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
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 };
+ const int razor_margin = 600;
Value futility_margin(Depth d) { return Value(150 * d / ONE_PLY); }
// Futility and reductions lookup tables, initialized at startup
Move best = MOVE_NONE;
};
- Value DrawValue[COLOR_NB];
-
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
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_capture_stats(const Position& pos, Move move, Move* captures, int captureCnt, int bonus);
- bool pv_is_draw(Position& pos);
// perft() is our utility to verify move generation. All the leaf nodes up
// to the given depth are generated and counted, and the sum is returned.
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
- DrawValue[ us] = VALUE_DRAW - Value(contempt);
- DrawValue[~us] = VALUE_DRAW + Value(contempt);
-
if (rootMoves.empty())
{
rootMoves.emplace_back(MOVE_NONE);
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--)
multiPV = std::min(multiPV, rootMoves.size());
+ int contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ Eval::Contempt = (us == WHITE ? make_score(contempt, contempt / 2)
+ : -make_score(contempt, contempt / 2));
+
// Iterative deepening loop until requested to stop or the target depth is reached
while ( (rootDepth += ONE_PLY) < DEPTH_MAX
&& !Threads.stop
delta = Value(18);
alpha = std::max(rootMoves[PVIdx].previousScore - delta,-VALUE_INFINITE);
beta = std::min(rootMoves[PVIdx].previousScore + delta, VALUE_INFINITE);
+
+ // Adjust contempt based on current situation
+ contempt = Options["Contempt"] * PawnValueEg / 100; // From centipawns
+ contempt += bestValue > 500 ? 50: // Dynamic contempt
+ bestValue < -500 ? -50:
+ bestValue / 10;
+
+ Eval::Contempt = (us == WHITE ? make_score(contempt, contempt / 2)
+ : -make_score(contempt, contempt / 2));
}
// Start with a small aspiration window and, in the case of a fail
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 = DrawValue[us] == bestValue
- && Limits.time[us] - Time.elapsed() > Limits.time[~us]
- && ::pv_is_draw(rootPos);
-
- double unstablePvFactor = 1 + mainThread->bestMoveChanges + thinkHard;
+ double unstablePvFactor = 1 + mainThread->bestMoveChanges;
// if the bestMove is stable over several iterations, reduce time for this move,
// the longer the move has been stable, the more.
// Use part of the gained time from a previous stable move for the current move.
timeReduction = 1;
for (int i : {3, 4, 5})
- if (lastBestMoveDepth * i < completedDepth && !thinkHard)
+ if (lastBestMoveDepth * i < completedDepth )
timeReduction *= 1.3;
unstablePvFactor *= std::pow(mainThread->previousTimeReduction, 0.51) / timeReduction;
if ( rootMoves.size() == 1
- || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 628)
+ || Time.elapsed() > Time.optimum() * unstablePvFactor * improvingFactor / 605)
{
// If we are allowed to ponder do not stop the search now but
// keep pondering until the GUI sends "ponderhit" or "stop".
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;
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())
{
// 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)
- : DrawValue[pos.side_to_move()];
+ 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
// 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 (!pos.capture_or_promotion(ttMove))
update_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
- else
- update_capture_stats(pos, 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())
&& !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;
+ }
}
}
}
ss->staticEval, TT.generation());
}
- if (skipEarlyPruning)
+ 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)
+ && eval + razor_margin <= alpha)
{
if (depth <= ONE_PLY)
return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
- Value ralpha = alpha - razor_margin[depth / ONE_PLY];
+ Value ralpha = alpha - razor_margin;
Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
if (v <= ralpha)
return v;
if ( !rootNode
&& depth < 7 * ONE_PLY
&& eval - futility_margin(depth) >= beta
- && eval < VALUE_KNOWN_WIN // Do not return unproven wins
- && pos.non_pawn_material(pos.side_to_move()))
+ && eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
&& eval >= beta
- && (ss->staticEval >= beta - 35 * (depth / ONE_PLY - 6) || depth >= 13 * ONE_PLY)
- && pos.non_pawn_material(pos.side_to_move()))
+ && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
+ && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
{
assert(eval - beta >= 0);
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
+ // 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, false>(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;
}
movedPiece = 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.check_squares(type_of(movedPiece)) & to_sq(move)
: pos.gives_check(move);
moveCountPruning = depth < 16 * ONE_PLY
if (!moveCount)
bestValue = excludedMove ? alpha
- : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+ : inCheck ? mated_in(ss->ply) : VALUE_DRAW;
else if (bestMove)
{
// Quiet best move: update move sorting heuristics
&& 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 :
const bool PvNode = NT == PV;
- assert(InCheck == !!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);
// 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)
- : DrawValue[pos.side_to_move()];
+ return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos) : VALUE_DRAW;
assert(0 <= ss->ply && ss->ply < MAX_PLY);
if (bestValue >= beta)
{
if (!ttHit)
- tte->save(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
+ tte->save(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER,
DEPTH_NONE, MOVE_NONE, ss->staticEval, TT.generation());
return bestValue;
assert(is_ok(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.check_squares(type_of(pos.moved_piece(move))) & to_sq(move)
: pos.gives_check(move);
moveCount++;
// Don't search moves with negative SEE values
if ( (!InCheck || evasionPrunable)
- && type_of(move) != PROMOTION
&& !pos.see_ge(move))
continue;
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.update(moved_piece, to_sq(move), captured, bonus);
// Decrease all the other played capture moves
for (int i = 0; i < captureCnt; ++i)
}
}
-
- // 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.
if (Threads.ponder)
return;
- if ( (Limits.use_time_management() && elapsed > Time.maximum())
+ 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;
ProbeDepth = Options["SyzygyProbeDepth"] * ONE_PLY;
Cardinality = Options["SyzygyProbeLimit"];
- // Don't filter any moves if the user requested analysis on multiple
- if (Options["MultiPV"] != 1)
- return;
-
// Skip TB probing when no TB found: !TBLargest -> !TB::Cardinality
if (Cardinality > MaxCardinality)
{
if (Cardinality < popcount(pos.pieces()) || pos.can_castle(ANY_CASTLING))
return;
+ // Don't filter any moves if the user requested analysis on multiple
+ if (Options["MultiPV"] != 1)
+ 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);
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;
}