// Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]
- Depth reduction(bool i, Depth d, int mn, bool rangeReduction) {
+ Depth reduction(bool i, Depth d, int mn, bool rangeReduction, Value delta, Value rootDelta) {
int r = Reductions[d] * Reductions[mn];
- return (r + 534) / 1024 + (!i && r > 904) + rangeReduction;
+ return (r + 1358 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 904) + rangeReduction;
}
constexpr int futility_move_count(bool improving, Depth depth) {
Value value_from_tt(Value v, int ply, int r50c);
void update_pv(Move* pv, Move move, 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, int depth);
+ 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,
Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth);
mainThread->iterValue[i] = mainThread->bestPreviousScore;
}
- std::copy(&lowPlyHistory[2][0], &lowPlyHistory.back().back() + 1, &lowPlyHistory[0][0]);
- std::fill(&lowPlyHistory[MAX_LPH - 2][0], &lowPlyHistory.back().back() + 1, 0);
-
size_t multiPV = size_t(Options["MultiPV"]);
Skill skill(Options["Skill Level"], Options["UCI_LimitStrength"] ? int(Options["UCI_Elo"]) : 0);
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (142 + 6 * (mainThread->bestPreviousScore - bestValue)
- + 6 * (mainThread->bestPreviousAverageScore - bestValue)
- + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0;
+ double fallingEval = (142 + 12 * (mainThread->bestPreviousAverageScore - bestValue)
+ + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0;
fallingEval = std::clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
bool givesCheck, improving, didLMR, priorCapture;
- bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
- ttCapture, singularQuietLMR;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount, bestMoveCount, improvement;
if (!excludedMove)
ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
- // Update low ply history for previous move if we are near root and position is or has been in PV
- if ( ss->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);
-
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& ss->ttHit
{
// Bonus for a quiet ttMove that fails high
if (!ttCapture)
- update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
+ update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
// Extra penalty for early quiet moves of the previous ply
if ((ss-1)->moveCount <= 2 && !priorCapture)
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
- &thisThread->lowPlyHistory,
&captureHistory,
contHist,
countermove,
- ss->killers,
- ss->ply);
+ ss->killers);
value = bestValue;
- singularQuietLMR = moveCountPruning = false;
+ moveCountPruning = 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.
// Calculate new depth for this move
newDepth = depth - 1;
+ Value delta = beta - alpha;
+
// Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding.
if ( !rootNode
&& pos.non_pawn_material(us)
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
- int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0);
+ int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta), 0);
if ( captureOrPromotion
|| givesCheck)
&& captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
continue;
+ // Futility pruning for captures
+ if ( !pos.empty(to_sq(move))
+ && !givesCheck
+ && !PvNode
+ && lmrDepth < 6
+ && !ss->inCheck
+ && ss->staticEval + 342 + 238 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 8 < alpha)
+ continue;
+
// SEE based pruning
if (!pos.see_ge(move, Value(-218) * depth)) // (~25 Elo)
continue;
history += thisThread->mainHistory[us][from_to(move)];
- lmrDepth = std::max(0, lmrDepth - (beta - alpha < thisThread->rootDelta / 4));
-
// Futility pruning: parent node (~5 Elo)
if ( !ss->inCheck
&& lmrDepth < 8
// 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 >= 7
+ && depth >= 6 + 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
extension = -2;
}
- // Capture extensions for PvNodes and cutNodes
- else if ( (PvNode || cutNode)
- && captureOrPromotion
- && moveCount != 1)
- extension = 1;
-
// Check extensions
else if ( givesCheck
&& depth > 6
// Step 15. Make the move
pos.do_move(move, st, givesCheck);
+ bool doDeeperSearch = false;
+
// Step 16. Late moves reduction / extension (LMR, ~200 Elo)
// We use various heuristics for the sons of a node after the first son has
// been searched. In general we would like to reduce them, but there are many
|| !captureOrPromotion
|| (cutNode && (ss-1)->moveCount > 1)))
{
- Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
+ Depth r = reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta);
// Decrease reduction at some PvNodes (~2 Elo)
if ( PvNode
- && bestMoveCount <= 3
- && beta - alpha >= thisThread->rootDelta / 4)
+ && bestMoveCount <= 3)
r--;
// Decrease reduction if position is or has been on the PV
&& !likelyFailLow)
r -= 2;
- // Increase reduction at non-PV nodes
- if (!PvNode)
- r++;
-
// Decrease reduction if opponent's move count is high (~1 Elo)
if ((ss-1)->moveCount > 13)
r--;
- // Decrease reduction if ttMove has been singularly extended (~1 Elo)
- if (singularQuietLMR)
- r--;
-
// Increase reduction for cut nodes (~3 Elo)
if (cutNode && move != ss->killers[0])
r += 2;
// If the son is reduced and fails high it will be re-searched at full depth
doFullDepthSearch = value > alpha && d < newDepth;
+ doDeeperSearch = value > alpha + 88;
didLMR = true;
}
else
// Step 17. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
{
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth + doDeeperSearch, !cutNode);
// If the move passed LMR update its stats
if (didLMR && !captureOrPromotion)
if (!pos.capture_or_promotion(bestMove))
{
// Increase stats for the best move in case it was a quiet move
- update_quiet_stats(pos, ss, bestMove, bonus2, depth);
+ update_quiet_stats(pos, ss, bestMove, bonus2);
// Decrease stats for all non-best quiet moves
for (int i = 0; i < quietCount; ++i)
// update_quiet_stats() updates move sorting heuristics
- void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth) {
+ void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus) {
// Update killers
if (ss->killers[0] != move)
Square prevSq = to_sq((ss-1)->currentMove);
thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move;
}
-
- // Update low ply history
- if (depth > 11 && ss->ply < MAX_LPH)
- thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7);
}
// When playing with strength handicap, choose best move among a set of RootMoves
projects / stockfish / blobdiff