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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
// Different node types, used as a template parameter
enum NodeType { NonPV, PV };
+ constexpr uint64_t TtHitAverageWindow = 4096;
+ constexpr uint64_t TtHitAverageResolution = 1024;
+
// Razor and futility margins
- constexpr int RazorMargin = 661;
+ constexpr int RazorMargin = 531;
Value futility_margin(Depth d, bool improving) {
- return Value(198 * (d / ONE_PLY - improving));
+ return Value(217 * (d - improving));
}
// Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]
Depth reduction(bool i, Depth d, int mn) {
- int r = Reductions[d / ONE_PLY] * Reductions[mn];
- return ((r + 520) / 1024 + (!i && r > 999)) * ONE_PLY;
+ int r = Reductions[d] * Reductions[mn];
+ return (r + 511) / 1024 + (!i && r > 1007);
}
- constexpr int futility_move_count(bool improving, int depth) {
- return (5 + depth * depth) * (1 + improving) / 2;
+ constexpr int futility_move_count(bool improving, Depth depth) {
+ return (4 + depth * depth) / (2 - improving);
}
// History and stats update bonus, based on depth
- int stat_bonus(Depth depth) {
- int d = depth / ONE_PLY;
- return d > 17 ? -8 : 22 * d * d + 151 * d - 140;
+ int stat_bonus(Depth d) {
+ return d > 15 ? -8 : 19 * d * d + 155 * d - 132;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
- Value value_draw(Depth depth, Thread* thisThread) {
- return depth < 4 * ONE_PLY ? VALUE_DRAW
- : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
+ Value value_draw(Thread* thisThread) {
+ return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
}
// Skill structure is used to implement strength limit
struct Skill {
explicit Skill(int l) : level(l) {}
bool enabled() const { return level < 20; }
- bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
+ bool time_to_pick(Depth depth) const { return depth == 1 + level; }
Move pick_best(size_t multiPV);
int level;
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT>
- Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO);
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = 0);
Value value_to_tt(Value v, int ply);
- Value value_from_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_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
- void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietCount, int bonus);
- void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCount, int bonus);
+ void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth);
+ 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);
// perft() is our utility to verify move generation. All the leaf nodes up
// to the given depth are generated and counted, and the sum is returned.
StateInfo st;
uint64_t cnt, nodes = 0;
- const bool leaf = (depth == 2 * ONE_PLY);
+ const bool leaf = (depth == 2);
for (const auto& m : MoveList<LEGAL>(pos))
{
- if (Root && depth <= ONE_PLY)
+ if (Root && depth <= 1)
cnt = 1, nodes++;
else
{
pos.do_move(m, st);
- cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
+ cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - 1);
nodes += cnt;
pos.undo_move(m);
}
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int(23.4 * std::log(i));
+ Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i));
}
if (Limits.perft)
{
- nodes = perft<true>(rootPos, Limits.perft * ONE_PLY);
+ nodes = perft<true>(rootPos, Limits.perft);
sync_cout << "\nNodes searched: " << nodes << "\n" << sync_endl;
return;
}
Thread* bestThread = this;
// Check if there are threads with a better score than main thread
- if ( Options["MultiPV"] == 1
+ if ( int(Options["MultiPV"]) == 1
&& !Limits.depth
- && !(Skill(Options["Skill Level"]).enabled() || Options["UCI_LimitStrength"])
+ && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"]))
&& rootMoves[0].pv[0] != MOVE_NONE)
{
std::map<Move, int64_t> votes;
Value minScore = this->rootMoves[0].score;
- // Find out minimum score
+ // Find minimum score
for (Thread* th: Threads)
minScore = std::min(minScore, th->rootMoves[0].score);
votes[th->rootMoves[0].pv[0]] +=
(th->rootMoves[0].score - minScore + 14) * int(th->completedDepth);
- if (bestThread->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY)
+ if (abs(bestThread->rootMoves[0].score) >= VALUE_TB_WIN_IN_MAX_PLY)
{
- // Make sure we pick the shortest mate
+ // Make sure we pick the shortest mate / TB conversion or stave off mate the longest
if (th->rootMoves[0].score > bestThread->rootMoves[0].score)
bestThread = th;
}
- else if ( th->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY
- || votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]])
+ else if ( th->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY
+ || ( th->rootMoves[0].score > VALUE_TB_LOSS_IN_MAX_PLY
+ && votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]]))
bestThread = th;
}
}
- previousScore = bestThread->rootMoves[0].score;
+ bestPreviousScore = bestThread->rootMoves[0].score;
// Send again PV info if we have a new best thread
if (bestThread != this)
Move pv[MAX_PLY+1];
Value bestValue, alpha, beta, delta;
Move lastBestMove = MOVE_NONE;
- Depth lastBestMoveDepth = DEPTH_ZERO;
+ Depth lastBestMoveDepth = 0;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
double timeReduction = 1, totBestMoveChanges = 0;
Color us = rootPos.side_to_move();
+ int iterIdx = 0;
std::memset(ss-7, 0, 10 * sizeof(Stack));
for (int i = 7; i > 0; i--)
- (ss-i)->continuationHistory = &this->continuationHistory[NO_PIECE][0]; // Use as sentinel
+ (ss-i)->continuationHistory = &this->continuationHistory[0][0][NO_PIECE][0]; // Use as a sentinel
+
ss->pv = pv;
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
- size_t multiPV = Options["MultiPV"];
+ if (mainThread)
+ {
+ if (mainThread->bestPreviousScore == VALUE_INFINITE)
+ for (int i = 0; i < 4; ++i)
+ mainThread->iterValue[i] = VALUE_ZERO;
+ else
+ for (int i = 0; i < 4; ++i)
+ 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"]);
// Pick integer skill levels, but non-deterministically round up or down
// such that the average integer skill corresponds to the input floating point one.
