H. G. Muller wrote on Tue, May 21, 2019 07:16 PM UTC:
I now managed to have KingSlayer play some CwDA games against Fairy-Max, which it eventually could do without illegal-move complaints (and even win some). This is just the basics (move generator and check test); the material table is not implemented yet. The non-standard a-side castling of the Clobberers works, though. No bent or ski-sliders yet, so also no Dragons Army.
This already touched on some compatibility issues. Like Fairy-Max KingSlayer now supports two methods for variant selection: in variant 'fairy' the armies are decided based on White Army / Black Army engine options. This is compatible with Fairy-Max, which has a single engine option to select a pair of armies, but the options have to be set by hand anyway, and mean nothing to WinBoard. The other method is through the variant names, but the names are incompatible with those in use by Fairy-Max; I currently programmed names like "fide~nutters~(cwda)" (all lower case; the space existing WinBoard versions reserve for these names in the New Variant dialog is rather small, and capitals take more space). This we obviously have to sync between ChessV, Quaddrox and KingSlayer, and then I will adapt the names in Fairy-Max' ini file likewise.
The other issue is the piece IDs. I currently use the same as Fairy-Max already used. These are not very satisfactory, though; many were picked to match the piece symbol I picked to represent the piece in WinBoard (e.g. U for Charging Knight because I displayed it as a Unicorn, E for Waffle because I displayed it as an Elephant). They make no sense in a GUI that would use a less fanciful representation.
Promotion to an opponent piece will always be somewhat problematic in KingSlayer, as it can only support 7 piece types per army (including Pawn and King), now that I patched it to allow use of the formerly unused type code 7. So that could be its own pieces plus the opponent's super-piece. But then under-promotion to an opponent piece will always be impossible. This is not very important for the purpose I wanted to use it for, but it makes it a somewhat incomplete implementation of the official rules. Things could be stretched a bit further by dynamically assigning the piece type during the game. But that would not remove all limitations, and add a lot of cumbersome code for something that would be almost entirely hypothetical.
I also discovered a problem in WinBoard: it does not relay castling rights in a FEN when the corner piece is not a Rook. This never hurt Fairy-Max, as this relies on the 'edit' command rather than 'setboard', which does not relay any info on castling rights. So Fairy-Max would reconstruct these just based on the corner piece being the one from the initial setup. KingSlayer takes the rights in the FEN seriously, though, and in an engine-engine game the initial setup specified by the first engine would be loaded in the second engine, which then would lose its castling rights. (With external configuration of the initial position both engines would lose these rights, if they rely on 'setboard'.) There is a WinBoard command-line option that can force the castling field to a desired value, though (to force compatibility with the broken Arena Chess960 FEN), so I suppose that would be a work-around. Obviously I have to fix this in WinBoard.
I now managed to have KingSlayer play some CwDA games against Fairy-Max, which it eventually could do without illegal-move complaints (and even win some). This is just the basics (move generator and check test); the material table is not implemented yet. The non-standard a-side castling of the Clobberers works, though. No bent or ski-sliders yet, so also no Dragons Army.
This already touched on some compatibility issues. Like Fairy-Max KingSlayer now supports two methods for variant selection: in variant 'fairy' the armies are decided based on White Army / Black Army engine options. This is compatible with Fairy-Max, which has a single engine option to select a pair of armies, but the options have to be set by hand anyway, and mean nothing to WinBoard. The other method is through the variant names, but the names are incompatible with those in use by Fairy-Max; I currently programmed names like "fide~nutters~(cwda)" (all lower case; the space existing WinBoard versions reserve for these names in the New Variant dialog is rather small, and capitals take more space). This we obviously have to sync between ChessV, Quaddrox and KingSlayer, and then I will adapt the names in Fairy-Max' ini file likewise.
The other issue is the piece IDs. I currently use the same as Fairy-Max already used. These are not very satisfactory, though; many were picked to match the piece symbol I picked to represent the piece in WinBoard (e.g. U for Charging Knight because I displayed it as a Unicorn, E for Waffle because I displayed it as an Elephant). They make no sense in a GUI that would use a less fanciful representation.
Promotion to an opponent piece will always be somewhat problematic in KingSlayer, as it can only support 7 piece types per army (including Pawn and King), now that I patched it to allow use of the formerly unused type code 7. So that could be its own pieces plus the opponent's super-piece. But then under-promotion to an opponent piece will always be impossible. This is not very important for the purpose I wanted to use it for, but it makes it a somewhat incomplete implementation of the official rules. Things could be stretched a bit further by dynamically assigning the piece type during the game. But that would not remove all limitations, and add a lot of cumbersome code for something that would be almost entirely hypothetical.
I also discovered a problem in WinBoard: it does not relay castling rights in a FEN when the corner piece is not a Rook. This never hurt Fairy-Max, as this relies on the 'edit' command rather than 'setboard', which does not relay any info on castling rights. So Fairy-Max would reconstruct these just based on the corner piece being the one from the initial setup. KingSlayer takes the rights in the FEN seriously, though, and in an engine-engine game the initial setup specified by the first engine would be loaded in the second engine, which then would lose its castling rights. (With external configuration of the initial position both engines would lose these rights, if they rely on 'setboard'.) There is a WinBoard command-line option that can force the castling field to a desired value, though (to force compatibility with the broken Arena Chess960 FEN), so I suppose that would be a work-around. Obviously I have to fix this in WinBoard.