X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=a1834ab99b303387f505cd4011ee2f1cc4a25026;hb=38e830af4bfa6c9e9c11279a8e6a60b6ca4ec2cd;hp=76d055e3039e3b3a8245eeee9a8520343d75d392;hpb=9cd563cb54b4091c48e16b524b3c9c15b7824c4f;p=stockfish
diff --git a/src/search.cpp b/src/search.cpp
index 76d055e3..a1834ab9 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -16,25 +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"
-#include "nnue/evaluate_nnue.h"
namespace Stockfish {
@@ -63,16 +72,17 @@ namespace {
enum NodeType { NonPV, PV, Root };
// Futility margin
- Value futility_margin(Depth d, bool improving) {
- return Value(140 * (d - improving));
+ Value futility_margin(Depth d, bool noTtCutNode, bool improving) {
+ return Value((126 - 42 * noTtCutNode) * (d - improving));
}
// 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 + 1372 - int(delta) * 1073 / int(rootDelta)) / 1024 + (!i && r > 936);
+ int reductionScale = Reductions[d] * Reductions[mn];
+ return (reductionScale + 1560 - int(delta) * 945 / int(rootDelta)) / 1024
+ + (!i && reductionScale > 791);
}
constexpr int futility_move_count(bool improving, Depth depth) {
@@ -82,7 +92,7 @@ namespace {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
- return std::min(336 * d - 547, 1561);
+ return std::min(334 * d - 531, 1538);
}
// Add a small random component to draw evaluations to avoid 3-fold blindness
@@ -90,10 +100,12 @@ namespace {
return VALUE_DRAW - 1 + Value(thisThread->nodes & 0x2);
}
- // 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 a match (TC 60+0.6)
- // results spanning a wide range of k values.
+ // Skill structure is used to implement strength limit.
+ // If we have a UCI_Elo, we convert it to an appropriate skill level, anchored to the Stash engine.
+ // This method is based on a fit of the Elo results for games played between the master at various
+ // skill levels and various versions of the Stash engine, all ranked at CCRL.
+ // Skill 0 .. 19 now covers CCRL Blitz Elo from 1320 to 3190, approximately
+ // Reference: https://github.com/vondele/Stockfish/commit/a08b8d4e9711c20acedbfe17d618c3c384b339ec
struct Skill {
Skill(int skill_level, int uci_elo) {
if (uci_elo)
@@ -162,7 +174,7 @@ namespace {
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
- Reductions[i] = int((20.57 + std::log(Threads.size()) / 2) * std::log(i));
+ Reductions[i] = int((20.37 + std::log(Threads.size()) / 2) * std::log(i));
}
@@ -262,10 +274,9 @@ void MainThread::search() {
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 statScore and killer initialization.
+ // Allocate stack with extra size to allow access from (ss-7) to (ss+2)
+ // (ss-7) is needed for update_continuation_histories(ss-1, ...) which accesses (ss-6)
+ // (ss+2) is needed for initialization of statScore and killers
Stack stack[MAX_PLY+10], *ss = stack+7;
Move pv[MAX_PLY+1];
Value alpha, beta, delta;
@@ -306,7 +317,7 @@ void Thread::search() {
// When playing with strength handicap enable MultiPV search that we will
// use behind-the-scenes to retrieve a set of possible moves.
