Chess engine: Willow 3.1 NNUE (Windows and Linux)

 

Willow - UCI engines   Rating CEDR=3071
A chess engine I am currently working on, written in C (WORK IN PROGRESS)
Compiled in Windows, works on BanksiaGUI with limited UCI support right now.

v.3.1:

New Features:

NNUE: Willow's new net is now a 512x2 perspective net, trained on 530m positions (all self-play still). I also did a bunch of testing with datagen in order to get more optimal data than what I currently have. The result is a significantly more accurate evaluation of positions, with only a slight loss of style/aggressiveness.

Search: Willow had a lot of existing heuristics tweaked, and some new ones added. Most notably:

-Removing delta pruning - this gained a whopping 60 elo. I'm not sure what it is about Willow that hates qsearch pruning so much, but it is what it is.

-History gravity

-Countermoves history

-Prefetching the TT and only using the specific entry

-history in LMR

-parameters changed for LMR, SEE pruning, futility pruning, NMP, and more.

SMP:

Willow now supports multithreading! It is still a bit of a work in progress since I was rushing for a release, so please notify me if a crash occurs while running Willow on multiple threads so that I can fix whatever the problem is. One thing is for sure, though; adding more threads definitely increases Willow's strength.

List of things to do in future:

-SPSA

-experiment with net bucketing

-FRC?

-staged movegen and take a good long hard look at speed improvements in general

-clean up the code so that others can learn better from it

Willow 3.1 NNUE download

Willow rating CEDR progress:

Pl	Engine	Rating	Score	Games	%
890	Willow 3.0	3071.1	73.00	194	37.63
966	Willow 2.8	2955.6	70.00	221	31.67
987	Willow 2.9	2930.9	13.50	68	19.85
1127	Willow 2.7	2713.5	39.00	123	31.71
1382	Willow 2.5.11	2287.2	10.00	51	19.61
1460	Willow 2.6	2122.4	13.00	186	6.99