// for match (TC 60+0.6) results spanning a wide range of k values.
PRNG rng(now());
double floatLevel = Options["UCI_LimitStrength"] ?
- clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) :
+ Utility::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) :
double(Options["Skill Level"]);
int intLevel = int(floatLevel) +
((floatLevel - int(floatLevel)) * 1024 > rng.rand<unsigned>() % 1024 ? 1 : 0);
multiPV = std::max(multiPV, (size_t)4);
multiPV = std::min(multiPV, rootMoves.size());
+ ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2;
int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns
contempt = (us == WHITE ? make_score(ct, ct / 2)
: -make_score(ct, ct / 2));
+ int searchAgainCounter = 0;
+
// Iterative deepening loop until requested to stop or the target depth is reached
- while ( (rootDepth += ONE_PLY) < DEPTH_MAX
+ while ( ++rootDepth < MAX_PLY
&& !Threads.stop
- && !(Limits.depth && mainThread && rootDepth / ONE_PLY > Limits.depth))
+ && !(Limits.depth && mainThread && rootDepth > Limits.depth))
{
// Age out PV variability metric
if (mainThread)
size_t pvFirst = 0;
pvLast = 0;
+ if (!Threads.increaseDepth)
+ searchAgainCounter++;
+
// MultiPV loop. We perform a full root search for each PV line
for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx)
{
selDepth = 0;
// Reset aspiration window starting size
- if (rootDepth >= 4 * ONE_PLY)
+ if (rootDepth >= 4)
{
- Value previousScore = rootMoves[pvIdx].previousScore;
- delta = Value(23);
- alpha = std::max(previousScore - delta,-VALUE_INFINITE);
- beta = std::min(previousScore + delta, VALUE_INFINITE);
+ Value prev = rootMoves[pvIdx].previousScore;
+ delta = Value(21);
+ 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 + 86 * previousScore / (abs(previousScore) + 176);
+ int dct = ct + (102 - ct / 2) * prev / (abs(prev) + 157);
contempt = (us == WHITE ? make_score(dct, dct / 2)
: -make_score(dct, dct / 2));
int failedHighCnt = 0;
while (true)
{
- Depth adjustedDepth = std::max(ONE_PLY, rootDepth - failedHighCnt * ONE_PLY);
+ Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (354 + 10 * (mainThread->previousScore - bestValue)) / 692.0;
- fallingEval = clamp(fallingEval, 0.5, 1.5);
+ double fallingEval = (332 + 6 * (mainThread->bestPreviousScore - bestValue)
+ + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0;
+ fallingEval = Utility::clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
- timeReduction = lastBestMoveDepth + 9 * ONE_PLY < completedDepth ? 1.97 : 0.98;
- double reduction = (1.36 + mainThread->previousTimeReduction) / (2.29 * timeReduction);
+ timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.94 : 0.91;
+ double reduction = (1.41 + mainThread->previousTimeReduction) / (2.27 * timeReduction);
// Use part of the gained time from a previous stable move for the current move
for (Thread* th : Threads)
else
Threads.stop = true;
}
+ else if ( Threads.increaseDepth
+ && !mainThread->ponder
+ && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6)
+ Threads.increaseDepth = false;
+ else
+ Threads.increaseDepth = true;
}
+
+ mainThread->iterValue[iterIdx] = bestValue;
+ iterIdx = (iterIdx + 1) & 3;
}
if (!mainThread)
&& !rootNode
&& pos.has_game_cycle(ss->ply))
{
- alpha = value_draw(depth, pos.this_thread());
+ alpha = value_draw(pos.this_thread());
if (alpha >= beta)
return alpha;
}
// Dive into quiescence search when the depth reaches zero
- if (depth < ONE_PLY)
+ if (depth <= 0)
return qsearch<NT>(pos, ss, alpha, beta);
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
- assert(DEPTH_ZERO < depth && depth < DEPTH_MAX);
+ assert(0 < depth && depth < MAX_PLY);
assert(!(PvNode && cutNode));
- assert(depth / ONE_PLY * ONE_PLY == depth);
Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[64];
StateInfo st;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue;
- bool ttHit, ttPv, inCheck, givesCheck, improving, doLMR;
- bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
+ bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture;
+ bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
+ ttCapture, singularQuietLMR;
Piece movedPiece;
- int moveCount, captureCount, quietCount, singularLMR;
+ int moveCount, captureCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
- inCheck = pos.checkers();
+ ss->inCheck = pos.checkers();
+ priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
- moveCount = captureCount = quietCount = singularLMR = ss->moveCount = 0;
+ moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
if ( Threads.stop.load(std::memory_order_relaxed)
|| pos.is_draw(ss->ply)
|| ss->ply >= MAX_PLY)
- return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos)
- : value_draw(depth, pos.this_thread());
