}
// 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));
}
// Use part of the gained time from a previous stable move for the current move
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
: 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;
- // Shuffle extension
- else if(pos.rule50_count() > 14 && ss->ply > 14 && depth < 3 * ONE_PLY && PvNode)
- extension = ONE_PLY;
-
// Castling extension
else if (type_of(move) == CASTLING)
extension = ONE_PLY;
+ // 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
newDepth = depth - ONE_PLY + extension;
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)
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;