WinBoard, exotic version

[hgm]

The new version at http://hgm.nubati.net/WinBoard-4.5.beta.zip now uses the move-number field in the FEN to decide which board the update is for. NebiyuReversi-Alien did faithfully emit the move numbers in its setup FENs, and the whole scheme seems to work now. Even the loading of a previous game, and later stepping through it. During loading there is some flashing, though, because first it displays the unmodified board, and then the correction made toit by the engine.

[Daniel Shawul]

Yes it works for the Reversi as well as Go & checkers when the right engine is loaded. Pasting and loading using menu both work as expected. The FEN Nebiyu reads/writes always has the move-number so that is no problem. It also reads the enpassant square just in case it is used in the future f.i as an indicator for ko status in go , but right now nebiyu can not construct the full internal state of go board from fen. I will upload them when I am done with an exclusive alien variant.

[hgm]

I don't realy know Go, but the ko rule is a repetition rule, isn't it? If so, should we want it to be encoded in FEN? In Chess, repetition info is not given by the FEN, you would need game history for that. In Xiangqi the FEN does also not encode if checking moves are forbidden because of repetition.

[Greg Strong]

I don't realy know Go, but the ko rule is a repetition rule, isn't it? If so, should we want it to be encoded in FEN? In Chess, repetition info is not given by the FEN, you would need game history for that. In Xiangqi the FEN does also not encode if checking moves are forbidden because of repetition.

Ko is a repetition rule, but it should definitely be encoded in the hash as its occurance is very common. Fortunately, Ko only prevents repetition on the move immediate following. As soon as another move is made repetition is again allowed.

You should check out Go - it's a thing of beauty. The rules are about as simple as can be, but the strategic complexity is extreme...

[Daniel Shawul]

The ko rule prevents you from capturing a stone in atari if it would
repeat a previous position. So it sounds similar to enpassant square.
The enpassant square allows you to do one additinal special move (ep capture) and
the ko square prevents you from making a specific type of capture. Maybe this is not important,
after all Go is almost always started from empty board except in handicap games
where a few stones are placed at the corners.

About martian chess, there seems to be lots of confusion regarding rules of
how the pieces move. Almost every piece's movement has different interpretations.
Most intersting aspect of the game is that pawns dont promote ! Meaning you have to
push them wisely otherwise they become useless once they reach 10th rank.
Also I am going to provide options on how the pieces move (based on the book's different
interpretations). So this game is really alien and you have no chance to make it non-alien
by providing legality testing and stuff

[hgm]

I never really looked at the rules of Jetan before now, but it seems like a 'regular' Chess variant, in the sense that all pieces capture by replacement. So there is no real need to play it as variant alien. Variant 10x10+0_fairy would do fine (with legality testing off).

A better candidate to exercise the alien capability of WinBoard would beUltima (sometimes called Baroque). Here pieces capture in the wildest ways (all different), so moves really need a lot of side effects:

By orthgonal sandwiching (somewhat Reversi like).
By jumping over (Checkers style)
By 'coordinating' (on intersection between orthogonals through piece and King)
By 'withdrawal' (the adjacent square you move away from)

[Daniel Shawul]

Ok that one seems a good candidate. I found such fake games like 'cheskers' which didn't do it for me.
If I have to define an alien variant it would be one where the move to be exchanged can not be easily represented. With the new winboard extension of comma, one can make almost any kind of move sequences ,it makes it hard to find a game where it fails. So thats is why I settled on a different interpretation of alien, which in this case is the literal definition

[Greg Strong]

Ultima is certainly one of the hardest games to implement... ChessV plays it. It would work under winboard if winboard knew all the side-affects of a move. Otherwise, I guess it would have to be programmed to send out extra move info to inform it of the captures. Probably wouldn't be too bad, though.

[Daniel Shawul]

Greg,
I am sad to inform you that it is already done in winboard
Just send a 'setup' command after every move and winboard will update its board accordingly. No need to know its side effects. Announce it as variant alien. That is all.

[Greg Strong]

Well, I better get around to implementing that ... especially if other Ultima engines start showing up!