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) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2018 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
enum NodeType { NonPV, PV };
// Sizes and phases of the skip-blocks, used for distributing search depths across the threads
- const int skipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
- const int skipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
-
- // Razoring and futility margin based on depth
- // razor_margin[0] is unused as long as depth >= ONE_PLY in search
- const int razor_margin[] = { 0, 570, 603, 554 };
- Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
+ const int SkipSize[] = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
+ const int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
+
+ // Razor and futility margins
+ const int RazorMargin1 = 590;
+ const int RazorMargin2 = 604;
+ Value futility_margin(Depth d, bool improving) {
+ return Value((175 - 50 * improving) * d / ONE_PLY);
+ }
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
- template <NodeType NT, bool InCheck>
+ template <NodeType NT>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO);
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_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);
+ void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus);
void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCnt, int bonus);
- bool pv_is_draw(Position& pos);
+
+ inline bool gives_check(const Position& pos, Move move) {
+ Color us = pos.side_to_move();
+ return type_of(move) == NORMAL && !(pos.blockers_for_king(~us) & pos.pieces(us))
+ ? pos.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
+ : pos.gives_check(move);
+ }
// 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.
} // namespace
-/// Search::init() is called during startup to initialize various lookup tables
+/// Search::init() is called at startup to initialize various lookup tables
void Search::init() {
Time.availableNodes = 0;
TT.clear();
-
- for (Thread* th : Threads)
- th->clear();
-
- Threads.main()->callsCnt = 0;
- Threads.main()->previousScore = VALUE_INFINITE;
- Threads.main()->previousTimeReduction = 1;
+ Threads.clear();
}
Time.init(Limits, us, rootPos.game_ply());
TT.new_search();
- int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
-
- Eval::Contempt = (us == WHITE ? make_score(contempt, contempt / 2)
- : -make_score(contempt, contempt / 2));
-
if (rootMoves.empty())
{
rootMoves.emplace_back(MOVE_NONE);
previousScore = bestThread->rootMoves[0].score;
- // Send new PV when needed
+ // Send again PV info if we have a new best thread
if (bestThread != this)
sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
Depth lastBestMoveDepth = DEPTH_ZERO;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
double timeReduction = 1.0;
+ Color us = rootPos.side_to_move();
std::memset(ss-4, 0, 7 * sizeof(Stack));
for (int i = 4; i > 0; i--)
- (ss-i)->contHistory = &this->contHistory[NO_PIECE][0]; // Use as sentinel
+ (ss-i)->contHistory = this->contHistory[NO_PIECE][0].get(); // Use as sentinel
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
if (mainThread)
- {
- mainThread->failedLow = false;
- mainThread->bestMoveChanges = 0;
- }
+ mainThread->bestMoveChanges = 0, mainThread->failedLow = false;
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
multiPV = std::min(multiPV, rootMoves.size());
+ int ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ Eval::Contempt = (us == WHITE ? make_score(ct, ct / 2)
+ : -make_score(ct, ct / 2));
+
// Iterative deepening loop until requested to stop or the target depth is reached
while ( (rootDepth += ONE_PLY) < DEPTH_MAX
&& !Threads.stop
&& !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth))
{
- // Distribute search depths across the threads
- if (idx)
+ // Distribute search depths across the helper threads
+ if (idx > 0)
{
int i = (idx - 1) % 20;
- if (((rootDepth / ONE_PLY + rootPos.game_ply() + skipPhase[i]) / skipSize[i]) % 2)
- continue;
+ if (((rootDepth / ONE_PLY + rootPos.game_ply() + SkipPhase[i]) / SkipSize[i]) % 2)
+ continue; // Retry with an incremented rootDepth
}
// Age out PV variability metric
if (mainThread)
- mainThread->bestMoveChanges *= 0.505, mainThread->failedLow = false;
+ mainThread->bestMoveChanges *= 0.517, 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.
delta = Value(18);
alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
+
+ ct = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+
+ // Adjust contempt based on current bestValue (dynamic contempt)
+ ct += int(std::round(48 * atan(float(bestValue) / 128)));
+
+ Eval::Contempt = (us == WHITE ? make_score(ct, ct / 2)
+ : -make_score(ct, ct / 2));
}
// Start with a small aspiration window and, in the case of a fail
- // high/low, re-search with a bigger window until we're not failing
+ // high/low, re-search with a bigger window until we don't fail
// high/low anymore.
while (true)
{
// search the already searched PV lines are preserved.
std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.end());
- // If search has been stopped, we break immediately. Sorting and
- // writing PV back to TT is safe because RootMoves is still
- // valid, although it refers to the previous iteration.
