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DecisionRank distils a generative LLM's ranking into a 1.7B decision model that runs 24.5 times faster than its teacher on TREC DL

AspireAI community · arXiv (cs.CL)
Decision models predict choices or scores directly instead of decoding autoregressively, which removes generation latency but makes it hard to inherit a generative LLM's ranking knowledge. DecisionRank trains one through item-space on-policy distillation: the student's rollout is built by sorting its document scores into a ranked sequence, and a generative teacher reads that ranking and gives conditional feedback that directly supervises those scores. Combined with offline ranking supervision, it reaches state-of-the-art results on TREC DL, BEIR and BRIGHT, and item-space on-policy distillation consistently beats alternative training objectives across four benchmarks. The headline is that at 1.7B parameters the model surpasses its 27B generative teacher on TREC DL19-23, and at 8B it runs 24.5 times faster than its generative listwise counterpart on TREC DL and 16.7 times faster on BRIGHT. The gains are measured on retrieval benchmarks with teacher-generated supervision, so they depend on that teacher quality.
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