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Update to Stockfish 12

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This commit is contained in:
Peter Osterlund
2020-09-09 21:41:22 +02:00
parent 6bcbd6d080
commit 94c39e402e
57 changed files with 3413 additions and 782 deletions
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297
DroidFishApp/src/main/cpp/stockfish/search.cpp
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@@ -1,8 +1,6 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -65,9 +63,9 @@ namespace {
constexpr uint64_t TtHitAverageResolution = 1024;
// Razor and futility margins
constexpr int RazorMargin = 527;
constexpr int RazorMargin = 510;
Value futility_margin(Depth d, bool improving) {
return Value(227 * (d - improving));
return Value(223 * (d - improving));
}
// Reductions lookup table, initialized at startup
@@ -75,7 +73,7 @@ namespace {
Depth reduction(bool i, Depth d, int mn) {
int r = Reductions[d] * Reductions[mn];
return (r + 570) / 1024 + (!i && r > 1018);
return (r + 509) / 1024 + (!i && r > 894);
}
constexpr int futility_move_count(bool improving, Depth depth) {
@@ -84,7 +82,7 @@ namespace {
// History and stats update bonus, based on depth
int stat_bonus(Depth d) {
return d > 15 ? 27 : 17 * d * d + 133 * d - 134;
return d > 13 ? 29 : 17 * d * d + 134 * d - 134;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
@@ -194,7 +192,7 @@ namespace {
void Search::init() {
for (int i = 1; i < MAX_MOVES; ++i)
Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i));
Reductions[i] = int((22.0 + std::log(Threads.size())) * std::log(i));
}
@@ -227,6 +225,8 @@ void MainThread::search() {
Time.init(Limits, us, rootPos.game_ply());
TT.new_search();
Eval::verify_NNUE();
if (rootMoves.empty())
{
rootMoves.emplace_back(MOVE_NONE);
@@ -263,10 +263,10 @@ void MainThread::search() {
Thread* bestThread = this;
if (int(Options["MultiPV"]) == 1 &&
!Limits.depth &&
!(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) &&
rootMoves[0].pv[0] != MOVE_NONE)
if ( int(Options["MultiPV"]) == 1
&& !Limits.depth
&& !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"]))
&& rootMoves[0].pv[0] != MOVE_NONE)
bestThread = Threads.get_best_thread();
bestPreviousScore = bestThread->rootMoves[0].score;
@@ -335,7 +335,7 @@ void Thread::search() {
// for match (TC 60+0.6) results spanning a wide range of k values.
PRNG rng(now());
double floatLevel = Options["UCI_LimitStrength"] ?
Utility::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) :
std::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) :
double(Options["Skill Level"]);
int intLevel = int(floatLevel) +
((floatLevel - int(floatLevel)) * 1024 > rng.rand<unsigned>() % 1024 ? 1 : 0);
@@ -403,12 +403,12 @@ void Thread::search() {
if (rootDepth >= 4)
{
Value prev = rootMoves[pvIdx].previousScore;
delta = Value(19);
delta = Value(17);
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 + (110 - ct / 2) * prev / (abs(prev) + 140);
int dct = ct + (105 - ct / 2) * prev / (abs(prev) + 149);
contempt = (us == WHITE ? make_score(dct, dct / 2)
: -make_score(dct, dct / 2));
@@ -506,13 +506,13 @@ void Thread::search() {
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
double fallingEval = (296 + 6 * (mainThread->bestPreviousScore - bestValue)
+ 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 725.0;
fallingEval = Utility::clamp(fallingEval, 0.5, 1.5);
double fallingEval = (318 + 6 * (mainThread->bestPreviousScore - bestValue)
+ 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 825.0;
fallingEval = std::clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
timeReduction = lastBestMoveDepth + 10 < completedDepth ? 1.92 : 0.95;
double reduction = (1.47 + mainThread->previousTimeReduction) / (2.22 * timeReduction);
timeReduction = lastBestMoveDepth + 9 < completedDepth ? 1.92 : 0.95;
double reduction = (1.47 + mainThread->previousTimeReduction) / (2.32 * timeReduction);
// Use part of the gained time from a previous stable move for the current move
for (Thread* th : Threads)
@@ -525,7 +525,7 @@ void Thread::search() {
double totalTime = rootMoves.size() == 1 ? 0 :
Time.optimum() * fallingEval * reduction * bestMoveInstability;
// Stop the search if we have exceeded the totalTime, at least 1ms search.
