(pv.size() == 1);
- pos.do_move(pv[0], st);
- TTEntry* tte = TT.probe(pos.key(), found);
- Move m = found ? tte->move() : MOVE_NONE;
- if (!MoveList<LEGAL>(pos).contains(m))
- m = MOVE_NONE;
-
+ pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos)));
+ TTEntry* tte = TT.probe(pos.key(), ttHit);
pos.undo_move(pv[0]);
- pv.push_back(m);
- return m;
+
+ if (ttHit)
+ {
+ Move m = tte->move(); // Local copy to be SMP safe
+ if (MoveList<LEGAL>(pos).contains(m))
+ return pv.push_back(m), true;
+ }
+
+ return false;
}
// 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 = splitPointsSize ? activeSplitPoint : NULL;
+ SplitPoint* this_sp = activeSplitPoint;
- assert(!this_sp || (this_sp->masterThread == this && searching));
+ assert(!this_sp || (this_sp->master == this && searching));
- while (!exit)
+ while (!exit && !(this_sp && this_sp->slavesMask.none()))
{
// If this thread has been assigned work, launch a search
while (searching)
{
- Threads.mutex.lock();
+ spinlock.acquire();
assert(activeSplitPoint);
SplitPoint* sp = activeSplitPoint;
- Threads.mutex.unlock();
+ 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->mutex.lock();
+ sp->spinlock.acquire();
- assert(activePosition == NULL);
+ assert(activePosition == nullptr);
activePosition = &pos;
assert(searching);
searching = false;
- activePosition = NULL;
+ 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->masterThread
- && sp->slavesMask.none())
- {
- assert(!sp->masterThread->searching);
- sp->masterThread->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->mutex.unlock();
+ sp->spinlock.release();
// Try to late join to another split point if none of its slaves has
// already finished.
- if (Threads.size() > 2)
- for (size_t i = 0; i < Threads.size(); ++i)
+ 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))
{
- const int size = Threads[i]->splitPointsSize; // Local copy
- sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+ 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 ( sp
- && sp->allSlavesSearching
- && available_to(Threads[i]))
+ if (level < minLevel)
{
- // Recheck the conditions under lock protection
- Threads.mutex.lock();
- sp->mutex.lock();
-
- if ( sp->allSlavesSearching
- && available_to(Threads[i]))
- {
- sp->slavesMask.set(idx);
- activeSplitPoint = sp;
- searching = true;
- }
-
- sp->mutex.unlock();
- Threads.mutex.unlock();
-
- break; // Just a single attempt
+ bestSp = sp;
+ minLevel = level;
}
}
- }
+ }
- // Grab the lock to avoid races with Thread::notify_one()
- mutex.lock();
+ if (bestSp)
+ {
+ sp = bestSp;
- // If we are master and all slaves have finished then exit idle_loop
- if (this_sp && this_sp->slavesMask.none())
- {
- assert(!searching);
- mutex.unlock();
- break;
+ // Recheck the conditions under lock protection
+ sp->spinlock.acquire();
+
+ if ( sp->allSlavesSearching
+ && sp->slavesMask.count() < MAX_SLAVES_PER_SPLITPOINT)
+ {
+ spinlock.acquire();
+
+ if (can_join(sp))
+ {
+ sp->slavesMask.set(idx);
+ activeSplitPoint = sp;
+ searching = true;
+ }
+
+ spinlock.release();
+ }
+
+ sp->spinlock.release();
+ }
}
- // 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(mutex);
+ // If search is finished then sleep, otherwise just yield
+ if (!Threads.main()->thinking)
+ {
+ assert(!this_sp);
- mutex.unlock();
+ std::unique_lock<Mutex> lk(mutex);
+ while (!exit && !Threads.main()->thinking)
+ sleepCondition.wait(lk);
+ }
+ else
+ std::this_thread::yield(); // Wait for a new job or for our slaves to finish
}
}
void check_time() {
- static Time::point lastInfoTime = Time::now();
- Time::point elapsed = Time::now() - SearchTime;
+ static TimePoint lastInfoTime = now();
+ int elapsed = Time.elapsed();
- if (Time::now() - lastInfoTime >= 1000)
+ if (now() - lastInfoTime >= 1000)
{
- lastInfoTime = Time::now();
+ lastInfoTime = now();
dbg_print();
}
{
bool stillAtFirstMove = Signals.firstRootMove
&& !Signals.failedLowAtRoot
- && elapsed > TimeMgr.available_time() * 75 / 100;
+ && elapsed > Time.available() * 75 / 100;
if ( stillAtFirstMove
- || elapsed > TimeMgr.maximum_time() - 2 * TimerThread::Resolution)
+ || elapsed > Time.maximum() - 2 * TimerThread::Resolution)
Signals.stop = true;
}
else if (Limits.movetime && elapsed >= Limits.movetime)
else if (Limits.nodes)
{
- Threads.mutex.lock();
-
int64_t nodes = RootPos.nodes_searched();
// Loop across all split points and sum accumulated SplitPoint nodes plus
// all the currently active positions nodes.
- for (size_t i = 0; i < Threads.size(); ++i)
- for (int j = 0; j < Threads[i]->splitPointsSize; ++j)
+ // FIXME: Racy...
+ for (Thread* th : Threads)
+ for (size_t i = 0; i < th->splitPointsSize; ++i)
{
- SplitPoint& sp = Threads[i]->splitPoints[j];
+ SplitPoint& sp = th->splitPoints[i];
- sp.mutex.lock();
+ sp.spinlock.acquire();
nodes += sp.nodes;
if (sp.slavesMask.test(idx) && Threads[idx]->activePosition)
nodes += Threads[idx]->activePosition->nodes_searched();
- sp.mutex.unlock();
+ sp.spinlock.release();
}
- Threads.mutex.unlock();
-
if (nodes >= Limits.nodes)
Signals.stop = true;
}
projects / stockfish / blobdiff