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Merge remote-tracking branch 'upstream/master' into clusterMergeMaster7

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This commit is contained in:
Joost VandeVondele
2019-10-20 09:20:34 +02:00
parent 0b3c13107a 12d58adc68
commit 8a9d269855
32 changed files with 476 additions and 440 deletions
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src/search.cpp
+195 -144
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@@ -63,17 +63,17 @@ namespace {
enum NodeType { NonPV, PV };
// Razor and futility margins
constexpr int RazorMargin = 600;
constexpr int RazorMargin = 661;
Value futility_margin(Depth d, bool improving) {
return Value((175 - 50 * improving) * d / ONE_PLY);
return Value(198 * (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 + 512) / 1024 + (!i && r > 1024)) * ONE_PLY;
int r = Reductions[d] * Reductions[mn];
return (r + 520) / 1024 + (!i && r > 999);
}
constexpr int futility_move_count(bool improving, int depth) {
@@ -81,37 +81,36 @@ namespace {
}
// History and stats update bonus, based on depth
int stat_bonus(Depth depth) {
int d = depth / ONE_PLY;
return d > 17 ? 0 : 29 * d * d + 138 * d - 134;
int stat_bonus(Depth d) {
return d > 17 ? -8 : 22 * d * d + 151 * d - 140;
}
// 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;
Move best = MOVE_NONE;
};
// Breadcrumbs are used to mark nodes as being searched by a given thread.
// Breadcrumbs are used to mark nodes as being searched by a given thread
struct Breadcrumb {
std::atomic<Thread*> thread;
std::atomic<Key> key;
};
std::array<Breadcrumb, 1024> breadcrumbs;
// ThreadHolding keeps track of which thread left breadcrumbs at the given node for potential reductions.
// A free node will be marked upon entering the moves loop, and unmarked upon leaving that loop, by the ctor/dtor of this struct.
// ThreadHolding structure keeps track of which thread left breadcrumbs at the given
// node for potential reductions. A free node will be marked upon entering the moves
// loop by the constructor, and unmarked upon leaving that loop by the destructor.
struct ThreadHolding {
explicit ThreadHolding(Thread* thisThread, Key posKey, int ply) {
location = ply < 8 ? &breadcrumbs[posKey & (breadcrumbs.size() - 1)] : nullptr;
@@ -119,7 +118,7 @@ namespace {
owning = false;
if (location)
{
// see if another already marked this location, if not, mark it ourselves.
// See if another already marked this location, if not, mark it ourselves
Thread* tmp = (*location).thread.load(std::memory_order_relaxed);
if (tmp == nullptr)
{
@@ -134,7 +133,7 @@ namespace {
}
~ThreadHolding() {
if (owning) // free the marked location.
if (owning) // Free the marked location
(*location).thread.store(nullptr, std::memory_order_relaxed);
}
@@ -149,7 +148,7 @@ namespace {
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);
@@ -165,16 +164,16 @@ namespace {
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);
}
@@ -192,7 +191,7 @@ namespace {
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
Reductions[i] = int(22.9 * std::log(i));
Reductions[i] = int((23.4 + std::log(Threads.size()) / 2) * std::log(i));
}
@@ -216,9 +215,10 @@ void MainThread::search() {
if (Limits.perft)
{
nodes = perft<true>(rootPos, Limits.perft * ONE_PLY);
nodes = perft<true>(rootPos, Limits.perft);
if (Cluster::is_root())
sync_cout << "\nNodes searched: " << nodes << "\n" << sync_endl;
return;
}
@@ -277,13 +277,13 @@ void MainThread::search() {
// Check if there are threads with a better score than main thread
if ( Options["MultiPV"] == 1
&& !Limits.depth
&& !Skill(Options["Skill Level"]).enabled()
&& !(Skill(Options["Skill Level"]).enabled() || 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 and reset votes for moves which can be voted
// Find out minimum score
for (Thread* th: Threads)
minScore = std::min(minScore, th->rootMoves[0].score);
@@ -293,7 +293,14 @@ void MainThread::search() {
votes[th->rootMoves[0].pv[0]] +=
(th->rootMoves[0].score - minScore + 14) * int(th->completedDepth);
if (votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]])
if (bestThread->rootMoves[0].score >= VALUE_MATE_IN_MAX_PLY)
{
// Make sure we pick the shortest mate
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]])
bestThread = th;
}
}
@@ -350,25 +357,33 @@ void Thread::search() {
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();
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;
multiPV = Options["MultiPV"];
size_t multiPV = 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.
// UCI_Elo is converted to a suitable fractional skill level, using anchoring
// to CCRL Elo (goldfish 1.13 = 2000) and a fit through Ordo derived Elo
// for match (TC 60+0.6) results spanning a wide range of k values.
