// Futility margin
Value futility_margin(Depth d, bool improving) {
- return Value(154 * (d - improving));
+ return Value(140 * (d - improving));
}
// Reductions lookup table, initialized at startup
Depth reduction(bool i, Depth d, int mn, Value delta, Value rootDelta) {
int r = Reductions[d] * Reductions[mn];
- return (r + 1449 - int(delta) * 937 / int(rootDelta)) / 1024 + (!i && r > 941);
+ return (r + 1372 - int(delta) * 1073 / int(rootDelta)) / 1024 + (!i && r > 936);
}
constexpr int futility_move_count(bool improving, Depth depth) {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return std::min(341 * d - 470, 1710);
+ return std::min(336 * d - 547, 1561);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int((19.47 + std::log(Threads.size()) / 2) * std::log(i));
+ Reductions[i] = int((20.57 + std::log(Threads.size()) / 2) * std::log(i));
}
// Reset aspiration window starting size
Value prev = rootMoves[pvIdx].averageScore;
- delta = Value(10) + int(prev) * prev / 16502;
+ delta = Value(10) + int(prev) * prev / 15799;
alpha = std::max(prev - delta,-VALUE_INFINITE);
beta = std::min(prev + delta, VALUE_INFINITE);
// Adjust optimism based on root move's previousScore
- int opt = 102 * prev / (std::abs(prev) + 147);
+ int opt = 109 * prev / (std::abs(prev) + 141);
optimism[ us] = Value(opt);
optimism[~us] = -optimism[us];
else
break;
- delta += delta / 4 + 2;
+ delta += delta / 3;
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
}
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
- && ss->ttHit
&& !excludedMove
&& tte->depth() > depth - (tte->bound() == BOUND_EXACT)
- && ttValue != VALUE_NONE // Possible in case of TT access race
+ && ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
{
// If ttMove is quiet, update move sorting heuristics on TT hit (~2 Elo)
// Use static evaluation difference to improve quiet move ordering (~4 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
- int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1920, 1920);
+ int bonus = std::clamp(-18 * int((ss-1)->staticEval + ss->staticEval), -1817, 1817);
thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
}
// margin and the improving flag are used in various pruning heuristics.
improvement = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval - (ss-2)->staticEval
: (ss-4)->staticEval != VALUE_NONE ? ss->staticEval - (ss-4)->staticEval
- : 156;
+ : 173;
improving = improvement > 0;
// Step 7. Razoring (~1 Elo).
// If eval is really low check with qsearch if it can exceed alpha, if it can't,
// return a fail low.
- if (eval < alpha - 426 - 256 * depth * depth)
+ if (eval < alpha - 456 - 252 * depth * depth)
{
value = qsearch<NonPV>(pos, ss, alpha - 1, alpha);
if (value < alpha)
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 9
- && eval - futility_margin(depth, improving) - (ss-1)->statScore / 280 >= beta
+ && eval - futility_margin(depth, improving) - (ss-1)->statScore / 306 >= beta
&& eval >= beta
- && eval < 25128) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
+ && eval < 24923) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval;
// Step 9. Null move search with verification search (~35 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 18755
+ && (ss-1)->statScore < 17329
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 20 * depth - improvement / 13 + 253
+ && ss->staticEval >= beta - 21 * depth - improvement * 99 / 1300 + 258
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly))
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and eval
