}
constexpr int futility_move_count(bool improving, Depth depth) {
- return (3 + depth * depth) / (2 - improving);
+ return improving ? (3 + depth * depth)
+ : (3 + depth * depth) / 2;
}
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return std::min((9 * d + 270) * d - 311 , 2145);
+ return std::min((8 * d + 240) * d - 276 , 1907);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
- Value value_draw(Thread* thisThread) {
- return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
+ Value value_draw(const Thread* thisThread) {
+ return VALUE_DRAW - 1 + Value(thisThread->nodes & 0x2);
}
// Skill structure is used to implement strength limit. If we have an uci_elo then
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply, int r50c);
- void update_pv(Move* pv, Move move, Move* childPv);
+ void update_pv(Move* pv, Move move, const Move* childPv);
void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus);
void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq,
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, -VALUE_INFINITE, VALUE_INFINITE) << sync_endl;
multiPV = std::min(multiPV, rootMoves.size());
- complexityAverage.set(202, 1);
+ complexityAverage.set(174, 1);
trend = SCORE_ZERO;
optimism[ us] = Value(39);
int failedHighCnt = 0;
while (true)
{
- Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
+ // Adjust the effective depth searched, but ensuring at least one effective increment for every
+ // four searchAgain steps (see issue #2717).
+ Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - 3 * (searchAgainCounter + 1) / 4);
bestValue = Stockfish::search<Root>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
// If the bestMove is stable over several iterations, reduce time accordingly
timeReduction = lastBestMoveDepth + 10 < completedDepth ? 1.63 : 0.73;
double reduction = (1.56 + mainThread->previousTimeReduction) / (2.20 * timeReduction);
- double bestMoveInstability = 1.073 + std::max(1.0, 2.25 - 9.9 / rootDepth)
- * totBestMoveChanges / Threads.size();
+ double bestMoveInstability = 1 + 1.7 * totBestMoveChanges / Threads.size();
int complexity = mainThread->complexityAverage.value();
- double complexPosition = std::clamp(1.0 + (complexity - 326) / 1618.1, 0.5, 1.5);
+ double complexPosition = std::min(1.0 + (complexity - 277) / 1819.1, 1.5);
double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability * complexPosition;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
- bool givesCheck, improving, didLMR, priorCapture;
+ bool givesCheck, improving, didLMR, priorCapture, singularQuietLMR;
bool capture, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount, improvement, complexity;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
- thisThread->depth = depth;
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
(ss+1)->ttPv = false;
(ss+1)->excludedMove = bestMove = MOVE_NONE;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+ (ss+2)->cutoffCnt = 0;
ss->doubleExtensions = (ss-1)->doubleExtensions;
- ss->depth = depth;
Square prevSq = to_sq((ss-1)->currentMove);
// Initialize statScore to zero for the grandchildren of the current position.
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& ss->ttHit
- && tte->depth() > depth - (thisThread->id() % 2 == 1)
+ && tte->depth() > depth - ((int)thisThread->id() & 0x1) - (tte->bound() == BOUND_EXACT)
&& ttValue != VALUE_NONE // Possible in case of TT access race
- && (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
- : (tte->bound() & BOUND_UPPER)))
+ && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
{
// If ttMove is quiet, update move sorting heuristics on TT hit (~1 Elo)
if (ttMove)
// Never assume anything about values stored in TT
ss->staticEval = eval = tte->eval();
if (eval == VALUE_NONE)
- ss->staticEval = eval = evaluate(pos);
+ ss->staticEval = eval = evaluate(pos, &complexity);
+ else // Fall back to (semi)classical complexity for TT hits, the NNUE complexity is lost
+ complexity = abs(ss->staticEval - pos.psq_eg_stm());
// Randomize draw evaluation
if (eval == VALUE_DRAW)
}
else
{
- ss->staticEval = eval = evaluate(pos);
+ ss->staticEval = eval = evaluate(pos, &complexity);
// Save static evaluation into transposition table
if (!excludedMove)
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
+ thisThread->complexityAverage.update(complexity);
+
// Use static evaluation difference to improve quiet move ordering (~3 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
improvement = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval - (ss-2)->staticEval
: (ss-4)->staticEval != VALUE_NONE ? ss->staticEval - (ss-4)->staticEval
: 175;
-
improving = improvement > 0;
- complexity = abs(ss->staticEval - (us == WHITE ? eg_value(pos.psq_score()) : -eg_value(pos.psq_score())));
-
- thisThread->complexityAverage.update(complexity);
// Step 7. Razoring.
