Stockfish and endgame K-KBN

[hgm]

I have tested this condition in real games and never found a pv node where beta - alpha == 1

Okay, so they are very rare However there are only a handful of PV-Nodes/game, so this condition is true 99.999% of time. 0.001% cases won't lead to crash, so it's okay

I think it is theoretically impossible for a null window to occur in a PV node: a search with such a window can only fail low or high. A PV needs to have an exact score.

[zamar]

Okay, I finally figured it out. search_pv is called after search-call when (value > alpha && value < beta). It's impossible to fullfil this condition when alpha = beta - 1.

Just a newbie mistake

BTW Marco, I think I found a new bug related to your qsearch-TT implementation, but I think I'd better send it by email. (This discussion doesn't belong to "Tournaments and Matches" category anyway.)