- Depth R = std::min(int(eval - beta) / 172, 6) + depth / 3 + 4;
+ Depth R = std::min(int(eval - beta) / 173, 6) + depth / 3 + 4;
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
}
}
- probCutBeta = beta + 186 - 54 * improving;
+ probCutBeta = beta + 168 - 61 * improving;
// Step 10. ProbCut (~10 Elo)
// If we have a good enough capture (or queen promotion) and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
- && depth > 4
+ && depth > 3
&& abs(beta) < VALUE_TB_WIN_IN_MAX_PLY
// if value from transposition table is lower than probCutBeta, don't attempt probCut
// there and in further interactions with transposition table cutoff depth is set to depth - 3
// because probCut search has depth set to depth - 4 but we also do a move before it
// so effective depth is equal to depth - 3
- && !( ss->ttHit
- && tte->depth() >= depth - 3
+ && !( tte->depth() >= depth - 3
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
return qsearch<PV>(pos, ss, alpha, beta);
if ( cutNode
- && depth >= 7
+ && depth >= 8
&& !ttMove)
depth -= 2;
moves_loop: // When in check, search starts here
// Step 12. A small Probcut idea, when we are in check (~4 Elo)
- probCutBeta = beta + 391;
+ probCutBeta = beta + 413;
if ( ss->inCheck
&& !PvNode
- && depth >= 2
&& ttCapture
&& (tte->bound() & BOUND_LOWER)
- && tte->depth() >= depth - 3
+ && tte->depth() >= depth - 4
&& ttValue >= probCutBeta
&& abs(ttValue) <= VALUE_KNOWN_WIN
&& abs(beta) <= VALUE_KNOWN_WIN)
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
- int lmrDepth = std::max(newDepth - r, 0);
+ int lmrDepth = newDepth - r;
if ( capture
|| givesCheck)
{
// Futility pruning for captures (~2 Elo)
if ( !givesCheck
- && lmrDepth < 6
+ && lmrDepth < 7
&& !ss->inCheck
- && ss->staticEval + 182 + 230 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ && ss->staticEval + 197 + 248 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
continue;
- Bitboard occupied;
// SEE based pruning (~11 Elo)
- if (!pos.see_ge(move, occupied, Value(-206) * depth))
- {
- if (depth < 2 - capture)
+ if (!pos.see_ge(move, Value(-205) * depth))
continue;
- // Don't prune the move if opp. King/Queen/Rook gets a discovered attack during or after the exchanges
- Bitboard leftEnemies = pos.pieces(~us, KING, QUEEN, ROOK);
- Bitboard attacks = 0;
- occupied |= to_sq(move);
- while (leftEnemies && !attacks)
- {
- Square sq = pop_lsb(leftEnemies);
- attacks = pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
- // Exclude Queen/Rook(s) which were already threatened before SEE (opp King can't be in check when it's our turn)
- if (attacks && sq != pos.square<KING>(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us)))
- attacks = 0;
- }
- if (!attacks)
- continue;
- }
}
else
{
+ (*contHist[3])[movedPiece][to_sq(move)];
// Continuation history based pruning (~2 Elo)
- if ( lmrDepth < 5
- && history < -4405 * (depth - 1))
+ if ( lmrDepth < 6
+ && history < -3832 * depth)
continue;
history += 2 * thisThread->mainHistory[us][from_to(move)];
- lmrDepth += history / 7278;
+ lmrDepth += history / 7011;
lmrDepth = std::max(lmrDepth, -2);
// Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
- && lmrDepth < 13
- && ss->staticEval + 103 + 138 * lmrDepth <= alpha)
+ && lmrDepth < 12
+ && ss->staticEval + 112 + 138 * lmrDepth <= alpha)
continue;
lmrDepth = std::max(lmrDepth, 0);
// Prune moves with negative SEE (~4 Elo)
- if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 16 * lmrDepth)))
+ if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth)))
continue;
}
}
// 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.
