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Merge branch 'master' into clusterMergeMaster13

Browse Source 
brings the cluster branch to SF 14.1

Fixes minor conflicts

local testing cluster 4x4T vs master 4T, 10+0.1s, noob_3moves:

Score of cluster vs master: 6 - 0 - 94  [0.530] 100
Elo difference: 20.9 +/- 16.2, LOS: 99.3 %, DrawRatio: 94.0 %

No functional change
This commit is contained in:
Joost VandeVondele
2021-10-31 16:17:24 +01:00
parent 43c887d367 7262fd5d14
commit b79ec2e0b2
52 changed files with 3202 additions and 2150 deletions
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src/search.cpp
+232 -290
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@@ -60,22 +60,19 @@ using namespace Search;
namespace {
// Different node types, used as a template parameter
enum NodeType { NonPV, PV };
constexpr uint64_t TtHitAverageWindow = 4096;
constexpr uint64_t TtHitAverageResolution = 1024;
enum NodeType { NonPV, PV, Root };
// Futility margin
Value futility_margin(Depth d, bool improving) {
return Value(234 * (d - improving));
return Value(214 * (d - improving));
}
// Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]
Depth reduction(bool i, Depth d, int mn) {
Depth reduction(bool i, Depth d, int mn, bool rangeReduction) {
int r = Reductions[d] * Reductions[mn];
return (r + 503) / 1024 + (!i && r > 915);
return (r + 534) / 1024 + (!i && r > 904) + rangeReduction;
}
constexpr int futility_move_count(bool improving, Depth depth) {
@@ -84,7 +81,7 @@ namespace {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
return d > 14 ? 66 : 6 * d * d + 231 * d - 206;
return std::min((6 * d + 229) * d - 215 , 2000);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -92,6 +89,30 @@ namespace {
return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
}
// Check if the current thread is in a search explosion
ExplosionState search_explosion(Thread* thisThread) {
uint64_t nodesNow = thisThread->nodes;
bool explosive = thisThread->doubleExtensionAverage[WHITE].is_greater(2, 100)
|| thisThread->doubleExtensionAverage[BLACK].is_greater(2, 100);
if (explosive)
thisThread->nodesLastExplosive = nodesNow;
else
thisThread->nodesLastNormal = nodesNow;
if ( explosive
&& thisThread->state == EXPLOSION_NONE
&& nodesNow - thisThread->nodesLastNormal > 6000000)
thisThread->state = MUST_CALM_DOWN;
if ( thisThread->state == MUST_CALM_DOWN
&& nodesNow - thisThread->nodesLastExplosive > 6000000)
thisThread->state = EXPLOSION_NONE;
return thisThread->state;
}
// Skill structure is used to implement strength limit
struct Skill {
explicit Skill(int l) : level(l) {}
@@ -103,53 +124,10 @@ namespace {
Move best = MOVE_NONE;
};
// 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 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;
otherThread = false;
owning = false;
if (location)
{
// See if another already marked this location, if not, mark it ourselves
Thread* tmp = (*location).thread.load(std::memory_order_relaxed);
if (tmp == nullptr)
{
(*location).thread.store(thisThread, std::memory_order_relaxed);
(*location).key.store(posKey, std::memory_order_relaxed);
owning = true;
}
else if ( tmp != thisThread
&& (*location).key.load(std::memory_order_relaxed) == posKey)
otherThread = true;
}
}
~ThreadHolding() {
if (owning) // Free the marked location
(*location).thread.store(nullptr, std::memory_order_relaxed);
}
bool marked() { return otherThread; }
private:
Breadcrumb* location;
bool otherThread, owning;
};
template <NodeType NT>
template <NodeType nodeType>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
template <NodeType NT>
template <NodeType nodeType>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = 0);
Value value_to_tt(Value v, int ply);
@@ -166,7 +144,7 @@ namespace {
uint64_t perft(Position& pos, Depth depth) {
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize);
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
uint64_t cnt, nodes = 0;
const bool leaf = (depth == 2);
@@ -196,7 +174,7 @@ namespace {
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
Reductions[i] = int((21.3 + 2 * std::log(Threads.size())) * std::log(i + 0.25 * std::log(i)));
Reductions[i] = int((21.9 + std::log(Threads.size()) / 2) * std::log(i));
}
@@ -325,7 +303,7 @@ void Thread::search() {
// To allow access to (ss-7) up to (ss+2), the stack must be oversized.
