Lc0 v0.25 has been released - Leela Chess Zero

Lc0 v0.25 has been released.
(and it’s actually already at v0.25.1 due to hot bugfixes after the initial release).

What’s new in this version

Moves left head

All of Lc0 backends support a new “moves left head”, so we are starting to train networks which have it.

Moves left head makes it possible for a neural network to predict the remaining game length.

Once such networks are trained, potential uses will include:

Making search take the shorter route towards winning (hopefully reducing “shuffling”).
Doing the same logic during generating training games (hopefully teaching the network to focus on non-shuffling moves even without using MLH in search)
Better time management.
Displaying this information to human, maybe they will find it useful.

FRC chess

The last required pieces for Chess960 support are also included into v0.25 run, and it’s possible to start the training.

GTX GPU optimizations

Cudnn backend has more optimizations which allows better nps on GTX GPUs.

Time manager

The time management code was reorganized to allow more experimenting.

There is a new time manager, which is not tested but potentially supposed to be better. Enable using --time-manager=smooth-experimental command line flag.

Training and NN format specific changes

Added input format type 3 support to encoder/training data/search
(allowing board flips and rotations).
More ways to configure temperature decay.
Fixed castling in pgn parsing for chess 960 start positions.
Support for selfplay from books with fen tag.
Switch to v5 training data.

Bugfixes and other minor changes

Lc0 can now see draws a bit earlier due to certainty propagation.
Added option to start counting time with go uci command.
That it how it should be according to the standard, but some GUIs start clock from position command.
Added a flag to allow go nodes to takes reused nodes into account.
Shared collisions support between threads, should increase strentgh per node a bit.
We changed win probability to centipawn value formula again. New formula is cp = 90 × tan(1.5637541897 × q).
Some chess GUIs didn’t like chess engines returning depth 0, changed Lc0 to never do that.
Have a separate eigen backend.
Tensorflow (C++) backend is also there (if you can compile it).
Relaxed C++17 requirement a bit. Lc0 still needs C++17, but also is compilable on compilers without <charconv> header. We also output better error message if compiler doesn’t support required features.
Most parts of FEN command are now optional.
More checks for uci input errors.
Fix for starting fens that differ only in 50 move ply.
Allowed ranges for several parameters were extended.