+ return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos)
+ : 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
excludedMove = ss->excludedMove;
posKey = pos.key() ^ Key(excludedMove << 16); // Isn't a very good hash
tte = TT.probe(posKey, ttHit);
- ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
: ttHit ? tte->move() : MOVE_NONE;
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))
+ 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
+ thisThread->ttHitAverage = (TtHitAverageWindow - 1) * thisThread->ttHitAverage / TtHitAverageWindow
+ + TtHitAverageResolution * ttHit;
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
if (ttValue >= beta)
{
if (!pos.capture_or_promotion(ttMove))
- update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
+ update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
// Extra penalty for early quiet moves of the previous ply
- if ((ss-1)->moveCount <= 2 && !pos.captured_piece())
- update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+ if ((ss-1)->moveCount <= 2 && !priorCapture)
+ update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1));
}
// Penalty for a quiet ttMove that fails low
else if (!pos.capture_or_promotion(ttMove))
update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
}
}
- return ttValue;
+
+ if (pos.rule50_count() < 90)
+ return ttValue;
}
// Step 5. Tablebases probe
int drawScore = TB::UseRule50 ? 1 : 0;
- value = wdl < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
- : wdl > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
- : VALUE_DRAW + 2 * wdl * drawScore;
+ // use the range VALUE_MATE_IN_MAX_PLY to VALUE_TB_WIN_IN_MAX_PLY to score
+ value = wdl < -drawScore ? VALUE_MATED_IN_MAX_PLY + ss->ply + 1
+ : wdl > drawScore ? VALUE_MATE_IN_MAX_PLY - ss->ply - 1
+ : VALUE_DRAW + 2 * wdl * drawScore;
Bound b = wdl < -drawScore ? BOUND_UPPER
: wdl > drawScore ? BOUND_LOWER : BOUND_EXACT;
|| (b == BOUND_LOWER ? value >= beta : value <= alpha))
{
tte->save(posKey, value_to_tt(value, ss->ply), ttPv, b,
- std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY),
+ std::min(MAX_PLY - 1, depth + 6),
MOVE_NONE, VALUE_NONE);
return value;
}
}
+ CapturePieceToHistory& captureHistory = thisThread->captureHistory;
+
// Step 6. Static evaluation of the position
- if (inCheck)
+ if (ss->inCheck)
{
ss->staticEval = eval = VALUE_NONE;
improving = false;
if (eval == VALUE_NONE)
ss->staticEval = eval = evaluate(pos);
+ if (eval == VALUE_DRAW)
+ eval = value_draw(thisThread);
+
// Can ttValue be used as a better position evaluation?
if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)))
ss->staticEval = eval = evaluate(pos) + bonus;
}
else
- ss->staticEval = eval = -(ss-1)->staticEval + 2 * Eval::Tempo;
+ ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo;
tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
- // Step 7. Razoring (~2 Elo)
+ // Step 7. Razoring (~1 Elo)
if ( !rootNode // The required rootNode PV handling is not available in qsearch
- && depth < 2 * ONE_PLY
+ && depth == 1
&& eval <= alpha - RazorMargin)
return qsearch<NT>(pos, ss, alpha, beta);
- improving = ss->staticEval >= (ss-2)->staticEval
- || (ss-2)->staticEval == VALUE_NONE;
+ improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval > (ss-4)->staticEval
+ || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval > (ss-2)->staticEval;
- // Step 8. Futility pruning: child node (~30 Elo)
+ // Step 8. Futility pruning: child node (~50 Elo)
if ( !PvNode
- && depth < 7 * ONE_PLY
+ && depth < 6
&& 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 < 22661
+ && (ss-1)->statScore < 23397
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 33 * depth / ONE_PLY + 299 - improving * 30
+ && ss->staticEval >= beta - 32 * depth - 30 * improving + 120 * ttPv + 292
&& !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 = ((835 + 70 * depth / ONE_PLY) / 256 + std::min(int(eval - beta) / 185, 3)) * ONE_PLY;
+ Depth R = (854 + 68 * depth) / 258 + std::min(int(eval - beta) / 192, 3);
ss->currentMove = MOVE_NULL;
- ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0];
+ ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
pos.do_null_move(st);
if (nullValue >= beta)
{
- // Do not return unproven mate scores
- if (nullValue >= VALUE_MATE_IN_MAX_PLY)
+ // Do not return unproven mate or TB scores
+ if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY)
nullValue = beta;
- if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 13 * ONE_PLY))
+ if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 13))
return nullValue;
assert(!thisThread->nmpMinPly); // Recursive verification is not allowed
// Do verification search at high depths, with null move pruning disabled
// for us, until ply exceeds nmpMinPly.
- thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / (4 * ONE_PLY);
+ thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
thisThread->nmpColor = us;
Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
// 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 * ONE_PLY
- && abs(beta) < VALUE_MATE_IN_MAX_PLY)
+ && depth >= 5
+ && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
{
- Value raisedBeta = std::min(beta + 191 - 46 * improving, VALUE_INFINITE);
- MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory);
+ Value raisedBeta = beta + 189 - 45 * improving;
+ assert(raisedBeta < VALUE_INFINITE);
+ MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory);
int probCutCount = 0;
- while ( (move = mp.next_move()) != MOVE_NONE
- && probCutCount < 2 + 2 * cutNode)
+ while ( (move = mp.next_move()) != MOVE_NONE
+ && probCutCount < 2 + 2 * cutNode
+ && !( move == ttMove
+ && tte->depth() >= depth - 4
+ && ttValue < raisedBeta))
if (move != excludedMove && pos.legal(move))
{
+ assert(pos.capture_or_promotion(move));
+ assert(depth >= 5);
+
+ captureOrPromotion = true;
probCutCount++;
ss->currentMove = move;
- ss->continuationHistory = &thisThread->continuationHistory[pos.moved_piece(move)][to_sq(move)];
-
- assert(depth >= 5 * ONE_PLY);
+ ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
+ [captureOrPromotion]
+ [pos.moved_piece(move)]
+ [to_sq(move)];
pos.do_move(move, st);
// If the qsearch held, perform the regular search
if (value >= raisedBeta)
- value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4 * ONE_PLY, !cutNode);
+ value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4, !cutNode);
pos.undo_move(move);
}
}
- // Step 11. Internal iterative deepening (~2 Elo)
- if (depth >= 7 * ONE_PLY && !ttMove)
+ // Step 11. Internal iterative deepening (~1 Elo)
+ if (depth >= 7 && !ttMove)
{
- search<NT>(pos, ss, alpha, beta, depth - 7 * ONE_PLY, cutNode);
+ search<NT>(pos, ss, alpha, beta, depth - 7, cutNode);
tte = TT.probe(posKey, ttHit);
- ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
}
moves_loop: // When in check, search starts from here
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
- nullptr, (ss-4)->continuationHistory,
- nullptr, (ss-6)->continuationHistory };
+ nullptr , (ss-4)->continuationHistory,
+ nullptr , (ss-6)->continuationHistory };
Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
- &thisThread->captureHistory,
+ &thisThread->lowPlyHistory,
+ &captureHistory,
contHist,
countermove,
- ss->killers);
+ ss->killers,
+ depth > 12 ? ss->ply : MAX_PLY);
- value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
- moveCountPruning = false;
+ value = bestValue;
+ singularQuietLMR = moveCountPruning = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Mark this node as being searched
ss->moveCount = ++moveCount;
if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
- sync_cout << "info depth " << depth / ONE_PLY
+ sync_cout << "info depth " << depth
<< " currmove " << UCI::move(move, pos.is_chess960())
<< " currmovenumber " << moveCount + thisThread->pvIdx << sync_endl;
if (PvNode)
(ss+1)->pv = nullptr;
- extension = DEPTH_ZERO;
+ extension = 0;
captureOrPromotion = pos.capture_or_promotion(move);
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);
- // Step 13. Extensions (~70 Elo)
+ // Calculate new depth for this move
+ newDepth = depth - 1;
+
+ // Step 13. Pruning at shallow depth (~200 Elo)
+ if ( !rootNode
+ && pos.non_pawn_material(us)
+ && bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
+ {
+ // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
+ moveCountPruning = moveCount >= futility_move_count(improving, depth);
+
+ // Reduced depth of the next LMR search
+ int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
+
+ if ( !captureOrPromotion
+ && !givesCheck)
+ {
+ // Countermoves based pruning (~20 Elo)
+ if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
+ && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
+ && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
+ continue;
+
+ // Futility pruning: parent node (~5 Elo)
+ if ( lmrDepth < 6
+ && !ss->inCheck
+ && ss->staticEval + 235 + 172 * lmrDepth <= alpha
+ && (*contHist[0])[movedPiece][to_sq(move)]
+ + (*contHist[1])[movedPiece][to_sq(move)]
+ + (*contHist[3])[movedPiece][to_sq(move)] < 27400)
+ continue;
+
+ // Prune moves with negative SEE (~20 Elo)
+ if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
+ continue;
+ }
+ else
+ {
+ // Capture history based pruning when the move doesn't give check
+ if ( !givesCheck
+ && lmrDepth < 1
+ && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
+ continue;
+
+ // Futility pruning for captures
+ if ( !givesCheck
+ && lmrDepth < 6
+ && !(PvNode && abs(bestValue) < 2)
+ && !ss->inCheck
+ && ss->staticEval + 270 + 384 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
+ continue;
- // Singular extension search (~60 Elo). If all moves but one fail low on a
+ // See based pruning
+ if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo)
+ continue;
+ }
+ }
+
+ // Step 14. Extensions (~75 Elo)
+
+ // Singular extension search (~70 Elo). If all moves but one fail low on a
// 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.
