int FutilityMoveCounts[2][16]; // [improving][depth]
int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
- // Threshold used for countermoves based pruning
- const int CounterMovePruneThreshold = 0;
-
template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
}
// Skill structure is used to implement strength limit
struct Skill {
- Skill(int l) : level(l) {}
+ explicit 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);
int level;
Move best = MOVE_NONE;
};
- // EasyMoveManager structure is used to detect an 'easy move'. When the PV is stable
- // across multiple search iterations, we can quickly 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 the 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.do_move(newPv[1], st[1]);
- expectedPosKey = pos.key();
- pos.undo_move(newPv[1]);
- pos.undo_move(newPv[0]);
- }
- }
-
- int stableCnt;
- Key expectedPosKey;
- Move pv[3];
- };
-
- EasyMoveManager EasyMove;
Value DrawValue[COLOR_NB];
template <NodeType NT>
void update_pv(Move* pv, Move move, Move* childPv);
void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus);
+ bool pv_is_draw(Position& pos);
+
+ // perft() is our utility to verify move generation. All the leaf nodes up
+ // to the given depth are generated and counted, and the sum is returned.
+ template<bool Root>
+ uint64_t perft(Position& pos, Depth depth) {
+
+ StateInfo st;
+ uint64_t cnt, nodes = 0;
+ const bool leaf = (depth == 2 * ONE_PLY);
+
+ for (const auto& m : MoveList<LEGAL>(pos))
+ {
+ if (Root && depth <= ONE_PLY)
+ cnt = 1, nodes++;
+ else
+ {
+ pos.do_move(m, st);
+ cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
+ nodes += cnt;
+ pos.undo_move(m);
+ }
+ if (Root)
+ sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl;
+ }
+ return nodes;
+ }
} // namespace
TT.clear();
for (Thread* th : Threads)
- {
- th->counterMoves.fill(MOVE_NONE);
- th->mainHistory.fill(0);
-
- for (auto& to : th->contHistory)
- for (auto& h : to)
- h.fill(0);
-
- th->contHistory[NO_PIECE][0].fill(CounterMovePruneThreshold - 1);
- }
+ th->clear();
Threads.main()->callsCnt = 0;
Threads.main()->previousScore = VALUE_INFINITE;
+ Threads.main()->previousTimeReduction = 1;
}
-/// 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 is returned.
-template<bool Root>
-uint64_t Search::perft(Position& pos, Depth depth) {
-
- StateInfo st;
- uint64_t cnt, nodes = 0;
- const bool leaf = (depth == 2 * ONE_PLY);
-
- for (const auto& m : MoveList<LEGAL>(pos))
- {
- if (Root && depth <= ONE_PLY)
- cnt = 1, nodes++;
- else
- {
- pos.do_move(m, st);
- cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
- nodes += cnt;
- pos.undo_move(m);
- }
- if (Root)
- sync_cout << UCI::move(m, pos.is_chess960()) << ": " << cnt << sync_endl;
- }
- return nodes;
-}
-
-template uint64_t Search::perft<true>(Position&, Depth);
-
-
/// MainThread::search() is called by the main thread when the program receives
/// the UCI 'go' command. It searches from the root position and outputs the "bestmove".
void MainThread::search() {
+ if (Limits.perft)
+ {
+ nodes = perft<true>(rootPos, Limits.perft * ONE_PLY);
+ sync_cout << "\nNodes searched: " << nodes << "\n" << sync_endl;
+ return;
+ }
+
Color us = rootPos.side_to_move();
Time.init(Limits, us, rootPos.game_ply());
TT.new_search();
if (rootMoves.empty())
{
- rootMoves.push_back(RootMove(MOVE_NONE));
+ rootMoves.emplace_back(MOVE_NONE);
sync_cout << "info depth 0 score "
<< UCI::value(rootPos.checkers() ? -VALUE_MATE : VALUE_DRAW)
<< sync_endl;
Thread::search(); // Let's start searching!
}
- // When playing in 'nodes as time' mode, subtract the searched nodes from
- // the available ones before exiting.
- 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
// Threads.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
// GUI sends a "stop" or "ponderhit" command. We therefore simply wait here
// until the GUI sends one of those commands (which also raises Threads.stop).
- if (!Threads.stop && (Threads.ponder || Limits.infinite))
- {
- Threads.stopOnPonderhit = true;
- wait(Threads.stop);
- }
+ Threads.stopOnPonderhit = true;
+
+ while (!Threads.stop && (Threads.ponder || Limits.infinite))
+ {} // Busy wait for a stop or a ponder reset
- // Stop the threads if not already stopped
+ // Stop the threads if not already stopped (also raise the stop if
+ // "ponderhit" just reset Threads.ponder).