if (skill.enabled())
- multiPV = std::max(multiPV, (size_t)4);
+ multiPV = std::max(multiPV, size_t(4));
multiPV = std::min(multiPV, rootMoves.size());
@@ -348,12 +359,12 @@ void Thread::search() {
// Reset aspiration window starting size
Value prev = rootMoves[pvIdx].averageScore;
- delta = Value(10) + int(prev) * prev / 15799;
+ delta = Value(10) + int(prev) * prev / 17470;
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);
+ // Adjust optimism based on root move's previousScore (~4 Elo)
+ int opt = 113 * prev / (std::abs(prev) + 109);
optimism[ us] = Value(opt);
optimism[~us] = -optimism[us];
@@ -515,10 +526,13 @@ namespace {
constexpr bool PvNode = nodeType != NonPV;
constexpr bool rootNode = nodeType == Root;
+ // Dive into quiescence search when the depth reaches zero
+ if (depth <= 0)
+ return qsearch(pos, ss, alpha, beta);
+
// 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))
{
@@ -527,16 +541,12 @@ namespace {
return alpha;
}
- // Dive into quiescence search when the depth reaches zero
- if (depth <= 0)
- return qsearch(pos, ss, alpha, beta);
-
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(0 < depth && depth < MAX_PLY);
assert(!(PvNode && cutNode));
- Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[64];
+ Move pv[MAX_PLY+1], capturesSearched[32], quietsSearched[32];
StateInfo st;
ASSERT_ALIGNED(&st, Eval::NNUE::CacheLineSize);
@@ -548,7 +558,7 @@ namespace {
bool givesCheck, improving, priorCapture, singularQuietLMR;
bool capture, moveCountPruning, ttCapture;
Piece movedPiece;
- int moveCount, captureCount, quietCount, improvement;
+ int moveCount, captureCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
@@ -616,7 +626,7 @@ namespace {
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& !excludedMove
- && tte->depth() > depth - (tte->bound() == BOUND_EXACT)
+ && tte->depth() > depth
&& ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
{
@@ -708,12 +718,11 @@ namespace {
// Skip early pruning when in check
ss->staticEval = eval = VALUE_NONE;
improving = false;
- improvement = 0;
goto moves_loop;
}
else if (excludedMove)
{
- // Providing the hint that this node's accumulator will be used often brings significant Elo gain (13 Elo)
+ // 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;
}
@@ -741,45 +750,49 @@ namespace {
// 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(-18 * int((ss-1)->staticEval + ss->staticEval), -1817, 1817);
+ int bonus = std::clamp(-18 * int((ss-1)->staticEval + ss->staticEval), -1812, 1812);
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
- : 173;
- 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).
+ // 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 - 456 - 252 * depth * depth)
+ // Adjust razor margin according to cutoffCnt. (~1 Elo)
+ if (eval < alpha - 492 - (257 - 200 * ((ss+1)->cutoffCnt > 3)) * depth * depth)
{
value = qsearch(pos, ss, alpha - 1, alpha);
if (value < alpha)
return value;
}
- // Step 8. Futility pruning: child node (~40 Elo).
+ // Step 8. Futility pruning: child node (~40 Elo)
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 9
- && eval - futility_margin(depth, improving) - (ss-1)->statScore / 306 >= beta
+ && eval - futility_margin(depth, cutNode && !ss->ttHit, improving) - (ss-1)->statScore / 321 >= beta
&& eval >= beta
- && eval < 24923) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
+ && eval < 29462 // smaller than TB wins
+ && !( !ttCapture
+ && ttMove
+ && thisThread->mainHistory[us][from_to(ttMove)] < 989))
return eval;
// Step 9. Null move search with verification search (~35 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 17329
+ && (ss-1)->statScore < 17257
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 21 * depth + 258
+ && ss->staticEval >= beta - 24 * depth + 281
&& !excludedMove
&& pos.non_pawn_material(us)
&& ss->ply >= thisThread->nmpMinPly
@@ -788,7 +801,7 @@ namespace {
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and eval
- Depth R = std::min(int(eval - beta) / 173, 6) + depth / 3 + 4;
+ Depth R = std::min(int(eval - beta) / 152, 6) + depth / 3 + 4;
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -837,7 +850,7 @@ namespace {
&& !ttMove)
depth -= 2;
- probCutBeta = beta + 168 - 61 * improving;
+ probCutBeta = beta + 168 - 70 * improving;
// Step 11. ProbCut (~10 Elo)