// Stop the search if we have exceeded the totalTime, at least 1ms search
if (Time.elapsed() > totalTime)
{
// If we are allowed to ponder do not stop the search now but
@@ -537,7 +537,7 @@ void Thread::search() {
}
else if ( Threads.increaseDepth
&& !mainThread->ponder
&& Time.elapsed() > totalTime * 0.56)
&& Time.elapsed() > totalTime * 0.58)
Threads.increaseDepth = false;
else
Threads.increaseDepth = true;
@@ -596,8 +596,8 @@ namespace {
Key posKey;
Move ttMove, move, excludedMove, bestMove;
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue;
bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
bool ttHit, formerPv, givesCheck, improving, didLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
ttCapture, singularQuietLMR;
Piece movedPiece;
@@ -627,7 +627,7 @@ namespace {
|| pos.is_draw(ss->ply)
|| ss->ply >= MAX_PLY)
return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos)
: value_draw(pos.this_thread());
: value_draw(pos.this_thread());
// Step 3. Mate distance pruning. Even if we mate at the next move our score
// would be at best mate_in(ss->ply+1), but if alpha is already bigger because
@@ -644,6 +644,7 @@ namespace {
assert(0 <= ss->ply && ss->ply < MAX_PLY);
(ss+1)->ply = ss->ply + 1;
(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);
@@ -662,15 +663,20 @@ namespace {
// search to overwrite a previous full search TT value, so we use a different
// position key in case of an excluded move.
excludedMove = ss->excludedMove;
posKey = pos.key() ^ (Key(excludedMove) << 48); // Isn't a very good hash
posKey = excludedMove == MOVE_NONE ? pos.key() : pos.key() ^ make_key(excludedMove);
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
: ttHit ? tte->move() : MOVE_NONE;
ttPv = PvNode || (ttHit && tte->is_pv());
formerPv = ttPv && !PvNode;
if (!excludedMove)
ss->ttPv = PvNode || (ttHit && tte->is_pv());
formerPv = ss->ttPv && !PvNode;
if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove))
if ( ss->ttPv
&& depth > 12
&& ss->ply - 1 < MAX_LPH
&& !priorCapture
&& 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
@@ -744,7 +750,7 @@ namespace {
if ( b == BOUND_EXACT
|| (b == BOUND_LOWER ? value >= beta : value <= alpha))
{
tte->save(posKey, value_to_tt(value, ss->ply), ttPv, b,
tte->save(posKey, value_to_tt(value, ss->ply), ss->ttPv, b,
std::min(MAX_PLY - 1, depth + 6),
MOVE_NONE, VALUE_NONE);
@@ -767,9 +773,10 @@ namespace {
// Step 6. Static evaluation of the position
if (ss->inCheck)
{
// Skip early pruning when in check
ss->staticEval = eval = VALUE_NONE;
improving = false;
goto moves_loop; // Skip early pruning when in check
goto moves_loop;
}
else if (ttHit)
{
@@ -789,15 +796,11 @@ namespace {
else
{
if ((ss-1)->currentMove != MOVE_NULL)
{
int bonus = -(ss-1)->statScore / 512;
ss->staticEval = eval = evaluate(pos) + bonus;
}
ss->staticEval = eval = evaluate(pos);
else
ss->staticEval = eval = -(ss-1)->staticEval + 2 * Tempo;
tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
// Step 7. Razoring (~1 Elo)
@@ -806,12 +809,13 @@ namespace {
&& eval <= alpha - RazorMargin)
return qsearch<NT>(pos, ss, alpha, beta);
improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval > (ss-4)->staticEval
|| (ss-4)->staticEval == VALUE_NONE) : ss->staticEval > (ss-2)->staticEval;
improving = (ss-2)->staticEval == VALUE_NONE
? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE
: ss->staticEval > (ss-2)->staticEval;
// Step 8. Futility pruning: child node (~50 Elo)
if ( !PvNode
&& depth < 6
&& depth < 8
&& eval - futility_margin(depth, improving) >= beta
&& eval < VALUE_KNOWN_WIN) // Do not return unproven wins
