}
// Reductions lookup table, initialized at startup
- int Reductions[64]; // [depth or moveNumber]
+ int Reductions[MAX_MOVES]; // [depth or moveNumber]
template <bool PvNode> Depth reduction(bool i, Depth d, int mn) {
- int r = Reductions[std::min(d / ONE_PLY, 63)] * Reductions[std::min(mn, 63)] / 1024;
+ int r = Reductions[d / ONE_PLY] * Reductions[mn] / 1024;
return ((r + 512) / 1024 + (!i && r > 1024) - PvNode) * ONE_PLY;
}
// Add a small random component to draw evaluations to avoid 3fold-blindness
Value value_draw(Depth depth, Thread* thisThread) {
- return depth < 4 ? VALUE_DRAW
- : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
+ return depth < 4 * ONE_PLY ? VALUE_DRAW
+ : VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1);
}
// Skill structure is used to implement strength limit
void Search::init() {
- for (int i = 1; i < 64; ++i)
+ for (int i = 1; i < MAX_MOVES; ++i)
Reductions[i] = int(1024 * std::log(i) / std::sqrt(1.95));
}
else
{
for (Thread* th : Threads)
+ {
+ th->bestMoveChanges = 0;
if (th != this)
th->start_searching();
+ }
Thread::search(); // Let's start searching!
}
Move lastBestMove = MOVE_NONE;
Depth lastBestMoveDepth = DEPTH_ZERO;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
- double timeReduction = 1.0;
+ double timeReduction = 1, totBestMoveChanges = 0;
Color us = rootPos.side_to_move();
std::memset(ss-7, 0, 10 * sizeof(Stack));
bestValue = delta = alpha = -VALUE_INFINITE;
beta = VALUE_INFINITE;
- if (mainThread)
- mainThread->bestMoveChanges = 0;
-
size_t multiPV = Options["MultiPV"];
Skill skill(Options["Skill Level"]);
{
// Age out PV variability metric
if (mainThread)
- mainThread->bestMoveChanges *= 0.517;
+ totBestMoveChanges /= 2;
// 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.
&& !Threads.stop
&& !mainThread->stopOnPonderhit)
{
- double fallingEval = (306 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
+ double fallingEval = (314 + 9 * (mainThread->previousScore - bestValue)) / 581.0;
fallingEval = clamp(fallingEval, 0.5, 1.5);
// If the bestMove is stable over several iterations, reduce time accordingly
double reduction = std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction;
// Use part of the gained time from a previous stable move for the current move
- double bestMoveInstability = 1.0 + mainThread->bestMoveChanges;
+ for (Thread* th : Threads)
+ {
+ totBestMoveChanges += th->bestMoveChanges;
+ th->bestMoveChanges = 0;
+ }
+ double bestMoveInstability = 1 + totBestMoveChanges / Threads.size();
// Stop the search if we have only one legal move, or if available time elapsed
if ( rootMoves.size() == 1
assert(0 <= ss->ply && ss->ply < MAX_PLY);
(ss+1)->ply = ss->ply + 1;
- ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
- ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0];
+ (ss+1)->excludedMove = bestMove = MOVE_NONE;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
Square prevSq = to_sq((ss-1)->currentMove);
: ttHit ? tte->move() : MOVE_NONE;
ttPv = (ttHit && tte->is_pv()) || (PvNode && depth > 4 * ONE_PLY);
- // if position has been searched at higher depths and we are shuffling, return value_draw
- if (pos.rule50_count() > 36
- && ss->ply > 36
- && depth < 3 * ONE_PLY
- && ttHit
- && tte->depth() > depth
- && pos.count<PAWN>() > 0)
- return VALUE_DRAW;
-
// At non-PV nodes we check for an early TT cutoff
if ( !PvNode
&& ttHit
if (!pos.capture_or_promotion(ttMove))
update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth));
- // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted
- if ( ((ss-1)->moveCount == 1 || (ss-1)->currentMove == (ss-1)->killers[0])
- && !pos.captured_piece())
+ // Extra penalty for early quiet moves of the previous ply
+ if ((ss-1)->moveCount <= 2 && !pos.captured_piece())
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY));
}
// Penalty for a quiet ttMove that fails low
// 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->nmpMinPly = ss->ply + 3 * (depth-R) / (4 * ONE_PLY);
thisThread->nmpColor = us;
Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
&& pos.legal(move))
{
Value singularBeta = ttValue - 2 * depth / ONE_PLY;
+ Depth halfDepth = depth / (2 * ONE_PLY) * ONE_PLY; // ONE_PLY invariant
ss->excludedMove = move;
- value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode);
+ value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode);
ss->excludedMove = MOVE_NONE;
if (value < singularBeta)
&& (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
extension = ONE_PLY;
+ // Castling extension
+ else if (type_of(move) == CASTLING)
+ extension = ONE_PLY;
+
// Shuffle extension
- else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode)
+ else if ( PvNode
+ && pos.rule50_count() > 18
+ && depth < 3 * ONE_PLY
+ && ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid too deep searches
extension = ONE_PLY;
- // Castling extension
- else if (type_of(move) == CASTLING)
+ // Passed pawn extension
+ else if ( move == ss->killers[0]
+ && pos.advanced_pawn_push(move)
+ && pos.pawn_passed(us, to_sq(move)))
extension = ONE_PLY;
// Calculate new depth for this move
continue;
// Reduced depth of the next LMR search
- int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
+ int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO);
+ lmrDepth /= ONE_PLY;
// Countermoves based pruning (~20 Elo)
if ( lmrDepth < 3 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1)
// We record how often the best move has been changed in each
// iteration. This information is used for time management: When
// the best move changes frequently, we allocate some more time.
- if (moveCount > 1 && thisThread == Threads.main())
- ++static_cast<MainThread*>(thisThread)->bestMoveChanges;
+ if (moveCount > 1)
+ ++thisThread->bestMoveChanges;
}
else
// All other moves but the PV are set to the lowest value: this
Thread* thisThread = pos.this_thread();
(ss+1)->ply = ss->ply + 1;
- ss->currentMove = bestMove = MOVE_NONE;
- ss->continuationHistory = &thisThread->continuationHistory[NO_PIECE][0];
+ bestMove = MOVE_NONE;
inCheck = pos.checkers();
moveCount = 0;
projects / stockfish / blobdiff