// The former is needed to allow update_continuation_histories(ss-1, ...),
// which accesses its argument at ss-6, also near the root.
// The latter is needed for statScores and killer initialization.
// The latter is needed for statScore and killer initialization.
Stack stack[MAX_PLY+10], *ss = stack+7;
Move pv[MAX_PLY+1];
Value bestValue, alpha, beta, delta;
@@ -340,6 +318,9 @@ void Thread::search() {
for (int i = 7; i > 0; i--)
(ss-i)->continuationHistory = &this->continuationHistory[0][0][NO_PIECE][0]; // Use as a sentinel
for (int i = 0; i <= MAX_PLY + 2; ++i)
(ss+i)->ply = i;
ss->pv = pv;
bestValue = delta = alpha = -VALUE_INFINITE;
@@ -379,21 +360,14 @@ void Thread::search() {
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
doubleExtensionAverage[WHITE].set(0, 100); // initialize the running average at 0%
doubleExtensionAverage[BLACK].set(0, 100); // initialize the running average at 0%
// In analysis mode, adjust contempt in accordance with user preference
if (Limits.infinite || Options["UCI_AnalyseMode"])
ct = Options["Analysis Contempt"] == "Off" ? 0
: Options["Analysis Contempt"] == "Both" ? ct
: Options["Analysis Contempt"] == "White" && us == BLACK ? -ct
: Options["Analysis Contempt"] == "Black" && us == WHITE ? -ct
: ct;
// Evaluation score is from the white point of view
contempt = (us == WHITE ? make_score(ct, ct / 2)
: -make_score(ct, ct / 2));
nodesLastExplosive = nodes;
nodesLastNormal = nodes;
state = EXPLOSION_NONE;
trend = SCORE_ZERO;
int searchAgainCounter = 0;
@@ -440,21 +414,21 @@ void Thread::search() {
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 + (113 - ct / 2) * prev / (abs(prev) + 147);
// Adjust trend based on root move's previousScore (dynamic contempt)
int tr = 113 * prev / (abs(prev) + 147);
contempt = (us == WHITE ? make_score(dct, dct / 2)
: -make_score(dct, dct / 2));
trend = (us == WHITE ? make_score(tr, tr / 2)
: -make_score(tr, tr / 2));
}
// Start with a small aspiration window and, in the case of a fail
// high/low, re-search with a bigger window until we don't fail
// high/low anymore.
failedHighCnt = 0;
int failedHighCnt = 0;
while (true)
{
Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
bestValue = Stockfish::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
bestValue = Stockfish::search<Root>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
// is done with a stable algorithm because all the values but the
@@ -557,8 +531,8 @@ void Thread::search() {
totBestMoveChanges += th->bestMoveChanges;
th->bestMoveChanges = 0;
}
double bestMoveInstability = 1 + 2 * totBestMoveChanges / Threads.size();
double bestMoveInstability = 1.073 + std::max(1.0, 2.25 - 9.9 / rootDepth)
* totBestMoveChanges / Threads.size();
double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability;
// Cap used time in case of a single legal move for a better viewer experience in tournaments
@@ -604,18 +578,26 @@ namespace {
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType NT>
template <NodeType nodeType>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
constexpr bool PvNode = NT == PV;
const bool rootNode = PvNode && ss->ply == 0;
Thread* thisThread = pos.this_thread();
// Step 0. Limit search explosion
if ( ss->ply > 10
&& search_explosion(thisThread) == MUST_CALM_DOWN
&& depth > (ss-1)->depth)
depth = (ss-1)->depth;
constexpr bool PvNode = nodeType != NonPV;
constexpr bool rootNode = nodeType == Root;
const Depth maxNextDepth = rootNode ? depth : depth + 1;
// Check if we have an upcoming move which draws by repetition, or
// if the opponent had an alternative move earlier to this position.
