/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2022 The Stockfish developers (see AUTHORS file)
+ Copyright (C) 2004-2023 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
// Futility margin
Value futility_margin(Depth d, bool improving) {
- return Value(165 * (d - improving));
+ return Value(158 * (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 + 1642 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 916);
+ return (r + 1460 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 937);
}
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((12 * d + 282) * d - 349 , 1480);
+ return std::min(350 * d - 400, 1650);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
struct Skill {
Skill(int skill_level, int uci_elo) {
if (uci_elo)
- level = std::clamp(std::pow((uci_elo - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0);
+ {
+ double e = double(uci_elo - 1320) / (3190 - 1320);
+ level = std::clamp((((37.2473 * e - 40.8525) * e + 22.2943) * e - 0.311438), 0.0, 19.0);
+ }
else
level = double(skill_level);
}
bestPreviousScore = bestThread->rootMoves[0].score;
bestPreviousAverageScore = bestThread->rootMoves[0].averageScore;
- for (Thread* th : Threads)
- th->previousDepth = bestThread->completedDepth;
-
// Send again PV info if we have a new best thread
if (bestThread != this)
sync_cout << UCI::pv(bestThread->rootPos, bestThread->completedDepth) << sync_endl;
int iterIdx = 0;
std::memset(ss-7, 0, 10 * sizeof(Stack));
- for (int i = 7; i > 0; i--)
+ for (int i = 7; i > 0; --i)
+ {
(ss-i)->continuationHistory = &this->continuationHistory[0][0][NO_PIECE][0]; // Use as a sentinel
+ (ss-i)->staticEval = VALUE_NONE;
+ }
for (int i = 0; i <= MAX_PLY + 2; ++i)
(ss+i)->ply = i;
multiPV = std::min(multiPV, rootMoves.size());
- complexityAverage.set(155, 1);
+ complexityAverage.set(153, 1);
optimism[us] = optimism[~us] = VALUE_ZERO;
if (rootDepth >= 4)
{
Value prev = rootMoves[pvIdx].averageScore;
- delta = Value(10) + int(prev) * prev / 15620;
+ delta = Value(10) + int(prev) * prev / 15400;
alpha = std::max(prev - delta,-VALUE_INFINITE);
beta = std::min(prev + delta, VALUE_INFINITE);
// Adjust optimism based on root move's previousScore
- int opt = 118 * prev / (std::abs(prev) + 169);
+ int opt = 116 * prev / (std::abs(prev) + 170);
optimism[ us] = Value(opt);
optimism[~us] = -optimism[us];
}
// 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), -1914, 1914);
+ int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1940, 1940);
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
- : 168;
+ : 172;
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 - 369 - 254 * depth * depth)
+ if (eval < alpha - 394 - 255 * 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 < 8
- && eval - futility_margin(depth, improving) - (ss-1)->statScore / 303 >= beta
+ && eval - futility_margin(depth, improving) - (ss-1)->statScore / 304 >= beta
&& eval >= beta
- && eval < 28031) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
+ && eval < 28580) // 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 < 17139
+ && (ss-1)->statScore < 18200
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 20 * depth - improvement / 13 + 233 + complexity / 25
+ && ss->staticEval >= beta - 20 * depth - improvement / 14 + 235 + complexity / 24
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth, eval and complexity of position
- Depth R = std::min(int(eval - beta) / 168, 7) + depth / 3 + 4 - (complexity > 861);
+ Depth R = std::min(int(eval - beta) / 165, 6) + depth / 3 + 4 - (complexity > 800);
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
}
}
- probCutBeta = beta + 191 - 54 * improving;
+ probCutBeta = beta + 180 - 54 * improving;
// Step 10. ProbCut (~10 Elo)
// If we have a good enough capture and a reduced search returns a value
moves_loop: // When in check, search starts here
// Step 12. A small Probcut idea, when we are in check (~4 Elo)
- probCutBeta = beta + 417;
+ probCutBeta = beta + 402;
if ( ss->inCheck
&& !PvNode
&& depth >= 2
&& !PvNode
&& lmrDepth < 7
&& !ss->inCheck
- && ss->staticEval + 180 + 201 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ && ss->staticEval + 185 + 203 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 6 < alpha)
continue;
// SEE based pruning (~11 Elo)
- if (!pos.see_ge(move, Value(-222) * depth))
+ if (!pos.see_ge(move, Value(-220) * depth))
continue;
}
else
// Continuation history based pruning (~2 Elo)
if ( lmrDepth < 5
- && history < -3875 * (depth - 1))
+ && history < -4180 * (depth - 1))
continue;
history += 2 * thisThread->mainHistory[us][from_to(move)];
+ lmrDepth += history / 7208;
+ lmrDepth = std::max(lmrDepth, -2);
+
// Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
&& lmrDepth < 13
- && ss->staticEval + 106 + 145 * lmrDepth + history / 52 <= alpha)
+ && ss->staticEval + 103 + 136 * lmrDepth <= alpha)
continue;
+ lmrDepth = std::max(lmrDepth, 0);
+
// Prune moves with negative SEE (~4 Elo)
- if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 15 * lmrDepth)))
+ if (!pos.see_ge(move, Value(-25 * 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->previousDepth > 24) + 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 */
// Check extensions (~1 Elo)
else if ( givesCheck
&& depth > 9
- && abs(ss->staticEval) > 82)
+ && abs(ss->staticEval) > 78)
extension = 1;
// Quiet ttMove extensions (~1 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
- && (*contHist[0])[movedPiece][to_sq(move)] >= 5177)
+ && (*contHist[0])[movedPiece][to_sq(move)] >= 5600)
extension = 1;
}
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 4433;
+ - 4467;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
+ r -= ss->statScore / (12800 + 4410 * (depth > 7 && depth < 19));
// 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 + 64 + 11 * (newDepth - d));
+ const bool doDeeperSearch = value > (alpha + 66 + 11 * (newDepth - d));
const bool doEvenDeeperSearch = value > alpha + 582 && ss->doubleExtensions <= 5;
const bool doShallowerSearch = value < bestValue + newDepth;
// Step 18. Full depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
else if (!PvNode || moveCount > 1)
{
+ // Increase reduction for cut nodes and not ttMove (~1 Elo)
+ if (!ttMove && cutNode)
+ r += 2;
+
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
}
quietsSearched, quietCount, capturesSearched, captureCount, depth);
// Bonus for prior countermove that caused the fail low
- else if ( (depth >= 5 || PvNode)
+ else if ( (depth >= 5 || PvNode || bestValue < alpha - 65 * depth)
&& !priorCapture)
{
- //Assign extra bonus if current node is PvNode or cutNode
- //or fail low was really bad
- bool extraBonus = PvNode
- || cutNode
- || bestValue < alpha - 62 * depth;
-
- update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus));
+ // Extra bonuses for PV/Cut nodes or bad fail lows
+ int bonus = 1 + (PvNode || cutNode) + (bestValue < alpha - 88 * depth);
+ update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
}
if (PvNode)
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 153;
+ futilityBase = bestValue + 158;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
if (!pos.capture(bestMove))
{
- int bonus2 = bestValue > beta + 137 ? bonus1 // larger bonus
+ int bonus2 = bestValue > beta + 146 ? bonus1 // larger bonus
: stat_bonus(depth); // smaller bonus
// Increase stats for the best move in case it was a quiet move
projects / stockfish / blobdiff