MEGABYTE: Predicting Million-byte Sequences with Multiscale Transformers
Authors: name: Lili Yu; name: Dániel Simig; name: Colin Flaherty; name: Armen Aghajanyan; name: Luke Zettlemoyer; name: Mike Lewis
Published: 2023-05-12 00:55:41

Abstract: Autoregressive transformers are spectacular models for short sequences but
scale poorly to long sequences such as high-resolution images, podcasts, code,
or books. We proposed Megabyte, a multi-scale decoder architecture that enables
end-to-end differentiable modeling of sequences of over one million bytes.
Megabyte segments sequences into patches and uses a local submodel within
patches and a global model between patches. This enables sub-quadratic
self-attention, much larger feedforward layers for the same compute, and
improved parallelism during decoding -- unlocking better performance at reduced
cost for both training and generation. Extensive experiments show that Megabyte
allows byte-level models to perform competitively with subword models on long
context language modeling, achieve state-of-the-art density estimation on
ImageNet, and model audio from raw files. Together, these results establish the
viability of tokenization-free autoregressive sequence modeling at scale.