while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
// Age out PV variability metric
- BestMoveChanges *= 0.8;
+ BestMoveChanges *= 0.8f;
// Save last iteration's scores before first PV line is searched and all
// the move scores but the (new) PV are set to -VALUE_INFINITE.
singularExtensionNode = !RootNode
&& !SpNode
- && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
+ && depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
ext = ONE_PLY;
else if (givesCheck && pos.see_sign(move) >= 0)
- ext = ONE_PLY / 2;
+ ext = inCheck || ss->staticEval <= alpha ? ONE_PLY : ONE_PLY / 2;
// Singular extension search. If all moves but one fail low on a search of
// (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
// Step 15. Reduced depth search (LMR). If the move fails high will be
// re-searched at full depth.
- if ( depth > 3 * ONE_PLY
+ if ( depth >= 3 * ONE_PLY
&& !pvMove
&& !captureOrPromotion
&& move != ttMove
Square m2to = to_sq(second);
// The piece is the same or second's destination was vacated by the first move
- if (m1to == m2from || m2to == m1from)
+ // We exclude the trivial case where a sliding piece does in two moves what
+ // it could do in one move: eg. Ra1a2, Ra2a3.
+ if ( m2to == m1from
+ || (m1to == m2from && !squares_aligned(m1from, m2from, m2to)))
return true;
// Second one moves through the square vacated by first one