return eval;
@@ -819,10 +823,10 @@ namespace {
// Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 23824
&& (ss-1)->statScore < 22977
&& eval >= beta
&& eval >= ss->staticEval
&& ss->staticEval >= beta - 33 * depth - 33 * improving + 112 * ttPv + 311
&& ss->staticEval >= beta - 30 * depth - 28 * improving + 84 * ss->ttPv + 182
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
@@ -830,7 +834,7 @@ namespace {
assert(eval - beta >= 0);
// Null move dynamic reduction based on depth and value
Depth R = (737 + 77 * depth) / 246 + std::min(int(eval - beta) / 192, 3);
Depth R = (817 + 71 * depth) / 213 + std::min(int(eval - beta) / 192, 3);
ss->currentMove = MOVE_NULL;
ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -866,23 +870,41 @@ namespace {
}
}
probCutBeta = beta + 176 - 49 * improving;
// Step 10. ProbCut (~10 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
&& depth > 4
&& abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
&& abs(beta) < VALUE_TB_WIN_IN_MAX_PLY
// 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
&& !( ttHit
&& tte->depth() >= depth - 3
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
Value raisedBeta = beta + 176 - 49 * improving;
assert(raisedBeta < VALUE_INFINITE);
MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory);
// if ttMove is a capture and value from transposition table is good enough produce probCut
// cutoff without digging into actual probCut search
if ( 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
&& !( move == ttMove
&& tte->depth() >= depth - 4
&& ttValue < raisedBeta))
&& probCutCount < 2 + 2 * cutNode)
if (move != excludedMove && pos.legal(move))
{
assert(pos.capture_or_promotion(move));
@@ -900,28 +922,34 @@ namespace {
pos.do_move(move, st);
// Perform a preliminary qsearch to verify that the move holds
value = -qsearch<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1);
value = -qsearch<NonPV>(pos, ss+1, -probCutBeta, -probCutBeta+1);
// If the qsearch held, perform the regular search
if (value >= raisedBeta)
value = -search<NonPV>(pos, ss+1, -raisedBeta, -raisedBeta+1, depth - 4, !cutNode);
if (value >= probCutBeta)
value = -search<NonPV>(pos, ss+1, -probCutBeta, -probCutBeta+1, depth - 4, !cutNode);
pos.undo_move(move);
if (value >= raisedBeta)
if (value >= probCutBeta)
{
// if transposition table doesn't have equal or more deep info write probCut data into it
if ( !(ttHit
&& tte->depth() >= depth - 3
&& ttValue != VALUE_NONE))
tte->save(posKey, value_to_tt(value, ss->ply), ttPv,
BOUND_LOWER,
depth - 3, move, ss->staticEval);
return value;
}
}
ss->ttPv = ttPv;
}
// Step 11. Internal iterative deepening (~1 Elo)
if (depth >= 7 && !ttMove)
{
search<NT>(pos, ss, alpha, beta, depth - 7, cutNode);
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE;
ttMove = ttHit ? tte->move() : MOVE_NONE;
}
// Step 11. If the position is not in TT, decrease depth by 2
if ( PvNode
&& depth >= 6
&& !ttMove)
depth -= 2;
moves_loop: // When in check, search starts from here
@@ -963,6 +991,10 @@ moves_loop: // When in check, search starts from here
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)
@@ -1001,17 +1033,17 @@ moves_loop: // When in check, search starts from here
continue;
// Futility pruning: parent node (~5 Elo)
if ( lmrDepth < 6
if ( lmrDepth < 7
&& !ss->inCheck
&& ss->staticEval + 284 + 188 * lmrDepth <= alpha
&& ss->staticEval + 283 + 170 * 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)] / 2 < 28388)
+ (*contHist[5])[movedPiece][to_sq(move)] / 2 < 27376)
continue;
// Prune moves with negative SEE (~20 Elo)
