Two ways to be strong
Pikafish is built for speed. It looks at more than a million positions a second and judges each one by rules written by hand. AB-JChess is built from Pikafish too, but it judges positions with a neural network trained on about a billion jieqi positions. It looks at about fifty times fewer positions, and understands each one better. Its training code is public in the same repository, under abjchess-nnue-pytorch.
Where it sits
AB-JChess is at the top of the jieqi bot list, above Level 8. Levels 1 to 8 stay Pikafish, and Level 4 is still where a new player starts. It does not take a level number: the top place holds the strongest jieqi engine we have measured, under its own name. Its rating on the bots page, 2354 against Level 8's 2226, comes from the same bot-against-bot games that rate the levels. Its authors are training stronger networks; when one is released, we will play it against this one and switch if it wins.
While writing this post we found a bug in how our Pikafish bot scored reveals. It is fixed; a follow-up post covers what it was and what it cost.
Thanks
AB-JChess is open source under the GPL-3.0 licence, at github.com/lxsgx23/AB-JChess. Its authors let us use the engine and its network on Mistboard. The network is downloaded from their own release each time we build the site, never copied. Thank you, Huorongrong and Laoxu.