/*
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) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
constexpr uint64_t TtHitAverageResolution = 1024;
// Razor and futility margins
- constexpr int RazorMargin = 516;
+ constexpr int RazorMargin = 527;
Value futility_margin(Depth d, bool improving) {
- return Value(224 * (d - improving));
+ return Value(227 * (d - improving));
}
// Reductions lookup table, initialized at startup
Depth reduction(bool i, Depth d, int mn) {
int r = Reductions[d] * Reductions[mn];
- return (r + 529) / 1024 + (!i && r > 1050);
+ return (r + 570) / 1024 + (!i && r > 1018);
}
constexpr int futility_move_count(bool improving, Depth depth) {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return d > 15 ? 28 : 19 * d * d + 135 * d - 136;
+ return d > 15 ? 27 : 17 * d * d + 133 * d - 134;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int((24.9 + std::log(Threads.size())) * std::log(i));
+ Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i));
}
Time.init(Limits, us, rootPos.game_ply());
TT.new_search();
+ Eval::verify_NNUE();
+
if (rootMoves.empty())
{
rootMoves.emplace_back(MOVE_NONE);
Thread* bestThread = this;
- if (int(Options["MultiPV"]) == 1 &&
- !Limits.depth &&
- !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) &&
- rootMoves[0].pv[0] != MOVE_NONE)
+ if ( int(Options["MultiPV"]) == 1
+ && !Limits.depth
+ && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"]))
+ && rootMoves[0].pv[0] != MOVE_NONE)
bestThread = Threads.get_best_thread();
bestPreviousScore = bestThread->rootMoves[0].score;
if (rootDepth >= 4)
{
Value prev = rootMoves[pvIdx].previousScore;
- delta = Value(21);
+ delta = Value(19);
alpha = std::max(prev - delta,-VALUE_INFINITE);
beta = std::min(prev + delta, VALUE_INFINITE);
// Adjust contempt based on root move's previousScore (dynamic contempt)
- int dct = ct + (104 - ct / 2) * prev / (abs(prev) + 143);
+ int dct = ct + (110 - ct / 2) * prev / (abs(prev) + 140);
contempt = (us == WHITE ? make_score(dct, dct / 2)
: -make_score(dct, dct / 2));
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (293 + 6 * (mainThread->bestPreviousScore - bestValue)
- + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 742.0;
+ double fallingEval = (296 + 6 * (mainThread->bestPreviousScore - bestValue)
+ + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 725.0;
fallingEval = Utility::clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
- timeReduction = lastBestMoveDepth + 10 < completedDepth ? 1.93 : 0.96;
- double reduction = (1.36 + mainThread->previousTimeReduction) / (2.21 * timeReduction);
+ timeReduction = lastBestMoveDepth + 10 < completedDepth ? 1.92 : 0.95;
+ double reduction = (1.47 + mainThread->previousTimeReduction) / (2.22 * timeReduction);
// Use part of the gained time from a previous stable move for the current move
for (Thread* th : Threads)
double totalTime = rootMoves.size() == 1 ? 0 :
Time.optimum() * fallingEval * reduction * bestMoveInstability;
- // Stop the search if we have exceeded the totalTime, at least 1ms search.
+ // Stop the search if we have exceeded the totalTime, at least 1ms search
if (Time.elapsed() > totalTime)
{
// If we are allowed to ponder do not stop the search now but
}
else if ( Threads.increaseDepth
&& !mainThread->ponder
- && Time.elapsed() > totalTime * 0.57)
+ && Time.elapsed() > totalTime * 0.56)
Threads.increaseDepth = false;
else
Threads.increaseDepth = true;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
- Value bestValue, value, ttValue, eval, maxValue;
+ Value bestValue, value, ttValue, eval, maxValue, probcutBeta;
bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
ttCapture, singularQuietLMR;
|| pos.is_draw(ss->ply)
|| ss->ply >= MAX_PLY)
return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos)
- : value_draw(pos.this_thread());
+ : value_draw(pos.this_thread());
// 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 << 16); // Isn't a very good hash
+ posKey = excludedMove == MOVE_NONE ? pos.key() : pos.key() ^ make_key(excludedMove);
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
ttPv = PvNode || (ttHit && tte->is_pv());
formerPv = ttPv && !PvNode;
- if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove))
+ if ( ttPv
+ && depth > 12
+ && ss->ply - 1 < MAX_LPH
+ && !priorCapture
+ && is_ok((ss-1)->currentMove))
thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5);
