Eman is a stockfish-derived engine, but there's some very interesting peculiarity, I'm not exhaggerating: the author has opened a new door that could lead
a whole new world for computer chess Alpha-Beta engines.
Usually there is an opening database, an engine calculating the middlegame and an ending database used by the engine as help to finish the game or even doing it
by only using this support, when you have not more than 5 pieces; the case of Eman is very peculiar: through file called 'experience' the program can "remember" some pattern and use it in a second time. In other words we are speaking of a
sort of "middlegame database". The topic is very appetizing...
Ironical: I was thinking that something like this could be useful right before knowing Eman...
The fact of having a single experience file is surely an advantage respect to invasive programs like ShashChess, which I refused to host on this website just because
it created tons of different files, while everything could be well managed by a single one or two at worst, like the new Raubfisch sl.
These last months Eman is the engine used by the top players on Playchess.
The structural point of view of this engine is the future of the Alpha-Beta chess programs (classic nowadays chess engines), although the menace of Neural Network engines is always more consistant...
The only negative point of Eman is that it's hard to get it, but I can understand the author, wanting to keep a niche group of users and avoiding the same old GPL breaking law bothering.
Eman was equipped by a merging and defragmenting application for the experience files; I don't know if it's still usable/useful with the most recent versions (I got it with Eman 2), but I'll keep it, just in case...
The Eman engine with Eman tools for merging/defragmenting experience files and my experience file:
Eman official website: https://eman.zohosites.com/.