If I have it right, then some time ago, contempt/optimism was re-introduced into the
NNUE versions of Stockfish. However, while in the HCE versions one had detailed control
over contempt/drawscore, in the present version of SF, optimism isn't just enabled by
default, but always. While this may benefit the practical playing strength, it is a distinct
disadvantage for analysis, since the eval of a variation can jump up and down
drastically for no reason on the board--purely depending on whether the line ends in a
leaf node with either White or Black to move.
I just saw that Windfishballad has made an SF fork with Optimism disabled (along with
TB modifications), but wouldn't it be more convenient to give the user control through a
UCI option? It's completely fine to have Optimism enabled by default (as it was with the
old Contempt), but analysis isn't really a marginal application, and there a neutral eval
is much better.
Thanks if someone who knows his way around the code could implement this!