Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
namespace Search {
- volatile SignalsType Signals;
+ SignalsType Signals;
LimitsType Limits;
- StateStackPtr SetupStates;
}
namespace Tablebases {
namespace {
- // Different node types, used as template parameter
- enum NodeType { Root, PV, NonPV };
+ // Different node types, used as a template parameter
+ enum NodeType { NonPV, PV };
// Razoring and futility margin based on depth
- int razor_margin[4] = {483, 570, 603, 554};
- 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(150 * d / ONE_PLY); }
// Futility and reductions lookup tables, initialized at startup
- int FutilityMoveCounts[2][16]; // [improving][depth]
- Depth Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
+ int FutilityMoveCounts[2][16]; // [improving][depth]
+ int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
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)];
+ return Reductions[PvNode][i][std::min(d / ONE_PLY, 63)][std::min(mn, 63)] * ONE_PLY;
}
- // Skill struct is used to implement strength limiting
+ // Skill structure is used to implement strength limit
struct Skill {
Skill(int l) : level(l) {}
bool enabled() const { return level < 20; }
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.
+ // 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() {
assert(newPv.size() >= 3);
- // Keep track of how many times in a row 3rd ply remains stable
+ // 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.gives_check(newPv[0], CheckInfo(pos)));
- pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1], CheckInfo(pos)));
+ pos.do_move(newPv[0], st[0], pos.gives_check(newPv[0]));
+ pos.do_move(newPv[1], st[1], pos.gives_check(newPv[1]));
expectedPosKey = pos.key();
pos.undo_move(newPv[1]);
pos.undo_move(newPv[0]);
Move pv[3];
};
+ // Set of rows with half bits set to 1 and half to 0. It is used to allocate
+ // the search depths across the threads.
+ typedef std::vector<int> Row;
+
+ const Row HalfDensity[] = {
+ {0, 1},
+ {1, 0},
+ {0, 0, 1, 1},
+ {0, 1, 1, 0},
+ {1, 1, 0, 0},
+ {1, 0, 0, 1},
+ {0, 0, 0, 1, 1, 1},
+ {0, 0, 1, 1, 1, 0},
+ {0, 1, 1, 1, 0, 0},
+ {1, 1, 1, 0, 0, 0},
+ {1, 1, 0, 0, 0, 1},
+ {1, 0, 0, 0, 1, 1},
+ {0, 0, 0, 0, 1, 1, 1, 1},
+ {0, 0, 0, 1, 1, 1, 1, 0},
+ {0, 0, 1, 1, 1, 1, 0 ,0},
+ {0, 1, 1, 1, 1, 0, 0 ,0},
+ {1, 1, 1, 1, 0, 0, 0 ,0},
+ {1, 1, 1, 0, 0, 0, 0 ,1},
+ {1, 1, 0, 0, 0, 0, 1 ,1},
+ {1, 0, 0, 0, 0, 1, 1 ,1},
+ };
+
+ const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
+
EasyMoveManager EasyMove;
- double BestMoveChanges;
Value DrawValue[COLOR_NB];
- CounterMovesHistoryStats CounterMovesHistory;
+ CounterMoveHistoryStats CounterMoveHistory;
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
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 update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus);
+ void update_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, Value bonus);
+ void check_time();
} // namespace
void Search::init() {
- 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)
- 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];
+ for (int imp = 0; imp <= 1; ++imp)
+ for (int d = 1; d < 64; ++d)
+ for (int mc = 1; mc < 64; ++mc)
+ {
+ double r = log(d) * log(mc) / 2;
+ if (r < 0.80)
+ continue;
- if (r >= 1.5)
- Reductions[pv][imp][d][mc] = int(r) * ONE_PLY;
+ Reductions[NonPV][imp][d][mc] = int(std::round(r));
+ Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
- // 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;
- }
+ // Increase reduction for non-PV nodes when eval is not improving
+ if (!imp && Reductions[NonPV][imp][d][mc] >= 2)
+ Reductions[NonPV][imp][d][mc]++;
+ }
for (int d = 0; d < 16; ++d)
{
}
-/// Search::reset() clears all search memory, to obtain reproducible search results
+/// Search::clear() resets search state to zero, to obtain reproducible results
-void Search::reset () {
+void Search::clear() {
TT.clear();
- CounterMovesHistory.clear();
+ CounterMoveHistory.clear();
for (Thread* th : Threads)
{
- th->History.clear();
- th->Countermoves.clear();
+ th->history.clear();
+ th->counterMoves.clear();
+ th->fromTo.clear();
}
+
+ Threads.main()->previousScore = VALUE_INFINITE;
}
/// 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.