if ( pos.rule50_count() >= 3
if ( !rootNode
&& pos.rule50_count() >= 3
&& alpha < VALUE_DRAW
&& !rootNode
&& pos.has_game_cycle(ss->ply))
{
alpha = value_draw(pos.this_thread());
@@ -625,7 +607,7 @@ namespace {
// Dive into quiescence search when the depth reaches zero
if (depth <= 0)
return qsearch<NT>(pos, ss, alpha, beta);
return qsearch<PvNode ? PV : NonPV>(pos, ss, alpha, beta);
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
@@ -634,28 +616,26 @@ namespace {
Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[64];
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize);
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
TTEntry* tte;
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
bool formerPv, givesCheck, improving, didLMR, priorCapture;
bool givesCheck, improving, didLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
ttCapture, singularQuietLMR;
Piece movedPiece;
int moveCount, captureCount, quietCount;
int moveCount, captureCount, quietCount, bestMoveCount, improvement;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
ss->distanceFromPv = (PvNode ? 0 : ss->distanceFromPv);
ss->inCheck = pos.checkers();
priorCapture = pos.captured_piece();
Color us = pos.side_to_move();
moveCount = bestMoveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
// Check for the available remaining time
if (thisThread == Threads.main())
@@ -688,11 +668,15 @@ namespace {
assert(0 <= ss->ply && ss->ply < MAX_PLY);
(ss+1)->ply = ss->ply + 1;
(ss+1)->ttPv = false;
(ss+1)->ttPv = false;
(ss+1)->excludedMove = bestMove = MOVE_NONE;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
Square prevSq = to_sq((ss-1)->currentMove);
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
ss->doubleExtensions = (ss-1)->doubleExtensions;
ss->depth = depth;
Square prevSq = to_sq((ss-1)->currentMove);
// Update the running average statistics for double extensions
thisThread->doubleExtensionAverage[us].update(ss->depth > (ss-1)->depth);
// Initialize statScore to zero for the grandchildren of the current position.
// So statScore is shared between all grandchildren and only the first grandchild
@@ -711,9 +695,9 @@ namespace {
ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
: ss->ttHit ? tte->move() : MOVE_NONE;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
if (!excludedMove)
ss->ttPv = PvNode || (ss->ttHit && tte->is_pv());
formerPv = ss->ttPv && !PvNode;
// Update low ply history for previous move if we are near root and position is or has been in PV
if ( ss->ttPv
@@ -723,14 +707,10 @@ namespace {
&& 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 * ss->ttHit;
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& ss->ttHit
&& tte->depth() >= depth
&& tte->depth() > depth - (thisThread->id() % 2 == 1)
&& ttValue != VALUE_NONE // Possible in case of TT access race
&& (ttValue >= beta ? (tte->bound() & BOUND_LOWER)
: (tte->bound() & BOUND_UPPER)))
@@ -741,7 +721,7 @@ namespace {
if (ttValue >= beta)
{
// Bonus for a quiet ttMove that fails high
if (!pos.capture_or_promotion(ttMove))
if (!ttCapture)
update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth);
// Extra penalty for early quiet moves of the previous ply
@@ -749,7 +729,7 @@ namespace {
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))
else if (!ttCapture)
{
int penalty = -stat_bonus(depth);
thisThread->mainHistory[us][from_to(ttMove)] << penalty;
@@ -824,6 +804,7 @@ namespace {
// Skip early pruning when in check
ss->staticEval = eval = VALUE_NONE;
improving = false;
improvement = 0;
goto moves_loop;
}
else if (ss->ttHit)
@@ -844,35 +825,34 @@ namespace {
}
else
{
// In case of null move search use previous static eval with a different sign
// and addition of two tempos
if ((ss-1)->currentMove != MOVE_NULL)
ss->staticEval = eval = evaluate(pos);
else
ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo;
ss->staticEval = eval = evaluate(pos);
// Save static evaluation into transposition table
Cluster::save(thisThread, tte,
posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
eval);
if (!excludedMove)
Cluster::save(thisThread, tte,
posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
eval);
}
// Use static evaluation difference to improve quiet move ordering
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval - 2 * Tempo), -1000, 1000);
int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval), -1000, 1000);
thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
}
// Set up improving flag that is used in various pruning heuristics
// We define position as improving if static evaluation of position is better
// Than the previous static evaluation at our turn
// In case of us being in check at our previous move we look at move prior to it
improving = (ss-2)->staticEval == VALUE_NONE
? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
: ss->staticEval > (ss-2)->staticEval;
// Set up the improvement variable, which is the difference between the current
// static evaluation and the previous static evaluation at our turn (if we were
// in check at our previous move we look at the move prior to it). The improvement
// margin and the improving flag are used in various pruning heuristics.
