Most common chess variant?

[stegemma]

In this time that i'm like a rocket for chess software development, i'm asking which is the most common and interesting 8x8 variant that i could add to satana. I'm not interested in chess960 but on those variant that uses new kind of piece moving.

Anybody can give me an hint from where to start?

Thanks.

PS: i'm interested only in perft, for now... teh playing software will be added later

[Ozymandias]

FICS wild chess, Style 0.
http://www.freechess.org/Help/HelpFiles/wild.html

Not chess960, no "new kind of piece moving", but very common, in the sense that you can actually see it, in many beginner's games

[stegemma]

Thanks, but all this can already be played with standard chess engine, despite from castling and maybe en-passant rules.

After a little search, maybe Makruk could be the simplest variant to try at first, because it has some new piece moving (sorry for my bad english) and the other rules are pretty similar to chess.

Arimaa could be interesting too but it is very different from chess.

[hgm]

Wild 0 does not really require a special engine, provided that the castling code was general enough to handle castling from the d-file.

The original question is hard to answer. ICS usually only offer variants that can be played with standard pieces. The most popular of those are then Suicide and Crazyhouse. But from the viewpoint of an engine both are quite drastic departures from normal Chess: Suicide has mandatory capture and needs a completely different search to do it well. (And it is arguable whether it still counts as Chess, because there is no royal piece.) Crazyhouse has piece drops.

The most popular variant with unorthodox piece moves is Capablanca/Gothic Chess, which features B+N and R+N compounds. But it is played on a larger board, which usually also would require a pretty drastic redesign of the engine. Seirawan Chess does have these same pieces on 8x8, but features a rather exotic mechanism ('gating') to introduce these pieces onto the board. (The game start with these pieces in hand.) It is a bit of a pain to implement that in an engine (although I managed to do it for Fruit).

Personally I like Knightmate (King moves as Knight, and vice versa) and Spartan Chess (black starts with two Kings, and all his other pieces move in unorthodox ways). There are a lot of engines playing these. But it seems these games are not played very much by humans. 'Chess with Different Armies' is somewhat more popular with humans. Like Spartan Chess this is an asymmetric variant, (i.e. white and black have different pieces), but with a more conventional army composition of one King and eight Pawns (all normal), and then 4 different piece types that move in an unorthodox way.

Makruk (Thai Chess) is an interesting variant not too far from normal Chess, and played by about a million people as their primary board game. There it is just the Queen and Bishops that move differently (but not too weird). Most exotic feature there is that promotion already occurs on the 6th rank.

There exist a lot of 'modest' variants, which just replace one piece by something else (like Queen by Amazon, which moves as Q or N). The problem with those is that they tend to use a very powerful piece, which gets traded in no time. After which you are left with a boring end-game of normal Chess. (The difference again shows up after you promote, but at that stage the game is usually already decided, and the checkmating with the exotic piece rather than Queen is usually pretty easy.) So variants like that are usually not very interesting. In Knightmate the unorthodoxy is 'frozen in', because you cannot trade Kings. Some Shogi variants have rules that make it very difficult to trade key pieces, and I tried to design some modest variants myself that borrowed these rules to avoid the sketched problem (Mighty-Lion Chess and Werewolf Chess). But of course no one plays them (yet?), and the unorthodox piece they feature is rather exotic (capable of double capture) in both cases.

[stegemma]

[...]
Makruk (Thai Chess) is an interesting variant not too far from normal Chess, and played by about a million people as their primary board game. There it is just the Queen and Bishops that move differently (but not too weird). Most exotic feature there is that promotion already occurs on the 6th rank.

Thanks, in fact i've found Makruk googling around and it seems the most interesting game variant to try. I think that i could add to satana this simple variant, in a few hours.

Maybe i can think about bigger chessboards but not at present. I work on chess on spare time... between compilation of large business software

[hgm]

The gratifying thing about Makruk is that a good engine probably would have lots of users, many more than any engine for FIDE Chess (if it isn't at least as strong as Stockfish).

Note that Makruk has some quite complex 'counting rules', which is basically a variable version of the 50-move rule (depending on what material you have). But they kick in only after the opponent runs out of Pawns. So as far as I could see an engine would not really have to bother with them as long as you build in a bias against stripping the opponent of all his Pawns. In FIDE you would already devaluate positions where the leading side has no Pawns, but in Makruk this should also be done when the side that is behind has no Pawns, because it will always be difficult to checkmate such an opponent, as the number of moves you get to do it might not be enough, and gets tighter the more you are ahead.