// thisThread->ttHitAverage can be used to approximate the running average of ttHit
// Step 6. Static evaluation of the position
if (ss->inCheck)
{
+ // Skip early pruning when in check
ss->staticEval = eval = VALUE_NONE;
improving = false;
- goto moves_loop; // Skip early pruning when in check
+ goto moves_loop;
}
else if (ttHit)
{
// Step 8. Futility pruning: child node (~50 Elo)
if ( !PvNode
- && depth < 6
+ && depth < 8
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
// Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 24714
+ && (ss-1)->statScore < 23824
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 29 * depth - 31 * improving + 119 * ttPv + 299
+ && ss->staticEval >= beta - 28 * depth - 28 * improving + 94 * ttPv + 200
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
- Depth R = (793 + 70 * depth) / 252 + std::min(int(eval - beta) / 192, 3);
+ Depth R = (737 + 77 * depth) / 246 + std::min(int(eval - beta) / 192, 3);
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
}
}
+ probcutBeta = beta + 176 - 49 * improving;
+
// Step 10. ProbCut (~10 Elo)
// 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
- && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
+ && depth > 4
+ && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY
+ && !( ttHit
+ && tte->depth() >= depth - 3
+ && ttValue != VALUE_NONE
+ && ttValue < probcutBeta))
{
- Value raisedBeta = beta + 182 - 48 * improving;
- assert(raisedBeta < VALUE_INFINITE);
- MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory);
+ if ( ttHit
+ && tte->depth() >= depth - 3
+ && ttValue != VALUE_NONE
+ && ttValue >= probcutBeta
+ && ttMove
+ && pos.capture_or_promotion(ttMove))
+ return probcutBeta;
+
+ assert(probcutBeta < VALUE_INFINITE);
+ MovePicker mp(pos, ttMove, probcutBeta - ss->staticEval, &captureHistory);
int probCutCount = 0;
while ( (move = mp.next_move()) != MOVE_NONE
- && probCutCount < 2 + 2 * cutNode
- && !( move == ttMove
- && tte->depth() >= depth - 4
- && ttValue < raisedBeta))
+ && probCutCount < 2 + 2 * cutNode)
if (move != excludedMove && pos.legal(move))
{
assert(pos.capture_or_promotion(move));
pos.do_move(move, st);
// Perform a preliminary qsearch to verify that the move holds
- value = -qsearch<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1);
+ value = -qsearch<NonPV>(pos, ss+1, -probcutBeta, -probcutBeta+1);
// If the qsearch held, perform the regular search
- if (value >= raisedBeta)
- value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 5, !cutNode);
+ if (value >= probcutBeta)
+ value = -search<NonPV>(pos, ss+1, -probcutBeta, -probcutBeta+1, depth - 4, !cutNode);
pos.undo_move(move);
- if (value >= raisedBeta)
+ if (value >= probcutBeta)
+ {
+ if ( !(ttHit
+ && tte->depth() >= depth - 3
+ && ttValue != VALUE_NONE))
+ tte->save(posKey, value_to_tt(value, ss->ply), ttPv,
+ BOUND_LOWER,
+ depth - 3, move, ss->staticEval);
return value;
+ }
}
}
thisThread->rootMoves.begin() + thisThread->pvLast, move))
continue;
+ // Check for legality
+ if (!rootNode && !pos.legal(move))
+ continue;
+
ss->moveCount = ++moveCount;
if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
continue;
// Futility pruning: parent node (~5 Elo)
- if ( lmrDepth < 6
+ if ( lmrDepth < 8
&& !ss->inCheck
- && ss->staticEval + 252 + 176 * lmrDepth <= alpha
+ && ss->staticEval + 284 + 188 * lmrDepth <= alpha
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- + (*contHist[5])[movedPiece][to_sq(move)] / 2 < 30251)
+ + (*contHist[5])[movedPiece][to_sq(move)] / 2 < 28388)
continue;
// Prune moves with negative SEE (~20 Elo)
- if (!pos.see_ge(move, Value(-(31 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
+ if (!pos.see_ge(move, Value(-(29 - std::min(lmrDepth, 17)) * lmrDepth * lmrDepth)))
continue;
}
else
if ( !givesCheck
&& lmrDepth < 6
&& !(PvNode && abs(bestValue) < 2)
+ && PieceValue[MG][type_of(movedPiece)] >= PieceValue[MG][type_of(pos.piece_on(to_sq(move)))]
&& !ss->inCheck
- && ss->staticEval + 264 + 397 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
+ && ss->staticEval + 178 + 261 * lmrDepth
+ + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
continue;
// See based pruning
- if (!pos.see_ge(move, Value(-192) * depth)) // (~25 Elo)
+ if (!pos.see_ge(move, Value(-202) * depth)) // (~25 Elo)
continue;
}
}
// 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.