improvement = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval - (ss-2)->staticEval
: (ss-4)->staticEval != VALUE_NONE ? ss->staticEval - (ss-4)->staticEval
: 200;
// Step 7. Futility pruning: child node (~50 Elo)
improving = improvement > 0;
// Step 7. Futility pruning: child node (~50 Elo).
// The depth condition is important for mate finding.
if ( !PvNode
&& depth < 9
&& eval - futility_margin(depth, improving) >= beta
@@ -882,10 +862,10 @@ namespace {
// Step 8. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 24185
&& (ss-1)->statScore < 23767
&& eval >= beta
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 24 * depth - 34 * improving + 162 * ss->ttPv + 159
&& ss->staticEval >= beta - 20 * depth - improvement / 15 + 204
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -893,7 +873,7 @@ namespace {
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = (1062 + 68 * depth) / 256 + std::min(int(eval - beta) / 190, 3);
Depth R = std::min(int(eval - beta) / 205, 3) + depth / 3 + 4;
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -931,7 +911,7 @@ namespace {
probCutBeta = beta + 209 - 44 * improving;
// Step 9. ProbCut (~10 Elo)
// Step 9. ProbCut (~4 Elo)
// 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
@@ -946,31 +926,19 @@ namespace {
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
// if ttMove is a capture and value from transposition table is good enough produce probCut
// cutoff without digging into actual probCut search
if ( ss->ttHit
&& tte->depth() >= depth - 3
&& ttValue != VALUE_NONE
&& ttValue >= probCutBeta
&& ttMove
&& pos.capture_or_promotion(ttMove))
return probCutBeta;
assert(probCutBeta < VALUE_INFINITE);
MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory);
int probCutCount = 0;
bool ttPv = ss->ttPv;
ss->ttPv = false;
while ( (move = mp.next_move()) != MOVE_NONE
&& probCutCount < 2 + 2 * cutNode)
while ((move = mp.next_move()) != MOVE_NONE)
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[ss->inCheck]
@@ -1004,18 +972,23 @@ namespace {
ss->ttPv = ttPv;
}
// Step 10. If the position is not in TT, decrease depth by 2
// Step 10. If the position is not in TT, decrease depth by 2 or 1 depending on node type
if ( PvNode
&& depth >= 6
&& !ttMove)
depth -= 2;
moves_loop: // When in check, search starts from here
if ( cutNode
&& depth >= 9
&& !ttMove)
depth--;
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
moves_loop: // When in check, search starts here
int rangeReduction = 0;
// Step 11. A small Probcut idea, when we are in check
probCutBeta = beta + 400;
probCutBeta = beta + 409;
if ( ss->inCheck
&& !PvNode
&& depth >= 4
@@ -1046,8 +1019,12 @@ moves_loop: // When in check, search starts from here
value = bestValue;
singularQuietLMR = moveCountPruning = false;
// Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply);
// 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.
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
&& tte->depth() >= depth;
// Step 12. Loop through all pseudo-legal moves until no moves remain
// or a beta cutoff occurs.