[stegemma]

The gratifying thing about Makruk is that a good engine probably would have lots of users, many more than any engine for FIDE Chess (if it isn't at least as strong as Stockfish).[...]

Implementing the Makruk rules for piece moving has required less than half an hour! You can leave castling unchanged (it would be disabled in FEN), put some if statement to avoid 2 pushes of the pawns and under-promotions, accept S/M instead of B/Q in FEN and sligthly change move generation of Queens and Bishops... et voilà!

Now i'm testing perft, then i can add alfabeta and see what happens.

[Aleks Peshkov]

Wild 0 does not really require a special engine, provided that the castling code was general enough to handle castling from the d-file.

Special enough being incompatible with Chess960 castling rules.

[Evert]

In this time that i'm like a rocket for chess software development, i'm asking which is the most common and interesting 8x8 variant that i could add to satana. I'm not interested in chess960 but on those variant that uses new kind of piece moving.

Anybody can give me an hint from where to start?

http://www.eglebbk.dds.nl/program/chess-index.html


A more serious answer is http://www.chessvariants.org/ but the site infrastructure is getting a bit dated (it's basically a wiki from before wiki's existed).

For my personal opinion, the most interesting 8x8 variant is probably Spartan Chess. The minimal variation from orthochess with new pieces is probably Seirawan, but it suffers from having three powerful pieces on a cramped 8x8 board (Capablanca/Gothic Chess are better in my opinion). Shatranj is interesting as a historical oddity, but I don't think anyone still plays it. I see you've already added Makruk, which is a very good (and easy) addition. Personally I like Sittuyin (Burmese Chess), which starts with piece drops and Shatar (Mongolian Chess), but that mainly has different rules for delivering mate (the only piece that really moves different from orthochess pieces is the Bers).

[Evert]

The original question is hard to answer. ICS usually only offer variants that can be played with standard pieces. The most popular of those are then Suicide and Crazyhouse. But from the viewpoint of an engine both are quite drastic departures from normal Chess: Suicide has mandatory capture and needs a completely different search to do it well. (And it is arguable whether it still counts as Chess, because there is no royal piece.) Crazyhouse has piece drops.

Do you really need a different search for suicide chess? I never really looked at it because I don't find it particularly interesting, but I figured that making the piece values negative would do it?

The most popular variant with unorthodox piece moves is Capablanca/Gothic Chess, which features B+N and R+N compounds. But it is played on a larger board, which usually also would require a pretty drastic redesign of the engine. Seirawan Chess does have these same pieces on 8x8, but features a rather exotic mechanism ('gating') to introduce these pieces onto the board. (The game start with these pieces in hand.) It is a bit of a pain to implement that in an engine (although I managed to do it for Fruit).

The really painful thing with that (I find) is that you need to test whether the piece was pinned before deciding whether you can gate or not. An in-check test afterwards isn't quite enough (it is if you treat the start square of the piece that just moved as empty though). The game itself suffers from the board being a bit cramped with three super pieces.

Personally I like Knightmate (King moves as Knight, and vice versa) and Spartan Chess (black starts with two Kings, and all his other pieces move in unorthodox ways). There are a lot of engines playing these. But it seems these games are not played very much by humans. 'Chess with Different Armies' is somewhat more popular with humans. Like Spartan Chess this is an asymmetric variant, (i.e. white and black have different pieces), but with a more conventional army composition of one King and eight Pawns (all normal), and then 4 different piece types that move in an unorthodox way.

I like Spartan, but Knightmate and CWDA always felt too gimmicky for my tastes. The problem with any variant (for over-the-board play) is that you need a nice set of different pieces for both sides, and then you need to find someone who is willing to invest the time to learn the game.
There's also "Superchess" (they do or did offer some nice variant pieces), but that's also a bit too gimmicky for my taste.

Some Shogi variants have rules that make it very difficult to trade key pieces, and I tried to design some modest variants myself that borrowed these rules to avoid the sketched problem (Mighty-Lion Chess and Werewolf Chess). But of course no one plays them (yet?), and the unorthodox piece they feature is rather exotic (capable of double capture) in both cases.

The Lion is a very complicated piece, but interesting. Do you have rules for Werewolf Chess up somewhere?