X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=76d0545ac50bd7f619f88db3785ee6c0f3e4c316;hb=3c0e86a91e48baea273306e45fb6cf13a59373cf;hp=eccb97fd12c198cbf5efc1a1d19c2e26e7d91c92;hpb=085cace4574bf561472d8d3d3afe50c2c536b4e3;p=stockfish
diff --git a/src/search.cpp b/src/search.cpp
index eccb97fd..76d0545a 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -16,24 +16,34 @@
along with this program. If not, see .
*/
+#include "search.h"
+
#include
+#include
+#include
#include
#include
-#include // For std::memset
+#include
+#include
+#include
#include
#include
+#include
+#include
+#include "bitboard.h"
#include "evaluate.h"
#include "misc.h"
#include "movegen.h"
#include "movepick.h"
+#include "nnue/evaluate_nnue.h"
+#include "nnue/nnue_common.h"
#include "position.h"
-#include "search.h"
+#include "syzygy/tbprobe.h"
#include "thread.h"
#include "timeman.h"
#include "tt.h"
#include "uci.h"
-#include "syzygy/tbprobe.h"
namespace Stockfish {
@@ -62,16 +72,16 @@ namespace {
enum NodeType { NonPV, PV, Root };
// Futility margin
- Value futility_margin(Depth d, bool improving) {
- return Value(158 * (d - improving));
+ Value futility_margin(Depth d, bool noTtCutNode, bool improving) {
+ return Value((140 - 40 * noTtCutNode) * (d - improving));
}
- // Reductions lookup table, initialized at startup
+ // Reductions lookup table initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]
Depth reduction(bool i, Depth d, int mn, Value delta, Value rootDelta) {
int r = Reductions[d] * Reductions[mn];
- return (r + 1460 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 937);
+ return (r + 1372 - int(delta) * 1073 / int(rootDelta)) / 1024 + (!i && r > 936);
}
constexpr int futility_move_count(bool improving, Depth depth) {
@@ -81,7 +91,7 @@ namespace {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return std::min(350 * d - 400, 1650);
+ return std::min(336 * d - 547, 1561);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -91,7 +101,7 @@ namespace {
// Skill structure is used to implement strength limit. If we have an uci_elo then
// we convert it 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)
+ // (goldfish 1.13 = 2000) and a fit through Ordo derived Elo for a match (TC 60+0.6)
// results spanning a wide range of k values.
struct Skill {
Skill(int skill_level, int uci_elo) {
@@ -161,7 +171,7 @@ namespace {
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int((20.26 + std::log(Threads.size()) / 2) * std::log(i));
+ Reductions[i] = int((20.57 + std::log(Threads.size()) / 2) * std::log(i));
}
@@ -287,8 +297,7 @@ void Thread::search() {
ss->pv = pv;
- bestValue = delta = alpha = -VALUE_INFINITE;
- beta = VALUE_INFINITE;
+ bestValue = -VALUE_INFINITE;
if (mainThread)
{
@@ -304,16 +313,12 @@ void Thread::search() {
Skill skill(Options["Skill Level"], Options["UCI_LimitStrength"] ? int(Options["UCI_Elo"]) : 0);
// When playing with strength handicap enable MultiPV search that we will
- // use behind the scenes to retrieve a set of possible moves.
+ // use behind-the-scenes to retrieve a set of possible moves.
if (skill.enabled())
multiPV = std::max(multiPV, (size_t)4);
multiPV = std::min(multiPV, rootMoves.size());
- complexityAverage.set(153, 1);
-
- optimism[us] = optimism[~us] = VALUE_ZERO;
-
int searchAgainCounter = 0;
// Iterative deepening loop until requested to stop or the target depth is reached
@@ -325,7 +330,7 @@ void Thread::search() {
if (mainThread)
totBestMoveChanges /= 2;
- // Save the last iteration's scores before first PV line is searched and
+ // Save the last iteration's scores before the first PV line is searched and
// all the move scores except the (new) PV are set to -VALUE_INFINITE.
for (RootMove& rm : rootMoves)
rm.previousScore = rm.score;
@@ -334,7 +339,7 @@ void Thread::search() {
pvLast = 0;
if (!Threads.increaseDepth)
- searchAgainCounter++;
+ searchAgainCounter++;
// MultiPV loop. We perform a full root search for each PV line
for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx)
@@ -351,18 +356,15 @@ void Thread::search() {
selDepth = 0;
// Reset aspiration window starting size
- if (rootDepth >= 4)
- {
- Value prev = rootMoves[pvIdx].averageScore;
- delta = Value(10) + int(prev) * prev / 15400;
- alpha = std::max(prev - delta,-VALUE_INFINITE);
- beta = std::min(prev + delta, VALUE_INFINITE);
-
- // Adjust optimism based on root move's previousScore
- int opt = 116 * prev / (std::abs(prev) + 170);
- optimism[ us] = Value(opt);
- optimism[~us] = -optimism[us];
- }
+ Value prev = rootMoves[pvIdx].averageScore;
+ delta = Value(10) + int(prev) * prev / 15799;
+ alpha = std::max(prev - delta,-VALUE_INFINITE);
+ beta = std::min(prev + delta, VALUE_INFINITE);
+
+ // Adjust optimism based on root move's previousScore
+ int opt = 109 * prev / (std::abs(prev) + 141);
+ optimism[ us] = Value(opt);
+ optimism[~us] = -optimism[us];
// 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
@@ -370,16 +372,16 @@ void Thread::search() {
int failedHighCnt = 0;
while (true)
{
- // Adjust the effective depth searched, but ensuring at least one effective increment for every
+ // Adjust the effective depth searched, but ensure at least one effective increment for every
// four searchAgain steps (see issue #2717).
Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - 3 * (searchAgainCounter + 1) / 4);
bestValue = Stockfish::search(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
- // first and eventually the new best one are set to -VALUE_INFINITE
+ // first and eventually the new best one is set to -VALUE_INFINITE
// and we want to keep the same order for all the moves except the
- // new PV that goes to the front. Note that in case of MultiPV
+ // new PV that goes to the front. Note that in the case of MultiPV
// search the already searched PV lines are preserved.
std::stable_sort(rootMoves.begin() + pvIdx, rootMoves.begin() + pvLast);
@@ -416,7 +418,7 @@ void Thread::search() {
else
break;
- delta += delta / 4 + 2;
+ delta += delta / 3;
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
}
@@ -432,9 +434,10 @@ void Thread::search() {
if (!Threads.stop)
completedDepth = rootDepth;
- if (rootMoves[0].pv[0] != lastBestMove) {
- lastBestMove = rootMoves[0].pv[0];
- lastBestMoveDepth = rootDepth;
+ if (rootMoves[0].pv[0] != lastBestMove)
+ {
+ lastBestMove = rootMoves[0].pv[0];
+ lastBestMoveDepth = rootDepth;
}
// Have we found a "mate in x"?
@@ -446,7 +449,7 @@ void Thread::search() {
if (!mainThread)
continue;
- // If skill level is enabled and time is up, pick a sub-optimal best move
+ // If the skill level is enabled and time is up, pick a sub-optimal best move
if (skill.enabled() && skill.time_to_pick(rootDepth))
skill.pick_best(multiPV);
@@ -462,18 +465,16 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (71 + 12 * (mainThread->bestPreviousAverageScore - bestValue)
- + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 656.7;
+ double fallingEval = (69 + 13 * (mainThread->bestPreviousAverageScore - bestValue)
+ + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 619.6;
fallingEval = std::clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
- timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.37 : 0.65;
- double reduction = (1.4 + mainThread->previousTimeReduction) / (2.15 * timeReduction);
- double bestMoveInstability = 1 + 1.7 * totBestMoveChanges / Threads.size();
- int complexity = mainThread->complexityAverage.value();
- double complexPosition = std::min(1.0 + (complexity - 261) / 1738.7, 1.5);
+ timeReduction = lastBestMoveDepth + 8 < completedDepth ? 1.57 : 0.65;
+ double reduction = (1.4 + mainThread->previousTimeReduction) / (2.08 * timeReduction);
+ double bestMoveInstability = 1 + 1.8 * totBestMoveChanges / Threads.size();
- double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability * complexPosition;
+ double totalTime = Time.optimum() * fallingEval * reduction * bestMoveInstability;
// Cap used time in case of a single legal move for a better viewer experience in tournaments
// yielding correct scores and sufficiently fast moves.
@@ -491,7 +492,7 @@ void Thread::search() {
Threads.stop = true;
}
else if ( !mainThread->ponder
- && Time.elapsed() > totalTime * 0.53)
+ && Time.elapsed() > totalTime * 0.50)
Threads.increaseDepth = false;
else
Threads.increaseDepth = true;
@@ -506,7 +507,7 @@ void Thread::search() {
mainThread->previousTimeReduction = timeReduction;
- // If skill level is enabled, swap best PV line with the sub-optimal one
+ // If the skill level is enabled, swap the best PV line with the sub-optimal one
if (skill.enabled())
std::swap(rootMoves[0], *std::find(rootMoves.begin(), rootMoves.end(),
skill.best ? skill.best : skill.pick_best(multiPV)));
@@ -523,10 +524,9 @@ namespace {
constexpr bool PvNode = nodeType != NonPV;
constexpr bool rootNode = nodeType == Root;
- // Check if we have an upcoming move which draws by repetition, or
+ // Check if we have an upcoming move that draws by repetition, or
// if the opponent had an alternative move earlier to this position.
if ( !rootNode
- && pos.rule50_count() >= 3
&& alpha < VALUE_DRAW
&& pos.has_game_cycle(ss->ply))
{
@@ -556,7 +556,7 @@ namespace {
bool givesCheck, improving, priorCapture, singularQuietLMR;
bool capture, moveCountPruning, ttCapture;
Piece movedPiece;
- int moveCount, captureCount, quietCount, improvement, complexity;
+ int moveCount, captureCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
@@ -588,8 +588,8 @@ namespace {
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
// a shorter mate was found upward in the tree then there is no need to search
// because we will never beat the current alpha. Same logic but with reversed
- // signs applies also in the opposite condition of being mated instead of giving
- // mate. In this case return a fail-high score.
+ // signs apply also in the opposite condition of being mated instead of giving
+ // mate. In this case, return a fail-high score.
alpha = std::max(mated_in(ss->ply), alpha);
beta = std::min(mate_in(ss->ply+1), beta);
if (alpha >= beta)
@@ -600,20 +600,12 @@ namespace {
assert(0 <= ss->ply && ss->ply < MAX_PLY);
- (ss+1)->ttPv = false;
(ss+1)->excludedMove = bestMove = MOVE_NONE;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
(ss+2)->cutoffCnt = 0;
ss->doubleExtensions = (ss-1)->doubleExtensions;
- Square prevSq = to_sq((ss-1)->currentMove);
-
- // Initialize statScore to zero for the grandchildren of the current position.
- // So statScore is shared between all grandchildren and only the first grandchild
- // starts with statScore = 0. Later grandchildren start with the last calculated
- // statScore of the previous grandchild. This influences the reduction rules in
- // LMR which are based on the statScore of parent position.
- if (!rootNode)
- (ss+2)->statScore = 0;
+ Square prevSq = is_ok((ss-1)->currentMove) ? to_sq((ss-1)->currentMove) : SQ_NONE;
+ ss->statScore = 0;
// Step 4. Transposition table lookup.
excludedMove = ss->excludedMove;
@@ -622,7 +614,7 @@ 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(ttMove);
+ ttCapture = ttMove && pos.capture_stage(ttMove);
// At this point, if excluded, skip straight to step 6, static eval. However,
// to save indentation, we list the condition in all code between here and there.