if (!pos.see_ge(move, Value(-(29 - std::min(lmrDepth, 17)) * lmrDepth * lmrDepth)))
if (!pos.see_ge(move, Value(-(29 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
continue;
}
else
@@ -1026,12 +1058,14 @@ moves_loop: // When in check, search starts from here
if ( !givesCheck
&& lmrDepth < 6
&& !(PvNode && abs(bestValue) < 2)
&& PieceValue[MG][type_of(movedPiece)] >= PieceValue[MG][type_of(pos.piece_on(to_sq(move)))]
&& !ss->inCheck
&& ss->staticEval + 267 + 391 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
&& ss->staticEval + 169 + 244 * lmrDepth
+ PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha)
continue;
// See based pruning
if (!pos.see_ge(move, Value(-202) * depth)) // (~25 Elo)
if (!pos.see_ge(move, Value(-221) * depth)) // (~25 Elo)
continue;
}
}
@@ -1042,16 +1076,15 @@ moves_loop: // When in check, search starts from here
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
// a reduced search on all the other moves but the ttMove and if the
// result is lower than ttValue minus a margin then we will extend the ttMove.
if ( depth >= 6
// result is lower than ttValue minus a margin, then we will extend the ttMove.
if ( 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
&& pos.legal(move))
&& tte->depth() >= depth - 3)
{
Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2;
Depth singularDepth = (depth - 1 + 3 * formerPv) / 2;
@@ -1073,8 +1106,8 @@ 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 an other move that
// pushes it over beta, if so also produce a cutoff
// 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.
else if (ttValue >= beta)
{
ss->excludedMove = move;
@@ -1091,19 +1124,14 @@ moves_loop: // When in check, search starts from here
&& (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
extension = 1;
// Passed pawn extension
else if ( move == ss->killers[0]
&& pos.advanced_pawn_push(move)
&& pos.pawn_passed(us, to_sq(move)))
extension = 1;
// Last captures extension
else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg
&& pos.non_pawn_material() <= 2 * RookValueMg)
extension = 1;
// Castling extension
if (type_of(move) == CASTLING)
if ( type_of(move) == CASTLING
&& popcount(pos.pieces(us) & ~pos.pieces(PAWN) & (to_sq(move) & KingSide ? KingSide : QueenSide)) <= 2)
extension = 1;
// Late irreversible move extension
@@ -1118,13 +1146,6 @@ 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 (!rootNode && !pos.legal(move))
{
ss->moveCount = --moveCount;
continue;
}
// Update the current move (this must be done after singular extension search)
ss->currentMove = move;
ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck]
@@ -1138,26 +1159,32 @@ moves_loop: // When in check, search starts from here
// Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3
&& moveCount > 1 + 2 * rootNode
&& (!rootNode || thisThread->best_move_count(move) == 0)
&& moveCount > 1 + 2 * rootNode + 2 * (PvNode && abs(bestValue) < 2)
&& ( !captureOrPromotion
|| moveCountPruning
|| ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha
|| cutNode
|| thisThread->ttHitAverage < 415 * TtHitAverageResolution * TtHitAverageWindow / 1024))
|| thisThread->ttHitAverage < 427 * TtHitAverageResolution * TtHitAverageWindow / 1024))
{
Depth r = reduction(improving, depth, moveCount);
// Decrease reduction if the ttHit running average is large
if (thisThread->ttHitAverage > 473 * TtHitAverageResolution * TtHitAverageWindow / 1024)
// Decrease reduction at non-check cut nodes for second move at low depths
if ( cutNode
&& depth <= 10
&& moveCount <= 2
&& !ss->inCheck)
r--;
// Reduction if other threads are searching this position.
