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
const int razor_margin[4] = { 483, 570, 603, 554 };
- Value futility_margin(Depth d) { return Value(200 * d); }
+ Value futility_margin(Depth d) { return Value(150 * d); }
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
return Reductions[PvNode][i][std::min(d, 63 * ONE_PLY)][std::min(mn, 63)];
}
- // 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))
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;
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);
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)) * ONE_PLY;
+ Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - ONE_PLY, DEPTH_ZERO);
- // 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 * ONE_PLY)
+ Reductions[NonPV][imp][d][mc] += ONE_PLY;
+ }
for (int d = 0; d < 16; ++d)
{
}
-/// Search::clear() resets to zero search state, to obtain reproducible results
+/// Search::clear() resets search state to zero, to obtain reproducible results
void Search::clear() {
TT.clear();
- CounterMovesHistory.clear();
+ CounterMoveHistory.clear();
for (Thread* th : Threads)
{
th->history.clear();
th->counterMoves.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) {
/// MainThread::search() is called by the main thread when the program receives
-/// the UCI 'go' command. It searches from root position and at the end prints
-/// the "bestmove" to output.
+/// the UCI 'go' command. It searches from the root position and outputs the "bestmove".
void MainThread::search() {
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->rootDepth = DEPTH_ZERO;
if (th != this)
- {
- th->rootPos = Position(rootPos, th);
- th->rootMoves = rootMoves;
th->start_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();
Thread* bestThread = this;
if ( !this->easyMovePlayed
&& Options["MultiPV"] == 1
- && !Skill(Options["Skill Level"]).enabled())
+ && !Limits.depth
+ && !Skill(Options["Skill Level"]).enabled()
+ && rootMoves[0].pv[0] != MOVE_NONE)
{
for (Thread* th : Threads)
if ( th->completedDepth > bestThread->completedDepth
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;
// 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() {
- Stack stack[MAX_PLY+4], *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;
multiPV = std::min(multiPV, rootMoves.size());
- // Iterative deepening loop until requested to stop or target depth reached
- while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || rootDepth <= Limits.depth))
+ // Iterative deepening loop until requested to stop or the target depth is reached.
+ while (++rootDepth < DEPTH_MAX && !Signals.stop && (!Limits.depth || Threads.main()->rootDepth <= Limits.depth))
{
- // Set up the new depth for the helper threads skipping in average each
- // 2nd ply (using a half density map similar to a Hadamard matrix).
+ // Set up the new depths for the helper threads skipping on average every
+ // 2nd ply (using a half-density matrix).
if (!mainThread)
{
- int d = rootDepth + rootPos.game_ply();
-
- if (idx <= 6 || idx > 24)
- {
- if (((d + idx) >> (msb(idx + 1) - 1)) % 2)
- continue;
- }
- else
- {
- // Table of values of 6 bits with 3 of them set
- static const int HalfDensityMap[] = {
- 0x07, 0x0b, 0x0d, 0x0e, 0x13, 0x16, 0x19, 0x1a, 0x1c,
- 0x23, 0x25, 0x26, 0x29, 0x2c, 0x31, 0x32, 0x34, 0x38
- };
-
- if ((HalfDensityMap[idx - 7] >> (d % 6)) & 1)
- continue;
- }
+ const Row& row = HalfDensity[(idx - 1) % HalfDensitySize];
+ if (row[(rootDepth + rootPos.game_ply()) % row.size()])
+ continue;
}
// Age out PV variability metric
// high/low anymore.
while (true)
{
- bestValue = ::search<Root>(rootPos, ss, alpha, beta, rootDepth, 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;
std::stable_sort(rootMoves.begin(), rootMoves.begin() + PVIdx + 1);
if (!mainThread)
- break;
+ continue;
if (Signals.stop)
sync_cout << "info nodes " << Threads.nodes_searched()
{
if (!Signals.stop && !Signals.stopOnPonderhit)
{
- // Take some extra time if the best move has changed
- if (rootDepth > 4 * ONE_PLY && multiPV == 1)
- Time.pv_instability(mainThread->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() * (mainThread->failedLow ? 641 : 315) / 640
- || (mainThread->easyMovePlayed = ( rootMoves[0].pv[0] == easyMove
- && mainThread->bestMoveChanges < 0.03
- && Time.elapsed() > Time.available() / 8)))
+ || 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".