@@ -631,10 +623,9 @@ namespace {
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
- && ss->ttHit
&& !excludedMove
- && tte->depth() > depth - (tte->bound() == BOUND_EXACT)
- && ttValue != VALUE_NONE // Possible in case of TT access race
+ && tte->depth() > depth
+ && ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
{
// If ttMove is quiet, update move sorting heuristics on TT hit (~2 Elo)
@@ -647,7 +638,7 @@ namespace {
update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
// Extra penalty for early quiet moves of the previous ply (~0 Elo on STC, ~2 Elo on LTC)
- if ((ss-1)->moveCount <= 2 && !priorCapture)
+ if (prevSq != SQ_NONE && (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 (~1 Elo)
@@ -725,24 +716,22 @@ namespace {
// Skip early pruning when in check
ss->staticEval = eval = VALUE_NONE;
improving = false;
- improvement = 0;
- complexity = 0;
goto moves_loop;
}
- else if (excludedMove) {
- // excludeMove implies that we had a ttHit on the containing non-excluded search with ss->staticEval filled from TT
- // However static evals from the TT aren't good enough (-13 elo), presumably due to changing optimism context
- // Recalculate value with current optimism (without updating thread avgComplexity)
- ss->staticEval = eval = evaluate(pos, &complexity);
+ else if (excludedMove)
+ {
+ // Providing the hint that this node's accumulator will be used often brings significant Elo gain (13 Elo)
+ Eval::NNUE::hint_common_parent_position(pos);
+ eval = ss->staticEval;
}
else if (ss->ttHit)
{
// Never assume anything about values stored in TT
ss->staticEval = eval = tte->eval();
if (eval == VALUE_NONE)
- ss->staticEval = eval = evaluate(pos, &complexity);
- else // Fall back to (semi)classical complexity for TT hits, the NNUE complexity is lost
- complexity = abs(ss->staticEval - pos.psq_eg_stm());
+ ss->staticEval = eval = evaluate(pos);
+ else if (PvNode)
+ Eval::NNUE::hint_common_parent_position(pos);
// ttValue can be used as a better position evaluation (~7 Elo)
if ( ttValue != VALUE_NONE
@@ -751,32 +740,31 @@ namespace {
}
else
{
- ss->staticEval = eval = evaluate(pos, &complexity);
- // Save static evaluation into transposition table
+ ss->staticEval = eval = evaluate(pos);
+ // Save static evaluation into the transposition table
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
- thisThread->complexityAverage.update(complexity);
// Use static evaluation difference to improve quiet move ordering (~4 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
- int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1940, 1940);
+ int bonus = std::clamp(-18 * int((ss-1)->staticEval + ss->staticEval), -1817, 1817);
thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus;
}
- // 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
- : 172;
- improving = improvement > 0;
+ // Set up the improving flag, which is true if current static evaluation is
+ // bigger than the previous static evaluation at our turn (if we were in
+ // check at our previous move we look at static evaluation at move prior to it
+ // and if we were in check at move prior to it flag is set to true) and is
+ // false otherwise. The improving flag is used in various pruning heuristics.
+ improving = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval > (ss-2)->staticEval
+ : (ss-4)->staticEval != VALUE_NONE ? ss->staticEval > (ss-4)->staticEval
+ : true;
// Step 7. Razoring (~1 Elo).
// If eval is really low check with qsearch if it can exceed alpha, if it can't,
// return a fail low.
- if (eval < alpha - 394 - 255 * depth * depth)
+ if (eval < alpha - 456 - 252 * depth * depth)
{
value = qsearch(pos, ss, alpha - 1, alpha);
if (value < alpha)
@@ -786,27 +774,28 @@ namespace {
// Step 8. Futility pruning: child node (~40 Elo).
// The depth condition is important for mate finding.
if ( !ss->ttPv
- && depth < 8
- && eval - futility_margin(depth, improving) - (ss-1)->statScore / 304 >= beta
+ && depth < 9
+ && eval - futility_margin(depth, cutNode && !ss->ttHit, improving) - (ss-1)->statScore / 306 >= beta
&& eval >= beta
- && eval < 28580) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
+ && eval < 24923) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval;
// Step 9. Null move search with verification search (~35 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 18200
+ && (ss-1)->statScore < 17329
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 20 * depth - improvement / 14 + 235 + complexity / 24
+ && ss->staticEval >= beta - 21 * depth + 258
&& !excludedMove
&& pos.non_pawn_material(us)
- && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
+ && ss->ply >= thisThread->nmpMinPly
+ && beta > VALUE_TB_LOSS_IN_MAX_PLY)
{
assert(eval - beta >= 0);
- // Null move dynamic reduction based on depth, eval and complexity of position
- Depth R = std::min(int(eval - beta) / 165, 6) + depth / 3 + 4 - (complexity > 800);
+ // Null move dynamic reduction based on depth and eval
+ Depth R = std::min(int(eval - beta) / 173, 6) + depth / 3 + 4;
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -820,18 +809,16 @@ namespace {
if (nullValue >= beta)
{
// Do not return unproven mate or TB scores
- if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY)
- nullValue = beta;
+ nullValue = std::min(nullValue, VALUE_TB_WIN_IN_MAX_PLY-1);
- if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 14))
+ if (thisThread->nmpMinPly || depth < 14)
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.
+ // until ply exceeds nmpMinPly.
thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
- thisThread->nmpColor = us;
Value v = search(pos, ss, beta-1, beta, depth-R, false);
@@ -842,20 +829,34 @@ namespace {
}
}
- probCutBeta = beta + 180 - 54 * improving;
+ // Step 10. If the position doesn't have a ttMove, decrease depth by 2
+ // (or by 4 if the TT entry for the current position was hit and the stored depth is greater than or equal to the current depth).
