Chess engine: Blunder 8.0.0 (Windows, Mac, Linux)
Blunder - UCI chess engine
Author: Christian Dean, Rating CEDR=2569
v.8.0.0
This release is very similar in spirit to that of 5.0.0, in the sense that much of the work done has been improvement and optimization of the code base through slow, large-scale refactoring, which has brought about Elo gains, although several new strength-gaining features have been implemented. Blunder 8.0.0 is estimated to be about 50 Elo stronger than 7.6.0 at bullet time controls.
It'd be impossible to list every last change, but a summary of some of the major areas will be listed below.
Improvements to Blunder's move generator have been made, improving it's speed by 10-15%. Thanks in particular to Koivisto, for giving me the idea to store the hash of a position as part of it's irreversible state, leading to a nice speed increase.
Small tweaks have been made to the UCI that's made it a bit more user friendly and hopefully
more straightforward to use.
Magic bitboard generation code and comments have also been improved and cleaned-up.
Perhaps the biggest and move effective change, the tuner for Blunder has been updated from using a naieve local optimization algorithm, to gradient descent, specfically AdaGrad. The speed and efficeny of the new tuner in allowing me to quickly add, tune, and reject evaluation ideas and improvements allowed me to very quickly tune a stronger, and more streamlined evaluation, than the one I had in Blunder 7.6.0.
I'll be uploading a paper shortly to this repository mostly outlining the math behind the process of getting the tuner working, although parts of the code will be touched upon. The hope is that such a document will be useful to those who were in the position I was in several months ago.
The time manager code has had quite a large overhaul, making the code cleaner, and the API easier to use. Time managament in games with no increment or bonus time (a.k.a "sudden death"), has also been improved, using the assumption that it's better to spend less time in the opening phase, and more towards the end of the game.
For now WAC testing (a.k.a "iq testing") has been removed from Blunder for now, as well code in blunder/tuner to generate tuning data for Blunder.
Both hadn't been very useful, although I plan on experimenting with generating custom tuning data back into Blunder very soon, so that code, at least, will be added back into later versions.
A logo has been created by myself for Blunder. It's nothing too complicated, as I'm not an artist, but it's an original design I had a while ago, and I think it suits Blunder well. See the README, or blunder/logo for the logo. Thanks to Marcel Vanthoor, author of Rustic, for giving advice on creating a logo that now looks at least a little better than the first drafts did, despite my skills.
Much of the code has been updated to make benefit from new features added in Go 1.18,
most notably generics, which have allowed me to clean up much of the code-base, including
the transposition table.
As far as some of the new strength gaining features, they're listed below:
Engine
Update PSQT and material incrementally
Search
Internal Iterative Deepening
Razoring
Consider checks for checks in quiescence search.
Add buckets to transposition table, and use a depth-replace and always-replace scheme
Evaluation
Basic rook structure
Bishop pair
Make mobility for knight's safe with regards to pawns
Drawn and drawish endgame recognition improvement
Lastly, the release of Go 1.18 has also come with the ability to target certain, extended
AMD 64 instruction sets. The makefile has been updated to allow compiling builds which
target some of these instruction sets, although I've not had the opportunity to extensively
test if there are any speed gains. I've also included pre-builds, for windows, macOS, and
linux in the version release.
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