PRNG rng(now());
int intLevel = int(Options["Skill Level"]) +
((Options["Skill Level"] - int(Options["Skill Level"])) * 1024 > rng.rand<unsigned>() % 1024 ? 1 : 0);
double floatLevel = Options["UCI_LimitStrength"] ?
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);
Skill skill(intLevel);
// When playing with strength handicap enable MultiPV search that we will
@@ -393,9 +408,9 @@ void Thread::search() {
: -make_score(ct, ct / 2));
// 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 && Cluster::is_root() && rootDepth / ONE_PLY > Limits.depth))
&& !(Limits.depth && mainThread && Cluster::is_root() && rootDepth > Limits.depth))
{
// Age out PV variability metric
if (mainThread)
@@ -425,15 +440,15 @@ void Thread::search() {
selDepth = 0;
// Reset aspiration window starting size
if (rootDepth >= 5 * ONE_PLY)
if (rootDepth >= 4)
{
Value previousScore = rootMoves[pvIdx].previousScore;
delta = Value(20);
delta = Value(21 + abs(previousScore) / 128);
alpha = std::max(previousScore - delta,-VALUE_INFINITE);
beta = std::min(previousScore + delta, VALUE_INFINITE);
// Adjust contempt based on root move's previousScore (dynamic contempt)
int dct = ct + 88 * previousScore / (abs(previousScore) + 200);
int dct = ct + 86 * previousScore / (abs(previousScore) + 176);
contempt = (us == WHITE ? make_score(dct, dct / 2)
: -make_score(dct, dct / 2));
@@ -445,7 +460,7 @@ void Thread::search() {
int failedHighCnt = 0;
while (true)
{
Depth adjustedDepth = std::max(ONE_PLY, rootDepth - failedHighCnt * ONE_PLY);
Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt);
bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
@@ -491,7 +506,10 @@ void Thread::search() {
++failedHighCnt;
}
else
{
++rootMoves[pvIdx].bestMoveCount;
break;
}
delta += delta / 4 + 5;
@@ -535,12 +553,12 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
double fallingEval = (314 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
double fallingEval = (354 + 10 * (mainThread->previousScore - bestValue)) / 692.0;
fallingEval = clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
timeReduction = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0;
double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.97 : 0.98;
double reduction = (1.36 + mainThread->previousTimeReduction) / (2.29 * timeReduction);
// Use part of the gained time from a previous stable move for the current move
for (Thread* th : Threads)
@@ -593,20 +611,19 @@ namespace {
&& !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;
@@ -615,7 +632,7 @@ namespace {
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue;
bool ttHit, ttPv, inCheck, givesCheck, improving;
bool ttHit, ttPv, inCheck, givesCheck, improving, doLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount, singularLMR;
@@ -623,6 +640,7 @@ namespace {
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = captureCount = quietCount = singularLMR = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
@@ -643,7 +661,7 @@ namespace {
|| pos.is_draw(ss->ply)
|| ss->ply >= MAX_PLY)
return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos)
: value_draw(depth, pos.this_thread());
: 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
@@ -670,9 +688,9 @@ namespace {
// statScore of the previous grandchild. This influences the reduction rules in
// LMR which are based on the statScore of parent position.
if (rootNode)
(ss + 4)->statScore = 0;
(ss+4)->statScore = 0;
else
(ss + 2)->statScore = 0;
(ss+2)->statScore = 0;
// Step 4. Transposition table lookup. We don't want the score of a partial
// search to overwrite a previous full search TT value, so we use a different
@@ -702,8 +720,8 @@ namespace {
update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(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))
@@ -751,7 +769,7 @@ namespace {
{
Cluster::save(thisThread, tte,
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;
@@ -782,6 +800,9 @@ namespace {
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)))
@@ -805,7 +826,7 @@ namespace {
// Step 7. Razoring (~2 Elo)
if ( !rootNode // The required rootNode PV handling is not available in qsearch
&& depth < 2 * ONE_PLY
&& depth < 2
&& eval <= alpha - RazorMargin)
return qsearch<NT>(pos, ss, alpha, beta);
@@ -814,7 +835,7 @@ namespace {
// Step 8. Futility pruning: child node (~30 Elo)
if ( !PvNode
&& depth < 7 * ONE_PLY
&& depth < 7
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
@@ -822,9 +843,10 @@ namespace {
// Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 23200
&& (ss-1)->statScore < 22661
&& eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 33 * depth + 299 - improving * 30
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -832,10 +854,10 @@ namespace {
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min(int(eval - beta) / 200, 3)) * ONE_PLY;
Depth R = (835 + 70 * depth) / 256 + std::min(int(eval - beta) / 185, 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);
@@ -849,14 +871,14 @@ namespace {
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 12 * 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);
@@ -872,10 +894,10 @@ namespace {
// 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
&& depth >= 5
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
Value raisedBeta = std::min(beta + 216 - 48 * improving, VALUE_INFINITE);
Value raisedBeta = std::min(beta + 191 - 46 * improving, VALUE_INFINITE);
MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory);
int probCutCount = 0;
@@ -883,12 +905,17 @@ namespace {
&& probCutCount < 2 + 2 * cutNode)
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[inCheck]
[captureOrPromotion]
[pos.moved_piece(move)]
[to_sq(move)];
pos.do_move(move, st);
@@ -897,7 +924,7 @@ namespace {
// 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);
@@ -907,9 +934,9 @@ namespace {
}
// Step 11. Internal iterative deepening (~2 Elo)
if (depth >= 8 * ONE_PLY && !ttMove)
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;
@@ -919,8 +946,8 @@ namespace {
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];
@@ -930,11 +957,11 @@ moves_loop: // When in check, search starts from here
countermove,
ss->killers);
value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
value = bestValue;
moveCountPruning = false;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
// Mark this node as being searched.
// Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply);
// Step 12. Loop through all pseudo-legal moves until no moves remain
@@ -957,19 +984,13 @@ moves_loop: // When in check, search starts from here
ss->moveCount = ++moveCount;
if (rootNode && Cluster::is_root() && 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;
// In MultiPV mode also skip moves which will be searched later as PV moves
if (rootNode && std::count(thisThread->rootMoves.begin() + thisThread->pvIdx + 1,
thisThread->rootMoves.begin() + thisThread->multiPV, move))
continue;
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);
@@ -981,28 +1002,28 @@ moves_loop: // When in check, search starts from here
// 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 >= 8 * 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 - 2 * depth;
Depth halfDepth = depth / 2;
ss->excludedMove = move;
value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode);
ss->excludedMove = MOVE_NONE;
if (value < singularBeta)
{
extension = ONE_PLY;
extension = 1;
singularLMR++;
if (value < singularBeta - std::min(3 * depth / ONE_PLY, 39))
if (value < singularBeta - std::min(4 * depth, 36))
singularLMR++;
}
@@ -1019,27 +1040,27 @@ moves_loop: // When in check, search starts from here
// 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;
extension = 1;
// Shuffle extension
else if ( PvNode
&& pos.rule50_count() > 18
&& depth < 3 * ONE_PLY
&& depth < 3
&& ++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;
extension = 1;
// Castling extension
if (type_of(move) == CASTLING)
extension = 1;
// Calculate new depth for this move
newDepth = depth - ONE_PLY + extension;
newDepth = depth - 1 + extension;
// Step 14. Pruning at shallow depth (~170 Elo)
if ( !rootNode
@@ -1047,7 +1068,7 @@ moves_loop: // When in check, search starts from here
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
// Skip quiet moves if movecount exceeds our FutilityMoveCount threshold
moveCountPruning = moveCount >= futility_move_count(improving, depth / ONE_PLY);
moveCountPruning = moveCount >= futility_move_count(improving, depth);
if ( !captureOrPromotion
&& !givesCheck
@@ -1058,27 +1079,26 @@ moves_loop: // When in check, search starts from here
continue;
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), DEPTH_ZERO);
lmrDepth /= ONE_PLY;
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
// Countermoves based pruning (~20 Elo)
if ( lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
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 (~2 Elo)
if ( lmrDepth < 7
if ( lmrDepth < 6
&& !inCheck
&& ss->staticEval + 256 + 200 * lmrDepth <= alpha)
&& ss->staticEval + 250 + 211 * lmrDepth <= alpha)
continue;
// Prune moves with negative SEE (~10 Elo)
if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
if (!pos.see_ge(move, Value(-(31 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
continue;
}
else if ( (!givesCheck || !extension)
&& !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
else if ( !(givesCheck && extension)
&& !pos.see_ge(move, Value(-199) * depth)) // (~20 Elo)
continue;
}
@@ -1094,83 +1114,108 @@ moves_loop: // When in check, search starts from here
// 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[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
// re-searched at full depth.