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_ZERO < depth && depth < DEPTH_MAX);
+ assert(!(PvNode && cutNode));
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 available remaining time
+ // Check for the available remaining time
if (thisThread->resetCalls.load(std::memory_order_relaxed))
{
thisThread->resetCalls = false;
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.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY)
assert(0 <= ss->ply && ss->ply < MAX_PLY);
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;
posKey = excludedMove ? pos.exclusion_key() : pos.key();
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
- ttMove = RootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
+ ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
: ttHit ? tte->move() : MOVE_NONE;
// At non-PV nodes we check for an early TT cutoff
}
// 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);
}
// 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);
assert((ss-1)->currentMove != MOVE_NONE);
assert((ss-1)->currentMove != MOVE_NULL);
- MovePicker mp(pos, ttMove, thisThread->history, PieceValue[MG][pos.captured_piece_type()]);
+ MovePicker mp(pos, ttMove, PieceValue[MG][pos.captured_piece_type()]);
CheckInfo ci(pos);
while ((move = mp.next_move()) != MOVE_NONE)
if (pos.legal(move, ci.pinned))
{
ss->currentMove = move;
+ ss->counterMoves = &CounterMoveHistory[pos.moved_piece(move)][to_sq(move)];
pos.do_move(move, st, pos.gives_check(move, ci));
value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
pos.undo_move(move);
{
Depth d = depth - 2 * ONE_PLY - (PvNode ? DEPTH_ZERO : depth / 4);
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 prevSq = to_sq((ss-1)->currentMove);
- Move cm = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
- const CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+ 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, cmh, cm, ss);
+ MovePicker mp(pos, ttMove, depth, ss);
CheckInfo ci(pos);
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,
+ if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->PVIdx,
thisThread->rootMoves.end(), move))
continue;
ss->moveCount = ++moveCount;
- if (RootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
+ 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;
extension = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
+ moved_piece = pos.moved_piece(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];
+
// 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
newDepth = depth - ONE_PLY + extension;
// Step 13. Pruning at shallow depth
- if ( !RootNode
+ if ( !rootNode
&& !captureOrPromotion
&& !inCheck
&& !givesCheck
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
- if ( depth < 16 * ONE_PLY
- && moveCount >= FutilityMoveCounts[improving][depth])
+ if (moveCountPruning)
continue;
- // History based pruning
+ // Countermoves based pruning
if ( depth <= 4 * ONE_PLY
&& move != ss->killers[0]
- && thisThread->history[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO
- && cmh[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO)
+ && (!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;
- 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)
+ 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)
{
- futilityValue = ss->staticEval + futility_margin(predictedDepth) + 256;
+ Value see_v = predictedDepth < 4 * ONE_PLY ? VALUE_ZERO
+ : -PawnValueMg * 2 * int(predictedDepth - 3 * ONE_PLY);
- if (futilityValue <= alpha)
- {
- bestValue = std::max(bestValue, futilityValue);
+ 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)
- continue;
}
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
- if (!RootNode && !pos.legal(move, ci.pinned))
+ if (!rootNode && !pos.legal(move, ci.pinned))
{
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);
&& !captureOrPromotion)
{
Depth r = reduction<PvNode>(improving, depth, moveCount);
-
- // Increase reduction for cut nodes and moves with a bad history
- if ( (!PvNode && cutNode)
- || ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] < VALUE_ZERO
- && cmh[pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO))
- r += ONE_PLY;
-
- // Decrease reduction for moves with a good history
- if ( thisThread->history[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO
- && cmh[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO)
- r = std::max(DEPTH_ZERO, r - ONE_PLY);
-
- // Decrease reduction for moves that escape a capture
- if ( r
- && 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 = std::max(DEPTH_ZERO, r - ONE_PLY);
+ 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);
+
+ // 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
+ int rHist = (val - 10000) / 20000;
+ r = std::max(DEPTH_ZERO, r - rHist * ONE_PLY);
Depth d = std::max(newDepth - r, ONE_PLY);
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.load(std::memory_order_relaxed))
return VALUE_ZERO;
- if (RootNode)
+ if (rootNode)
{
RootMove& rm = *std::find(thisThread->rootMoves.begin(),
thisThread->rootMoves.end(), move);
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
// Bonus for prior countermove that caused the fail low
else if ( depth >= 3 * ONE_PLY
&& !bestMove
- && !inCheck
&& !pos.captured_piece_type()
- && is_ok((ss - 1)->currentMove)
- && is_ok((ss - 2)->currentMove))
+ && is_ok((ss-1)->currentMove))
{
- Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);
- Square prevPrevSq = to_sq((ss - 2)->currentMove);
- CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
- prevCmh.update(pos.piece_on(prevSq), prevSq, bonus);
+ Square prevSq = to_sq((ss-1)->currentMove);
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + 2 * depth / ONE_PLY - 2);
+ if ((ss-2)->counterMoves)
+ (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);
+
+ if ((ss-3)->counterMoves)
+ (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);
+
+ if ((ss-5)->counterMoves)
+ (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, bonus);
}
tte->save(posKey, value_to_tt(bestValue, ss->ply),
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));
// 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, to_sq((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Check for new best move
+ // Check for a new best move
if (value > bestValue)
{
bestValue = value;
}
- // update_stats() updates killers, history, countermove and countermove
- // history when a new quiet best move is found.
