return Value((175 - 50 * improving) * d / ONE_PLY);
}
- // Margin for pruning capturing moves: almost linear in depth
- constexpr int CapturePruneMargin[] = { 0,
- 1 * PawnValueEg * 1055 / 1000,
- 2 * PawnValueEg * 1042 / 1000,
- 3 * PawnValueEg * 963 / 1000,
- 4 * PawnValueEg * 1038 / 1000,
- 5 * PawnValueEg * 950 / 1000,
- 6 * PawnValueEg * 930 / 1000
- };
-
// Futility and reductions lookup tables, initialized at startup
int FutilityMoveCounts[2][16]; // [improving][depth]
int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber]
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
double timeReduction = 1.0;
Color us = rootPos.side_to_move();
+ bool failedLow;
std::memset(ss-4, 0, 7 * sizeof(Stack));
for (int i = 4; i > 0; i--)
beta = VALUE_INFINITE;
if (mainThread)
- mainThread->bestMoveChanges = 0, mainThread->failedLow = false;
+ mainThread->bestMoveChanges = 0, failedLow = false;
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
// Age out PV variability metric
if (mainThread)
- mainThread->bestMoveChanges *= 0.517, mainThread->failedLow = false;
+ mainThread->bestMoveChanges *= 0.517, failedLow = false;
// Save the last iteration's scores before 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;
- size_t PVFirst = 0;
- PVLast = 0;
+ size_t pvFirst = 0;
+ pvLast = 0;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < multiPV && !Threads.stop; ++PVIdx)
+ for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx)
{
- if (PVIdx == PVLast)
+ if (pvIdx == pvLast)
{
- PVFirst = PVLast;
- for (PVLast++; PVLast < rootMoves.size(); PVLast++)
- if (rootMoves[PVLast].TBRank != rootMoves[PVFirst].TBRank)
+ pvFirst = pvLast;
+ for (pvLast++; pvLast < rootMoves.size(); pvLast++)
+ if (rootMoves[pvLast].tbRank != rootMoves[pvFirst].tbRank)
break;
}
// Reset aspiration window starting size
if (rootDepth >= 5 * ONE_PLY)
{
- Value previousScore = rootMoves[PVIdx].previousScore;
+ Value previousScore = rootMoves[pvIdx].previousScore;
delta = Value(18);
alpha = std::max(previousScore - delta,-VALUE_INFINITE);
beta = std::min(previousScore + delta, 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
// search the already searched PV lines are preserved.
- std::stable_sort(rootMoves.begin() + PVIdx, rootMoves.begin() + PVLast);
+ std::stable_sort(rootMoves.begin() + pvIdx, rootMoves.begin() + pvLast);
// If search has been stopped, we break immediately. Sorting is
// safe because RootMoves is still valid, although it refers to
if (mainThread)
{
- mainThread->failedLow = true;
+ failedLow = true;
Threads.stopOnPonderhit = false;
}
}
}
// Sort the PV lines searched so far and update the GUI
- std::stable_sort(rootMoves.begin() + PVFirst, rootMoves.begin() + PVIdx + 1);
+ std::stable_sort(rootMoves.begin() + pvFirst, rootMoves.begin() + pvIdx + 1);
if ( mainThread
- && (Threads.stop || PVIdx + 1 == multiPV || Time.elapsed() > 3000))
+ && (Threads.stop || pvIdx + 1 == multiPV || Time.elapsed() > 3000))
sync_cout << UCI::pv(rootPos, rootDepth, alpha, beta) << sync_endl;
}
&& !Threads.stop
&& !Threads.stopOnPonderhit)
{
- const int F[] = { mainThread->failedLow,
+ const int F[] = { failedLow,
bestValue - mainThread->previousScore };
int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1]));
template <NodeType NT>
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
- // Use quiescence search when needed
- if (depth < ONE_PLY)
- return qsearch<NT>(pos, ss, alpha, beta);
-
constexpr bool PvNode = NT == PV;
const bool rootNode = PvNode && ss->ply == 0;
+ // Check if we have an upcoming move which draws by repetition, or
+ // if the opponent had an alternative move earlier to this position.