// If eval is really low check with qsearch if it can exceed alpha, if it can't,
&& (ss-1)->statScore < 14695
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 15 * depth - improvement / 15 + 198 + complexity / 28
+ && ss->staticEval >= beta - 15 * depth - improvement / 15 + 201 + 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) / 147, 5) + depth / 3 + 4 - (complexity > 753);
+ Depth R = std::min(int(eval - beta) / 147, 5) + depth / 3 + 4 - (complexity > 650);
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
assert(probCutBeta < VALUE_INFINITE);
MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, depth - 3, &captureHistory);
- bool ttPv = ss->ttPv;
- bool captureOrPromotion;
- ss->ttPv = false;
while ((move = mp.next_move()) != MOVE_NONE)
if (move != excludedMove && pos.legal(move))
{
assert(pos.capture(move) || promotion_type(move) == QUEEN);
- captureOrPromotion = true;
-
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
- [captureOrPromotion]
+ [true]
[pos.moved_piece(move)]
[to_sq(move)];
if (value >= probCutBeta)
{
- // if transposition table doesn't have equal or more deep info write probCut data into it
- if ( !(ss->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);
+ // Save ProbCut data into transposition table
+ tte->save(posKey, value_to_tt(value, ss->ply), ss->ttPv, BOUND_LOWER, depth - 3, move, ss->staticEval);
return value;
}
}
- ss->ttPv = ttPv;
}
- // Step 11. If the position is not in TT, decrease depth by 2 or 1 depending on node type (~3 Elo)
- if ( PvNode
- && depth >= 3
+ // Step 11. If the position is not in TT, decrease depth by 3.
+ // Use qsearch if depth is equal or below zero (~4 Elo)
+ if ( PvNode
&& !ttMove)
- depth -= 2;
+ depth -= 3;
- if ( cutNode
- && depth >= 8
+ if (depth <= 0)
+ return qsearch<PV>(pos, ss, alpha, beta);
+
+ if ( cutNode
+ && depth >= 8
&& !ttMove)
depth--;
ss->killers);
value = bestValue;
- moveCountPruning = false;
+ moveCountPruning = singularQuietLMR = false;
// Indicate PvNodes that will probably fail low if the node was searched
// at a depth equal or greater than the current depth, and the result of this search was a fail low.
&& history < -3875 * (depth - 1))
continue;
- history += thisThread->mainHistory[us][from_to(move)];
+ history += 2 * thisThread->mainHistory[us][from_to(move)];
// Futility pruning: parent node (~9 Elo)
if ( !ss->inCheck
// 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 + 2 * (PvNode && tte->is_pv())
+ && depth >= 4 - (thisThread->previousDepth > 27) + 2 * (PvNode && tte->is_pv())
&& move == ttMove
&& !excludedMove // Avoid recursive singular search
/* && ttValue != VALUE_NONE Already implicit in the next condition */
if (value < singularBeta)
{
extension = 1;
+ singularQuietLMR = !ttCapture;
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
// If the eval of ttMove is greater than beta, we reduce it (negative extension)
else if (ttValue >= beta)
extension = -2;
+
+ // If the eval of ttMove is less than alpha and value, we reduce it (negative extension)
+ else if (ttValue <= alpha && ttValue <= value)
+ extension = -1;
}
// Check extensions (~1 Elo)
r--;
// Increase reduction for cut nodes (~3 Elo)
- if (cutNode && move != ss->killers[0])
+ if (cutNode)
r += 2;
// Increase reduction if ttMove is a capture (~3 Elo)
if (ttCapture)
r++;
- // Decrease reduction at PvNodes if bestvalue
- // is vastly different from static evaluation
- if (PvNode && !ss->inCheck && abs(ss->staticEval - bestValue) > 250)
- r--;
-
// Decrease reduction for PvNodes based on depth
if (PvNode)
- r -= 1 + 15 / ( 3 + depth );
+ r -= 1 + 15 / (3 + depth);
- ss->statScore = thisThread->mainHistory[us][from_to(move)]
+ // Decrease reduction if ttMove has been singularly extended (~1 Elo)
+ if (singularQuietLMR)
+ r--;
+
+ // Increase reduction if next ply has a lot of fail high else reset count to 0
+ if ((ss+1)->cutoffCnt > 3 && !PvNode)
+ r++;
+
+ ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / 15914;
- // In general we want to cap the LMR depth search at newDepth. But if reductions
- // are really negative and movecount is low, we allow this move to be searched
- // deeper than the first move (this may lead to hidden double extensions).