+ // 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) {
ss->killers[0] = move;
}
- Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + depth / ONE_PLY - 1);
+ Value bonus = Value((depth / ONE_PLY) * (depth / ONE_PLY) + 2 * depth / ONE_PLY - 2);
Square prevSq = to_sq((ss-1)->currentMove);
- CounterMovesStats& cmh = CounterMovesHistory[pos.piece_on(prevSq)][prevSq];
+ CounterMoveStats* cmh = (ss-1)->counterMoves;
+ CounterMoveStats* fmh = (ss-2)->counterMoves;
+ CounterMoveStats* fmh2 = (ss-4)->counterMoves;
Thread* thisThread = pos.this_thread();
thisThread->history.update(pos.moved_piece(move), to_sq(move), bonus);
- if (is_ok((ss-1)->currentMove))
+ if (cmh)
{
thisThread->counterMoves.update(pos.piece_on(prevSq), prevSq, move);
- cmh.update(pos.moved_piece(move), to_sq(move), bonus);
+ cmh->update(pos.moved_piece(move), to_sq(move), bonus);
}
+ if (fmh)
+ fmh->update(pos.moved_piece(move), to_sq(move), bonus);
+
+ if (fmh2)
+ fmh2->update(pos.moved_piece(move), to_sq(move), bonus);
+
// Decrease all the other played quiet moves
for (int i = 0; i < quietsCnt; ++i)
{
thisThread->history.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
- if (is_ok((ss-1)->currentMove))
- cmh.update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+ if (cmh)
+ cmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+
+ if (fmh)
+ fmh->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
+
+ if (fmh2)
+ fmh2->update(pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
// Extra penalty for a quiet TT move in previous ply when it gets refuted
- if ( (ss-1)->moveCount == 1
- && !pos.captured_piece_type()
- && is_ok((ss-2)->currentMove))
+ if ((ss-1)->moveCount == 1 && !pos.captured_piece_type())
{
- Square prevPrevSq = to_sq((ss-2)->currentMove);
- CounterMovesStats& prevCmh = CounterMovesHistory[pos.piece_on(prevPrevSq)][prevPrevSq];
- prevCmh.update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY);
+ if ((ss-2)->counterMoves)
+ (ss-2)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1);
+
+ if ((ss-3)->counterMoves)
+ (ss-3)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1);
+
+ if ((ss-5)->counterMoves)
+ (ss-5)->counterMoves->update(pos.piece_on(prevSq), prevSq, -bonus - 2 * (depth + 1) / ONE_PLY - 1);
}
}
Move Skill::pick_best(size_t multiPV) {
- const Search::RootMoveVector& rootMoves = Threads.main()->rootMoves;
+ 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 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.
+ // 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
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
+/// 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.
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]);
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);
+ }
+
+ pos.undo_move(pv[0]);
+ return pv.size() > 1;
+}
+
+void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) {
+
+ Hits = 0;
+ RootInTB = false;
+ UseRule50 = Options["Syzygy50MoveRule"];
+ ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
+ Cardinality = Options["SyzygyProbeLimit"];
+
+ // Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
+ if (Cardinality > MaxCardinality)
+ {
+ Cardinality = MaxCardinality;
+ ProbeDepth = DEPTH_ZERO;
+ }
+
+ if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING))
+ return;
+
+ // 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);
+
+ if (RootInTB)
+ 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 the draw or the win.
+ RootInTB = root_probe_wdl(pos, rootMoves, TB::Score);
+
+ // Only probe during search if winning
+ if (TB::Score <= VALUE_DRAW)
+ Cardinality = 0;
}
- return false;
+ 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