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About this paper

Ruizhe Shi, Yifang Chen, Yushi Hu, Alisa Liu, Hannaneh Hajishirzi, Noah A. Smith, Simon S. Du

An algorithm named Multi-Objective Decoding (MOD) aligns language models to multiple objectives dynamically at inference time without retraining, by combining independently trained single-objective models' predictive distributions. It surpasses parameter-merging methods by up to 12.8% relative reward improvement on multi-objective tasks and can combine diverse models to improve metrics like coding ability and safety while reducing toxicity to nearly 0%.

Key insights

  • A critical bijection exists between optimal policies and rewards under f-divergence regularization, enabling a principled approach to multi-objective alignment.
  • Parameter-merging techniques are theoretically sub-optimal for f-divergence regularized policies, leading to "reward mis-specification."
  • The framework provides precise control over objective trade-offs, including the ability to use negative weightings to steer away from specific traits, and unifies various decoding-time alignment methods.

Summary by alphaXiv.

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