Contextual Relevance and Adaptive Sampling for LLM-Based Document Reranking
For complex queries involving multifaceted requirements and nuanced semantics, document relevance becomes highly context-dependent, rendering conventional re-ranking methods inadequate. To address this, we propose a “contextual relevance” modeling framework that formalizes relevance as the joint probability distribution over candidate document sets, revealing the substantial impact of document composition and ordering on large language model (LLM) relevance judgments. We introduce TS-SetRank—a novel algorithm integrating Bayesian uncertainty estimation with Thompson sampling—to enable uncertainty-aware, adaptive set-level sampling and re-ranking. Evaluated on BRIGHT and BEIR benchmarks, TS-SetRank achieves 15–25% and 6–21% improvements in nDCG@10, respectively, outperforming state-of-the-art retrieval and re-ranking approaches. Our core contributions are: (i) the first formal definition of contextual relevance, and (ii) the establishment of a set-level, uncertainty-driven re-ranking paradigm.