Grande Acedrex

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Please beware that the website history.chess.free.fr is not completely up to date. I exchanged a few e-mails with Jaen-Louis Cazaux (the website owner), and it turned out that his current opinion on the Rhino move is different from what that website states (although he still does not consider it completely impossible that the historic rules were as the website states). The website shows the Rhino having a diagonal slide that goes absolutely forward after the initial Knight leg. The move that he currently considers most likely (and that I also prefer) would make this diagonal slide relatively forward, i.e. in the direction that most closely resemble that of the initial Knight jump. For a white Rhino on e6 this would be f4-g3-h2 or c7-b6-a5.

Ok, that does make slightly more sense, and it's then a symmetric piece (which I like).

The Rhino is even more complex, because in XBetza multi-leg moves have to describe all their legs with the same atom, so that you would need to use the 'smallest common divisor' for all legs. Which usually means describing the path square for square with the aid of King steps even for squares it leaps over. So Rhino is mpafsyafW, which adds the W squares as 'ghost squares' to the trajectory (with mp rights, so that the move can continue irrespective of the occupancy without any side effect on it), then continues at 45-degrees (fs) to finish the Knight jump, and then toggles to slider (y) continuing in the forward direction.

For this, I'm not going to try to generate Betza from the move tables, or convert Betza to the move tables - so I'm happy to just stick the string in the piece meta-data and send it along.

Also note that there is a naming confusion here: the common English name for the piece presented here as Aanca is 'Griffon/Gryphon', which apparently is not even a correct translation. But unfortunately Ralph Betza introduced another piece (moving very much like the Rhino here, except that it actually visits the W squares, but at the time this was not known) as diagonal counterpart to the Griffon, which he did call Aanca. So a Griffon is a sort of double-barrel Rook, while Betza's Aanca is a double-barrel Bishop. So on Spanish 'Aanca' now means something different then in English. This is not unprecedented, though: 'Alfil' in English refers to the old Shatranj 'Elephant', jumping 2 diagonal, while in Spanish it is the name of the modern Bishop.

Nice.

As to what XBoard pieces to use for this variant: I always prefer to represent pieces by how they move, rather than by how they are called. (If only because names can differ between languages.) In this policy the 'Giraffe' shoudl be represented by the Zebra pictogram, which is one of the new pieces (the 25th in the pieceToCharTable) that will be added to XBoard 4.9. The Rhino was actually called 'Vnicorno' in the old Spanish manuscript, so representation by XBoard's Unicorn symbol seems logical. (Also because the Rhino is an enhanced Knight, and the Unicorn (the 21st piece) looks like one.) I would always use a Bishop symbol for a piece that moves as a Bishop, no matter how it is called.

Agreed on all those.

Unfortunately the XBoard Lion cannot be used for the piece called Lion here, because XBoard subjects it to the Chu-Shogi anti-trading rules. I would recommend usage of the Camel pictogram here (the new 24th piece), because it is an enhanced Camel.

Can do, although I currently use C for the actual Camel (which is a piece in Tamerlane). However, I'd like to request a "free" lion without the associated Chu-baggage, similar to the Amazon spear that doesn't have the associated pawn behaviour.

XBoard has no standard piece associated with the move of the Griffon, but the latter at least has some bird-like aspects (and Aanca does seem to refer to just a monster bird more than to the mythological eagle-lion chimera anyway) the the Falcon symbol (the 18th piece) suggests itself.

Agreed here as well.

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I have a move generator that appears to be working. I'm probably missing a trick when it comes to detecting the end of a ray though because it feels like I'm testing for collisions with other pieces far too often.
It assumes all pieces perform a leap (which may be 0) followed by a slide (which may also be 0). The slide optionally skips a number of squares that must be empty (needed for Tamerlane).

At the moment it allows for pieces to move in an anti-symmetric way (differently for white and black) but I may scrap that if the only piece that it applies to is the pawn...

I'm using the following startup FEN:

Code: Select all

rluzbakbzulr/12/12/pppppppppppp/12/12/12/12/PPPPPPPPPPPP/12/12/RLUZBAKBZULR w Kk 0 1

[hgm]

Ok, that does make slightly more sense, and it's then a symmetric piece (which I like).