+ // If search has been stopped, we break immediately. Sorting is
+ // safe because RootMoves is still valid, although it refers to
+ // the previous iteration.
if (Threads.stop)
break;
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)
+ if ( Limits.use_time_management()
+ && !Threads.stop
+ && !Threads.stopOnPonderhit)
{
- // Stop the search if only one legal move is available, or if all
- // 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]));
- Color us = rootPos.side_to_move();
- bool thinkHard = bestValue == VALUE_DRAW
- && Limits.time[us] - Time.elapsed() > Limits.time[~us]
- && ::pv_is_draw(rootPos);
+ int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1]));
- 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;
+ // If the bestMove is stable over several iterations, reduce time accordingly
+ timeReduction = 1.0;
for (int i : {3, 4, 5})
- if (lastBestMoveDepth * i < completedDepth && !thinkHard)
- timeReduction *= 1.3;
- unstablePvFactor *= std::pow(mainThread->previousTimeReduction, 0.51) / timeReduction;
+ if (lastBestMoveDepth * i < completedDepth)
+ timeReduction *= 1.25;
+
+ // Use part of the gained time from a previous stable move for the current move
+ double unstablePvFactor = 1.0 + mainThread->bestMoveChanges;
+ unstablePvFactor *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
+ // Stop the search if we have only one legal move, or if available time elapsed
if ( rootMoves.size() == 1
- || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628)
+ || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 581)
{
// 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 (!mainThread)
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval;
+ Value bestValue, value, ttValue, eval, maxValue;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact;
Piece movedPiece;
Thread* thisThread = pos.this_thread();
inCheck = pos.checkers();
moveCount = captureCount = quietCount = ss->moveCount = 0;
- ss->statScore = 0;
bestValue = -VALUE_INFINITE;
+ maxValue = VALUE_INFINITE;
// Check for the available remaining time
if (thisThread == Threads.main())
if (!rootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Threads.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
- return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos) : VALUE_DRAW;
+ if ( Threads.stop.load(std::memory_order_relaxed)
+ || pos.is_draw(ss->ply)
+ || ss->ply >= MAX_PLY)
+ return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) : VALUE_DRAW;
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
(ss+1)->ply = ss->ply + 1;
ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- ss->contHistory = &thisThread->contHistory[NO_PIECE][0];
+ ss->contHistory = thisThread->contHistory[NO_PIECE][0].get();
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
Square prevSq = to_sq((ss-1)->currentMove);
+ // Initialize statScore to zero for the grandchildren of the current position.
+ // So statScore is shared between all grandchildren and only the first grandchild
+ // starts with statScore = 0. Later grandchildren start with the last calculated
+ // statScore of the previous grandchild. This influences the reduction rules in
+ // LMR which are based on the statScore of parent position.
+ (ss+2)->statScore = 0;
+
// 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 = pos.key() ^ Key(excludedMove);
+ posKey = pos.key() ^ Key(excludedMove << 16); // Isn't a very good hash
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
if (ttValue >= beta)
{
if (!pos.capture_or_promotion(ttMove))
- update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
+ update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ((ss-1)->moveCount == 1 && !pos.captured_piece())
else if (!pos.capture_or_promotion(ttMove))
{
int penalty = -stat_bonus(depth);
- thisThread->mainHistory.update(pos.side_to_move(), ttMove, penalty);
+ thisThread->mainHistory[pos.side_to_move()][from_to(ttMove)] << penalty;
update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
}
}
return ttValue;
}
- // Step 4a. Tablebase probe
+ // Step 5. Tablebases probe
if (!rootNode && TB::Cardinality)
{
int piecesCount = pos.count<ALL_PIECES>();
&& !pos.can_castle(ANY_CASTLING))
{
TB::ProbeState err;
- TB::WDLScore v = Tablebases::probe_wdl(pos, &err);
+ TB::WDLScore wdl = Tablebases::probe_wdl(pos, &err);
if (err != TB::ProbeState::FAIL)
{
int drawScore = TB::UseRule50 ? 1 : 0;
- value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
- : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
- : VALUE_DRAW + 2 * v * drawScore;
+ value = wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
+ : wdl > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
+ : VALUE_DRAW + 2 * wdl * drawScore;
+
+ Bound b = wdl < -drawScore ? BOUND_UPPER
+ : wdl > drawScore ? BOUND_LOWER : BOUND_EXACT;
- tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
- std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
- MOVE_NONE, VALUE_NONE, TT.generation());
+ if ( b == BOUND_EXACT
+ || (b == BOUND_LOWER ? value >= beta : value <= alpha))
+ {
+ tte->save(posKey, value_to_tt(value, ss->ply), b,
+ std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+ MOVE_NONE, VALUE_NONE, TT.generation());
- return value;
+ return value;
+ }
+
+ if (PvNode)
+ {
+ if (b == BOUND_LOWER)
+ bestValue = value, alpha = std::max(alpha, bestValue);
+ else
+ maxValue = value;
+ }
}
}
}
- // Step 5. Evaluate the position statically
+ // Step 6. Evaluate the position statically
if (inCheck)
{
ss->staticEval = eval = VALUE_NONE;
+ improving = false;
goto moves_loop;
}
-
else if (ttHit)
{
// Never assume anything on values stored in TT
eval = ss->staticEval = evaluate(pos);
// Can ttValue be used as a better position evaluation?