@@ -1084,18 +1061,10 @@ moves_loop: // When in check, search starts from here
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);
// Indicate PvNodes that will probably fail low if node was searched with non-PV search
// at depth equal or greater to current depth and result of this search was far below alpha
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
&& ttValue < alpha + 200 + 100 * depth
&& tte->depth() >= depth;
// Calculate new depth for this move
newDepth = depth - 1;
// Step 13. Pruning at shallow depth (~200 Elo)
// Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding.
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
@@ -1104,7 +1073,7 @@ moves_loop: // When in check, search starts from here
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0);
if ( captureOrPromotion
|| givesCheck)
@@ -1121,24 +1090,21 @@ moves_loop: // When in check, search starts from here
}
else
{
// 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)
// Continuation history based pruning (~20 Elo)
if (lmrDepth < 5
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)] < -3000 * depth + 3000)
continue;
// Futility pruning: parent node (~5 Elo)
if ( lmrDepth < 7
&& !ss->inCheck
&& ss->staticEval + 174 + 157 * lmrDepth <= alpha
&& (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
+ (*contHist[5])[movedPiece][to_sq(move)] / 3 < 28255)
if ( !ss->inCheck
&& lmrDepth < 8
&& ss->staticEval + 172 + 145 * lmrDepth <= alpha)
continue;
// Prune moves with negative SEE (~20 Elo)
if (!pos.see_ge(move, Value(-(30 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
if (!pos.see_ge(move, Value(-21 * lmrDepth * lmrDepth - 21 * lmrDepth)))
continue;
}
}
@@ -1150,17 +1116,18 @@ 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 >= 7
if ( !rootNode
&& depth >= 7
&& 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)
{
Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
Value singularBeta = ttValue - 3 * depth;
Depth singularDepth = (depth - 1) / 2;
ss->excludedMove = move;
value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
ss->excludedMove = MOVE_NONE;
@@ -1169,6 +1136,12 @@ moves_loop: // When in check, search starts from here
{
extension = 1;
singularQuietLMR = !ttCapture;
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
&& value < singularBeta - 75
&& ss->doubleExtensions <= 6)
extension = 2;
}
// Multi-cut pruning
@@ -1179,31 +1152,33 @@ moves_loop: // When in check, search starts from here
else if (singularBeta >= beta)
return singularBeta;
// If the eval of ttMove is greater than beta we try also if there is another
// move that pushes it over beta, if so also produce a cutoff.
// If the eval of ttMove is greater than beta, we reduce it (negative extension)
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;
}
extension = -2;
}
// Check extension (~2 Elo)
else if ( givesCheck
&& (pos.is_discovered_check_on_king(~us, move) || pos.see_ge(move)))
// Capture extensions for PvNodes and cutNodes
else if ( (PvNode || cutNode)
&& captureOrPromotion
&& moveCount != 1)
extension = 1;
// Last captures extension
else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg
&& pos.non_pawn_material() <= 2 * RookValueMg)
// Check extensions
else if ( givesCheck
&& depth > 6
&& abs(ss->staticEval) > 100)
extension = 1;
// Quiet ttMove extensions
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
&& (*contHist[0])[movedPiece][to_sq(move)] >= 10000)
extension = 1;
// Add extension to new depth
newDepth += extension;
ss->doubleExtensions = (ss-1)->doubleExtensions + (extension == 2);
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
@@ -1218,109 +1193,75 @@ moves_loop: // When in check, search starts from here
// Step 15. Make the move
pos.do_move(move, st, givesCheck);
(ss+1)->distanceFromPv = ss->distanceFromPv + moveCount - 1;
// 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
// cases where we extend a son if it has good chances to be "interesting".