// If we have a good enough capture (or queen promotion) and a reduced search returns a value
@@ -893,19 +906,19 @@ namespace {
moves_loop: // When in check, search starts here
// Step 12. A small Probcut idea, when we are in check (~4 Elo)
- probCutBeta = beta + 413;
+ probCutBeta = beta + 416;
if ( ss->inCheck
&& !PvNode
&& ttCapture
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 4
&& ttValue >= probCutBeta
- && abs(ttValue) <= VALUE_KNOWN_WIN
- && abs(beta) <= VALUE_KNOWN_WIN)
+ && abs(ttValue) < VALUE_TB_WIN_IN_MAX_PLY
+ && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
return probCutBeta;
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
- nullptr , (ss-4)->continuationHistory,
+ (ss-3)->continuationHistory, (ss-4)->continuationHistory,
nullptr , (ss-6)->continuationHistory };
Move countermove = prevSq != SQ_NONE ? thisThread->counterMoves[pos.piece_on(prevSq)][prevSq] : MOVE_NONE;
@@ -920,7 +933,8 @@ 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 to 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)
@@ -935,18 +949,17 @@ moves_loop: // When in check, search starts here
if (move == excludedMove)
continue;
+ // Check for legality
+ if (!pos.legal(move))
+ 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 that have been already searched and those
- // of lower "TB rank" if we are in a TB root position.
+ // Move List. 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))
continue;
- // Check for legality
- if (!rootNode && !pos.legal(move))
- continue;
-
ss->moveCount = ++moveCount;
if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
@@ -974,7 +987,8 @@ moves_loop: // When in check, search starts here
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
{
// Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~8 Elo)
- moveCountPruning = moveCount >= futility_move_count(improving, depth);
+ if (!moveCountPruning)
+ moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
int lmrDepth = newDepth - r;
@@ -986,32 +1000,13 @@ moves_loop: // When in check, search starts here
if ( !givesCheck
&& lmrDepth < 7
&& !ss->inCheck
- && ss->staticEval + 197 + 248 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))]
+ && ss->staticEval + 188 + 206 * lmrDepth + PieceValue[pos.piece_on(to_sq(move))]
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha)
continue;
- Bitboard occupied;
- // SEE based pruning (~11 Elo)
- if (!pos.see_ge(move, occupied, Value(-205) * depth))
- {
- if (depth < 2 - capture)
- continue;
- // Don't prune the move if opponent Queen/Rook is under discovered attack after the exchanges
- // Don't prune the move if opponent King is under discovered attack after or during the exchanges
- Bitboard leftEnemies = (pos.pieces(~us, KING, QUEEN, ROOK)) & occupied;
- Bitboard attacks = 0;
- occupied |= to_sq(move);
- while (leftEnemies && !attacks)
- {
- Square sq = pop_lsb(leftEnemies);
- attacks |= pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied;
- // Don't consider pieces that were already threatened/hanging before SEE exchanges
- if (attacks && (sq != pos.square(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))))
- attacks = 0;
- }
- if (!attacks)
- continue;
- }
+ // SEE based pruning for captures and checks (~11 Elo)
+ if (!pos.see_ge(move, Value(-185) * depth))
+ continue;
}
else
{
@@ -1021,24 +1016,24 @@ moves_loop: // When in check, search starts here
// Continuation history based pruning (~2 Elo)
if ( lmrDepth < 6
- && history < -3832 * depth)
+ && history < -3232 * depth)
continue;
history += 2 * thisThread->mainHistory[us][from_to(move)];
- lmrDepth += history / 7011;
+ lmrDepth += history / 5793;
lmrDepth = std::max(lmrDepth, -2);
// Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
- && lmrDepth < 12
- && ss->staticEval + 112 + 138 * lmrDepth <= alpha)
+ && lmrDepth < 13
+ && ss->staticEval + 115 + 122 * lmrDepth <= alpha)
continue;
lmrDepth = std::max(lmrDepth, 0);
// Prune moves with negative SEE (~4 Elo)
- if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth)))
+ if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth)))
continue;
}
}
@@ -1050,21 +1045,21 @@ moves_loop: // When in check, search starts here
// Singular extension search (~94 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
- // a reduced search on all the other moves but the ttMove and if the
- // result is lower than ttValue minus a margin, then we will extend the ttMove.