Threads.stop = true;
// Wait until all threads have finished
if (th != this)
th->wait_for_search_finished();
+ // When playing in 'nodes as time' mode, subtract the searched nodes from
+ // the available ones before exiting.
+ if (Limits.npmsec)
+ Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
+
// Check if there are threads with a better score than main thread
Thread* bestThread = this;
- if ( !this->easyMovePlayed
- && Options["MultiPV"] == 1
+ if ( Options["MultiPV"] == 1
&& !Limits.depth
&& !Skill(Options["Skill Level"]).enabled()
&& rootMoves[0].pv[0] != MOVE_NONE)
Depth depthDiff = th->completedDepth - bestThread->completedDepth;
Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score;
- if (scoreDiff > 0 && depthDiff >= 0)
+ // Select the thread with the best score, always if it is a mate
+ if ( scoreDiff > 0
+ && (depthDiff >= 0 || th->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY))
bestThread = th;
}
}
void Thread::search() {
- Stack stack[MAX_PLY+7], *ss = stack+4; // To allow referencing (ss-4) and (ss+2)
+ Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2)
Value bestValue, alpha, beta, delta;
- Move easyMove = MOVE_NONE;
+ Move lastBestMove = MOVE_NONE;
+ Depth lastBestMoveDepth = DEPTH_ZERO;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
+ double timeReduction = 1.0;
std::memset(ss-4, 0, 7 * sizeof(Stack));
for (int i = 4; i > 0; i--)
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
- completedDepth = DEPTH_ZERO;
if (mainThread)
{
- easyMove = EasyMove.get(rootPos.key());
- EasyMove.clear();
- mainThread->easyMovePlayed = mainThread->failedLow = false;
+ mainThread->failedLow = false;
mainThread->bestMoveChanges = 0;
}
// Sort the PV lines searched so far and update the GUI
std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1);
- if (!mainThread)
- continue;
-
- if (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000)
+ if ( mainThread
+ && (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000))
sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
}
if (!Threads.stop)
completedDepth = rootDepth;
- if (!mainThread)
- 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);
+ if (rootMoves[0].pv[0] != lastBestMove) {
+ lastBestMove = rootMoves[0].pv[0];
+ lastBestMoveDepth = rootDepth;
+ }
// Have we found a "mate in x"?
if ( Limits.mate
&& VALUE_MATE - bestValue <= 2 * Limits.mate)
Threads.stop = true;
+ if (!mainThread)
+ 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);
+
// Do we have time for the next iteration? Can we stop searching now?
if (Limits.use_time_management())
{
if (!Threads.stop && !Threads.stopOnPonderhit)
{
// Stop the search if only one legal move is available, or if all
- // of the available time has been used, or if we matched an easyMove
- // from the previous search and just did a fast verification.
+ // of the available time has been used
const int F[] = { mainThread->failedLow,
bestValue - mainThread->previousScore };
-
int improvingFactor = std::max(229, std::min(715, 357 + 119 * F[0] - 6 * F[1]));
- double unstablePvFactor = 1 + mainThread->bestMoveChanges;
- bool doEasyMove = rootMoves[0].pv[0] == easyMove
- && mainThread->bestMoveChanges < 0.03
- && Time.elapsed() > Time.optimum() * 5 / 44;
+ Color us = rootPos.side_to_move();
+ bool thinkHard = DrawValue[us] == bestValue
+ && Limits.time[us] - Time.elapsed() > Limits.time[~us]
+ && ::pv_is_draw(rootPos);
+
+ double unstablePvFactor = 1 + mainThread->bestMoveChanges + thinkHard;
+
+ // if the bestMove is stable over several iterations, reduce time for this move,
+ // the longer the move has been stable, the more.
+ // Use part of the gained time from a previous stable move for the current move.
+ timeReduction = 1;
+ for (int i : {3, 4, 5})
+ if (lastBestMoveDepth * i < completedDepth && !thinkHard)
+ timeReduction *= 1.3;
+ unstablePvFactor *= std::pow(mainThread->previousTimeReduction, 0.51) / timeReduction;
if ( rootMoves.size() == 1
- || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628
- || (mainThread->easyMovePlayed = doEasyMove, doEasyMove))
+ || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628)
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".
