arXiv Machine Learning
22h ago

CacheGraft: Enhancing Retrieval-Augmented Generation via Latent-Space Document Enrichment

CacheGraft is a retrieval‑augmented generation system that enriches a small language model’s latent space by injecting fused key‑value cache representations of corpus passages, encoded offline by a larger model. The approach eliminates the need to run the larger model at inference time, and on five QA benchmarks it improves answer quality in 29 of 30 comparisons, with 17 statistically significant gains. These results demonstrate that latent‑space document enrichment can boost RAG performance, especially when only a small model can be deployed.

By Vihan Lakshman, Peter Baile Chen, Zhuohan Gu, Michael Cafarella
arXiv Machine Learning
Oct 15

Latent Compaction with Test-Time Training

Latent Compaction is a test‑time training method that learns a compact, document‑specific key–value cache for large‑context language models. It initializes cache entries using reconstruction importance, teacher attention, and key‑space diversity, then fits attention outputs and log‑normalizers to the full cache before jointly optimizing the entire cache via end‑to‑end distillation. Experiments on RULER, LongBench, and Phonebook Lookup show significant accuracy gains over budget‑matched compression baselines, achieving 96.7% accuracy at 32× compression on RULER and transferring well across model scales and families.

By Yingfa Chen, Xingyu Shen, Chaojun Xiao, Xu Han
arXiv AI
Aug 19

DEPT: Document Embedding Preservation Tuning for Unified Query Expansion and Retrieval

The paper introduces DEPT, a method that trains a single decoder-only large language model to both expand queries and encode documents for retrieval. By preserving document embeddings close to their initial cached values while allowing gradients to flow through the generator, DEPT stabilizes retrieval targets and enables efficient index reuse and online hard‑negative mining. Experiments on the BEIR benchmark with Qwen3‑4B‑Instruct‑2507 and LLaMA‑3.2‑3B‑Instruct show that DEPT outperforms training‑free, independently trained, and staged unified baselines, with ablations confirming the benefits of preservation, whitening, end‑to‑end expansion training, and online negatives.

By Jingyuan Wang, Richong Zhang, Zhijie Nie, Mingxin Li, Yanzhao Zhang