H. G. Muller wrote on Sun, Sep 11, 2016 07:15 AM UTC:
> Does the new fairymax support 15x10 boards?
Not if there are Knights. To understand that answer requires some explanation: Internally Fairy-Max uses a 16x16 board, unfolded to a 1-dimensional array. So the first 16 elements are rank 1, the next 16 rank 2 etc. That means that the board wraps around, and the left edge (a-file) borders the right edge (p-file) upshifted one rank (i.e. if you step one squere right from p1 you end up on a2). To prevent pieces from making such offsetted Cylinder Chess (Screw Chess?) moves, a 'guard band' of unused squares is needed between the end of one rank and the start of the next. If this guard band would consist of only the p-file, Knights could leap over it, e.g. from o1 to a3. So to prevent sideway Kight moves from wrapping, you need a guard band of at least two files, so that the width can be at most 14. If Camels or Zebras participate, the guard band would have to be 3 wide to contain them, and the maximum width would be 13. (Which was just enough for Wildebeest Chess!) So the maximum number of usable board files depends on the largest sideway leap of the participating pieces.
No such separator is needed in the 'vertical' dimension; no matter how far pieces leap forward or backward, their moves would never wrap back onto the board. So you can always use all 16 ranks. This limitation is set by the fact that square numbers must not exceed 256, to fit in 8-bit variables. So it would be possible to make a 10x15 board. But that would not not handle Pawn promotions and evaluation in the desired way.
> Does the new fairymax support 15x10 boards?
Not if there are Knights. To understand that answer requires some explanation: Internally Fairy-Max uses a 16x16 board, unfolded to a 1-dimensional array. So the first 16 elements are rank 1, the next 16 rank 2 etc. That means that the board wraps around, and the left edge (a-file) borders the right edge (p-file) upshifted one rank (i.e. if you step one squere right from p1 you end up on a2). To prevent pieces from making such offsetted Cylinder Chess (Screw Chess?) moves, a 'guard band' of unused squares is needed between the end of one rank and the start of the next. If this guard band would consist of only the p-file, Knights could leap over it, e.g. from o1 to a3. So to prevent sideway Kight moves from wrapping, you need a guard band of at least two files, so that the width can be at most 14. If Camels or Zebras participate, the guard band would have to be 3 wide to contain them, and the maximum width would be 13. (Which was just enough for Wildebeest Chess!) So the maximum number of usable board files depends on the largest sideway leap of the participating pieces.
No such separator is needed in the 'vertical' dimension; no matter how far pieces leap forward or backward, their moves would never wrap back onto the board. So you can always use all 16 ranks. This limitation is set by the fact that square numbers must not exceed 256, to fit in 8-bit variables. So it would be possible to make a 10x15 board. But that would not not handle Pawn promotions and evaluation in the desired way.