Because razoring verification after qsearch() cuts more
then 40% of candidates, do not waste a costly qsearch for
nodes at depth one that will be probably discarded anyway
by futility.
Also tight razoring conditions to keep dangerous false
negatives below 0,05%. Still not clear if it is enough.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
// Null move search not allowed, try razoring
else if ( !value_is_mate(beta)
&& approximateEval < beta - RazorMargin
- && depth < RazorDepth)
+ && depth < RazorDepth
+ && depth > OnePly
+ && ttMove == MOVE_NONE
+ && !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
- if (v < beta - RazorMargin / 2)
+ if (v < beta - RazorMargin / 2 - int(depth - OnePly) * RazorMargin / 8)
return v;
}