CRED: Calibrated Relational Enhanced Distillation for LLM-Based Pointwise Reranking
In document reranking, rerankers based on Large Language Models (LLMs) demonstrate superior performance but are constrained by high memory consumption and latency. To develop lightweight yet high-performance LLM-based pointwise rerankers through knowledge distillation, we identify two critical limitations: teachers often yield over-smoothed and inaccurate supervision on hard negative samples, thereby hindering the student's optimization; furthermore, traditional methods underutilize the relevance score differences between candidates, which are crucial for ranking tasks. To address these challenges, we propose CRED (Calibrated Relational Enhanced Distillation), which integrates Adaptive Teacher Calibration (ATC) to calibrate teacher predictions and amplify score margins, while employing Preference Relation Alignment (PRA) to align the distributional patterns of relevance score differences, enabling the student to capture precise ranking structures. To support this approach, we also construct FineDistill, a dataset of 1M samples providing fine-grained score supervision. We distill an 8B teacher into a 0.6B pointwise student. Extensive experiments on TREC and BEIR benchmarks show that our model outperforms leading baselines in both performance and generalization.