Lexnet

A neural network to generate syntax highlighting for C code, with the weights generated entirely by Anthropic's Claude Fable 5.1.

The model has about 984 parameters, with the other 9,556 being basically dense params that don't do much but pad out the useful weight matrices so they can multiply nicely.

Usage

git clone https://huggingface.co/alpindale/lexnet.git && cd lexnet
cc -O3 -march=native -o lexnet lexnet.c -lm

./lexnet -w lexnet_weights.bin lexnet.c

Model Details

Developer	Claude Fable 5.1
Type	bidirectional recurrent network, per-character sequence tagger
Task	Token classification over C source
Input	bytes (ASCII; ≥128 mapped to a null row)
Output	one class id per byte
Parameters	984 non-zero; 9,566 dense
Recurrent state	18 units forward, 7 backward
Depth	6 forward layers, 2 backward layers, 1 linear head
Activations	Clip(x, 0, hi) — hi=1 (ReLU1) for logic units, ∞ for two accumulators, 14 for a counter
Precision	float64
Training data	None
Training compute	None

Performance

188 KB corpus, Apple M4 Pro:

executor	ns/char	K chars/s
numpy reference	17,000	59
lexnet --interp (CSR, ~1K MACs/char)	417	2,398
Pygments CLexer	447	2,238
lexnet compiled kernel	88	11,326
tree-sitter-c parse + highlight query	100	10,010
tree-sitter-c parse only	51	19,448