Challenge

[hgm]

Intuitively, having a pinned piece seems worse than merely having a piece that has no moves because it is locked in. Because you know the pinned piece is under attack, which is a very worrisome state for a piece with low mobility.

[Uri Blass]

You did not try movei
Movei does not use null move pruning here because black has not enough legal moves to justify using null move pruning.

If you check the number of legal moves before null-move try, isn't that a waste of time? I dont generate moves before null-move try. I intuit zugwang position are less than null-move cut positions, so generating moves before null move could be a wasting time, no?

It may be a waste of time but I always generate legal moves or at least count them even if I do not save them in a list.

when the king is not in check
number of legal moves for every piece is used for the mobility evaluation
and if I already calculate number of legal moves for every piece then calculating also the number of legal moves is relatively cheap.

You can say that it may be better not to count legal moves but I think that
not counting illegal moves for pinned pieces is better evaluation.

Uri

Then, as I understand, you are calling evaluation and mobilitiy in all internal nodes and not the leaf ones, isn't it?

Correct.

Movei evaluates every node and the exact value of evaluation is used for decisions if to prune or not to prune.

Uri

[cms271828]

I tried it with my engine, which solved it in 8 seconds

1. Rh1 d4
2. Ra1 d3
3. Ra3 bxa3+
4. Ka1 a2
5. Ba3 Kxf6
6. Bb2#
1-0

Kind of ironic that a simply engine like mine can out perform a complex engine with this type of position. I don't use null move pruning, which is why I didn't get complications with zugzwangs and stuff.