- int deeper = r >= -1 ? 0
- : moveCount <= 4 ? 2
- : PvNode && depth > 4 ? 1
- : cutNode && moveCount <= 8 ? 1
- : 0;
-
- Depth d = std::clamp(newDepth - r, 1, newDepth + deeper);
+ // In general we want to cap the LMR depth search at newDepth, but when
+ // reduction is negative, we allow this move a limited search extension
+ // beyond the first move depth. This may lead to hidden double extensions.
+ Depth d = std::clamp(newDepth - r, 1, newDepth + 1);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ {
alpha = value;
+
+ // Reduce other moves if we have found at least one score improvement
+ if ( depth > 2
+ && depth < 7
+ && beta < VALUE_KNOWN_WIN
+ && alpha > -VALUE_KNOWN_WIN)
+ depth -= 1;
+
+ assert(depth > 0);
+ }
else
{
+ ss->cutoffCnt++;
assert(value >= beta); // Fail high
break;
}
}
}
+ else
+ ss->cutoffCnt = 0;
+
// If the move is worse than some previously searched move, remember it to update its stats later
if (move != bestMove)
// qsearch() is the quiescence search function, which is called by the main search
// function with zero depth, or recursively with further decreasing depth per call.
+ // (~155 elo)
template <NodeType nodeType>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
&& ss->ttHit
&& tte->depth() >= ttDepth
&& ttValue != VALUE_NONE // Only in case of TT access race
- && (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
- : (tte->bound() & BOUND_UPPER)))
+ && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
return ttValue;
// Evaluate the position statically
[to_sq(move)];
// Continuation history based pruning (~2 Elo)
- if ( !capture
+ if ( !capture
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold)
continue;
// movecount pruning for quiet check evasions
- if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
+ if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& quietCheckEvasions > 1
&& !capture
&& ss->inCheck)
// update_pv() adds current move and appends child pv[]
- void update_pv(Move* pv, Move move, Move* childPv) {
+ void update_pv(Move* pv, Move move, const Move* childPv) {
for (*pv++ = move; childPv && *childPv != MOVE_NONE; )
*pv++ = *childPv++;
void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq,
Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth) {
- int bonus1, bonus2;
Color us = pos.side_to_move();
Thread* thisThread = pos.this_thread();
CapturePieceToHistory& captureHistory = thisThread->captureHistory;
Piece moved_piece = pos.moved_piece(bestMove);
PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
-
- bonus1 = stat_bonus(depth + 1);
- bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
- : stat_bonus(depth); // smaller bonus
+ int bonus1 = stat_bonus(depth + 1);
if (!pos.capture(bestMove))
{
+ int bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
+ : stat_bonus(depth); // smaller bonus
+
// Increase stats for the best move in case it was a quiet move
update_quiet_stats(pos, ss, bestMove, bonus2);
projects / stockfish / blobdiff