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
&& ( !captureOrPromotion
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
|| (!PvNode && !formerPv && captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 3678)
|| thisThread->ttHitAverage < 432 * TtHitAverageResolution * TtHitAverageWindow / 1024))
&& ( !ss->ttPv
|| !captureOrPromotion
|| (cutNode && (ss-1)->moveCount > 1)))
{
Depth r = reduction(improving, depth, moveCount);
Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
// Decrease reduction if the ttHit running average is large
if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024)
// Decrease reduction if on the PV (~2 Elo)
if ( PvNode
&& bestMoveCount <= 3)
r--;
// Increase reduction if other threads are searching this position
if (th.marked())
r++;
// Decrease reduction if position is or has been on the PV
// and node is not likely to fail low. (~10 Elo)
if (ss->ttPv && !likelyFailLow)
// and node is not likely to fail low. (~3 Elo)
if ( ss->ttPv
&& !likelyFailLow)
r -= 2;
// Increase reduction at root and non-PV nodes when the best move does not change frequently
if ((rootNode || !PvNode) && thisThread->rootDepth > 10 && thisThread->bestMoveChanges <= 2)
if ( (rootNode || !PvNode)
&& thisThread->bestMoveChanges <= 2)
r++;
// More reductions for late moves if position was not in previous PV
if (moveCountPruning && !formerPv)
r++;
// Decrease reduction if opponent's move count is high (~5 Elo)
// 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 (~3 Elo)
// Decrease reduction if ttMove has been singularly extended (~1 Elo)
if (singularQuietLMR)
r--;
if (captureOrPromotion)
{
// Unless giving check, this capture is likely bad
if ( !givesCheck
&& ss->staticEval + PieceValue[EG][pos.captured_piece()] + 210 * depth <= alpha)
r++;
}
else
{
// Increase reduction if ttMove is a capture (~5 Elo)
if (ttCapture)
r++;
// Increase reduction for cut nodes (~3 Elo)
if (cutNode && move != ss->killers[0])
r += 2;
// Increase reduction at root if failing high
r += rootNode ? thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512 : 0;
// Increase reduction if ttMove is a capture (~3 Elo)
if (ttCapture)
r++;
// Increase reduction for cut nodes (~10 Elo)
if (cutNode)
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)]
- 4923;
// 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(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
r -= 2 + ss->ttPv - (type_of(movedPiece) == PAWN);
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / 14721;
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)]
- 4741;
// 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 <= 5 ? 2
: PvNode && depth > 6 ? 1
: 0;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= -89 && (ss-1)->statScore < -116)
r--;
else if ((ss-1)->statScore >= -112 && ss->statScore < -100)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
// If we are not in check use statScore, but if we are in check we use
// the sum of main history and first continuation history with an offset.
if (ss->inCheck)
r -= (thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)] - 3833) / 16384;
else
r -= ss->statScore / 14790;
}
// In general we want to cap the LMR depth search at newDepth. But for nodes
// close to the principal variation the cap is at (newDepth + 1), which will
// allow these nodes to be searched deeper than the pv (up to 4 plies deeper).
Depth d = std::clamp(newDepth - r, 1, newDepth + ((ss+1)->distanceFromPv <= 4));
Depth d = std::clamp(newDepth - r, 1, newDepth + deeper);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
// Range reductions (~3 Elo)
if (ss->staticEval - value < 30 && depth > 7)
rangeReduction++;
// If the son is reduced and fails high it will be re-searched at full depth
doFullDepthSearch = value > alpha && d < newDepth;
didLMR = true;
@@ -1387,9 +1328,11 @@ moves_loop: // When in check, search starts from here
for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m)
rm.pv.push_back(*m);
// We record how often the best move has been changed in each
// iteration. This information is used for time management and LMR
if (moveCount > 1)
// We record how often the best move has been changed in each iteration.