+/// 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;
- CheckInfo ci(pos);
const bool leaf = (depth == 2 * ONE_PLY);
for (const auto& m : MoveList<LEGAL>(pos))
cnt = 1, nodes++;
else
{
- pos.do_move(m, st, pos.gives_check(m, ci));
+ pos.do_move(m, st, pos.gives_check(m));
cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
nodes += cnt;
pos.undo_move(m);
return nodes;
}
-template uint64_t Search::perft<true>(Position& pos, Depth depth);
+template uint64_t Search::perft<true>(Position&, Depth);
-/// MainThread::think() 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.
+/// 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::think() {
+void MainThread::search() {
Color us = rootPos.side_to_move();
Time.init(Limits, us, rootPos.game_ply());
DrawValue[ us] = VALUE_DRAW - Value(contempt);
DrawValue[~us] = VALUE_DRAW + Value(contempt);
- TB::Hits = 0;
- TB::RootInTB = false;
- TB::UseRule50 = Options["Syzygy50MoveRule"];
- TB::ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
- TB::Cardinality = Options["SyzygyProbeLimit"];
-
- // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
- if (TB::Cardinality > TB::MaxCardinality)
- {
- TB::Cardinality = TB::MaxCardinality;
- TB::ProbeDepth = DEPTH_ZERO;
- }
-
if (rootMoves.empty())
{
rootMoves.push_back(RootMove(MOVE_NONE));
}
else
{
- 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);
-
- 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);
-
- // Only probe during search if winning
- if (TB::Score <= VALUE_DRAW)
- TB::Cardinality = 0;
- }
-
- if (TB::RootInTB)
- {
- TB::Hits = rootMoves.size();
-
- if (!TB::UseRule50)
- TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
- : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
- : VALUE_DRAW;
- }
- }
-
for (Thread* th : Threads)
- {
- th->maxPly = 0;
- th->depth = DEPTH_ZERO;
- th->searching = true;
if (th != this)
- {
- th->rootPos = Position(rootPos, th);
- th->rootMoves = rootMoves;
- th->notify_one(); // Wake up the thread and start searching
- }
- }
+ th->start_searching();
- Threads.timer->run = true;
- Threads.timer->notify_one(); // Start the recurring timer
-
- search(true); // Let's start searching!
-
- // Stop the threads and the timer
- Signals.stop = true;
- Threads.timer->run = false;
-
- // Wait until all threads have finished
- for (Thread* th : Threads)
- if (th != this)
- th->wait_while(th->searching);
+ Thread::search(); // Let's start searching!
}
// When playing in 'nodes as time' mode, subtract the searched nodes from
- // the available ones before to exit.
+ // the available ones before exiting.
if (Limits.npmsec)
Time.availableNodes += Limits.inc[us] - Threads.nodes_searched();
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;
- 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());
+ // 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 ( !this->easyMovePlayed
+ && Options["MultiPV"] == 1
+ && !Limits.depth
+ && !Skill(Options["Skill Level"]).enabled()
+ && rootMoves[0].pv[0] != MOVE_NONE)
+ {
+ for (Thread* th : Threads)
+ if ( th->completedDepth > bestThread->completedDepth
+ && th->rootMoves[0].score > bestThread->rootMoves[0].score)
+ bestThread = th;
+ }
+
+ previousScore = bestThread->rootMoves[0].score;
+
+ // Send new PV when needed
+ 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 (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;
}
// 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.
+// consumed, the user stops the search, or the maximum search depth is reached.
-void Thread::search(bool isMainThread) {
+void Thread::search() {
- Stack* ss = stack + 2; // To allow referencing (ss-2) and (ss+2)
+ Stack stack[MAX_PLY+7], *ss = stack+5; // To allow referencing (ss-5) and (ss+2)
Value bestValue, alpha, beta, delta;
Move easyMove = MOVE_NONE;
+ MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
- std::memset(ss-2, 0, 5 * sizeof(Stack));
+ std::memset(ss-5, 0, 8 * sizeof(Stack));
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
+ completedDepth = DEPTH_ZERO;
- if (isMainThread)
+ if (mainThread)
{
easyMove = EasyMove.get(rootPos.key());
EasyMove.clear();
- BestMoveChanges = 0;
+ mainThread->easyMovePlayed = mainThread->failedLow = false;
+ mainThread->bestMoveChanges = 0;
TT.new_search();
}
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))
+ // Iterative deepening loop until requested to stop or the target depth is reached
+ while ( (rootDepth += ONE_PLY) < DEPTH_MAX
+ && !Signals.stop
+ && (!Limits.depth || Threads.main()->rootDepth / ONE_PLY <= Limits.depth))
{
- // Set up the new depth for the helper threads
- if (!isMainThread)
- depth = Threads.main()->depth + Depth(int(3 * log(1 + this->idx)));
+ // Set up the new depths for the helper threads skipping on average every
+ // 2nd ply (using a half-density matrix).