// Decrease reduction if the ttHit running average is large
if (thisThread->ttHitAverage > 509 * TtHitAverageResolution * TtHitAverageWindow / 1024)
r--;
// Reduction if other threads are searching this position
if (th.marked())
r++;
// Decrease reduction if position is or has been on the PV (~10 Elo)
if (ttPv)
if (ss->ttPv)
r -= 2;
if (moveCountPruning && !formerPv)
@@ -1186,23 +1213,23 @@ moves_loop: // When in check, search starts from here
// hence break make_move(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
r -= 2 + ttPv - (type_of(movedPiece) == PAWN);
r -= 2 + ss->ttPv - (type_of(movedPiece) == PAWN);
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)]
- 4826;
- 5287;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= -100 && (ss-1)->statScore < -112)
if (ss->statScore >= -106 && (ss-1)->statScore < -104)
r--;
else if ((ss-1)->statScore >= -125 && ss->statScore < -138)
else if ((ss-1)->statScore >= -119 && ss->statScore < -140)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= ss->statScore / 14615;
r -= ss->statScore / 14884;
}
else
{
@@ -1212,11 +1239,11 @@ moves_loop: // When in check, search starts from here
// Unless giving check, this capture is likely bad
if ( !givesCheck
&& ss->staticEval + PieceValue[EG][pos.captured_piece()] + 211 * depth <= alpha)
&& ss->staticEval + PieceValue[EG][pos.captured_piece()] + 213 * depth <= alpha)
r++;
}
Depth d = Utility::clamp(newDepth - r, 1, newDepth);
Depth d = std::clamp(newDepth - r, 1, newDepth);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
@@ -1289,7 +1316,7 @@ moves_loop: // When in check, search starts from here
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: When
// iteration. This information is used for time management: when
// the best move changes frequently, we allocate some more time.
if (moveCount > 1)
++thisThread->bestMoveChanges;
@@ -1364,8 +1391,17 @@ moves_loop: // When in check, search starts from here
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.
if (bestValue <= alpha)
ss->ttPv = ss->ttPv || ((ss-1)->ttPv && depth > 3);
// Otherwise, a counter move has been found and if the position is the last leaf
// in the search tree, remove the position from the search tree.
else if (depth > 3)
ss->ttPv = ss->ttPv && (ss+1)->ttPv;
if (!excludedMove && !(rootNode && thisThread->pvIdx))
tte->save(posKey, value_to_tt(bestValue, ss->ply), ttPv,
tte->save(posKey, value_to_tt(bestValue, ss->ply), ss->ttPv,
bestValue >= beta ? BOUND_LOWER :
PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
depth, bestMove, ss->staticEval);
@@ -1474,7 +1510,7 @@ moves_loop: // When in check, search starts from here
if (PvNode && bestValue > alpha)
alpha = bestValue;
futilityBase = bestValue + 141;
futilityBase = bestValue + 145;
}
const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory,
@@ -1483,8 +1519,8 @@ 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 promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
// be generated.
// queen and checking knight promotions, and other checks(only if depth >= DEPTH_QS_CHECKS)
// will be generated.
MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory,
&thisThread->captureHistory,
contHist,
@@ -1508,6 +1544,10 @@ moves_loop: // When in check, search starts from here
{
assert(type_of(move) != ENPASSANT); // Due to !pos.advanced_pawn_push
// moveCount pruning
if (moveCount > 2)
continue;
futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))];
if (futilityValue <= alpha)
@@ -1523,8 +1563,8 @@ moves_loop: // When in check, search starts from here
}
}
// Don't search moves with negative SEE values
if ( !ss->inCheck && !pos.see_ge(move))
// Do not search moves with negative SEE values
if (!ss->inCheck && !pos.see_ge(move))
continue;
// Speculative prefetch as early as possible
@@ -1543,6 +1583,12 @@ moves_loop: // When in check, search starts from here
[pos.moved_piece(move)]
[to_sq(move)];
if ( !captureOrPromotion
&& moveCount
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold
&& (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < CounterMovePruneThreshold)
continue;
// Make and search the move
pos.do_move(move, st, givesCheck);
value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth - 1);
@@ -1570,7 +1616,7 @@ moves_loop: // When in check, search starts from here
}
}
// All legal moves have been searched. A special case: If we're in check
// All legal moves have been searched. A special case: if we're in check
// and no legal moves were found, it is checkmate.