- // 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
+ // 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. Note
+ // that 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())
+ && depth >= 4 - (thisThread->completedDepth > 24) + 2 * (PvNode && tte->is_pv())
&& move == ttMove
&& !excludedMove // Avoid recursive singular search
/* && ttValue != VALUE_NONE Already implicit in the next condition */
- && abs(ttValue) < VALUE_KNOWN_WIN
+ && abs(ttValue) < VALUE_TB_WIN_IN_MAX_PLY
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3)
{
- Value singularBeta = ttValue - (82 + 65 * (ss->ttPv && !PvNode)) * depth / 64;
+ Value singularBeta = ttValue - (64 + 57 * (ss->ttPv && !PvNode)) * depth / 64;
Depth singularDepth = (depth - 1) / 2;
ss->excludedMove = move;
@@ -1078,19 +1073,19 @@ moves_loop: // When in check, search starts here
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
- && value < singularBeta - 21
+ && value < singularBeta - 18
&& ss->doubleExtensions <= 11)
{
extension = 2;
- depth += depth < 13;
+ depth += depth < 15;
}
}
// Multi-cut pruning
- // 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 softbound.
+ // 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 softbound.
else if (singularBeta >= beta)
return singularBeta;
@@ -1100,15 +1095,11 @@ moves_loop: // When in check, search starts here
// If we are on a cutNode, reduce it based on depth (negative extension) (~1 Elo)
else if (cutNode)
- extension = depth > 8 && depth < 17 ? -3 : -1;
+ extension = depth < 19 ? -2 : -1;
// If the eval of ttMove is less than value, we reduce it (negative extension) (~1 Elo)
else if (ttValue <= value)
extension = -1;
-
- // If the eval of ttMove is less than alpha, we reduce it (negative extension) (~1 Elo)
- else if (ttValue <= alpha)
- extension = -1;
}
// Check extensions (~1 Elo)
@@ -1120,7 +1111,7 @@ moves_loop: // When in check, search starts here
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
- && (*contHist[0])[movedPiece][to_sq(move)] >= 5168)
+ && (*contHist[0])[movedPiece][to_sq(move)] >= 4194)
extension = 1;
}
@@ -1141,15 +1132,14 @@ moves_loop: // When in check, search starts here
// Step 16. Make the move
pos.do_move(move, st, givesCheck);
- // Decrease reduction if position is or has been on the PV
- // and node is not likely to fail low. (~3 Elo)
+ // Decrease reduction if position is or has been on the PV and not likely to fail low. (~3 Elo)
// Decrease further on cutNodes. (~1 Elo)
if ( ss->ttPv
&& !likelyFailLow)
- r -= cutNode && tte->depth() >= depth + 3 ? 3 : 2;
+ r -= cutNode && tte->depth() >= depth ? 3 : 2;
// Decrease reduction if opponent's move count is high (~1 Elo)
- if ((ss-1)->moveCount > 8)
+ if ((ss-1)->moveCount > 7)
r--;
// Increase reduction for cut nodes (~3 Elo)
@@ -1160,18 +1150,24 @@ moves_loop: // When in check, search starts here
if (ttCapture)
r++;
- // Decrease reduction for PvNodes based on depth (~2 Elo)
+ // Decrease reduction for PvNodes (~2 Elo)
if (PvNode)
- r -= 1 + 12 / (3 + depth);
+ r--;
// Decrease reduction if ttMove has been singularly extended (~1 Elo)
if (singularQuietLMR)
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 (~5 Elo)
if ((ss+1)->cutoffCnt > 3)
r++;
+ // Decrease reduction for first generated move (ttMove)
else if (move == ttMove)
r--;