+ // Use qsearch if depth is equal or below zero (~9 Elo)
+ if ( PvNode
+ && !ttMove)
+ depth -= 2 + 2 * (ss->ttHit && tte->depth() >= depth);
+
+ if (depth <= 0)
+ return qsearch(pos, ss, alpha, beta);
- // Step 10. ProbCut (~10 Elo)
- // If we have a good enough capture and a reduced search returns a value
+ if ( cutNode
+ && depth >= 8
+ && !ttMove)
+ depth -= 2;
+
+ probCutBeta = beta + 168 - 61 * improving;
+
+ // Step 11. ProbCut (~10 Elo)
+ // If we have a good enough capture (or queen promotion) and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
- && depth > 4
+ && depth > 3
&& abs(beta) < VALUE_TB_WIN_IN_MAX_PLY
- // if value from transposition table is lower than probCutBeta, don't attempt probCut
+ // If value from transposition table is lower than probCutBeta, don't attempt probCut
// there and in further interactions with transposition table cutoff depth is set to depth - 3
// because probCut search has depth set to depth - 4 but we also do a move before it
- // so effective depth is equal to depth - 3
- && !( ss->ttHit
- && tte->depth() >= depth - 3
+ // So effective depth is equal to depth - 3
+ && !( tte->depth() >= depth - 3
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
@@ -866,7 +867,7 @@ namespace {
while ((move = mp.next_move()) != MOVE_NONE)
if (move != excludedMove && pos.legal(move))
{
- assert(pos.capture(move) || promotion_type(move) == QUEEN);
+ assert(pos.capture_stage(move));
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
@@ -892,44 +893,29 @@ namespace {
return value;
}
}
- }
-
- // Step 11. If the position is not in TT, decrease depth by 3.
- // Use qsearch if depth is equal or below zero (~9 Elo)
- if ( PvNode
- && !ttMove)
- depth -= 3;
- if (depth <= 0)
- return qsearch(pos, ss, alpha, beta);
-
- if ( cutNode
- && depth >= 9
- && !ttMove)
- depth -= 2;
+ Eval::NNUE::hint_common_parent_position(pos);
+ }
moves_loop: // When in check, search starts here
// Step 12. A small Probcut idea, when we are in check (~4 Elo)
- probCutBeta = beta + 402;
+ probCutBeta = beta + 413;
if ( ss->inCheck
&& !PvNode
- && depth >= 2
&& ttCapture
&& (tte->bound() & BOUND_LOWER)
- && tte->depth() >= depth - 3
+ && tte->depth() >= depth - 4
&& ttValue >= probCutBeta
&& abs(ttValue) <= VALUE_KNOWN_WIN
- && abs(beta) <= VALUE_KNOWN_WIN
- )
+ && abs(beta) <= VALUE_KNOWN_WIN)
return probCutBeta;
-
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
nullptr , (ss-4)->continuationHistory,
nullptr , (ss-6)->continuationHistory };
- Move countermove = thisThread->counterMoves[pos.piece_on(prevSq)][prevSq];
+ Move countermove = prevSq != SQ_NONE ? thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] : MOVE_NONE;
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&captureHistory,
@@ -941,7 +927,7 @@ moves_loop: // When in check, search starts here
moveCountPruning = singularQuietLMR = false;
// Indicate PvNodes that will probably fail low if the node was searched
- // at a depth equal or greater than the current depth, and the result of this search was a fail low.
+ // at a depth equal to or greater than the current depth, and the result of this search was a fail low.
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
@@ -957,8 +943,8 @@ moves_loop: // When in check, search starts here
continue;
// At root obey the "searchmoves" option and skip moves not listed in Root
- // Move List. As a consequence any illegal move is also skipped. In MultiPV
- // mode we also skip PV moves which have been already searched and those
+ // Move List. As a consequence, any illegal move is also skipped. In MultiPV
+ // mode we also skip PV moves that have been already searched and those
// of lower "TB rank" if we are in a TB root position.
if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->pvIdx,
thisThread->rootMoves.begin() + thisThread->pvLast, move))
@@ -978,7 +964,7 @@ moves_loop: // When in check, search starts here
(ss+1)->pv = nullptr;
extension = 0;
- capture = pos.capture(move);
+ capture = pos.capture_stage(move);
movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move);
@@ -987,6 +973,8 @@ moves_loop: // When in check, search starts here
Value delta = beta - alpha;
+ Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
+
// Step 14. Pruning at shallow depth (~120 Elo). Depth conditions are important for mate finding.
if ( !rootNode
&& pos.non_pawn_material(us)
@@ -996,22 +984,21 @@ moves_loop: // When in check, search starts here
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
- int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, delta, thisThread->rootDelta), 0);
+ int lmrDepth = newDepth - r;
if ( capture
|| givesCheck)
{
// Futility pruning for captures (~2 Elo)
if ( !givesCheck
- && !PvNode
&& lmrDepth < 7
&& !ss->inCheck
- && ss->staticEval + 185 + 203 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
- + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 6 < alpha)
+ && ss->staticEval + 197 + 248 * lmrDepth + PieceValue[pos.piece_on(to_sq(move))]
+ + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
continue;
- // SEE based pruning (~11 Elo)
- if (!pos.see_ge(move, Value(-220) * depth))
+ // SEE based pruning for captures and checks (~11 Elo)
+ if (!pos.see_ge(move, Value(-205) * depth))
continue;
}
else
@@ -1021,25 +1008,25 @@ moves_loop: // When in check, search starts here
+ (*contHist[3])[movedPiece][to_sq(move)];
// Continuation history based pruning (~2 Elo)
- if ( lmrDepth < 5
- && history < -4180 * (depth - 1))
+ if ( lmrDepth < 6
+ && history < -3832 * depth)
continue;
history += 2 * thisThread->mainHistory[us][from_to(move)];
- lmrDepth += history / 7208;
+ lmrDepth += history / 7011;
lmrDepth = std::max(lmrDepth, -2);
// Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
- && lmrDepth < 13
- && ss->staticEval + 103 + 136 * lmrDepth <= alpha)
+ && lmrDepth < 12
+ && ss->staticEval + 112 + 138 * lmrDepth <= alpha)
continue;
lmrDepth = std::max(lmrDepth, 0);
// Prune moves with negative SEE (~4 Elo)
- if (!pos.see_ge(move, Value(-25 * lmrDepth * lmrDepth - 16 * lmrDepth)))
+ if (!pos.see_ge(move, Value(-31 * lmrDepth * lmrDepth)))
continue;
}
}
@@ -1053,6 +1040,9 @@ moves_loop: // When in check, search starts 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.