if (ss->inCheck && bestValue == -VALUE_INFINITE)
return mated_in(ss->ply); // Plies to mate from the root
@@ -1587,7 +1633,7 @@ moves_loop: // When in check, search starts from here
// value_to_tt() adjusts a mate or TB score from "plies to mate from the root" to
// "plies to mate from the current position". standard scores are unchanged.
// "plies to mate from the current position". Standard scores are unchanged.
// The function is called before storing a value in the transposition table.
Value value_to_tt(Value v, int ply) {
@@ -1599,11 +1645,11 @@ moves_loop: // When in check, search starts from here
}
// value_from_tt() is the inverse of value_to_tt(): It adjusts a mate or TB score
// from the transposition table (which refers to the plies to mate/be mated
// from current position) to "plies to mate/be mated (TB win/loss) from the root".
// However, for mate scores, to avoid potentially false mate scores related to the 50 moves rule,
// and the graph history interaction, return an optimal TB score instead.
// value_from_tt() is the inverse of value_to_tt(): it adjusts a mate or TB score
// from the transposition table (which refers to the plies to mate/be mated from
// current position) to "plies to mate/be mated (TB win/loss) from the root". However,
// for mate scores, to avoid potentially false mate scores related to the 50 moves rule
// and the graph history interaction, we return an optimal TB score instead.
Value value_from_tt(Value v, int ply, int r50c) {
@@ -1725,7 +1771,7 @@ moves_loop: // When in check, search starts from here
}
if (depth > 11 && ss->ply < MAX_LPH)
thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 6);
thisThread->lowPlyHistory[ss->ply][from_to(move)] << stat_bonus(depth - 7);
}
// When playing with strength handicap, choose best move among a set of RootMoves
@@ -1763,6 +1809,7 @@ moves_loop: // When in check, search starts from here
} // namespace
/// MainThread::check_time() is used to print debug info and, more importantly,
/// to detect when we are out of available time and thus stop the search.
@@ -1813,12 +1860,15 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
{
bool updated = rootMoves[i].score != -VALUE_INFINITE;
if (depth == 1 && !updated)
if (depth == 1 && !updated && i > 0)
continue;
Depth d = updated ? depth : depth - 1;
Depth d = updated ? depth : std::max(1, depth - 1);
Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
if (v == -VALUE_INFINITE)
v = VALUE_ZERO;
bool tb = TB::RootInTB && abs(v) < VALUE_MATE_IN_MAX_PLY;
v = tb ? rootMoves[i].tbScore : v;
@@ -1831,6 +1881,9 @@ string UCI::pv(const Position& pos, Depth depth, Value alpha, Value beta) {
<< " multipv " << i + 1
<< " score " << UCI::value(v);
if (Options["UCI_ShowWDL"])
ss << UCI::wdl(v, pos.game_ply());
if (!tb && i == pvIdx)
ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
@@ -1913,7 +1966,7 @@ void Tablebases::rank_root_moves(Position& pos, Search::RootMoves& rootMoves) {
if (RootInTB)
{
// Sort moves according to TB rank
std::sort(rootMoves.begin(), rootMoves.end(),
std::stable_sort(rootMoves.begin(), rootMoves.end(),
[](const RootMove &a, const RootMove &b) { return a.tbRank > b.tbRank; } );
// Probe during search only if DTZ is not available and we are winning