if ( !rootNode
- && depth >= 4 - (thisThread->completedDepth > 21) + 2 * (PvNode && tte->is_pv())
+ && depth >= 4 - (thisThread->completedDepth > 22) + 2 * (PvNode && tte->is_pv())
&& move == ttMove
&& !excludedMove // Avoid recursive singular search
/* && ttValue != VALUE_NONE Already implicit in the next condition */
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3)
{
- Value singularBeta = ttValue - (3 + 2 * (ss->ttPv && !PvNode)) * depth / 2;
+ Value singularBeta = ttValue - (82 + 65 * (ss->ttPv && !PvNode)) * depth / 64;
Depth singularDepth = (depth - 1) / 2;
ss->excludedMove = move;
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
- && value < singularBeta - 25
- && ss->doubleExtensions <= 10)
+ && value < singularBeta - 21
+ && ss->doubleExtensions <= 11)
{
extension = 2;
depth += depth < 13;
}
// Check extensions (~1 Elo)
- else if ( givesCheck
- && depth > 10
- && abs(ss->staticEval) > 88)
+ else if ( givesCheck && depth > 8)
extension = 1;
// Quiet ttMove extensions (~1 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
- && (*contHist[0])[movedPiece][to_sq(move)] >= 5705)
+ && (*contHist[0])[movedPiece][to_sq(move)] >= 5168)
extension = 1;
}
r -= cutNode && tte->depth() >= depth + 3 ? 3 : 2;
// Decrease reduction if opponent's move count is high (~1 Elo)
- if ((ss-1)->moveCount > 7)
+ if ((ss-1)->moveCount > 8)
r--;
// Increase reduction for cut nodes (~3 Elo)
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 4082;
+ - 4006;
// Decrease/increase reduction for moves with a good/bad history (~25 Elo)
- r -= ss->statScore / (11079 + 4626 * (depth > 6 && depth < 19));
+ r -= ss->statScore / (11124 + 4740 * (depth > 5 && depth < 22));
// Step 17. Late moves reduction / extension (LMR, ~117 Elo)
// We use various heuristics for the sons of a node after the first son has
{
// Adjust full depth search based on LMR results - if result
// was good enough search deeper, if it was bad enough search shallower
- const bool doDeeperSearch = value > (alpha + 58 + 12 * (newDepth - d));
- const bool doEvenDeeperSearch = value > alpha + 588 && ss->doubleExtensions <= 5;
+ const bool doDeeperSearch = value > (bestValue + 64 + 11 * (newDepth - d));
+ const bool doEvenDeeperSearch = value > alpha + 711 && ss->doubleExtensions <= 6;
const bool doShallowerSearch = value < bestValue + newDepth;
ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch;
if (!ttMove && cutNode)
r += 2;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 3), !cutNode);
}
// For PV nodes only, do a full PV search on the first move or after a fail
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
+ if (value >= beta)
+ {
+ ss->cutoffCnt += 1 + !ttMove;
+ assert(value >= beta); // Fail high
+ break;
+ }
+ else
{
// Reduce other moves if we have found at least one score improvement (~1 Elo)
+ // Reduce more for depth > 3 and depth < 12 (~1 Elo)
if ( depth > 1
- && beta < 12535
- && value > -12535)
- depth -= 1;
+ && beta < 14362
+ && value > -12393)
+ depth -= depth > 3 && depth < 12 ? 2 : 1;
assert(depth > 0);
- alpha = value;
- }
- else
- {
- ss->cutoffCnt += 1 + !ttMove;
- assert(value >= beta); // Fail high
- break;
+ alpha = value; // Update alpha! Always alpha < beta
}
}
}
// Bonus for prior countermove that caused the fail low
else if (!priorCapture && prevSq != SQ_NONE)
{
- int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 97 * depth) + ((ss-1)->moveCount > 10);
+ int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 113 * depth) + ((ss-1)->moveCount > 12);
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
}
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
- && ss->ttHit
&& tte->depth() >= ttDepth
- && ttValue != VALUE_NONE // Only in case of TT access race
+ && ttValue != VALUE_NONE // Only in case of TT access race or if !ttHit
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
return ttValue;
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 168;
+ futilityBase = bestValue + 200;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
continue;
// Do not search moves with bad enough SEE values (~5 Elo)
- if (!pos.see_ge(move, Value(-110)))
+ if (!pos.see_ge(move, Value(-95)))
continue;
}
if (!pos.capture_stage(bestMove))
{
- int bonus2 = bestValue > beta + 153 ? bonus1 // larger bonus
+ int bonus2 = bestValue > beta + 145 ? bonus1 // larger bonus
: stat_bonus(depth); // smaller bonus
// Increase stats for the best move in case it was a quiet move
projects / stockfish / blobdiff