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Complicated problems most of the time have simple solutions. You could have put both Bishops on one side of the board, and both Knights on the other side. And the opponent will have them the other way around. Simple. 

Another solution would be to add an extra piece (A Shield Bearer/Scutier to protect the King) and make the board 10x8. 

The editor Fergus Duniho has revised this page.

I tried to correct the description on the Alphabetical Index page but couldn't. Mistakenly says

9x9 variant with extra Queen and Bishops conversion rule. (9x8, Cells: 72) By Carlos Cetina.

Could some editor change the text to this?:

Variant with two Queens flankink the King and Bishops Conversion Rule. (9x8, Cells: 72) By Carlos Cetina. 

Thanks beforehand!

I agree with you HG. The rule is clear and good. It would be nice if on computer play it would be possible to mark the Bishops as you suggest for woodware play.

This is more  criticism on how the pieces should be represented, than on the rule. In particular, whether the right or obligation to convert still exists should be 'hidden' (like castling rights) or explicitly visible. E.g. when playing with woodware, one could put the Bishops initially on a Draughts chip, to indicate they can convert. When one of the Bishops starts as a Wazir, you remove the chips from both. When it starts as a Bishop, you move its chip under the other, so that it stands on two chips, indicating it now must start as a Wazir.

I've just finished a game of Symmetric Chess. At first I was seduced by this rule of Bishop's conversion, but finally I am not so convinced. My opponent was playing with White, so his two Bishops were on white squares. He moved c-Bishop first, then he lost it. So, only his g-Bishop remained on its initial square unmoved and was waiting for a conversion non-capturing move that never came.

I found rather confusing looking at this chessboard with this unique remaining Bishop standing on g1 and unable to move on the diagonals. An observer coming at this moment would not understand why the Bishop cannot move and capture a piece on f2 or h2.

So the rule is clear, but I found this a bit bizarre after all.

I'm playing this interesting variant. Some remarks:

1) The presentation line says "9x9 variant with extra Queen and Bishops conversion rule". >> it should be corrected to 9x8 as it is not a 9x9 as originally designed.

2) As 9x8 its originality is weak too. In Pritchard's one can find two preceding CV, also briefly addressed in this website. Ultrachess attributed to D.Trouillon, early 1970s with the same setup, where it is possible to transpose B and N once. Also Active Chess (G.Kuzmichov, 1989) for which, apparently, some research had been done to find the best setup. Here the extra Queen is put on i- or j- file. Gollon also explored this game, preferring RBNQKQBNR baseline.

Another option to change the square color of one Bishop would have been the solution adopted in Not-Particularly-New Chess by Peter Aronson (2001): having that piece first moving as N (non capturing) and as B on subsequent moves. 

Well, having board other than 8x8, or piece IDs A or C, is also not compatible with the FEN spec. One has to do some amount of generalization to make it useful for variants. The 'castling field' in fact already is a field that indicates virginity of pieces. But only of those for which it matters, because under orthodox rules only castling is affected by virginity. (One could argue about Pawns, but the double-push is usually explained as a location-depended move rather than an initial one, as evidenced by the rules of Crazyhouse/Bughouse.)

I think it would be bad to have two fields that basically serve the same purpose. In Shredder-FEN notation the letters in this field already identify the piece, so there is no need to make separate fields for Kings+Rooks, Knights, Bishops and Queens. It seems much better to have a unified virginity field.

Likewise, the the e.p. field indicates the last-moved piece, in positions where that matters. So it would be logical to use it for any other type of last-moved piece as well.

I agree that leaving in the right of a non-existing piece is perhaps a bit contrived. But how about the other option: indicating an undetermined right by X? Then you would not have to look at the board. An X in the field means both Bishops are virgin and can convert. One gets captured without moving: the X remains, to indicate all remaining Bishops still have choice. If one moves, the rights disappear altogether when it converts, and change to indicate the file of the Bishop that now must convert.

If you have both converting Camels and Bishops, just use X for the Bishops and Y for the Camels. (Or more generally, adopt the convention that X indicates the outer-most piece type, working your way inwards when stepping through the alphabet.)

Extra fields should be avoided as much as possible

Sure.  I just checked and ChessV currently supports 200 games and it was only required to expand the FEN format on 5 of them (and 2 of the 5 are Apothecarys).  But when extra state must be stored, I do not agree that it is better to jam it into one of the existing fields to represent something different.  That is not compliant with the FEN spec anyway.

I don't like the use of the extra + at all

If the first Bishop is captured in the virgin state, you could leave its rights, implying that conversion of the one that is still there is still optional.

