Test positions that make you tear your hair out

[alessandro]

I'm well aware that trying to make your engine solve a single test position more quickly is a great way to lose elo. So no need to bring that up.

But this position really confounds Myrddin. I tried fifteen other engines in Myrddin's elo range (~2600 CCRL), and all but two found h5 in less than ten seconds, and most of those found it in less than two seconds. Myrddin, however, with eight cores, needs almost 15 MINUTES! And I cannot figure out why. I've tried the obvious things, like turning off null move, increasing/decreasing the aggressiveness of reductions, etc., etc. But Myrddin will only select either cxd5 or Qe3, with a score of about +0.7 for White. If I force h5, Myrddin sees the win in less than two seconds, with the score jumping to about +4.

[fen]r5n1/p2q3k/4b2p/3pB3/2PP1QpP/8/PP4P1/5RK1 w - - 1[/fen]

Not only am I asking for your thoughts on why this is happening, but also if you could share any test positions that are the bane of your engine, I would feel better about it.

jm

Do you have a root search which iterates and trigger alpha-beta on every moves, at root?

[JVMerlino]

Do you have a root search which iterates and trigger alpha-beta on every moves, at root?

Myrddin doesn't have a special search function for the root, but it also doesn't allow for reductions or pruning at the root. Is that what you were asking?