if ( depth >= 3 * ONE_PLY
&& moveCount > 1 + 3 * rootNode
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
&& (!rootNode || thisThread->best_move_count(move) == 0)
&& ( !captureOrPromotion
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha))
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode))
{
Depth r = reduction(improving, depth, moveCount);
// 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
if (ttPv)
r -= 2 * ONE_PLY;
r -= 2;
// Decrease reduction if opponent's move count is high (~10 Elo)
if ((ss-1)->moveCount > 15)
r -= ONE_PLY;
r--;
// Decrease reduction if move has been singularly extended
r -= singularLMR * ONE_PLY;
// Decrease reduction if ttMove has been singularly extended
r -= singularLMR;
if (!captureOrPromotion)
{
// Increase reduction if ttMove is a capture (~0 Elo)
if (ttCapture)
r += ONE_PLY;
r++;
// Increase reduction for cut nodes (~5 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)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(make_move(to_sq(move), from_sq(move))))
r -= 2 * ONE_PLY;
&& !pos.see_ge(reverse_move(move)))
r -= 2;
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)]
- 4000;
- 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;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= 0 && (ss-1)->statScore < 0)
r -= ONE_PLY;
if (ss->statScore >= -99 && (ss-1)->statScore < -116)
r--;
else if ((ss-1)->statScore >= 0 && ss->statScore < 0)
r += ONE_PLY;
else if ((ss-1)->statScore >= -117 && ss->statScore < -144)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / 16384 * ONE_PLY;
r -= ss->statScore / 16384;
}
Depth d = clamp(newDepth - r, ONE_PLY, newDepth);
Depth d = clamp(newDepth - r, 1, newDepth);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
doFullDepthSearch = (value > alpha && d != newDepth);
doFullDepthSearch = (value > alpha && d != newDepth), doLMR = true;
}
else
doFullDepthSearch = !PvNode || moveCount > 1;
doFullDepthSearch = !PvNode || moveCount > 1, doLMR = 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)
{
int bonus = value > alpha ? stat_bonus(newDepth)
: -stat_bonus(newDepth);
if (move == ss->killers[0])
bonus += bonus / 4;
update_continuation_histories(ss, movedPiece, to_sq(move), bonus);
}
}
// For PV nodes only, do a full PV search on the first move or after a fail
// high (in the latter case search only if value < beta), otherwise let the
// parent node fail low with value <= alpha and try another move.
@@ -1279,19 +1324,19 @@ moves_loop: // When in check, search starts from here
// 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)));
stat_bonus(depth + (bestValue > beta + PawnValueMg)));
update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + 1));
// 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));
&& !priorCapture)
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1));
}
// 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)
@@ -1319,8 +1364,7 @@ moves_loop: // When in check, search starts from here
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;
@@ -1329,7 +1373,7 @@ moves_loop: // When in check, search starts from here
Move ttMove, move, bestMove;
Depth ttDepth;
Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha;
bool ttHit, pvHit, inCheck, givesCheck, evasionPrunable;
bool ttHit, pvHit, inCheck, givesCheck, captureOrPromotion, evasionPrunable;
int moveCount;
if (PvNode)
@@ -1410,12 +1454,12 @@ moves_loop: // When in check, search starts from here
if (PvNode && bestValue > alpha)
alpha = bestValue;
futilityBase = bestValue + 128;
futilityBase = bestValue + 153;
}
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,
@@ -1432,6 +1476,7 @@ moves_loop: // When in check, search starts from here
assert(is_ok(move));
givesCheck = pos.gives_check(move);
captureOrPromotion = pos.capture_or_promotion(move);
moveCount++;
@@ -1460,7 +1505,7 @@ moves_loop: // When in check, search starts from here
// Detect non-capture evasions that are candidates to be pruned
evasionPrunable = inCheck
&& (depth != DEPTH_ZERO || moveCount > 2)
&& (depth != 0 || moveCount > 2)
&& bestValue > VALUE_MATED_IN_MAX_PLY
&& !pos.capture(move);
@@ -1481,11 +1526,14 @@ moves_loop: // When in check, search starts from here
}
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[pos.moved_piece(move)][to_sq(move)];
ss->continuationHistory = &thisThread->continuationHistory[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);
@@ -1611,6 +1659,9 @@ moves_loop: // When in check, search starts from here
thisThread->mainHistory[us][from_to(move)] << bonus;
update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus);
if (type_of(pos.moved_piece(move)) != PAWN)
thisThread->mainHistory[us][from_to(reverse_move(move))] << -bonus;
if (is_ok((ss-1)->currentMove))
{
Square prevSq = to_sq((ss-1)->currentMove);
@@ -1713,10 +1764,10 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
{
bool updated = (i <= pvIdx && 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;
@@ -1726,7 +1777,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
ss << "\n";
ss << "info"
<< " depth " << d / ONE_PLY
<< " depth " << d
<< " seldepth " << rootMoves[i].selDepth
<< " multipv " << i + 1
<< " score " << UCI::value(v);
@@ -1785,7 +1836,7 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
RootInTB = false;
UseRule50 = bool(Options["Syzygy50MoveRule"]);
ProbeDepth = int(Options["SyzygyProbeDepth"]) * ONE_PLY;
ProbeDepth = int(Options["SyzygyProbeDepth"]);
Cardinality = int(Options["SyzygyProbeLimit"]);
bool dtz_available = true;
@@ -1794,7 +1845,7 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
if (Cardinality > MaxCardinality)
{
Cardinality = MaxCardinality;
ProbeDepth = DEPTH_ZERO;
ProbeDepth = 0;
}
if (Cardinality >= popcount(pos.pieces()) && !pos.can_castle(ANY_CASTLING))