In-context Autoencoder for Context Compression in a Large Language Model
Authors: name: Tao Ge, name: Jing Hu, name: Xun Wang, name: Si-Qing Chen, name: Furu Wei

We propose the In-context Autoencoder (ICAE) for context compression in a
large language model (LLM). The ICAE has two modules: a learnable encoder
adapted with LoRA from an LLM for compressing a long context into a limited
number of memory slots, and a fixed decoder which is the target LLM that can
condition on the memory slots for various purposes. We first pretrain the ICAE
using both autoencoding and language modeling objectives on massive text data,
enabling it to generate memory slots that accurately and comprehensively
represent the original context. Then, we fine-tune the pretrained ICAE on a
small amount of instruct data to enhance its interaction with various prompts
for producing desirable responses. Our experimental results demonstrate that
the ICAE learned with our proposed pretraining and fine-tuning paradigm can
effectively produce memory slots with 4times context compression, which can
be well conditioned on by the target LLM to respond to various prompts. The
promising results demonstrate significant implications of the ICAE for its
novel approach to the long context problem and its potential to reduce
computation and memory overheads for LLM inference in practice, suggesting
further research effort in context management for an LLM. Our code and data
will be released shortly.