+ // Depth margin and singularBeta margin are known for having non-linear scaling.
+ // Their values are optimized to time controls of 180+1.8 and longer
+ // so changing them requires tests at this type of time controls.
if ( !rootNode
&& depth >= 4 - (thisThread->completedDepth > 22) + 2 * (PvNode && tte->is_pv())
&& move == ttMove
@@ -1062,11 +1052,10 @@ moves_loop: // When in check, search starts here
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3)
{
- Value singularBeta = ttValue - (3 + (ss->ttPv && !PvNode)) * depth;
+ Value singularBeta = ttValue - (82 + 65 * (ss->ttPv && !PvNode)) * depth / 64;
Depth singularDepth = (depth - 1) / 2;
ss->excludedMove = move;
- // the search with excludedMove will update ss->staticEval
value = search(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
ss->excludedMove = MOVE_NONE;
@@ -1077,11 +1066,11 @@ moves_loop: // When in check, search starts here
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
- && value < singularBeta - 25
- && ss->doubleExtensions <= 10)
+ && value < singularBeta - 21
+ && ss->doubleExtensions <= 11)
{
extension = 2;
- depth += depth < 12;
+ depth += depth < 13;
}
}
@@ -1089,30 +1078,33 @@ moves_loop: // When in check, search starts here
// Our ttMove is assumed to fail high, and now we failed high also on a reduced
// 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.
+ // a softbound.
else if (singularBeta >= beta)
return singularBeta;
- // If the eval of ttMove is greater than beta, we reduce it (negative extension)
+ // If the eval of ttMove is greater than beta, we reduce it (negative extension) (~7 Elo)
else if (ttValue >= beta)
- extension = -2;
+ extension = -2 - !PvNode;
- // If the eval of ttMove is less than alpha and value, we reduce it (negative extension)
- else if (ttValue <= alpha && ttValue <= value)
+ // If we are on a cutNode, reduce it based on depth (negative extension) (~1 Elo)
+ else if (cutNode)
+ extension = depth < 17 ? -3 : -1;
+
+ // If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
+ else if (ttValue <= value)
extension = -1;
}
// Check extensions (~1 Elo)
else if ( givesCheck
- && depth > 9
- && abs(ss->staticEval) > 78)
+ && depth > 9)
extension = 1;
// Quiet ttMove extensions (~1 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
- && (*contHist[0])[movedPiece][to_sq(move)] >= 5600)
+ && (*contHist[0])[movedPiece][to_sq(move)] >= 5168)
extension = 1;
}
@@ -1133,16 +1125,15 @@ moves_loop: // When in check, search starts here
// Step 16. Make the move
pos.do_move(move, st, givesCheck);
- Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
-
// Decrease reduction if position is or has been on the PV
// and node is not likely to fail low. (~3 Elo)
+ // Decrease further on cutNodes. (~1 Elo)
if ( ss->ttPv
&& !likelyFailLow)
- r -= 2;
+ r -= cutNode && tte->depth() >= depth + 3 ? 3 : 2;
// Decrease reduction if opponent's move count is high (~1 Elo)
- if ((ss-1)->moveCount > 7)
+ if ((ss-1)->moveCount > 8)
r--;
// Increase reduction for cut nodes (~3 Elo)
@@ -1153,40 +1144,38 @@ moves_loop: // When in check, search starts here
if (ttCapture)
r++;
- // Decrease reduction for PvNodes based on depth
+ // Decrease reduction for PvNodes (~2 Elo)
if (PvNode)
- r -= 1 + 11 / (3 + depth);
+ r--;
// Decrease reduction if ttMove has been singularly extended (~1 Elo)
if (singularQuietLMR)
r--;
- // Decrease reduction if we move a threatened piece (~1 Elo)
- if ( depth > 9
- && (mp.threatenedPieces & from_sq(move)))
- r--;
+ // Increase reduction on repetition (~1 Elo)
+ if ( move == (ss-4)->currentMove
+ && pos.has_repeated())
+ r += 2;
- // Increase reduction if next ply has a lot of fail high
+ // Increase reduction if next ply has a lot of fail high (~5 Elo)
if ((ss+1)->cutoffCnt > 3)
r++;
- // Decrease reduction if move is a killer and we have a good history
- if (move == ss->killers[0]
- && (*contHist[0])[movedPiece][to_sq(move)] >= 3600)
+ else if (move == ttMove)
r--;
ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 4467;
+ - 4006;
- // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- r -= ss->statScore / (12800 + 4410 * (depth > 7 && depth < 19));
+ // Decrease/increase reduction for moves with a good/bad history (~25 Elo)
+ r -= ss->statScore / (11124 + 4740 * (depth > 5 && depth < 22));
// Step 17. Late moves reduction / extension (LMR, ~117 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
+ // 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 >= 2
&& moveCount > 1 + (PvNode && ss->ply <= 1)
@@ -1201,13 +1190,13 @@ moves_loop: // When in check, search starts here
value = -search(pos, ss+1, -(alpha+1), -alpha, d, true);
- // Do full depth search when reduced LMR search fails high
+ // Do a full-depth search when reduced LMR search fails high
if (value > alpha && d < newDepth)
{
- // Adjust full depth search based on LMR results - if result
+ // Adjust full-depth search based on LMR results - if the result
// was good enough search deeper, if it was bad enough search shallower
- const bool doDeeperSearch = value > (alpha + 66 + 11 * (newDepth - d));
- const bool doEvenDeeperSearch = value > alpha + 582 && ss->doubleExtensions <= 5;
+ const bool doDeeperSearch = value > (bestValue + 64 + 11 * (newDepth - d));
+ const bool doEvenDeeperSearch = value > alpha + 711 && ss->doubleExtensions <= 6;
const bool doShallowerSearch = value < bestValue + newDepth;
ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch;
@@ -1217,27 +1206,27 @@ moves_loop: // When in check, search starts here
if (newDepth > d)
value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
- int bonus = value > alpha ? stat_bonus(newDepth)
- : -stat_bonus(newDepth);
+ int bonus = value <= alpha ? -stat_bonus(newDepth)
+ : value >= beta ? stat_bonus(newDepth)
+ : 0;
update_continuation_histories(ss, movedPiece, to_sq(move), bonus);
}
}
- // Step 18. Full depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
+ // Step 18. Full-depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
else if (!PvNode || moveCount > 1)
{
- // Increase reduction for cut nodes and not ttMove (~1 Elo)
- if (!ttMove && cutNode)
- r += 2;
+ // Increase reduction for cut nodes and not ttMove (~1 Elo)
+ if (!ttMove && cutNode)
+ r += 2;
- value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
+ value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 3), !cutNode);
}
- // 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.