@@ -1179,10 +1175,10 @@ moves_loop: // When in check, search starts here
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
+ (*contHist[3])[movedPiece][to_sq(move)]
- - 4006;
+ - 3848;
// Decrease/increase reduction for moves with a good/bad history (~25 Elo)
- r -= ss->statScore / (11124 + 4740 * (depth > 5 && depth < 22));
+ r -= ss->statScore / (10216 + 3855 * (depth > 5 && depth < 23));
// Step 17. Late moves reduction / extension (LMR, ~117 Elo)
// We use various heuristics for the sons of a node after the first son has
@@ -1206,8 +1202,8 @@ moves_loop: // When in check, search starts here
{
// 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 > (bestValue + 64 + 11 * (newDepth - d));
- const bool doEvenDeeperSearch = value > alpha + 711 && ss->doubleExtensions <= 6;
+ const bool doDeeperSearch = value > (bestValue + 51 + 10 * (newDepth - d));
+ const bool doEvenDeeperSearch = value > alpha + 700 && ss->doubleExtensions <= 6;
const bool doShallowerSearch = value < bestValue + newDepth;
ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch;
@@ -1235,10 +1231,9 @@ moves_loop: // When in check, search starts here
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;
@@ -1326,8 +1321,8 @@ moves_loop: // When in check, search starts here
// Reduce other moves if we have found at least one score improvement (~2 Elo)
if ( depth > 2
&& depth < 12
- && beta < 14362
- && value > -12393)
+ && beta < 13828
+ && value > -11369)
depth -= 2;
assert(depth > 0);
@@ -1338,12 +1333,12 @@ moves_loop: // When in check, search starts here
// If the move is worse than some previously searched move, remember it, to update its stats later
- if (move != bestMove)
+ if (move != bestMove && moveCount <= 32)
{
- if (capture && captureCount < 32)
+ if (capture)
capturesSearched[captureCount++] = move;
- else if (!capture && quietCount < 64)
+ else
quietsSearched[quietCount++] = move;
}
}
@@ -1376,8 +1371,9 @@ moves_loop: // When in check, search starts here
// Bonus for prior countermove that caused the fail low
else if (!priorCapture && prevSq != SQ_NONE)
{
- int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 113 * depth) + ((ss-1)->moveCount > 12);
+ int bonus = (depth > 6) + (PvNode || cutNode) + (bestValue < alpha - 653) + ((ss-1)->moveCount > 11);
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)
@@ -1414,6 +1410,16 @@ 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 ( 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);
@@ -1425,6 +1431,7 @@ moves_loop: // When in check, search starts here
Value bestValue, value, ttValue, futilityValue, futilityBase;
bool pvHit, givesCheck, capture;
int moveCount;
+ Color us = pos.side_to_move();
// Step 1. Initialize node
if (PvNode)
@@ -1497,14 +1504,14 @@ moves_loop: // When in check, search starts here
return bestValue;
}
- if (PvNode && bestValue > alpha)
+ if (bestValue > alpha)
alpha = bestValue;
- futilityBase = bestValue + 200;
+ futilityBase = std::min(ss->staticEval, bestValue) + 200;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
- nullptr , (ss-4)->continuationHistory,
+ (ss-3)->continuationHistory, (ss-4)->continuationHistory,
nullptr , (ss-6)->continuationHistory };
// Initialize a MovePicker object for the current position, and prepare
@@ -1535,30 +1542,42 @@ moves_loop: // When in check, search starts here
moveCount++;
// Step 6. Pruning.