// This information is used for time management and LMR. In MultiPV mode,
// we must take care to only do this for the first PV line.
if ( moveCount > 1
&& !thisThread->pvIdx)
++thisThread->bestMoveChanges;
}
else
@@ -1411,11 +1354,13 @@ moves_loop: // When in check, search starts from here
update_pv(ss->pv, move, (ss+1)->pv);
if (PvNode && value < beta) // Update alpha! Always alpha < beta
{
alpha = value;
bestMoveCount++;
}
else
{
assert(value >= beta); // Fail high
ss->statScore = 0;
break;
}
}
@@ -1448,8 +1393,9 @@ moves_loop: // When in check, search starts from here
assert(moveCount || !ss->inCheck || excludedMove || !MoveList<LEGAL>(pos).size());
if (!moveCount)
bestValue = excludedMove ? alpha
: ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW;
bestValue = excludedMove ? alpha :
ss->inCheck ? mated_in(ss->ply)
: VALUE_DRAW;
// If there is a move which produces search value greater than alpha we update stats of searched moves
else if (bestMove)
@@ -1459,7 +1405,7 @@ moves_loop: // When in check, search starts from here
// Bonus for prior countermove that caused the fail low
else if ( (depth >= 3 || PvNode)
&& !priorCapture)
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth));
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + (PvNode || cutNode)));
if (PvNode)
bestValue = std::min(bestValue, maxValue);
@@ -1489,10 +1435,11 @@ moves_loop: // When in check, search starts from here
// 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.
template <NodeType NT>
template <NodeType nodeType>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
constexpr bool PvNode = NT == PV;
static_assert(nodeType != Root);
constexpr bool PvNode = nodeType == PV;
assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
@@ -1500,7 +1447,7 @@ moves_loop: // When in check, search starts from here
Move pv[MAX_PLY+1];
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize);
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
TTEntry* tte;
Key posKey;
@@ -1518,7 +1465,6 @@ moves_loop: // When in check, search starts from here
}
Thread* thisThread = pos.this_thread();
(ss+1)->ply = ss->ply + 1;
bestMove = MOVE_NONE;
ss->inCheck = pos.checkers();
moveCount = 0;
@@ -1571,10 +1517,9 @@ moves_loop: // When in check, search starts from here
}
else
// In case of null move search use previous static eval with a different sign
// and addition of two tempos
ss->staticEval = bestValue =
(ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
: -(ss-1)->staticEval + 2 * Tempo;
: -(ss-1)->staticEval;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
@@ -1600,7 +1545,7 @@ moves_loop: // When in check, search starts from here
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
// queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
// queen promotions, and other checks (only if depth >= DEPTH_QS_CHECKS)
// will be generated.
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&thisThread->captureHistory,
@@ -1612,6 +1557,10 @@ moves_loop: // When in check, search starts from here
{
assert(is_ok(move));
// Check for legality
if (!pos.legal(move))
continue;
givesCheck = pos.gives_check(move);
captureOrPromotion = pos.capture_or_promotion(move);
@@ -1621,7 +1570,7 @@ moves_loop: // When in check, search starts from here
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
&& type_of(move) != PROMOTION)
{
if (moveCount > 2)
@@ -1650,20 +1599,13 @@ moves_loop: // When in check, search starts from here
// Speculative prefetch as early as possible
prefetch(TT.first_entry(pos.key_after(move)));
// Check for legality just before making the move
if (!pos.legal(move))
{
moveCount--;
continue;
}
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
[captureOrPromotion]
[pos.moved_piece(move)]
[to_sq(move)];
// CounterMove based pruning
// Continuation history based pruning
if ( !captureOrPromotion
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
@@ -1672,7 +1614,7 @@ moves_loop: // When in check, search starts from here
// Make and search the move
pos.do_move(move, st, givesCheck);
value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - 1);
value = -qsearch<nodeType>(pos, ss+1, -beta, -alpha, depth - 1);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
@@ -1786,8 +1728,8 @@ moves_loop: // When in check, search starts from here
PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
bonus1 = stat_bonus(depth + 1);
bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
: std::min(bonus1, stat_bonus(depth)); // smaller bonus
bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
: stat_bonus(depth); // smaller bonus
if (!pos.capture_or_promotion(bestMove))
{
@@ -2011,7 +1953,7 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
bool RootMove::extract_ponder_from_tt(Position& pos) {
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::kCacheLineSize);
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
bool ttHit;