- if (PvNode && (moveCount == 1 || (value > alpha && (rootNode || value < beta))))
+ // For PV nodes only, do a full PV search on the first move or after a fail high,
+ // otherwise let the parent node fail low with value <= alpha and try another move.
+ if (PvNode && (moveCount == 1 || value > alpha))
{
(ss+1)->pv = pv;
(ss+1)->pv[0] = MOVE_NONE;
@@ -1271,14 +1260,17 @@ moves_loop: // When in check, search starts here
rm.selDepth = thisThread->selDepth;
rm.scoreLowerbound = rm.scoreUpperbound = false;
- if (value >= beta) {
- rm.scoreLowerbound = true;
- rm.uciScore = beta;
+ if (value >= beta)
+ {
+ rm.scoreLowerbound = true;
+ rm.uciScore = beta;
}
- else if (value <= alpha) {
- rm.scoreUpperbound = true;
- rm.uciScore = alpha;
+ else if (value <= alpha)
+ {
+ rm.scoreUpperbound = true;
+ rm.uciScore = alpha;
}
+
rm.pv.resize(1);
assert((ss+1)->pv);
@@ -1294,7 +1286,7 @@ moves_loop: // When in check, search starts here
++thisThread->bestMoveChanges;
}
else
- // All other moves but the PV are set to the lowest value: this
+ // All other moves but the PV, are set to the lowest value: this
// is not a problem when sorting because the sort is stable and the
// move position in the list is preserved - just the PV is pushed up.
rm.score = -VALUE_INFINITE;
@@ -1311,30 +1303,29 @@ moves_loop: // When in check, search starts here
if (PvNode && !rootNode) // Update pv even in fail-high case
update_pv(ss->pv, move, (ss+1)->pv);
- if (PvNode && value < beta) // Update alpha! Always alpha < beta
+ if (value >= beta)
{
- alpha = value;
-
- // Reduce other moves if we have found at least one score improvement
- if ( depth > 1
- && depth < 6
- && beta < VALUE_KNOWN_WIN
- && alpha > -VALUE_KNOWN_WIN)
- depth -= 1;
-
- assert(depth > 0);
+ ss->cutoffCnt += 1 + !ttMove;
+ assert(value >= beta); // Fail high
+ break;
}
else
{
- ss->cutoffCnt++;
- assert(value >= beta); // Fail high
- break;
+ // Reduce other moves if we have found at least one score improvement (~2 Elo)
+ if ( depth > 2
+ && depth < 12
+ && beta < 14362
+ && value > -12393)
+ depth -= 2;
+
+ assert(depth > 0);
+ alpha = value; // Update alpha! Always alpha < beta
}
}
}
- // If the move is worse than some previously searched move, remember it to update its stats later
+ // If the move is worse than some previously searched move, remember it, to update its stats later
if (move != bestMove)
{
if (capture && captureCount < 32)
@@ -1346,7 +1337,7 @@ moves_loop: // When in check, search starts here
}
// The following condition would detect a stop only after move loop has been
- // completed. But in this case bestValue is valid because we have fully
+ // completed. But in this case, bestValue is valid because we have fully
// searched our subtree, and we can anyhow save the result in TT.
/*
if (Threads.stop)
@@ -1365,24 +1356,24 @@ moves_loop: // When in check, search starts here
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
+ // If there is a move that produces search value greater than alpha we update the stats of searched moves
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 (!priorCapture)
+ else if (!priorCapture && prevSq != SQ_NONE)
{
- // Extra bonuses for PV/Cut nodes or bad fail lows
- int bonus = (depth > 4) + (PvNode || cutNode) + (bestValue < alpha - 88 * depth);
+ int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 800) + ((ss-1)->moveCount > 12);
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus);
+ thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << stat_bonus(depth) * bonus / 2;
}
if (PvNode)
bestValue = std::min(bestValue, maxValue);
// If no good move is found and the previous position was ttPv, then the previous
- // opponent move is probably good and the new position is added to the search tree.
+ // opponent move is probably good and the new position is added to the search tree. (~7 Elo)
if (bestValue <= alpha)
ss->ttPv = ss->ttPv || ((ss-1)->ttPv && depth > 3);
@@ -1401,7 +1392,7 @@ moves_loop: // When in check, search starts 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.
