beta = std::min(avg + delta, VALUE_INFINITE);
// Adjust optimism based on root move's averageScore (~4 Elo)
- optimism[us] = 103 * avg / (std::abs(avg) + 119);
- optimism[~us] = -116 * avg / (std::abs(avg) + 123);
+ optimism[us] = 110 * avg / (std::abs(avg) + 121);
+ optimism[~us] = -optimism[us];
// Start with a small aspiration window and, in the case of a fail
// high/low, re-search with a bigger window until we don't fail
&& tte->depth() >= depth - 3)
{
Value singularBeta = ttValue - (64 + 57 * (ss->ttPv && !PvNode)) * depth / 64;
- Depth singularDepth = (depth - 1) / 2;
+ Depth singularDepth = newDepth / 2;
ss->excludedMove = move;
value =
else if (PvNode && move == ttMove && move == ss->killers[0]
&& (*contHist[0])[movedPiece][to_sq(move)] >= 4194)
extension = 1;
+
+ // Recapture extensions (~1 Elo)
+ else if (PvNode && move == ttMove && to_sq(move) == prevSq
+ && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))]
+ > 4000)
+ extension = 1;
}
// Add extension to new depth
// In general we want to cap the LMR depth search at newDepth, but when
// reduction is negative, we allow this move a limited search extension
// beyond the first move depth. This may lead to hidden double extensions.
- Depth d = std::clamp(newDepth - r, 1, newDepth + 1);
+ // To prevent problems when the max value is less than the min value,
+ // std::clamp has been replaced by a more robust implementation.
+ Depth d = std::max(1, std::min(newDepth - r, newDepth + 1));
value = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, d, true);
// 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 + 51 + 10 * (newDepth - d));
- const bool doEvenDeeperSearch = value > alpha + 700 && ss->doubleExtensions <= 6;
const bool doShallowerSearch = value < bestValue + newDepth;
- ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch;
-
- newDepth += doDeeperSearch - doShallowerSearch + doEvenDeeperSearch;
+ newDepth += doDeeperSearch - doShallowerSearch;
if (newDepth > d)
value = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, newDepth, !cutNode);