- if ( depth >= 6 * ONE_PLY
+ if ( depth >= 6
&& move == ttMove
&& !rootNode
&& !excludedMove // Avoid recursive singular search
/* && ttValue != VALUE_NONE Already implicit in the next condition */
&& abs(ttValue) < VALUE_KNOWN_WIN
&& (tte->bound() & BOUND_LOWER)
- && tte->depth() >= depth - 3 * ONE_PLY
+ && tte->depth() >= depth - 3
&& pos.legal(move))
{
- Value singularBeta = ttValue - 2 * depth / ONE_PLY;
- Depth halfDepth = depth / (2 * ONE_PLY) * ONE_PLY; // ONE_PLY invariant
+ Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
+ Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
ss->excludedMove = move;
- value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode);
+ value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
ss->excludedMove = MOVE_NONE;
if (value < singularBeta)
{
- extension = ONE_PLY;
- singularLMR++;
-
- if (value < singularBeta - std::min(4 * depth / ONE_PLY, 36))
- singularLMR++;
+ extension = 1;
+ singularQuietLMR = !ttCapture;
}
// Multi-cut pruning
// search without the ttMove. So we assume this expected Cut-node is not singular,
// that multiple moves fail high, and we can prune the whole subtree by returning
// a soft bound.
- else if ( eval >= beta
- && singularBeta >= beta)
+ 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
+ else if (ttValue >= beta)
+ {
+ ss->excludedMove = move;
+ value = search<NonPV>(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode);
+ ss->excludedMove = MOVE_NONE;
+
+ if (value >= beta)
+ return beta;
+ }
}
// Check extension (~2 Elo)
else if ( givesCheck
&& (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
- extension = ONE_PLY;
-
- // Castling extension
- else if (type_of(move) == CASTLING)
- extension = ONE_PLY;
-
- // Shuffle extension
- else if ( PvNode
- && pos.rule50_count() > 18
- && depth < 3 * ONE_PLY
- && ++thisThread->shuffleExts < thisThread->nodes.load(std::memory_order_relaxed) / 4) // To avoid too many extensions
- extension = ONE_PLY;
+ extension = 1;
// Passed pawn extension
else if ( move == ss->killers[0]
&& pos.advanced_pawn_push(move)
&& pos.pawn_passed(us, to_sq(move)))
- extension = ONE_PLY;
-
- // Calculate new depth for this move
- newDepth = depth - ONE_PLY + extension;
-
- // Step 14. Pruning at shallow depth (~170 Elo)
- if ( !rootNode
- && pos.non_pawn_material(us)
- && bestValue > VALUE_MATED_IN_MAX_PLY)
- {
- // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
- moveCountPruning = moveCount >= futility_move_count(improving, depth / ONE_PLY);
-
- if ( !captureOrPromotion
- && !givesCheck
- && (!pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg))
- {
- // Move count based pruning
- if (moveCountPruning)
- continue;
+ extension = 1;
- // Reduced depth of the next LMR search
- int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO);
- lmrDepth /= ONE_PLY;
+ // Last captures extension
+ else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg
+ && pos.non_pawn_material() <= 2 * RookValueMg)
+ extension = 1;
- // Countermoves based pruning (~20 Elo)
- if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
- && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
- && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
- continue;
+ // Castling extension
+ if (type_of(move) == CASTLING)
+ extension = 1;
- // Futility pruning: parent node (~2 Elo)
- if ( lmrDepth < 6
- && !inCheck
- && ss->staticEval + 250 + 211 * lmrDepth <= alpha)
- continue;
+ // Late irreversible move extension
+ if ( move == ttMove
+ && pos.rule50_count() > 80
+ && (captureOrPromotion || type_of(movedPiece) == PAWN))
+ extension = 2;
- // Prune moves with negative SEE (~10 Elo)
- if (!pos.see_ge(move, Value(-(31 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
- continue;
- }
- else if ( !(givesCheck && extension)
- && !pos.see_ge(move, Value(-199) * (depth / ONE_PLY))) // (~20 Elo)
- continue;
- }
+ // Add extension to new depth
+ newDepth += extension;
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
// Update the current move (this must be done after singular extension search)
ss->currentMove = move;
- ss->continuationHistory = &thisThread->continuationHistory[movedPiece][to_sq(move)];
+ ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
+ [captureOrPromotion]
+ [movedPiece]
+ [to_sq(move)];
// Step 15. Make the move
pos.do_move(move, st, givesCheck);
- // Step 16. Reduced depth search (LMR). If the move fails high it will be
+ // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
- if ( depth >= 3 * ONE_PLY
+ if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
&& (!rootNode || thisThread->best_move_count(move) == 0)
&& ( !captureOrPromotion
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
- || cutNode))
+ || cutNode
+ || thisThread->ttHitAverage < 375 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
+ // Decrease reduction if the ttHit running average is large
+ if (thisThread->ttHitAverage > 500 * TtHitAverageResolution * TtHitAverageWindow / 1024)
+ r--;
+
// Reduction if other threads are searching this position.
