Bigger board sizes (just for fun)

This is a just-for-fun side release of KataGo with a simple change to support board sizes up to 29x29, but not otherwise part of the "main" branch of development. This is because supporting larger board sizes currently has a major cost (which is why the normal KataGo releases don't support them by default).

See releases page, for more recent versions and newer and stronger neural nets.

Please mind these notes if using this side release:

• You should only use this version if specifically wanting to play larger sizes.
  • Memory usage will be significantly increased and possibly performance will be decreased a little in this version,
  • This effect on memory and performance will remain true even if using this version on board sizes 19x19 and smaller!
• KataGo's neural nets are NOT trained for sizes above 19x19 and might behave poorly in some cases.
  • However, they have had lots of training on different sizes 9x9 through 19x19 and so, even though there is no guarantee, most of the released nets can probably extrapolate somewhat beyond 19x19 and still usually do well.
  • How well different nets extrapolate might vary, there is some chance even that larger nets could do worse than smaller nets at extrapolation. In practice they all mostly seem very, very strong still.
  • The smaller the extrapolation (e.g. 21x21 and 23x23, instead of 27x27 or 29x29) very likely the better and stronger the net will still be.
  • Board evaluation may be a bit more biased or noisier on the larger boards, particularly precise estimation of the score in points, and possibly the net could fail to perceive and understand life/death/capture-races for extremely large dragons.
• The GTP protocol, which is the universal language that engines like KataGo use to talk to GUIs, does NOT normally support sizes larger than 25x25, so many GUIs might not work.
  • This is due to how the protocol was designed to use alphabetic coordinates, and having no specification for going beyond "Z".
  • KataGo will continue with "AA", "AB", etc (still skipping any use of the letter "I", to be consistent) , but it is quite likely that many GUIs will not have this implemented and will therefore not work with sizes past 25x25.
  • For example, Lizzie doesn't appear to work beyond 25x25 currently.
• On lower-end GPUs, there may be some chance that the biggest nets fail due to things like running your GPU out of memory due to such a huge board.
  • You might have to switch to a smaller net if you run into such issues.

And of course, there is some chance of a bug that makes KG itself not work on this branch (separately from any mistakes from the net) since large board sizes aren't tested heavily, if so, you can open an issue or otherwise let me know and I'll fix it. For OpenCL, this version might also re-run its tuning upon first startup.

Keeping the above details in mind though, KataGo should be able to provide some strong play on these larger board sizes even with no training for them, so have fun!