- if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
+ if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY && pos.non_pawn_material(us))
{
// Futility pruning and moveCount pruning (~10 Elo)
if ( !givesCheck
&& to_sq(move) != prevSq
- && futilityBase > -VALUE_KNOWN_WIN
+ && futilityBase > VALUE_TB_LOSS_IN_MAX_PLY
&& type_of(move) != PROMOTION)
{
if (moveCount > 2)
continue;
- futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))];
+ futilityValue = futilityBase + PieceValue[pos.piece_on(to_sq(move))];
+ // If static eval + value of piece we are going to capture is much lower
+ // than alpha we can prune this move
if (futilityValue <= alpha)
{
bestValue = std::max(bestValue, futilityValue);
continue;
}
+ // If static eval is much lower than alpha and move is not winning material
+ // we can prune this move
if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1))
{
bestValue = std::max(bestValue, futilityBase);
continue;
}
+
+ // If static exchange evaluation is much worse than what is needed to not
+ // fall below alpha we can prune this move
+ if (futilityBase > alpha && !pos.see_ge(move, (alpha - futilityBase) * 4))
+ {
+ bestValue = alpha;
+ continue;
+ }
}
// We prune after the second quiet check evasion move, where being 'in check' is
@@ -1574,7 +1593,7 @@ moves_loop: // When in check, search starts here
continue;
// Do not search moves with bad enough SEE values (~5 Elo)
- if (!pos.see_ge(move, Value(-95)))
+ if (!pos.see_ge(move, Value(-90)))
continue;
}
@@ -1609,7 +1628,7 @@ moves_loop: // When in check, search starts here
if (PvNode) // Update pv even in fail-high case
update_pv(ss->pv, move, (ss+1)->pv);
- if (PvNode && value < beta) // Update alpha here!
+ if (value < beta) // Update alpha here!
alpha = value;
else
break; // Fail high
@@ -1703,28 +1722,28 @@ moves_loop: // When in check, search starts here
Piece moved_piece = pos.moved_piece(bestMove);
PieceType captured;
- int bonus1 = stat_bonus(depth + 1);
+ int quietMoveBonus = stat_bonus(depth + 1);
if (!pos.capture_stage(bestMove))
{
- int bonus2 = bestValue > beta + 145 ? bonus1 // larger bonus
- : stat_bonus(depth); // smaller bonus
+ int bestMoveBonus = bestValue > beta + 168 ? 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
captured = type_of(pos.piece_on(to_sq(bestMove)));
- captureHistory[moved_piece][to_sq(bestMove)][captured] << bonus1;
+ captureHistory[moved_piece][to_sq(bestMove)][captured] << quietMoveBonus;
}
// Extra penalty for a quiet early move that was not a TT move or
@@ -1732,14 +1751,14 @@ moves_loop: // When in check, search starts here
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;
}
}
@@ -1749,13 +1768,13 @@ moves_loop: // When in check, search starts here
void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) {
- for (int i : {1, 2, 4, 6})
+ for (int i : {1, 2, 3, 4, 6})
{
// Only update the first 2 continuation histories if we are in check
if (ss->inCheck && i > 2)
break;
if (is_ok((ss-i)->currentMove))
- (*(ss-i)->continuationHistory)[pc][to] << bonus;
+ (*(ss-i)->continuationHistory)[pc][to] << bonus / (1 + 3 * (i == 3));
}
}
@@ -1794,7 +1813,7 @@ 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;
@@ -1829,7 +1848,7 @@ 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();
@@ -1846,9 +1865,9 @@ 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))
+ || (Limits.nodes && Threads.nodes_searched() >= uint64_t(Limits.nodes)))
Threads.stop = true;
}
@@ -1862,7 +1881,7 @@ string UCI::pv(const Position& pos, Depth depth) {
TimePoint elapsed = Time.elapsed() + 1;
const RootMoves& rootMoves = pos.this_thread()->rootMoves;
size_t pvIdx = pos.this_thread()->pvIdx;
- size_t multiPV = std::min((size_t)Options["MultiPV"], rootMoves.size());
+ size_t multiPV = std::min(size_t(Options["MultiPV"]), rootMoves.size());
uint64_t nodesSearched = Threads.nodes_searched();
uint64_t tbHits = Threads.tb_hits() + (TB::RootInTB ? rootMoves.size() : 0);