if (th.marked())
- r += ONE_PLY;
+ r++;
- // Decrease reduction if position is or has been on the PV
+ // Decrease reduction if position is or has been on the PV (~10 Elo)
if (ttPv)
- r -= 2 * ONE_PLY;
+ r -= 2;
+
+ if (moveCountPruning && !formerPv)
+ r++;
- // Decrease reduction if opponent's move count is high (~10 Elo)
- if ((ss-1)->moveCount > 15)
- r -= ONE_PLY;
+ // Decrease reduction if opponent's move count is high (~5 Elo)
+ if ((ss-1)->moveCount > 14)
+ r--;
- // Decrease reduction if ttMove has been singularly extended
- r -= singularLMR * ONE_PLY;
+ // Decrease reduction if ttMove has been singularly extended (~3 Elo)
+ if (singularQuietLMR)
+ r -= 1 + formerPv;
if (!captureOrPromotion)
{
- // Increase reduction if ttMove is a capture (~0 Elo)
+ // Increase reduction if ttMove is a capture (~5 Elo)
if (ttCapture)
- r += ONE_PLY;
+ r++;
- // Increase reduction for cut nodes (~5 Elo)
+ // Increase reduction for cut nodes (~10 Elo)
if (cutNode)
- r += 2 * ONE_PLY;
+ r += 2;
// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
- // hence break make_move(). (~5 Elo)
+ // hence break make_move(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
- r -= 2 * ONE_PLY;
+ r -= 2 + ttPv;
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)]
- - 4729;
-
- // Reset statScore to zero if negative and most stats shows >= 0
- if ( ss->statScore < 0
- && (*contHist[0])[movedPiece][to_sq(move)] >= 0
- && (*contHist[1])[movedPiece][to_sq(move)] >= 0
- && thisThread->mainHistory[us][from_to(move)] >= 0)
- ss->statScore = 0;
+ - 4926;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
- if (ss->statScore >= -99 && (ss-1)->statScore < -116)
- r -= ONE_PLY;
+ if (ss->statScore >= -102 && (ss-1)->statScore < -114)
+ r--;
- else if ((ss-1)->statScore >= -117 && ss->statScore < -144)
- r += ONE_PLY;
+ else if ((ss-1)->statScore >= -116 && ss->statScore < -154)
+ r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- r -= ss->statScore / 16384 * ONE_PLY;
+ r -= ss->statScore / 16434;
+ }
+ else
+ {
+ // Increase reduction for captures/promotions if late move and at low depth
+ if (depth < 8 && moveCount > 2)
+ r++;
+
+ // Unless giving check, this capture is likely bad
+ if ( !givesCheck
+ && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 200 * depth <= alpha)
+ r++;
}
- Depth d = clamp(newDepth - r, ONE_PLY, newDepth);
+ Depth d = Utility::clamp(newDepth - r, 1, newDepth);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
- doFullDepthSearch = (value > alpha && d != newDepth), doLMR = true;
+ doFullDepthSearch = value > alpha && d != newDepth;
+
+ didLMR = true;
}
else
- doFullDepthSearch = !PvNode || moveCount > 1, doLMR = false;
+ {
+ doFullDepthSearch = !PvNode || moveCount > 1;
+
+ didLMR = false;
+ }
// 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);
- if (doLMR && !captureOrPromotion)
+ if (didLMR && !captureOrPromotion)
{
int bonus = value > alpha ? stat_bonus(newDepth)
: -stat_bonus(newDepth);
// must be a mate or a stalemate. If we are in a singular extension search then
// return a fail low score.