+ if (!mainThread)
+ {
+ const Row& row = HalfDensity[(idx - 1) % HalfDensitySize];
+ if (row[(rootDepth / ONE_PLY + rootPos.game_ply()) % row.size()])
+ continue;
+ }
// Age out PV variability metric
- if (isMainThread)
- BestMoveChanges *= 0.5;
+ if (mainThread)
+ mainThread->bestMoveChanges *= 0.505, mainThread->failedLow = false;
// 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 (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
{
// Reset aspiration window starting size
- if (depth >= 5 * ONE_PLY)
+ if (rootDepth >= 5 * ONE_PLY)
{
delta = Value(18);
alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
// high/low anymore.
while (true)
{
- bestValue = ::search<Root>(rootPos, ss, alpha, beta, depth, false);
+ bestValue = ::search<PV>(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
// 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
+ // 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.
+ // valid, although it refers to the previous iteration.
if (Signals.stop)
break;
// When failing high/low give some update (without cluttering
// the UI) before a re-search.
- if ( isMainThread
+ if ( mainThread
&& multiPV == 1
&& (bestValue <= alpha || bestValue >= beta)
&& Time.elapsed() > 3000)
- sync_cout << UCI::pv(rootPos, depth, alpha, beta) << sync_endl;
+ 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.
beta = (alpha + beta) / 2;
alpha = std::max(bestValue - delta, -VALUE_INFINITE);
- if (isMainThread)
+ if (mainThread)
{
- Signals.failedLowAtRoot = true;
+ mainThread->failedLow = true;
Signals.stopOnPonderhit = false;
}
}
// Sort the PV lines searched so far and update the GUI
std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1);
- if (!isMainThread)
- break;
+ if (!mainThread)
+ continue;
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, depth, alpha, beta) << sync_endl;
+ sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
}
- if (!isMainThread)
+ if (!Signals.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(depth))
+ if (skill.enabled() && skill.time_to_pick(rootDepth))
skill.pick_best(multiPV);
// Have we found a "mate in x"?
{
if (!Signals.stop && !Signals.stopOnPonderhit)
{
- // 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
+ // 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.
+ 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 / 42;
+
if ( rootMoves.size() == 1
- || Time.elapsed() > Time.available()
- || ( rootMoves[0].pv[0] == easyMove
- && BestMoveChanges < 0.03
- && Time.elapsed() > Time.available() / 10))
+ || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628
+ || (mainThread->easyMovePlayed = doEasyMove))
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".
}
}
- searching = false;
- notify_one(); // Wake up main thread if is sleeping waiting for us
-
- if (!isMainThread)
+ 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 || Time.elapsed() < Time.available())
+ if (EasyMove.stableCnt < 6 || mainThread->easyMovePlayed)
EasyMove.clear();
// If skill level is enabled, swap best PV line with the sub-optimal one
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>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
- const bool RootNode = NT == Root;
- const bool PvNode = NT == PV || NT == Root;
+ const bool PvNode = NT == PV;
+ const bool rootNode = PvNode && (ss-1)->ply == 0;
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);
+ assert(!(PvNode && cutNode));
+ assert(depth / ONE_PLY * ONE_PLY == depth);
Move pv[MAX_PLY+1], quietsSearched[64];
StateInfo st;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth, predictedDepth;
- Value bestValue, value, ttValue, eval, nullValue, futilityValue;
+ Value bestValue, value, ttValue, eval, nullValue;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
- bool captureOrPromotion, doFullDepthSearch;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
+ Piece moved_piece;
int moveCount, quietCount;
// Step 1. Initialize node
bestValue = -VALUE_INFINITE;
ss->ply = (ss-1)->ply + 1;
+ // Check for the available remaining time
+ if (thisThread->resetCalls.load(std::memory_order_relaxed))
+ {
+ thisThread->resetCalls = false;
+ thisThread->callsCnt = 0;
+ }
+ if (++thisThread->callsCnt > 4096)
+ {
+ for (Thread* th : Threads)
+ th->resetCalls = true;
+
+ check_time();
+ }
+
// Used to send selDepth info to GUI
if (PvNode && thisThread->maxPly < ss->ply)
thisThread->maxPly = ss->ply;
- if (!RootNode)
+ 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
assert(0 <= ss->ply && ss->ply < MAX_PLY);
- ss->currentMove = ss->ttMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- (ss+1)->skipEarlyPruning = false; (ss+1)->reduction = DEPTH_ZERO;
+ ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
+ ss->counterMoves = nullptr;
+ (ss+1)->skipEarlyPruning = false;
(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();
+ posKey = pos.key() ^ Key(excludedMove);
tte = TT.probe(posKey, ttHit);
- ss->ttMove = ttMove = RootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE;
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ 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 prune 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 on TT hit
- if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove))
- update_stats(pos, ss, ttMove, depth, nullptr, 0);
+ if (ttValue >= beta && ttMove)
+ {
+ int d = depth / ONE_PLY;
+ if (!pos.capture_or_promotion(ttMove))
+ {
+ Value bonus = Value(d * d + 2 * d - 2);
+ update_stats(pos, ss, ttMove, nullptr, 0, bonus);
+ }
+
+ // Extra penalty for a quiet TT move in previous ply when it gets refuted
+ if ((ss-1)->moveCount == 1 && !pos.captured_piece())
+ {
+ Value penalty = Value(d * d + 4 * d + 1);
+ Square prevSq = to_sq((ss-1)->currentMove);
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
+ }
+ }
return ttValue;
}
// Step 4a. Tablebase probe
- if (!RootNode && TB::Cardinality)
+ if (!rootNode && TB::Cardinality)
{
int piecesCnt = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
if ( piecesCnt <= TB::Cardinality
&& (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth)
- && pos.rule50_count() == 0)
+ && pos.rule50_count() == 0
+ && !pos.can_castle(ANY_CASTLING))
{
int found, v = Tablebases::probe_wdl(pos, &found);
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)
// Step 6. Razoring (skipped when in check)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && eval + razor_margin[depth] <= alpha
- && ttMove == MOVE_NONE)
+ && ttMove == MOVE_NONE
+ && eval + razor_margin[depth / ONE_PLY] <= alpha)
{
if ( depth <= ONE_PLY
&& 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 / ONE_PLY];
Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
if (v <= ralpha)
return v;
}
// Step 7. Futility pruning: child node (skipped when in check)
- if ( !RootNode
+ if ( !rootNode
&& depth < 7 * ONE_PLY
&& eval - futility_margin(depth) >= beta
&& eval < VALUE_KNOWN_WIN // Do not return unproven wins
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
- && depth >= 2 * ONE_PLY
&& eval >= beta
+ && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
+ ss->counterMoves = nullptr;
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
- Depth R = ((823 + 67 * depth) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
+ Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
pos.do_null_move(st);
(ss+1)->skipEarlyPruning = true;
}
// 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.
+ // If we have a good enough capture 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, thisThread->History, CounterMovesHistory, PieceValue[MG][pos.captured_piece_type()]);
- CheckInfo ci(pos);
+ MovePicker mp(pos, ttMove, rbeta - ss->staticEval);
while ((move = mp.next_move()) != MOVE_NONE)
- if (pos.legal(move, ci.pinned))
+ if (pos.legal(move))
{
ss->currentMove = move;
- pos.do_move(move, st, pos.gives_check(move, ci));
+ ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)];
+ pos.do_move(move, st, pos.gives_check(move));
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
if (value >= rbeta)
}
// Step 10. Internal iterative deepening (skipped when in check)
- if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
+ if ( depth >= 6 * ONE_PLY
&& !ttMove
&& (PvNode || ss->staticEval + 256 >= beta))
{
- Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
+ Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY;
ss->skipEarlyPruning = true;
- search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d, true);
+ search<NT>(pos, ss, alpha, beta, d, cutNode);
ss->skipEarlyPruning = false;
tte = TT.probe(posKey, ttHit);
moves_loop: // When in check search starts from here
- Square prevMoveSq = to_sq((ss-1)->currentMove);
- Move countermove = thisThread->Countermoves[pos.piece_on(prevMoveSq)][prevMoveSq];
+ const CounterMoveStats* cmh = (ss-1)->counterMoves;
+ const CounterMoveStats* fmh = (ss-2)->counterMoves;
+ const CounterMoveStats* fmh2 = (ss-4)->counterMoves;
- MovePicker mp(pos, ttMove, depth, thisThread->History, CounterMovesHistory, countermove, ss);
- CheckInfo ci(pos);
+ MovePicker mp(pos, ttMove, depth, ss);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
improving = ss->staticEval >= (ss-2)->staticEval
- || ss->staticEval == VALUE_NONE
+ /* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */
||(ss-2)->staticEval == VALUE_NONE;
- singularExtensionNode = !RootNode
+ singularExtensionNode = !rootNode
&& depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
/* && ttValue != VALUE_NONE Already implicit in the next condition */
// 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(thisThread->rootMoves.begin() + thisThread->PVIdx, thisThread->rootMoves.end(), move))
+ if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
+ thisThread->rootMoves.end(), move))
continue;
ss->moveCount = ++moveCount;
- if (RootNode && thisThread == Threads.main())
- {
- Signals.firstRootMove = (moveCount == 1);
-
- if (Time.elapsed() > 3000)
- sync_cout << "info depth " << depth / ONE_PLY
- << " currmove " << UCI::move(move, pos.is_chess960())
- << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl;
- }
+ if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
+ sync_cout << "info depth " << depth / ONE_PLY
+ << " currmove " << UCI::move(move, pos.is_chess960())
+ << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl;
if (PvNode)
(ss+1)->pv = nullptr;
extension = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
+ moved_piece = pos.moved_piece(move);
+
+ givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates()
+ ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move)
+ : pos.gives_check(move);
- givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
- ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
- : pos.gives_check(move, ci);
+ moveCountPruning = depth < 16 * ONE_PLY
+ && moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
// Step 12. Extend checks
- if (givesCheck && pos.see_sign(move) >= VALUE_ZERO)
+ if ( givesCheck
+ && !moveCountPruning
+ && pos.see_sign(move) >= VALUE_ZERO)
extension = ONE_PLY;
// Singular extension search. If all moves but one fail low on a search of
if ( singularExtensionNode
&& move == ttMove
&& !extension
- && pos.legal(move, ci.pinned))
+ && pos.legal(move))
{
Value rBeta = ttValue - 2 * depth / ONE_PLY;
+ Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
ss->excludedMove = move;
ss->skipEarlyPruning = true;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode);
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode);
ss->skipEarlyPruning = false;
ss->excludedMove = MOVE_NONE;
newDepth = depth - ONE_PLY + extension;
// Step 13. Pruning at shallow depth
- if ( !RootNode
- && !captureOrPromotion
- && !inCheck
- && !givesCheck
- && !pos.advanced_pawn_push(move)
- && bestValue > VALUE_MATED_IN_MAX_PLY)
+ if ( !rootNode
+ && !inCheck
+ && bestValue > VALUE_MATED_IN_MAX_PLY)
{
- // Move count based pruning
- if ( depth < 16 * ONE_PLY
- && moveCount >= FutilityMoveCounts[improving][depth])
- continue;
+ if ( !captureOrPromotion
+ && !givesCheck
+ && !pos.advanced_pawn_push(move))
+ {
+ // Move count based pruning
+ if (moveCountPruning)
+ continue;
- predictedDepth = newDepth - reduction<PvNode>(improving, depth, moveCount);
+ predictedDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO);
- // Futility pruning: parent node
- if (predictedDepth < 7 * ONE_PLY)
- {
- futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256;
+ // Countermoves based pruning
+ if ( predictedDepth < 3 * ONE_PLY
+ && (!cmh || (*cmh )[moved_piece][to_sq(move)] < VALUE_ZERO)
+ && (!fmh || (*fmh )[moved_piece][to_sq(move)] < VALUE_ZERO)
+ && (!fmh2 || (*fmh2)[moved_piece][to_sq(move)] < VALUE_ZERO || (cmh && fmh)))
+ continue;
- if (futilityValue <= alpha)
- {
- bestValue = std::max(bestValue, futilityValue);
+ // Futility pruning: parent node
+ if ( predictedDepth < 7 * ONE_PLY
+ && ss->staticEval + 256 + 200 * predictedDepth / ONE_PLY <= alpha)
continue;
+
+ // Prune moves with negative SEE at low depths and below a decreasing
+ // threshold at higher depths.
+ if (predictedDepth < 8 * ONE_PLY)
+ {
+ Value see_v = predictedDepth < 4 * ONE_PLY ? VALUE_ZERO
+ : -PawnValueMg * 2 * int(predictedDepth - 3 * ONE_PLY) / ONE_PLY;
+
+ if (pos.see_sign(move) < see_v)
+ continue;
}
}
-
- // Prune moves with negative SEE at low depths
- if (predictedDepth < 4 * ONE_PLY && pos.see_sign(move) < VALUE_ZERO)
+ else if ( depth < 3 * ONE_PLY
+ && ( mp.see_sign() < 0
+ || (!mp.see_sign() && pos.see_sign(move) < VALUE_ZERO)))
continue;
}
prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
- if (!RootNode && !pos.legal(move, ci.pinned))
+ if (!rootNode && !pos.legal(move))
{
ss->moveCount = --moveCount;
continue;
}
ss->currentMove = move;
+ ss->counterMoves = &CounterMoveHistory[moved_piece][to_sq(move)];
// Step 14. Make the move
pos.do_move(move, st, givesCheck);
// re-searched at full depth.