- // (~155 elo)
+ // (~155 Elo)
template
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
@@ -1412,6 +1403,17 @@ moves_loop: // When in check, search starts here
assert(PvNode || (alpha == beta - 1));
assert(depth <= 0);
+ // Check if we have an upcoming move that draws by repetition, or
+ // if the opponent had an alternative move earlier to this position.
+ if ( depth < 0
+ && alpha < VALUE_DRAW
+ && pos.has_game_cycle(ss->ply))
+ {
+ alpha = value_draw(pos.this_thread());
+ if (alpha >= beta)
+ return alpha;
+ }
+
Move pv[MAX_PLY+1];
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
@@ -1447,7 +1449,8 @@ moves_loop: // When in check, search starts here
// 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 = ss->inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
- : DEPTH_QS_NO_CHECKS;
+ : DEPTH_QS_NO_CHECKS;
+
// Step 3. Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey, ss->ttHit);
@@ -1457,18 +1460,14 @@ moves_loop: // When in check, search starts here
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
- && ss->ttHit
&& tte->depth() >= ttDepth
- && ttValue != VALUE_NONE // Only in case of TT access race
+ && ttValue != VALUE_NONE // Only in case of TT access race or if !ttHit
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
return ttValue;
// Step 4. Static evaluation of the position
if (ss->inCheck)
- {
- ss->staticEval = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
- }
else
{
if (ss->ttHit)
@@ -1484,9 +1483,8 @@ moves_loop: // When in check, search starts here
}
else
// In case of null move search use previous static eval with a different sign
- ss->staticEval = bestValue =
- (ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
- : -(ss-1)->staticEval;
+ ss->staticEval = bestValue = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos)
+ : -(ss-1)->staticEval;
// Stand pat. Return immediately if static value is at least beta
if (bestValue >= beta)
@@ -1499,10 +1497,10 @@ moves_loop: // When in check, search starts here
return bestValue;
}
- if (PvNode && bestValue > alpha)
+ if (bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 158;
+ futilityBase = std::min(ss->staticEval, bestValue) + 200;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
@@ -1513,7 +1511,7 @@ moves_loop: // When in check, search starts here
// to search the moves. Because the depth is <= 0 here, only captures,
// queen promotions, and other checks (only if depth >= DEPTH_QS_CHECKS)
// will be generated.
- Square prevSq = to_sq((ss-1)->currentMove);
+ Square prevSq = is_ok((ss-1)->currentMove) ? to_sq((ss-1)->currentMove) : SQ_NONE;
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&thisThread->captureHistory,
contHist,
@@ -1525,98 +1523,98 @@ moves_loop: // When in check, search starts here
// or a beta cutoff occurs.
while ((move = mp.next_move()) != MOVE_NONE)
{
- assert(is_ok(move));
-
- // Check for legality
- if (!pos.legal(move))
- continue;
-
- givesCheck = pos.gives_check(move);
- capture = pos.capture(move);
-
- moveCount++;
+ assert(is_ok(move));
- // Step 6. Pruning.
- if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
- {
- // Futility pruning and moveCount pruning (~10 Elo)
- if ( !givesCheck
- && to_sq(move) != prevSq
- && futilityBase > -VALUE_KNOWN_WIN
- && type_of(move) != PROMOTION)
- {
- if (moveCount > 2)
- continue;
+ // Check for legality
+ if (!pos.legal(move))
+ continue;
- futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))];
+ givesCheck = pos.gives_check(move);
+ capture = pos.capture_stage(move);
- if (futilityValue <= alpha)
- {
- bestValue = std::max(bestValue, futilityValue);
- continue;
- }
+ moveCount++;
- if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1))
- {
- bestValue = std::max(bestValue, futilityBase);
- continue;
- }
- }
+ // Step 6. Pruning.
+ if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
+ {
+ // Futility pruning and moveCount pruning (~10 Elo)
+ if ( !givesCheck
+ && to_sq(move) != prevSq
+ && futilityBase > -VALUE_KNOWN_WIN
+ && type_of(move) != PROMOTION)
+ {
+ if (moveCount > 2)
+ continue;
- // We prune after 2nd quiet check evasion where being 'in check' is implicitly checked through the counter
- // and being a 'quiet' apart from being a tt move is assumed after an increment because captures are pushed ahead.
- if (quietCheckEvasions > 1)
- break;
+ futilityValue = futilityBase + PieceValue[pos.piece_on(to_sq(move))];
- // Continuation history based pruning (~3 Elo)
- if ( !capture
- && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < 0
- && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < 0)
- continue;
+ if (futilityValue <= alpha)
+ {
+ bestValue = std::max(bestValue, futilityValue);
+ continue;
+ }
- // Do not search moves with bad enough SEE values (~5 Elo)
- if (!pos.see_ge(move, Value(-108)))
- continue;
+ if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1))
+ {
+ bestValue = std::max(bestValue, futilityBase);
+ continue;
+ }
+ }
- }
+ // We prune after the second quiet check evasion move, where being 'in check' is
+ // implicitly checked through the counter, and being a 'quiet move' apart from
+ // being a tt move is assumed after an increment because captures are pushed ahead.