- assert(moveCount || !inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
+ assert(moveCount || !ss->inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
if (!moveCount)
bestValue = excludedMove ? alpha
- : inCheck ? mated_in(ss->ply) : VALUE_DRAW;
- else if (bestMove)
- {
- // Quiet best move: update move sorting heuristics
- if (!pos.capture_or_promotion(bestMove))
- update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount,
- stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO)));
+ : ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW;
- update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
-
- // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted
- if ( ((ss-1)->moveCount == 1 || ((ss-1)->currentMove == (ss-1)->killers[0]))
- && !pos.captured_piece())
- update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
+ else if (bestMove)
+ update_all_stats(pos, ss, bestMove, bestValue, beta, prevSq,
+ quietsSearched, quietCount, capturesSearched, captureCount, depth);
- }
// Bonus for prior countermove that caused the fail low
- else if ( (depth >= 3 * ONE_PLY || PvNode)
- && !pos.captured_piece())
+ else if ( (depth >= 3 || PvNode)
+ && !priorCapture)
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
if (PvNode)
bestValue = std::min(bestValue, maxValue);
- if (!excludedMove)
+ if (!excludedMove && !(rootNode && thisThread->pvIdx))
tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv,
bestValue >= beta ? BOUND_LOWER :
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
- assert(depth <= DEPTH_ZERO);
- assert(depth / ONE_PLY * ONE_PLY == depth);
+ assert(depth <= 0);
Move pv[MAX_PLY+1];
StateInfo st;
Move ttMove, move, bestMove;
Depth ttDepth;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
- bool ttHit, pvHit, inCheck, givesCheck, evasionPrunable;
+ bool ttHit, pvHit, givesCheck, captureOrPromotion;
int moveCount;
if (PvNode)
Thread* thisThread = pos.this_thread();
(ss+1)->ply = ss->ply + 1;
bestMove = MOVE_NONE;
- inCheck = pos.checkers();
+ ss->inCheck = pos.checkers();
moveCount = 0;
// Check for an immediate draw or maximum ply reached
if ( pos.is_draw(ss->ply)
|| ss->ply >= MAX_PLY)
- return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) : VALUE_DRAW;
+ return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos) : VALUE_DRAW;
assert(0 <= ss->ply && ss->ply < MAX_PLY);
// Decide whether or not to include checks: this fixes also the type of
// TT entry depth that we are going to use. Note that in qsearch we use
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
- ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+ ttDepth = ss->inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
// Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey, ttHit);
- ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
+ ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
pvHit = ttHit && tte->is_pv();
return ttValue;
// Evaluate the position statically
- if (inCheck)
+ if (ss->inCheck)
{
ss->staticEval = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
else
ss->staticEval = bestValue =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
- : -(ss-1)->staticEval + 2 * Eval::Tempo;
+ : -(ss-1)->staticEval + 2 * Tempo;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
{
if (!ttHit)
- tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, BOUND_LOWER,
+ tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER,
DEPTH_NONE, MOVE_NONE, ss->staticEval);
return bestValue;
if (PvNode && bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 153;
+ futilityBase = bestValue + 154;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
- nullptr, (ss-4)->continuationHistory,
- nullptr, (ss-6)->continuationHistory };
+ nullptr , (ss-4)->continuationHistory,
+ nullptr , (ss-6)->continuationHistory };
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
assert(is_ok(move));
givesCheck = pos.gives_check(move);
+ captureOrPromotion = pos.capture_or_promotion(move);
moveCount++;
// Futility pruning
- if ( !inCheck
+ if ( !ss->inCheck
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
}
}
- // Detect non-capture evasions that are candidates to be pruned
- evasionPrunable = inCheck
- && (depth != DEPTH_ZERO || moveCount > 2)
- && bestValue > VALUE_MATED_IN_MAX_PLY
- && !pos.capture(move);
-
// Don't search moves with negative SEE values
- if ( (!inCheck || evasionPrunable)
- && (!givesCheck || !(pos.blockers_for_king(~pos.side_to_move()) & from_sq(move)))
- && !pos.see_ge(move))
+ if ( !ss->inCheck && !pos.see_ge(move))
continue;
// Speculative prefetch as early as possible
}
ss->currentMove = move;
- ss->continuationHistory = &thisThread->continuationHistory[pos.moved_piece(move)][to_sq(move)];
+ ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
+ [captureOrPromotion]
+ [pos.moved_piece(move)]
+ [to_sq(move)];
// Make and search the move
pos.do_move(move, st, givesCheck);
- value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
+ value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - 1);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (inCheck && bestValue == -VALUE_INFINITE)
+ if (ss->inCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit,
}
- // value_to_tt() adjusts a mate score from "plies to mate from the root" to
- // "plies to mate from the current position". Non-mate scores are unchanged.
+ // 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.
// The function is called before storing a value in the transposition table.
Value value_to_tt(Value v, int ply) {
assert(v != VALUE_NONE);
- return v >= VALUE_MATE_IN_MAX_PLY ? v + ply
- : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v;
+ return v >= VALUE_TB_WIN_IN_MAX_PLY ? v + ply
+ : v <= VALUE_TB_LOSS_IN_MAX_PLY ? v - ply : v;
}
- // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score
+ // 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 from the root".
+ // 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 value_from_tt(Value v, int ply, int r50c) {
- Value value_from_tt(Value v, int ply) {
+ if (v == VALUE_NONE)
+ return VALUE_NONE;
+
+ if (v >= VALUE_TB_WIN_IN_MAX_PLY) // TB win or better
+ {
+ if (v >= VALUE_MATE_IN_MAX_PLY && VALUE_MATE - v > 99 - r50c)
+ return VALUE_MATE_IN_MAX_PLY - 1; // do not return a potentially false mate score
+
+ return v - ply;
+ }
- return v == VALUE_NONE ? VALUE_NONE
- : v >= VALUE_MATE_IN_MAX_PLY ? v - ply
- : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v;
+ if (v <= VALUE_TB_LOSS_IN_MAX_PLY) // TB loss or worse
+ {
+ if (v <= VALUE_MATED_IN_MAX_PLY && VALUE_MATE + v > 99 - r50c)
+ return VALUE_MATED_IN_MAX_PLY + 1; // do not return a potentially false mate score
+
+ return v + ply;
+ }
+
+ return v;
}
}
- // update_continuation_histories() updates histories of the move pairs formed
- // by moves at ply -1, -2, and -4 with current move.