if ( depth >= 3 * ONE_PLY
&& moveCount > 1
- && !captureOrPromotion
- && move != ss->killers[0]
- && move != ss->killers[1])
+ && (!captureOrPromotion || moveCountPruning))
{
- ss->reduction = reduction<PvNode>(improving, depth, moveCount);
-
- if ( (!PvNode && cutNode)
- || ( thisThread->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;
+ Depth r = reduction<PvNode>(improving, depth, moveCount);
- if ( thisThread->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
- if ( ss->reduction
- && type_of(move) == NORMAL
- && type_of(pos.piece_on(to_sq(move))) != PAWN
- && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO)
- ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
+ if (captureOrPromotion)
+ r -= r ? ONE_PLY : DEPTH_ZERO;
+ else
+ {
+ // Increase reduction for cut nodes
+ if (cutNode)
+ r += 2 * ONE_PLY;
+
+ // Decrease reduction for moves that escape a capture. Filter out
+ // castling moves, because they are coded as "king captures rook" and
+ // hence break make_move(). Also use see() instead of see_sign(),
+ // because the destination square is empty.
+ else if ( type_of(move) == NORMAL
+ && type_of(pos.piece_on(to_sq(move))) != PAWN
+ && pos.see(make_move(to_sq(move), from_sq(move))) < VALUE_ZERO)
+ r -= 2 * ONE_PLY;
+
+ // Decrease/increase reduction for moves with a good/bad history
+ Value val = thisThread->history[moved_piece][to_sq(move)]
+ + (cmh ? (*cmh )[moved_piece][to_sq(move)] : VALUE_ZERO)
+ + (fmh ? (*fmh )[moved_piece][to_sq(move)] : VALUE_ZERO)
+ + (fmh2 ? (*fmh2)[moved_piece][to_sq(move)] : VALUE_ZERO)
+ + thisThread->fromTo.get(~pos.side_to_move(), move);
+ int rHist = (val - 8000) / 20000;
+ r = std::max(DEPTH_ZERO, (r / ONE_PLY - rHist) * ONE_PLY);
+ }
- Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
+ Depth d = std::max(newDepth - r, ONE_PLY);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
- doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
- ss->reduction = DEPTH_ZERO;
+ doFullDepthSearch = (value > alpha && d != newDepth);
}
else
doFullDepthSearch = !PvNode || moveCount > 1;
- // Step 16. Full depth search, when LMR is skipped or fails high
+ // Step 16. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
value = newDepth < ONE_PLY ?
givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
// 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
- // parent node fail low with value <= alpha and to try another move.
- if (PvNode && (moveCount == 1 || (value > alpha && (RootNode || value < beta))))
+ // parent node fail low with value <= alpha and try another move.
+ if (PvNode && (moveCount == 1 || (value > alpha && (rootNode || value < beta))))
{
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 18. Check for new best move
+ // Step 18. Check for a new best move
// 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)
+ if (Signals.stop.load(std::memory_order_relaxed))
return VALUE_ZERO;
- if (RootNode)
+ if (rootNode)
{
- RootMove& rm = *std::find(thisThread->rootMoves.begin(), thisThread->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)
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
if (moveCount > 1 && thisThread == Threads.main())
- ++BestMoveChanges;
+ ++static_cast<MainThread*>(thisThread)->bestMoveChanges;
}
else
// All other moves but the PV are set to the lowest value: this is
bestMove = move;
- if (PvNode && !RootNode) // Update pv even in fail-high case
+ if (PvNode && !rootNode) // Update pv even in fail-high case
update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
quietsSearched[quietCount++] = move;
}
- // Following condition would detect a stop only after move loop has been
+ // The 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.
/*
// Step 20. Check for mate and stalemate
// All legal moves have been searched and if there are no legal moves, it
- // must be mate or stalemate. If we are in a singular extension search then
+ // must be a mate or a stalemate. If we are in a singular extension search then
// return a fail low score.