+ if (quietCheckEvasions > 1)
+ break;
+
+ // Continuation history based pruning (~3 Elo)
+ if ( !capture
+ && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < 0
+ && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < 0)
+ continue;
+
+ // Do not search moves with bad enough SEE values (~5 Elo)
+ if (!pos.see_ge(move, Value(-95)))
+ continue;
+ }
- // Speculative prefetch as early as possible
- prefetch(TT.first_entry(pos.key_after(move)));
+ // Speculative prefetch as early as possible
+ prefetch(TT.first_entry(pos.key_after(move)));
- // Update the current move
- ss->currentMove = move;
- ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
- [capture]
- [pos.moved_piece(move)]
- [to_sq(move)];
+ // Update the current move
+ ss->currentMove = move;
+ ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
+ [capture]
+ [pos.moved_piece(move)]
+ [to_sq(move)];
- quietCheckEvasions += !capture && ss->inCheck;
+ quietCheckEvasions += !capture && ss->inCheck;
- // Step 7. Make and search the move
- pos.do_move(move, st, givesCheck);
- value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1);
- pos.undo_move(move);
+ // Step 7. Make and search the move
+ pos.do_move(move, st, givesCheck);
+ value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1);
+ pos.undo_move(move);
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
+ assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 8. Check for a new best move
- if (value > bestValue)
- {
- bestValue = value;
+ // Step 8. Check for a new best move
+ if (value > bestValue)
+ {
+ bestValue = value;
- if (value > alpha)
- {
- bestMove = move;
+ if (value > alpha)
+ {
+ bestMove = move;
- if (PvNode) // Update pv even in fail-high case
- update_pv(ss->pv, move, (ss+1)->pv);
+ if (PvNode) // Update pv even in fail-high case
+ update_pv(ss->pv, move, (ss+1)->pv);
- if (PvNode && value < beta) // Update alpha here!
- alpha = value;
- else
- break; // Fail high
- }
- }
+ if (value < beta) // Update alpha here!
+ alpha = value;
+ else
+ break; // Fail high
+ }
+ }
}
// Step 9. Check for mate
@@ -1703,40 +1701,45 @@ moves_loop: // When in check, search starts here
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)));
- int bonus1 = stat_bonus(depth + 1);
+ PieceType captured;
- if (!pos.capture(bestMove))
+ int quietMoveBonus = stat_bonus(depth + 1);
+
+ if (!pos.capture_stage(bestMove))
{
- int bonus2 = bestValue > beta + 146 ? bonus1 // larger bonus
- : stat_bonus(depth); // smaller bonus
+ int bestMoveBonus = bestValue > beta + 145 ? quietMoveBonus // larger bonus
+ : stat_bonus(depth); // smaller bonus
// Increase stats for the best move in case it was a quiet move
- update_quiet_stats(pos, ss, bestMove, bonus2);
+ update_quiet_stats(pos, ss, bestMove, bestMoveBonus);
// Decrease stats for all 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);
+ thisThread->mainHistory[us][from_to(quietsSearched[i])] << -bestMoveBonus;
+ update_continuation_histories(ss, pos.moved_piece(quietsSearched[i]), to_sq(quietsSearched[i]), -bestMoveBonus);
}
}
else
+ {
// Increase stats for the best move in case it was a capture move
- captureHistory[moved_piece][to_sq(bestMove)][captured] << bonus1;
+ captured = type_of(pos.piece_on(to_sq(bestMove)));
+ captureHistory[moved_piece][to_sq(bestMove)][captured] << quietMoveBonus;
+ }
// Extra penalty for a quiet early move that was not a TT move or
// main killer move in previous ply when it gets refuted.
- if ( ((ss-1)->moveCount == 1 + (ss-1)->ttHit || ((ss-1)->currentMove == (ss-1)->killers[0]))
+ if ( prevSq != SQ_NONE
+ && ((ss-1)->moveCount == 1 + (ss-1)->ttHit || ((ss-1)->currentMove == (ss-1)->killers[0]))
&& !pos.captured_piece())
- update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -bonus1);
+ update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -quietMoveBonus);
// Decrease stats for all 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;
+ captureHistory[moved_piece][to_sq(capturesSearched[i])][captured] << -quietMoveBonus;
}
}
@@ -1748,7 +1751,7 @@ moves_loop: // When in check, search starts here
for (int i : {1, 2, 4, 6})
{
- // Only update first 2 continuation histories if we are in check
+ // Only update the first 2 continuation histories if we are in check
if (ss->inCheck && i > 2)
break;
if (is_ok((ss-i)->currentMove))
@@ -1781,7 +1784,7 @@ moves_loop: // When in check, search starts here
}
}
- // When playing with strength handicap, choose best move among a set of RootMoves
+ // When playing with strength handicap, choose the best move among a set of RootMoves
// using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
Move Skill::pick_best(size_t multiPV) {
@@ -1791,7 +1794,7 @@ moves_loop: // When in check, search starts here
// RootMoves are already sorted by score in descending order
Value topScore = rootMoves[0].score;
- int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValueMg);
+ int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValue);
int maxScore = -VALUE_INFINITE;
double weakness = 120 - 2 * level;
@@ -1826,7 +1829,7 @@ void MainThread::check_time() {
return;
// When using nodes, ensure checking rate is not lower than 0.1% of nodes
- callsCnt = Limits.nodes ? std::min(1024, int(Limits.nodes / 1024)) : 1024;
+ callsCnt = Limits.nodes ? std::min(512, int(Limits.nodes / 1024)) : 512;
static TimePoint lastInfoTime = now();
@@ -1843,7 +1846,7 @@ void MainThread::check_time() {
if (ponder)
return;
- if ( (Limits.use_time_management() && (elapsed > Time.maximum() - 10 || stopOnPonderhit))
+ if ( (Limits.use_time_management() && (elapsed > Time.maximum() || stopOnPonderhit))
|| (Limits.movetime && elapsed >= Limits.movetime)
|| (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes))
Threads.stop = true;
@@ -1912,7 +1915,7 @@ string UCI::pv(const Position& pos, Depth depth) {
/// RootMove::extract_ponder_from_tt() is called in case we have no ponder move
/// before exiting the search, for instance, in case we stop the search during a
/// fail high at root. We try hard to have a ponder move to return to the GUI,
-/// otherwise in case of 'ponder on' we have nothing to think on.
+/// otherwise in case of 'ponder on' we have nothing to think about.
bool RootMove::extract_ponder_from_tt(Position& pos) {