- if ( ttValue != VALUE_NONE
+ if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)))
eval = ttValue;
}
else
{
- eval = ss->staticEval =
+ ss->staticEval = eval =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
: -(ss-1)->staticEval + 2 * Eval::Tempo;
ss->staticEval, TT.generation());
}
+ improving = ss->staticEval >= (ss-2)->staticEval
+ ||(ss-2)->staticEval == VALUE_NONE;
+
if (skipEarlyPruning || !pos.non_pawn_material(pos.side_to_move()))
goto moves_loop;
- // Step 6. Razoring (skipped when in check)
- if ( !PvNode
- && depth < 4 * ONE_PLY
- && eval + razor_margin[depth / ONE_PLY] <= alpha)
+ // Step 7. Razoring (skipped when in check)
+ if ( !PvNode
+ && depth <= 2 * ONE_PLY)
{
- if (depth <= ONE_PLY)
- return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
+ if ( depth == ONE_PLY
+ && eval + RazorMargin1 <= alpha)
+ return qsearch<NonPV>(pos, ss, alpha, alpha+1);
- Value ralpha = alpha - razor_margin[depth / ONE_PLY];
- Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
- if (v <= ralpha)
- return v;
+ else if (eval + RazorMargin2 <= alpha)
+ {
+ Value ralpha = alpha - RazorMargin2;
+ Value v = qsearch<NonPV>(pos, ss, ralpha, ralpha+1);
+
+ if (v <= ralpha)
+ return v;
+ }
}
- // Step 7. Futility pruning: child node (skipped when in check)
+ // Step 8. Futility pruning: child node (skipped when in check)
if ( !rootNode
&& depth < 7 * ONE_PLY
- && eval - futility_margin(depth) >= beta
- && eval < VALUE_KNOWN_WIN) // Do not return unproven wins
+ && eval - futility_margin(depth, improving) >= beta
+ && eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
- // Step 8. Null move search with verification search (is omitted in PV nodes)
+ // Step 9. Null move search with verification search
if ( !PvNode
&& eval >= beta
- && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225)
+ && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+ && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{
-
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
ss->currentMove = MOVE_NULL;
- ss->contHistory = &thisThread->contHistory[NO_PIECE][0];
+ ss->contHistory = thisThread->contHistory[NO_PIECE][0].get();
pos.do_null_move(st);
- Value nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1)
+ Value nullValue = depth-R < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -beta, -beta+1)
: - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
pos.undo_null_move();
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
- if (depth < 12 * ONE_PLY && abs(beta) < VALUE_KNOWN_WIN)
+ if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply))
return nullValue;
- // Do verification search at high depths
- Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta)
+ // Do verification search at high depths. Disable null move pruning
+ // for side to move for the first part of the remaining search tree.
+ thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
+ thisThread->nmp_odd = ss->ply % 2;
+
+ Value v = depth-R < ONE_PLY ? qsearch<NonPV>(pos, ss, beta-1, beta)
: search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
+ thisThread->nmp_odd = thisThread->nmp_ply = 0;
+
if (v >= beta)
return nullValue;
}
}
- // Step 9. ProbCut (skipped when in check)
+ // Step 10. ProbCut (skipped when in check)
// 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)
{
- Value rbeta = std::min(beta + 200, VALUE_INFINITE);
-
assert(is_ok((ss-1)->currentMove));
+ Value rbeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
MovePicker mp(pos, ttMove, rbeta - ss->staticEval, &thisThread->captureHistory);
+ int probCutCount = 0;
- while ((move = mp.next_move()) != MOVE_NONE)
+ while ( (move = mp.next_move()) != MOVE_NONE
+ && probCutCount < 3)
if (pos.legal(move))
{
+ probCutCount++;
+
ss->currentMove = move;
- ss->contHistory = &thisThread->contHistory[pos.moved_piece(move)][to_sq(move)];
+ ss->contHistory = thisThread->contHistory[pos.moved_piece(move)][to_sq(move)].get();
assert(depth >= 5 * ONE_PLY);
+
pos.do_move(move, st);
- value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false);
+
+ // Perform a preliminary qsearch to verify that the move holds
+ value = -qsearch<NonPV>(pos, ss+1, -rbeta, -rbeta+1);
+
+ // If the qsearch held perform the regular search
+ if (value >= rbeta)
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, depth - 4 * ONE_PLY, !cutNode, false);
+
pos.undo_move(move);
+
if (value >= rbeta)
return value;
}
}
- // Step 10. Internal iterative deepening (skipped when in check)
+ // Step 11. Internal iterative deepening (skipped when in check)
if ( depth >= 6 * ONE_PLY
&& !ttMove
&& (PvNode || ss->staticEval + 256 >= beta))
{
- Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY;
+ Depth d = 3 * depth / 4 - 2 * ONE_PLY;
search<NT>(pos, ss, alpha, beta, d, cutNode, true);
tte = TT.probe(posKey, ttHit);
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
}
-moves_loop: // When in check search starts from here
+moves_loop: // When in check, search starts from here
const PieceToHistory* contHist[] = { (ss-1)->contHistory, (ss-2)->contHistory, nullptr, (ss-4)->contHistory };
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, contHist, countermove, ss->killers);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
- improving = ss->staticEval >= (ss-2)->staticEval
- /* || ss->staticEval == VALUE_NONE Already implicit in the previous condition */
- ||(ss-2)->staticEval == VALUE_NONE;
singularExtensionNode = !rootNode
&& depth >= 8 * ONE_PLY
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
+ // Step 12. Loop through all pseudo-legal moves until no moves remain
+ // or a beta cutoff occurs.
while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
{
assert(is_ok(move));
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);
movedPiece = pos.moved_piece(move);
-
- givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates()
- ? pos.check_squares(type_of(movedPiece)) & to_sq(move)
- : pos.gives_check(move);
+ givesCheck = gives_check(pos, move);
moveCountPruning = depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[improving][depth / ONE_PLY];
- // Step 12. Singular and Gives Check Extensions
+ // Step 13. Extensions
- // Singular extension search. If all moves but one fail low on a search of
- // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
- // is singular and should be extended. To verify this we do a reduced search
- // on all the other moves but the ttMove and if the result is lower than
- // ttValue minus a margin then we will extend the ttMove.
+ // Singular extension search. If all moves but one fail low on a search
+ // of (alpha-s, beta-s), and just one fails high on (alpha, beta), then
+ // that move is singular and should be extended. To verify this we do a
+ // reduced search on on all the other moves but the ttMove and if the
+ // result is lower than ttValue minus a margin then we will extend the ttMove.
if ( singularExtensionNode
&& move == ttMove
&& pos.legal(move))
{
Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
- Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
ss->excludedMove = move;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode, true);
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, cutNode, true);
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
extension = ONE_PLY;
}
- else if ( givesCheck
+ else if ( givesCheck // Check extension
&& !moveCountPruning
&& pos.see_ge(move))
extension = ONE_PLY;
// Calculate new depth for this move
newDepth = depth - ONE_PLY + extension;
- // Step 13. Pruning at shallow depth
+ // Step 14. Pruning at shallow depth
if ( !rootNode
&& pos.non_pawn_material(pos.side_to_move())
&& bestValue > VALUE_MATED_IN_MAX_PLY)
// Update the current move (this must be done after singular extension search)
ss->currentMove = move;
- ss->contHistory = &thisThread->contHistory[movedPiece][to_sq(move)];
+ ss->contHistory = thisThread->contHistory[movedPiece][to_sq(move)].get();
- // Step 14. Make the move
+ // Step 15. Make the move
pos.do_move(move, st, givesCheck);
- // Step 15. Reduced depth search (LMR). If the move fails high it will be
+ // Step 16. Reduced depth search (LMR). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3 * ONE_PLY
&& moveCount > 1
else
doFullDepthSearch = !PvNode || moveCount > 1;
- // Step 16. Full depth search when LMR is skipped or fails high
+ // Step 17. 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)
- : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
+ value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
// 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
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
- value = newDepth < ONE_PLY ?
- givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha)
- : -qsearch<PV, false>(pos, ss+1, -beta, -alpha)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
+ value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
}
- // Step 17. Undo move
+ // Step 18. Undo move
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 18. Check for a new best move
+ // Step 19. 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.
RootMove& rm = *std::find(thisThread->rootMoves.begin(),
thisThread->rootMoves.end(), move);
- // PV move or new best move ?
+ // PV move or new best move?
if (moveCount == 1 || value > alpha)
{
rm.score = value;
}
}
- if (!captureOrPromotion && move != bestMove && quietCount < 64)
- quietsSearched[quietCount++] = move;
- else if (captureOrPromotion && move != bestMove && captureCount < 32)
- capturesSearched[captureCount++] = move;
+ if (move != bestMove)
+ {
+ if (captureOrPromotion && captureCount < 32)
+ capturesSearched[captureCount++] = move;
+
+ else if (!captureOrPromotion && quietCount < 64)
+ quietsSearched[quietCount++] = move;
+ }
}
// The following condition would detect a stop only after move loop has been
{
// Quiet best move: update move sorting heuristics
if (!pos.capture_or_promotion(bestMove))
- update_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth));
+ update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth));
else
update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth));
&& is_ok((ss-1)->currentMove))
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
+ if (PvNode)
+ bestValue = std::min(bestValue, maxValue);
+
if (!excludedMove)
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
// qsearch() is the quiescence search function, which is called by the main
// search function with depth zero, or recursively with depth less than ONE_PLY.
-
- template <NodeType NT, bool InCheck>
+ template <NodeType NT>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
const bool PvNode = NT == PV;
+ const bool inCheck = bool(pos.checkers());
- assert(InCheck == bool(pos.checkers()));
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(depth <= DEPTH_ZERO);
TTEntry* tte;
Key posKey;
Move ttMove, move, bestMove;
+ Depth ttDepth;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
bool ttHit, givesCheck, evasionPrunable;
- Depth ttDepth;
int moveCount;
if (PvNode)
ss->pv[0] = MOVE_NONE;
}
- ss->currentMove = bestMove = MOVE_NONE;
(ss+1)->ply = ss->ply + 1;
+ ss->currentMove = bestMove = MOVE_NONE;
moveCount = 0;
- // Check for an instant draw or if the maximum ply has been reached
- if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
- return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : VALUE_DRAW;
+ // Check for an immediate draw or maximum ply reached
+ if ( pos.is_draw(ss->ply)
+ || ss->ply >= MAX_PLY)
+ return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) : VALUE_DRAW;
assert(0 <= ss->ply && ss->ply < MAX_PLY);
// Decide whether or not to include checks: this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
- ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_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);
- ttMove = ttHit ? tte->move() : MOVE_NONE;
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ttMove = ttHit ? tte->move() : MOVE_NONE;
if ( !PvNode
&& ttHit
return ttValue;
// Evaluate the position statically
- if (InCheck)
+ if (inCheck)
{
ss->staticEval = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
{
assert(is_ok(move));
- givesCheck = type_of(move) == NORMAL && !pos.discovered_check_candidates()
- ? pos.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
- : pos.gives_check(move);
+ givesCheck = gives_check(pos, move);
moveCount++;
// Futility pruning
- if ( !InCheck
+ if ( !inCheck
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
}
// Detect non-capture evasions that are candidates to be pruned
- evasionPrunable = InCheck
+ evasionPrunable = inCheck
&& (depth != DEPTH_ZERO || moveCount > 2)
&& bestValue > VALUE_MATED_IN_MAX_PLY
&& !pos.capture(move);
// Don't search moves with negative SEE values
- if ( (!InCheck || evasionPrunable)
- && type_of(move) != PROMOTION
- && !pos.see_ge(move))
+ if ( (!inCheck || evasionPrunable)
+ && !pos.see_ge(move))
continue;
// Speculative prefetch as early as possible
// Make and search the move