if (!moveCount)
bestValue = excludedMove ? alpha
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+ else if (bestMove)
+ {
+ int d = depth / ONE_PLY;
- // Quiet best move: update killers, history and countermoves
- else if (bestMove && !pos.capture_or_promotion(bestMove))
- update_stats(pos, ss, bestMove, depth, quietsSearched, quietCount);
+ // Quiet best move: update killers, history and countermoves
+ if (!pos.capture_or_promotion(bestMove))
+ {
+ Value bonus = Value(d * d + 2 * d - 2);
+ update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus);
+ }
- // Bonus for prior countermove that caused the fail low
- else if (!bestMove)
- {
- if (is_ok((ss - 2)->currentMove) && is_ok((ss - 1)->currentMove) && !pos.captured_piece_type() && !inCheck && depth>=3*ONE_PLY)
+ // Extra penalty for a quiet TT move in previous ply when it gets refuted
+ if ((ss-1)->moveCount == 1 && !pos.captured_piece())
{
- Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
- Square prevSq = to_sq((ss - 1)->currentMove);
- Square prevPrevSq = to_sq((ss - 2)->currentMove);
- HistoryStats& flMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
- flMoveCmh.updateCMH(pos.piece_on(prevSq), prevSq, bonus);
+ Value penalty = Value(d * d + 4 * d + 1);
+ Square prevSq = to_sq((ss-1)->currentMove);
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
}
}
+ // Bonus for prior countermove that caused the fail low
+ else if ( depth >= 3 * ONE_PLY
+ && !pos.captured_piece()
+ && is_ok((ss-1)->currentMove))
+ {
+ int d = depth / ONE_PLY;
+ Value bonus = Value(d * d + 2 * d - 2);
+ Square prevSq = to_sq((ss-1)->currentMove);
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus);
+ }
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
const bool PvNode = NT == PV;
- assert(NT == PV || NT == NonPV);
assert(InCheck == !!pos.checkers());
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
+ assert(depth / ONE_PLY * ONE_PLY == depth);
Move pv[MAX_PLY+1];
StateInfo st;
// 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, pos.this_thread()->History, CounterMovesHistory, to_sq((ss-1)->currentMove));
- CheckInfo ci(pos);
+ MovePicker mp(pos, ttMove, depth, 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)
{
assert(is_ok(move));
- givesCheck = type_of(move) == NORMAL && !ci.dcCandidates
- ? ci.checkSquares[type_of(pos.piece_on(from_sq(move)))] & to_sq(move)
- : pos.gives_check(move, ci);
+ givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates()
+ ? pos.check_squares(type_of(pos.piece_on(from_sq(move)))) & to_sq(move)
+ : pos.gives_check(move);
// Futility pruning
if ( !InCheck
prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
- if (!pos.legal(move, ci.pinned))
+ if (!pos.legal(move))
continue;
ss->currentMove = move;
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Check for new best move
+ // Check for a new best move
if (value > bestValue)
{
bestValue = value;
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;
}
- // update_stats() updates killers, history, countermove history and
- // countermoves stats for a quiet best move.
+ // update_cm_stats() updates countermove and follow-up move history
+
+ void update_cm_stats(Stack* ss, Piece pc, Square s, Value bonus) {
+
+ CounterMoveStats* cmh = (ss-1)->counterMoves;
+ CounterMoveStats* fmh1 = (ss-2)->counterMoves;
+ CounterMoveStats* fmh2 = (ss-4)->counterMoves;
+
+ if (cmh)
+ cmh->update(pc, s, bonus);
+
+ if (fmh1)
+ fmh1->update(pc, s, bonus);
+
+ if (fmh2)
+ fmh2->update(pc, s, bonus);
+ }
+
+
+ // update_stats() updates killers, history, countermove and countermove plus
+ // follow-up move 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) {
+ Move* quiets, int quietsCnt, Value bonus) {
if (ss->killers[0] != move)
{
ss->killers[0] = move;
}
- Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY));
-
- Square prevSq = to_sq((ss-1)->currentMove);
- HistoryStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+ Color c = pos.side_to_move();
Thread* thisThread = pos.this_thread();
+ thisThread->fromTo.update(c, move, bonus);
+ thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
+ update_cm_stats(ss, pos.moved_piece(move), to_sq(move), bonus);
- thisThread->History.updateH(pos.moved_piece(move), to_sq(move), bonus);
-
- if (is_ok((ss-1)->currentMove))
+ if ((ss-1)->counterMoves)
{
- thisThread->Countermoves.update(pos.piece_on(prevSq), prevSq, move);
- cmh.updateCMH(pos.moved_piece(move), to_sq(move), bonus);
+ Square prevSq = to_sq((ss-1)->currentMove);
+ thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
}
// Decrease all the other played quiet moves
for (int i = 0; i < quietsCnt; ++i)
{
- thisThread->History.updateH(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
-
- if (is_ok((ss-1)->currentMove))
- cmh.updateCMH(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
- }
-
- // 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 prevPrevSq = to_sq((ss-2)->currentMove);
- HistoryStats& ttMoveCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
- ttMoveCmh.updateCMH(pos.piece_on(prevSq), prevSq, -bonus - 2 * depth / ONE_PLY - 1);
+ thisThread->fromTo.update(c, quiets[i], -bonus);
+ thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+ update_cm_stats(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
}
Move Skill::pick_best(size_t multiPV) {
- // PRNG sequence should be non-deterministic, so we seed it with the time at init
- const Search::RootMoveVector& rootMoves = Threads.main()->rootMoves;
- static PRNG rng(now());
+ const RootMoves& 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
- // weakness. One deterministic and bigger for weaker levels, and one random,
- // then we choose the move with the resulting highest score.