+ if ( pos.rule50_count() >= 3
+ && alpha < VALUE_DRAW
+ && !rootNode
+ && pos.has_game_cycle(ss->ply))
+ {
+ alpha = VALUE_DRAW;
+ if (alpha >= beta)
+ return alpha;
+ }
+
+ // Dive into quiescence search when the depth reaches zero
+ if (depth < ONE_PLY)
+ return qsearch<NT>(pos, ss, alpha, beta);
+
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
assert(DEPTH_ZERO < depth && depth < DEPTH_MAX);
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
inCheck = pos.checkers();
+ Color us = pos.side_to_move();
moveCount = captureCount = quietCount = ss->moveCount = 0;
bestValue = -VALUE_INFINITE;
maxValue = VALUE_INFINITE;
beta = std::min(mate_in(ss->ply+1), beta);
if (alpha >= beta)
return alpha;
-
- // Check if there exists a move which draws by repetition, or an alternative
- // earlier move to this position.
- if ( pos.rule50_count() >= 3
- && alpha < VALUE_DRAW
- && pos.has_game_cycle(ss->ply))
- {
- alpha = VALUE_DRAW;
- if (alpha >= beta)
- return alpha;
- }
}
assert(0 <= ss->ply && ss->ply < MAX_PLY);
posKey = pos.key() ^ Key(excludedMove << 16); // Isn't a very good hash
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
- ttMove = rootNode ? thisThread->rootMoves[thisThread->PVIdx].pv[0]
+ ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
: ttHit ? tte->move() : MOVE_NONE;
// At non-PV nodes we check for an early TT cutoff
else if (!pos.capture_or_promotion(ttMove))
{
int penalty = -stat_bonus(depth);
- thisThread->mainHistory[pos.side_to_move()][from_to(ttMove)] << penalty;
+ thisThread->mainHistory[us][from_to(ttMove)] << penalty;
update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
}
}
&& eval >= beta
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& !excludedMove
- && pos.non_pawn_material(pos.side_to_move())
- && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))
+ && pos.non_pawn_material(us)
+ && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
{
assert(eval - beta >= 0);
if (nullValue >= VALUE_MATE_IN_MAX_PLY)
nullValue = beta;
- if (abs(beta) < VALUE_KNOWN_WIN && (depth < 12 * ONE_PLY || thisThread->nmp_ply))
+ if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 12 * ONE_PLY))
return nullValue;
- // Do verification search at high depths. Disable null move pruning
- // for side to move for the first part of the remaining search tree.
- thisThread->nmp_ply = ss->ply + 3 * (depth-R) / 4;
- thisThread->nmp_odd = ss->ply % 2;
+ assert(!thisThread->nmpMinPly); // Recursive verification is not allowed
+
+ // Do verification search at high depths, with null move pruning disabled
+ // for us, until ply exceeds nmpMinPly.
+ thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
+ thisThread->nmpColor = us;
Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
- thisThread->nmp_odd = thisThread->nmp_ply = 0;
+ thisThread->nmpMinPly = 0;
if (v >= beta)
return nullValue;
if ( depth >= 8 * ONE_PLY
&& !ttMove)
{
- Depth d = 3 * depth / 4 - 2 * ONE_PLY;
- search<NT>(pos, ss, alpha, beta, d, cutNode);
+ search<NT>(pos, ss, alpha, beta, depth - 7 * ONE_PLY, cutNode);
tte = TT.probe(posKey, ttHit);
ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE;
// 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
// 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))
+ if (rootNode && !std::count(thisThread->rootMoves.begin() + thisThread->pvIdx,
+ thisThread->rootMoves.begin() + thisThread->pvLast, move))
continue;
ss->moveCount = ++moveCount;
if (rootNode && thisThread == Threads.main() && Time.elapsed() > 3000)
sync_cout << "info depth " << depth / ONE_PLY
<< " currmove " << UCI::move(move, pos.is_chess960())
- << " currmovenumber " << moveCount + thisThread->PVIdx << sync_endl;
+ << " currmovenumber " << moveCount + thisThread->pvIdx << sync_endl;
if (PvNode)
(ss+1)->pv = nullptr;
// Step 14. Pruning at shallow depth (~170 Elo)
if ( !rootNode
- && pos.non_pawn_material(pos.side_to_move())
+ && pos.non_pawn_material(us)
&& bestValue > VALUE_MATED_IN_MAX_PLY)
{
if ( !captureOrPromotion
continue;
// Prune moves with negative SEE (~10 Elo)
- if ( lmrDepth < 8
- && !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth)))
+ if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
continue;
}
- else if ( depth < 7 * ONE_PLY // (~20 Elo)
- && !extension
- && !pos.see_ge(move, -Value(CapturePruneMargin[depth / ONE_PLY])))
+ else if ( !extension // (~20 Elo)
+ && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY)))
continue;
}
Depth r = reduction<PvNode>(improving, depth, moveCount);
if (captureOrPromotion) // (~5 Elo)
+ {
+ // Increase reduction by comparing opponent's stat score
+ if ((ss-1)->statScore >= 0)
+ r += ONE_PLY;
+
r -= r ? ONE_PLY : DEPTH_ZERO;
+ }
else
{
// Decrease reduction if opponent's move count is high (~5 Elo)
&& !pos.see_ge(make_move(to_sq(move), from_sq(move))))
r -= 2 * ONE_PLY;
- ss->statScore = thisThread->mainHistory[~pos.side_to_move()][from_to(move)]
+ 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)]
{
// Quiet best move: update move sorting heuristics
if (!pos.capture_or_promotion(bestMove))
- update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth));
+ update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount,
+ stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO)));
else
- update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth));
+ update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY));
// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ((ss-1)->moveCount == 1 && !pos.captured_piece())
std::stringstream ss;
TimePoint elapsed = Time.elapsed() + 1;
const RootMoves& rootMoves = pos.this_thread()->rootMoves;
- size_t PVIdx = pos.this_thread()->PVIdx;
+ size_t pvIdx = pos.this_thread()->pvIdx;
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);
for (size_t i = 0; i < multiPV; ++i)
{
- bool updated = (i <= PVIdx && rootMoves[i].score != -VALUE_INFINITE);
+ bool updated = (i <= pvIdx && rootMoves[i].score != -VALUE_INFINITE);
if (depth == ONE_PLY && !updated)
continue;
Value v = updated ? rootMoves[i].score : rootMoves[i].previousScore;
bool tb = TB::RootInTB && abs(v) < VALUE_MATE - MAX_PLY;
- v = tb ? rootMoves[i].TBScore : v;
+ v = tb ? rootMoves[i].tbScore : v;
if (ss.rdbuf()->in_avail()) // Not at first line
ss << "\n";
<< " multipv " << i + 1
<< " score " << UCI::value(v);
- if (!tb && i == PVIdx)
+ if (!tb && i == pvIdx)
ss << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
ss << " nodes " << nodesSearched
{
// Sort moves according to TB rank
std::sort(rootMoves.begin(), rootMoves.end(),
- [](const RootMove &a, const RootMove &b) { return a.TBRank > b.TBRank; } );
+ [](const RootMove &a, const RootMove &b) { return a.tbRank > b.tbRank; } );
// Probe during search only if DTZ is not available and we are winning
- if (dtz_available || rootMoves[0].TBScore <= VALUE_DRAW)
+ if (dtz_available || rootMoves[0].tbScore <= VALUE_DRAW)
Cardinality = 0;
}
else
{
// Assign the same rank to all moves
for (auto& m : rootMoves)
- m.TBRank = 0;
+ m.tbRank = 0;
}
}
projects / stockfish / blobdiff