pos.do_move(move, st, givesCheck);
- value = givesCheck ? -qsearch<NT, true>(pos, ss+1, -beta, -alpha, depth - ONE_PLY)
- : -qsearch<NT, false>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
+ value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (InCheck && bestValue == -VALUE_INFINITE)
+ if (inCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
tte->save(posKey, value_to_tt(bestValue, ss->ply),
for (int i : {1, 2, 4})
if (is_ok((ss-i)->currentMove))
- (ss-i)->contHistory->update(pc, to, bonus);
+ (*(ss-i)->contHistory)[pc][to] << bonus;
}
CapturePieceToHistory& captureHistory = pos.this_thread()->captureHistory;
Piece moved_piece = pos.moved_piece(move);
PieceType captured = type_of(pos.piece_on(to_sq(move)));
- captureHistory.update(moved_piece, to_sq(move), captured, bonus);
+ captureHistory[moved_piece][to_sq(move)][captured] << bonus;
// Decrease all the other played capture moves
for (int i = 0; i < captureCnt; ++i)
{
moved_piece = pos.moved_piece(captures[i]);
captured = type_of(pos.piece_on(to_sq(captures[i])));
- captureHistory.update(moved_piece, to_sq(captures[i]), captured, -bonus);
+ captureHistory[moved_piece][to_sq(captures[i])][captured] << -bonus;
}
}
- // update_stats() updates move sorting heuristics when a new quiet best move is found
+ // update_quiet_stats() updates move sorting heuristics when a new quiet best move is found
- void update_stats(const Position& pos, Stack* ss, Move move,
- Move* quiets, int quietsCnt, int bonus) {
+ void update_quiet_stats(const Position& pos, Stack* ss, Move move,
+ Move* quiets, int quietsCnt, int bonus) {
if (ss->killers[0] != move)
{
ss->killers[0] = move;
}
- Color c = pos.side_to_move();
+ Color us = pos.side_to_move();
Thread* thisThread = pos.this_thread();
- thisThread->mainHistory.update(c, move, bonus);
+ thisThread->mainHistory[us][from_to(move)] << bonus;
update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus);
if (is_ok((ss-1)->currentMove))
// Decrease all the other played quiet moves
for (int i = 0; i < quietsCnt; ++i)
{
- thisThread->mainHistory.update(c, quiets[i], -bonus);
+ thisThread->mainHistory[us][from_to(quiets[i])] << -bonus;
update_continuation_histories(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
}
}
-
- // 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.
} // namespace
- // 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.
+/// MainThread::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 MainThread::check_time() {
+void MainThread::check_time() {
- if (--callsCnt > 0)
- return;
+ if (--callsCnt > 0)
+ return;
- // At low node count increase the checking rate to about 0.1% of nodes
- // otherwise use a default value.
- callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) : 4096;
+ // When using nodes, ensure checking rate is not lower than 0.1% of nodes
+ callsCnt = Limits.nodes ? std::min(4096, int(Limits.nodes / 1024)) : 4096;
- static TimePoint lastInfoTime = now();
+ static TimePoint lastInfoTime = now();
- int elapsed = Time.elapsed();
- TimePoint tick = Limits.startTime + elapsed;
+ int elapsed = Time.elapsed();
+ TimePoint tick = Limits.startTime + elapsed;
- if (tick - lastInfoTime >= 1000)
- {
- lastInfoTime = tick;
- dbg_print();
- }
+ if (tick - lastInfoTime >= 1000)
+ {
+ lastInfoTime = tick;
+ dbg_print();
+ }
- // An engine may not stop pondering until told so by the GUI
- if (Threads.ponder)
- return;
+ // We should not stop pondering until told so by the GUI
+ if (Threads.ponder)
+ return;
- 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;
- }
+ if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10)
+ || (Limits.movetime && elapsed >= Limits.movetime)
+ || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
+ Threads.stop = true;
+}
/// UCI::pv() formats PV information according to the UCI protocol. UCI requires
return pv.size() > 1;
}
+
void Tablebases::filter_root_moves(Position& pos, Search::RootMoves& rootMoves) {
RootInTB = false;
TB::Score = TB::Score > VALUE_DRAW ? VALUE_MATE - MAX_PLY - 1
: TB::Score < VALUE_DRAW ? -VALUE_MATE + MAX_PLY + 1
: VALUE_DRAW;
+
+ // Since root_probe() and root_probe_wdl() dirty the root move scores,
+ // we reset them to -VALUE_INFINITE
+ for (RootMove& rm : rootMoves)
+ rm.score = -VALUE_INFINITE;
}
projects / stockfish / blobdiff