+ // update_all_stats() updates stats at the end of search() when a bestMove is found
- void update_continuation_histories(Stack* ss, Piece pc, Square to, 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) {
- for (int i : {1, 2, 4, 6})
- if (is_ok((ss-i)->currentMove))
- (*(ss-i)->continuationHistory)[pc][to] << bonus;
- }
+ 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
+
+ if (!pos.capture_or_promotion(bestMove))
+ {
+ update_quiet_stats(pos, ss, bestMove, bonus2, depth);
+
+ // Decrease all the non-best quiet moves
+ for (int i = 0; i < quietCount; ++i)
+ {
+ thisThread->mainHistory[us][from_to(quietsSearched[i])] << -bonus2;
+ update_continuation_histories(ss, pos.moved_piece(quietsSearched[i]), to_sq(quietsSearched[i]), -bonus2);
+ }
+ }
+ else
+ captureHistory[moved_piece][to_sq(bestMove)][captured] << bonus1;
+ // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted
+ if ( ((ss-1)->moveCount == 1 || ((ss-1)->currentMove == (ss-1)->killers[0]))
+ && !pos.captured_piece())
+ update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -bonus1);
- // update_capture_stats() updates move sorting heuristics when a new capture best move is found
+ // Decrease all the non-best capture moves
+ for (int i = 0; i < captureCount; ++i)
+ {
+ moved_piece = pos.moved_piece(capturesSearched[i]);
+ captured = type_of(pos.piece_on(to_sq(capturesSearched[i])));
+ captureHistory[moved_piece][to_sq(capturesSearched[i])][captured] << -bonus1;
+ }
+ }
- void update_capture_stats(const Position& pos, Move move,
- Move* captures, int captureCount, int bonus) {
- CapturePieceToHistory& captureHistory = pos.this_thread()->captureHistory;
- Piece moved_piece = pos.moved_piece(move);
- PieceType captured = type_of(pos.piece_on(to_sq(move)));
+ // update_continuation_histories() updates histories of the move pairs formed
+ // by moves at ply -1, -2, -4, and -6 with current move.
- if (pos.capture_or_promotion(move))
- captureHistory[moved_piece][to_sq(move)][captured] << bonus;
+ void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) {
- // Decrease all the other played capture moves
- for (int i = 0; i < captureCount; ++i)
- {
- moved_piece = pos.moved_piece(captures[i]);
- captured = type_of(pos.piece_on(to_sq(captures[i])));
- captureHistory[moved_piece][to_sq(captures[i])][captured] << -bonus;
- }
+ for (int i : {1, 2, 4, 6})
+ {
+ if (ss->inCheck && i > 2)
+ break;
+ if (is_ok((ss-i)->currentMove))
+ (*(ss-i)->continuationHistory)[pc][to] << bonus;
+ }
}
- // update_quiet_stats() updates move sorting heuristics when a new quiet best move is found
+ // update_quiet_stats() updates move sorting heuristics
- void update_quiet_stats(const Position& pos, Stack* ss, Move move,
- Move* quiets, int quietCount, int bonus) {
+ void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus, int depth) {
if (ss->killers[0] != move)
{
thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] = move;
}
- // Decrease all the other played quiet moves
- for (int i = 0; i < quietCount; ++i)
- {
- thisThread->mainHistory[us][from_to(quiets[i])] << -bonus;
- update_continuation_histories(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus);
- }
+ if (depth > 12 && 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
for (size_t i = 0; i < multiPV; ++i)
{
- bool updated = (i <= pvIdx && rootMoves[i].score != -VALUE_INFINITE);
+ bool updated = rootMoves[i].score != -VALUE_INFINITE;
- if (depth == ONE_PLY && !updated)
+ if (depth == 1 && !updated)
continue;
- Depth d = updated ? depth : depth - ONE_PLY;
+ Depth d = updated ? depth : depth - 1;
Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
- bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
+ bool tb = TB::RootInTB && abs(v) < VALUE_MATE_IN_MAX_PLY;
v = tb ? rootMoves[i].tbScore : v;
if (ss.rdbuf()->in_avail()) // Not at first line
ss << "\n";
ss << "info"
- << " depth " << d / ONE_PLY
+ << " depth " << d
<< " seldepth " << rootMoves[i].selDepth
<< " multipv " << i + 1
<< " score " << UCI::value(v);
RootInTB = false;
UseRule50 = bool(Options["Syzygy50MoveRule"]);
- ProbeDepth = int(Options["SyzygyProbeDepth"]) * ONE_PLY;
+ ProbeDepth = int(Options["SyzygyProbeDepth"]);
Cardinality = int(Options["SyzygyProbeLimit"]);
bool dtz_available = true;
if (Cardinality > MaxCardinality)
{
Cardinality = MaxCardinality;
- ProbeDepth = DEPTH_ZERO;
+ ProbeDepth = 0;
}
if (Cardinality >= popcount(pos.pieces()) && !pos.can_castle(ANY_CASTLING))
projects / stockfish / blobdiff