Threads.stop = true;
}
}
-
- if (rootMoves[0].pv.size() >= 3)
- EasyMove.update(rootPos, rootMoves[0].pv);
- else
- EasyMove.clear();
}
}
if (!mainThread)
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 || mainThread->easyMovePlayed)
- EasyMove.clear();
+ mainThread->previousTimeReduction = timeReduction;
// 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)));
+ std::swap(rootMoves[0], *std::find(rootMoves.begin(), rootMoves.end(),
+ skill.best ? skill.best : skill.pick_best(multiPV)));
}
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) {
const bool PvNode = NT == PV;
- const bool rootNode = PvNode && (ss-1)->ply == 0;
+ const bool rootNode = PvNode && ss->ply == 0;
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
Depth extension, newDepth;
Value bestValue, value, ttValue, eval;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
- bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
Piece movedPiece;
int moveCount, quietCount;
moveCount = quietCount = ss->moveCount = 0;
ss->statScore = 0;
bestValue = -VALUE_INFINITE;
- ss->ply = (ss-1)->ply + 1;
// Check for the available remaining time
if (thisThread == Threads.main())
static_cast<MainThread*>(thisThread)->check_time();
- // Used to send selDepth info to GUI
- if (PvNode && thisThread->selDepth < ss->ply)
- thisThread->selDepth = ss->ply;
+ // Used to send selDepth info to GUI (selDepth counts from 1, ply from 0)
+ if (PvNode && thisThread->selDepth < ss->ply + 1)
+ thisThread->selDepth = ss->ply + 1;
if (!rootNode)
{
assert(0 <= ss->ply && ss->ply < MAX_PLY);
+ (ss+1)->ply = ss->ply + 1;
ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->contHistory = &thisThread->contHistory[NO_PIECE][0];
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
int drawScore = TB::UseRule50 ? 1 : 0;
- value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply
- : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply
+ value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
+ : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
: VALUE_DRAW + 2 * v * drawScore;
tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
&& tte->depth() >= depth - 3 * ONE_PLY;
skipQuiets = false;
ttCapture = false;
+ pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT;
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
r -= r ? ONE_PLY : DEPTH_ZERO;
else
{
+ // Decrease reduction if opponent's move count is high
+ if ((ss-1)->moveCount > 15)
+ r -= ONE_PLY;
+
+ // Decrease reduction for exact PV nodes
+ if (pvExact)
+ r -= ONE_PLY;
+
// Increase reduction if ttMove is a capture
if (ttCapture)
r += ONE_PLY;
- 4000;
// Decrease/increase reduction by comparing opponent's stat score
- if (ss->statScore > 0 && (ss-1)->statScore < 0)
+ if (ss->statScore >= 0 && (ss-1)->statScore < 0)
r -= ONE_PLY;
- else if (ss->statScore < 0 && (ss-1)->statScore > 0)
+ else if ((ss-1)->statScore >= 0 && ss->statScore < 0)
r += ONE_PLY;
// Decrease/increase reduction for moves with a good/bad history
}
ss->currentMove = bestMove = MOVE_NONE;
- ss->ply = (ss-1)->ply + 1;
+ (ss+1)->ply = ss->ply + 1;
moveCount = 0;
// Check for an instant draw or if the maximum ply has been reached
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
-
// Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey, ttHit);
// 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.
- const PieceToHistory* contHist[4] = {};
- MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory, contHist, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, &pos.this_thread()->mainHistory, to_sq((ss-1)->currentMove));
// Loop through the moves until no moves remain or a beta cutoff occurs
while ((move = mp.next_move()) != MOVE_NONE)
}
+ // Is the PV leading to a draw position? Assumes all pv moves are legal
+ bool pv_is_draw(Position& pos) {
+
+ StateInfo st[MAX_PLY];
+ auto& pv = pos.this_thread()->rootMoves[0].pv;
+
+ for (size_t i = 0; i < pv.size(); ++i)
+ pos.do_move(pv[i], st[i]);
+
+ bool isDraw = pos.is_draw(pv.size());
+
+ for (size_t i = pv.size(); i > 0; --i)
+ pos.undo_move(pv[i-1]);
+
+ return isDraw;
+ }
+
+
// 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.
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];
if (Threads.ponder)
return;
- if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10)
+ if ( (Limits.use_time_management() && elapsed > Time.maximum())
|| (Limits.movetime && elapsed >= Limits.movetime)
|| (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
Threads.stop = true;
ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
Cardinality = Options["SyzygyProbeLimit"];
+ // Don't filter any moves if the user requested analysis on multiple
+ if (Options["MultiPV"] != 1)
+ return;
+
// Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
if (Cardinality > MaxCardinality)
{
projects / stockfish / blobdiff