That was also one of the arguments that helped convincing Jean-Louis Cazaux that this is a more likely interpretation. The other was that according to the description the move in the game was modeled on the real-life behavior of the beast, and that a Rhino is not known for its ability to make sharp turns.

Can do, although I currently use C for the actual Camel (which is a piece in Tamerlane). However, I'd like to request a "free" lion without the associated Chu-baggage, similar to the Amazon spear that doesn't have the associated pawn behaviour.

Good idea. I could add it as the 28th piece. I probably would make it a 'minor Lion', a bit smaller than the Chu Lion, as the latter is really very optically dominating due to its bulk, which would not be appropriate for a Rook-class piece.

Problem is that I would also have to provide bitmaps for all these new pieces in WinBoard, or it could not play the games specifying their use. When these pieces only served to play large Shogi variants I did not see that as a necessity, because for those the WinBoard Alien Edition already exists. But WinBoard at least should display something for them in one size (49x49). So I have to make a Zebra (that's the easy one, just providing a Knight with stripes), a Camel and a Lion (which I then probably won't size down). The Wolf I already added, and the duplicat of the Lance was of course trivial.

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I now also worked out the Betza for the Tamerlane Giraffe and picket/vanguard (http://history.chess.free.fr/tamerlane.htm). To anyone interested, they are

Code: Select all

Giraffe: yafsafmafF
Picket: yaffF

[hgm]

I now also worked out the Betza for the Tamerlane Giraffe and picket/vanguard (http://history.chess.free.fr/tamerlane.htm). To anyone interested, they are

Code: Select all

Giraffe: yafsafmafF
Picket: yaffF

Although the Giraffe description does what it must do, it is not the recommended one. It toggles the range to slider way to early. So this description really makes it a multiple-hook mover that turns 'corners' of 180 degrees in many different places. This makes it very hard on the move generator.

Better would be afsafyafF = mafsmafyafF. This keeps the initial 3 steps leaper-like (and thus uniquely defined), switching to slider only in the 4th (final) leg. On the Picket the second f is redundant: 'f' would be enough to single out the single forward move even on a King (as is also used in the 3rd and 4th leg of the Giraffe).

[Ferdy]

Please beware that the website history.chess.free.fr is not completely up to date. I exchanged a few e-mails with Jaen-Louis Cazaux (the website owner), and it turned out that his current opinion on the Rhino move is different from what that website states (although he still does not consider it completely impossible that the historic rules were as the website states). The website shows the Rhino having a diagonal slide that goes absolutely forward after the initial Knight leg. The move that he currently considers most likely (and that I also prefer) would make this diagonal slide relatively forward, i.e. in the direction that most closely resemble that of the initial Knight jump. For a white Rhino on e6 this would be f4-g3-h2 or c7-b6-a5.

From e6
1) f4-g3-h2
2) c7-b6-a5

I guess in (2) it should be
c5-b4-a3
[d]6k1/8/4N3/2N5/1N3N2/N5N1/7N/3K4 w - - 0 1
Or can be from e6, c7-b8.

[hgm]

Oops, you are right!

I was imagining the Rhino on e8 when I wrote the latter.

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From e6
1) f4-g3-h2
2) c7-b6-a5

I guess in (2) it should be
c5-b4-a3
[d]6k1/8/4N3/2N5/1N3N2/N5N1/7N/3K4 w - - 0 1
Or can be from e6, c7-b8.

I think this is what's intended:

[hgm]

Exactly. And unblockable on the W squares. (Unlike the Tamerline Giraffe, which is blockable on the squares of the Griffon move that it skips.)

A logical counterpart to the Griffon. In facts it provides some insight in the design process of this game: The leapers Ferz and and Knight from Shatranj were considered too weak for the large board, and their move was extended by a sliding continuation. The Ferz became the Griffon, and the Knight the Rhino.

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Although the Giraffe description does what it must do, it is not the recommended one. It toggles the range to slider way to early. So this description really makes it a multiple-hook mover that turns 'corners' of 180 degrees in many different places. This makes it very hard on the move generator.

Better would be afsafyafF = mafsmafyafF. This keeps the initial 3 steps leaper-like (and thus uniquely defined), switching to slider only in the 4th (final) leg.

Actually, I'm not entirely sure now it really does what it must do: the Giraffe is basically a lame-leaper for its initial move, moving once as F, then as nH and then finally sliding onward as a rook. Does that work?