Ok, this is something I had not considered.  I could do it but I am not sure it's better.  To find out if a conversion is mandatory, instead of checking the next character for a plus, you check to see if there is another conversion option and then see if that is invalid because the square does not contain a piece of the appropriate type.  This doesn't really seem simpler to me.  It may also be less extensible in the case of more than two converting pieces.

EDIT: I said this backwards.  If there is another character, then the conversion is optional.  If there isn't then it's mandatory.  I guess that is pretty simple.  This works for me.

Is there really no better solution for this? Extra fields should be avoided as much as possible, and I don't like the use of the extra + at all. E.g. WinBoard treats the castling field in Seirawan Chess as a general rights field, (indicating the virginity of all back-rank pieces, from which gating and castling rights follow), by mentioning their file.

The same could be done here: initially the Bishops would be in the rights field, as they can convert. If one converts the rights for both disappear. If one fails to convert on its first move, its conversion rights disappear. The rights that remain for the other now become an obligation. If the first Bishop is captured in the virgin state, you could leave its rights, implying that conversion of the one that is still there is still optional.

Or you could write an X in the rights field to indicate an undetermined conversion right exists. The X changes into the Bishop file ID to indicate that Bishop must convert, or disappears when no more conversion is allowed.

FEN Notation

The Bishop Conversion Rule requires additional state information to be preserved in the FEN for a position.  The purpose of this post is to document how I have encoded this information in ChessV.

The extended FEN format is:
{array} {current player} {castling} {en-passant} {bishop-conversion} {half-move clock} {turn number}

A new component has been inserted between the notation of the en passant square and the half-move ("50 move") counter.  The value for this field at the start of a game is "CGcg".  Like with castling privileges, the upper-case letters are for white and the lower-case letters are for black.  The letter is the file of the bishop, and its presence indicates that the bishop has the ability to convert.  Unlike castling privilege, however, bishop conversion can be mandatory. This is indicated by a "+" after the letter.  For example, if white moves the c-file bishop without converting, it become mandatory to convert the g-file bishop.  Thus, the notation becomes "G+cg".

Very good, having cleared the cache and deleted the cookies, the AI no longer commits the illegality of not converting the bishop. Now it plays 24 ... Qc4. Continuing the game it developed like this:

1.g3 d5 2.d4 f5 3.Bg2 e6 4.f4 Qb4 5.c3 Qb5 6.Nf2 g6 7.Nd3 a5 8.a4 Qc4 9.Nd2 Qc6 10.Ne5 Qb6 11.b3 Nc6 12.Ndf3 Qd6 13.Ba3 Qd8 14.Bc5 Qa6 15.Qf2 Nxe5 16.Nxe5 b6 17.Ba3 Nf7 18.Nxf7 Bxf7 19.O-O Qf6 20.c4 dxc4 21.Bxa8 Qxa8 22.Ki1 cxb3 23.Rb1 Qd5 24.Rxb3 Qc4 25.Rd3 b5 26.axb5 Qxb5 27.Qa1 i5 28.Rb1 Qd5 29.Bc5 Qa8 30.Qa4 c6 31.Bb6 Bd8 32.Bxd8 Kxd8 33.Rdb3 Qa6 34.Rb6 Qa7 35.Qxc6 h5 36.Qd6 Qd7 37.Rb8#

Thanks for showing me the solution. So when will we see the Interactive Diagram offered on the Google Apps Store?

When I paste that game up to move 24 back into the Diagram, and then play Rxb3, it doesn't reply with that same Bishop move. And when I play the (illegal) move Qa6 instead of Rxb3 it doesn't capture the Queen, but plays Bd8. Did you flush the browser cache, (Shift + reload in FireFox) to make sure you are using the latest version of the diagram script? You might have been using the old version where I hadn't implemented the rule yet. If you are sure you have flushed the cache you can paste the moves 1-23 back in the Diagram (in the dashed text box below the navigation buttons), and continue the game from there.

It seems that there is a bug such that the AI does not always make the conversion as can be seen in the following game on move 24 of the blue side:

1.g3 d5 2.d4 f5 3.Bg2 e6 4.f4 Qb4 5.c3 Qb5 6.Nf2 g6 7.Nd3 a5 8.a4 Qc4 9.Nd2 Qc6 10.Ne5 Qb6 11.b3 Nc6 12.Ndf3 Qd6 13.Ba3 Qd8 14.Bc5 Qa6 15.Qf2 Nxe5 16.Nxe5 b6 17.Ba3 Nf7 18.Nxf7 Bxf7 19.O-O Qf6 20.c4 dxc4 21.Bxa8 Qxa8 22.Ki1 cxb3 23.Rb1 Qd5 24.Rxb3 Bd7 25.Rc3 c5 26.Rd3 c4 27.Rd2 i5 etc

Magnificent! I encourage you to publish your Interactive Diagram in the aforementioned apps store since it is a very good showcase to spread ideas, in such a way that a certain number of variants could be played by default (including Symmetric Chess, of course!). I believe that you could get a fair remuneration in money for your work including banner ads. Using the app would be free. What do you say?