+ // Choose best move. For each move score we add two terms, both dependent on
+ // weakness. One is deterministic and bigger for weaker levels, and one is
+ // 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)
{
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() && elapsed > Time.maximum() - 10)
+ || (Limits.movetime && elapsed >= Limits.movetime)
+ || (Limits.nodes && Threads.nodes_searched() >= Limits.nodes))
+ Signals.stop = true;
+ }
+
} // namespace
std::stringstream ss;
int elapsed = Time.elapsed() + 1;
- const Search::RootMoveVector& rootMoves = pos.this_thread()->rootMoves;
+ const RootMoves& 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();
}
-/// RootMove::insert_pv_in_tt() is called at the end of a search iteration, and
-/// inserts the PV back into the TT. This makes sure the old PV moves are searched
-/// first, even if the old TT entries have been overwritten.
-
-void RootMove::insert_pv_in_tt(Position& pos) {
-
- StateInfo state[MAX_PLY], *st = state;
- bool ttHit;
-
- for (Move m : pv)
- {
- assert(MoveList<LEGAL>(pos).contains(m));
-
- 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());
-
- pos.do_move(m, *st++, pos.gives_check(m, CheckInfo(pos)));
- }
-
- for (size_t i = pv.size(); i > 0; )
- pos.undo_move(pv[--i]);
-}
-
-
-/// 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)
{
assert(pv.size() == 1);
- pos.do_move(pv[0], st, pos.gives_check(pv[0], CheckInfo(pos)));
+ pos.do_move(pv[0], st, pos.gives_check(pv[0]));
TTEntry* tte = TT.probe(pos.key(), ttHit);
- pos.undo_move(pv[0]);
if (ttHit)
{
Move m = tte->move(); // Local copy to be SMP safe
if (MoveList<LEGAL>(pos).contains(m))
- return pv.push_back(m), true;
+ pv.push_back(m);
}
- return false;
+ pos.undo_move(pv[0]);
+ return pv.size() > 1;
}
+void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) {
-/// 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.
+ Hits = 0;
+ RootInTB = false;
+ UseRule50 = Options["Syzygy50MoveRule"];
+ ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
+ Cardinality = Options["SyzygyProbeLimit"];
-void check_time() {
+ // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
+ if (Cardinality > MaxCardinality)
+ {
+ Cardinality = MaxCardinality;
+ ProbeDepth = DEPTH_ZERO;
+ }
- static TimePoint lastInfoTime = now();
- int elapsed = Time.elapsed();
+ if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING))
+ return;
- if (now() - lastInfoTime >= 1000)
- {
- lastInfoTime = now();
- dbg_print();
- }
+ // If the current root position is in the tablebases, then RootMoves
+ // contains only moves that preserve the draw or the win.
+ RootInTB = root_probe(pos, rootMoves, TB::Score);
- // An engine may not stop pondering until told so by the GUI
- if (Limits.ponder)
- return;
+ if (RootInTB)
+ Cardinality = 0; // Do not probe tablebases during the search
- if (Limits.use_time_management())
- {
- bool stillAtFirstMove = Signals.firstRootMove
- && !Signals.failedLowAtRoot
- && elapsed > Time.available() * 75 / 100;
+ else // If DTZ tables are missing, use WDL tables as a fallback
+ {
+ // Filter out moves that do not preserve the draw or the win.
+ RootInTB = root_probe_wdl(pos, rootMoves, TB::Score);
- if ( stillAtFirstMove
- || elapsed > Time.maximum() - 2 * TimerThread::Resolution)
- Signals.stop = true;
- }
- else if (Limits.movetime && elapsed >= Limits.movetime)
- Signals.stop = true;
+ // Only probe during search if winning
+ if (RootInTB && TB::Score <= VALUE_DRAW)
+ Cardinality = 0;
+ }
- else if (Limits.nodes && Threads.nodes_searched() >= Limits.nodes)
- Signals.stop = true;
+ if (RootInTB)
+ {
+ Hits = rootMoves.size();
+
+ if (!UseRule50)
+ TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
+ : TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
+ : VALUE_DRAW;
+ }
}
projects / stockfish / blobdiff