+ // result is lower than ttValue minus a margin, then we will extend the ttMove.
if ( depth >= 6
&& move == ttMove
&& !rootNode
/* && ttValue != VALUE_NONE Already implicit in the next condition */
&& abs(ttValue) < VALUE_KNOWN_WIN
&& (tte->bound() & BOUND_LOWER)
- && tte->depth() >= depth - 3
- && pos.legal(move))
+ && tte->depth() >= depth - 3)
{
Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
else if (singularBeta >= beta)
return singularBeta;
- // If the eval of ttMove is greater than beta we try also if there is an other move that
- // pushes it over beta, if so also produce a cutoff
+ // If the eval of ttMove is greater than beta we try also if there is another
+ // move that pushes it over beta, if so also produce a cutoff.
else if (ttValue >= beta)
{
ss->excludedMove = move;
// 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))
- {
- ss->moveCount = --moveCount;
- continue;
- }
-
// Update the current move (this must be done after singular extension search)
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
- || thisThread->ttHitAverage < 399 * TtHitAverageResolution * TtHitAverageWindow / 1024))
+ || thisThread->ttHitAverage < 415 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
+ // Decrease reduction at non-check cut nodes for second move at low depths
+ if ( cutNode
+ && depth <= 10
+ && moveCount <= 2
+ && !ss->inCheck)
+ r--;
+
// Decrease reduction if the ttHit running average is large
- if (thisThread->ttHitAverage > 492 * TtHitAverageResolution * TtHitAverageWindow / 1024)
+ if (thisThread->ttHitAverage > 473 * TtHitAverageResolution * TtHitAverageWindow / 1024)
r--;
- // Reduction if other threads are searching this position.
+ // Reduction if other threads are searching this position
if (th.marked())
r++;
r++;
// Decrease reduction if opponent's move count is high (~5 Elo)
- if ((ss-1)->moveCount > 14)
+ if ((ss-1)->moveCount > 13)
r--;
// Decrease reduction if ttMove has been singularly extended (~3 Elo)
// hence break make_move(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
- r -= 2 + ttPv;
+ r -= 2 + ttPv - (type_of(movedPiece) == PAWN);
ss->statScore = thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 4926;
+ - 4826;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
- if (ss->statScore >= -99 && (ss-1)->statScore < -116)
+ if (ss->statScore >= -100 && (ss-1)->statScore < -112)
r--;
- else if ((ss-1)->statScore >= -117 && ss->statScore < -150)
+ else if ((ss-1)->statScore >= -125 && ss->statScore < -138)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- r -= ss->statScore / 15896;
+ r -= ss->statScore / 14615;
}
else
{
// Unless giving check, this capture is likely bad
if ( !givesCheck
- && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 200 * depth <= alpha)
+ && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 211 * depth <= alpha)
r++;
}
rm.pv.push_back(*m);
// We record how often the best move has been changed in each
- // iteration. This information is used for time management: When
+ // iteration. This information is used for time management: when
// the best move changes frequently, we allocate some more time.
if (moveCount > 1)
++thisThread->bestMoveChanges;
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 138;
+ futilityBase = bestValue + 141;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
// Initialize a MovePicker object for the current position, and prepare
// 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.
+ // queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
+ // will be generated.
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&thisThread->captureHistory,
contHist,
}
}
- // Don't search moves with negative SEE values
+ // Do not search moves with negative SEE values
if ( !ss->inCheck && !pos.see_ge(move))
continue;
}
}
- // All legal moves have been searched. A special case: If we're in check
+ // All legal moves have been searched. A special case: if we're in check
// and no legal moves were found, it is checkmate.
if (ss->inCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
// value_to_tt() adjusts a mate or TB score from "plies to mate from the root" to
- // "plies to mate from the current position". standard scores are unchanged.
+ // "plies to mate from the current position". Standard scores are unchanged.
// The function is called before storing a value in the transposition table.
Value value_to_tt(Value v, int ply) {
}
- // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate or TB score
- // from the transposition table (which refers to the plies to mate/be mated
- // from current position) to "plies to mate/be mated (TB win/loss) from the root".
- // However, for mate scores, to avoid potentially false mate scores related to the 50 moves rule,
- // and the graph history interaction, return an optimal TB score instead.
+ // value_from_tt() is the inverse of value_to_tt(): it adjusts a mate or TB score
+ // from the transposition table (which refers to the plies to mate/be mated from
+ // current position) to "plies to mate/be mated (TB win/loss) from the root". However,
+ // for mate scores, to avoid potentially false mate scores related to the 50 moves rule
+ // and the graph history interaction, we return an optimal TB score instead.
Value value_from_tt(Value v, int ply, int r50c) {
thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move;
}
- if (depth > 12 && ss->ply < MAX_LPH)
- thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7);
+ if (depth > 11 && ss->ply < MAX_LPH)
+ thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 6);
}
// When playing with strength handicap, choose best move among a set of RootMoves
} // namespace
+
/// 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.
<< " multipv " << i + 1
<< " score " << UCI::value(v);
+ if (Options["UCI_ShowWDL"])
+ ss << UCI::wdl(v, pos.game_ply());
+
if (!tb && i == pvIdx)
ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
projects / stockfish / blobdiff