Do you think that the Interactive Diagram software could be used in the Android environment?

I know that for sure. It is browser-based, and every OS nowadays has a browser that understands HTML and JavaScript. So you don't need a separate App for it. (Of course the browser is also an App, but I assume everyone already has that.) It works fine on my Samsung Tablet.

Thank you very much, HG. It's a great improvement.

One of my biggest dreams is to see one day in the Google Apps Store one with which this chess variant can be played against the AI. Do you think that the Interactive Diagram software could be used in the Android environment?

I have implemented the bishop conversion rule now as a standard feature of the Interactive Diagram. So that it is now also possible to play Symmetric Chess against the AI (for which the trick of changing both bishop's piece types when one of them moved did not work). All that is now required is define the bishop with an extra initial iW move, and add a parameter conversion=N, where N is the number of the piece table of the piece to which the rule applies. (So here N=3). The first moves of pieces of this type are then forced to go to different square shades.

Thank you, H.G., for the explanation and directions. I could already run Nebiyu properly but unfortunately... playing chess it defeats me easily! 

That is because Nebiyu is an engine, and engines are not supposed to be used directly, but only through mediation of a Graphical User Interface like WinBoard. It is then WinBoard which will take care of launching the engine's .exe file, and send it the proper (text) commands to do something useful.

So the proper procedure is to start WinBoard (either as game viewer without any engine, or for playing against some other engine), then open the Engine -> Load first Engine menu dialog, use the 'browse button' behind the 'Engine' text entry to locate NebiyuAlien.exe, and then 'OK' the dialog. This will make WinBoard start Nebiyu in the background, (possibly terminating the engine that was in use before), and consult it through the appropriate communication whenever it needs it to make or suggest a move. You can then select one of the supported variants from the File -> New Variant dialog.

This procedure will also add NebiyuAlien to WinBoard's 'Engine List', which will be displayed in a listbox on the left in the Load Engine dialogs, so that you can just click on it when you want to use it again in a later session, without having to browse for it first. This Engine List will also be displayed in the comboboxes of WinBoard's Startup Dialog, so that a next time when you start WinBoard you can select Nebiyu immediately, as first or as second engine. (A second engine is only needed when you want to play two engines against each other, through the Mode -> Two Machines menu item.)

OK, I already downloaded Nebiyu 1.45 and unzipped NebiyuAlien; then double clicked on NebiyuAlien.exe and a window was opened but everything is black; there is only one blinking cursor; the window header says:

C:\Users\Carlos\Downloads\Nebiyu\NebiyuAlien.exe

But now I don't know what to do.

There are many more links on that page, which come into view when you scroll down. The Nebiyu version I know is at the link Nebiyu 1.45. There seems to be a newer version 1.5, but from the decription of it I am not sure it would be useful untill you train it first, and I never used it myself. IIRC the Nebiyu 1.45 package contains several executables (also covering games other than chess variants), but the one you should run for CVs is NebiyuAlien.exe. The game definitions for that are all in the file alien.ini, which is sort of self-documenting. The file starts with a series of piece definitions, after which a series of game definitions using those pieces follows.

There is Fairy-Stockfish, which is very much worth having. But it is not an independent app that goes accompanied with an installer. Just something you unzip in a folder of your choice, after which you have to point WinBoard to the executable through the Load Engine dialog, so that it can use it as an engine.

The same holds for Nebiyu, which is not as strong as Stockfish, but rather easy to configure for playing new chess variants.

Thank you very much for the info. Of the two, attracts me more Nebiyu. I'm somewhat confused on how to proceed with the installation because I don't see any link that be unique and clearly says "download". There are these 4 links:

egbbdll-cpu

egbbdll-gpu

nets-epd.zip

nets-ccrl.zip

Could you, please, tell me which of them to click? 

For the second, I would be grateful if you, Fergus, HG or anyone else tell me of any program (preferable of chess or chessvariants) that I could download.

There is Fairy-Stockfish, which is very much worth having. But it is not an independent app that goes accompanied with an installer. Just something you unzip in a folder of your choice, after which you have to point WinBoard to the executable through the Load Engine dialog, so that it can use it as an engine.

The same holds for Nebiyu, which is not as strong as Stockfish, but rather easy to configure for playing new chess variants.