Contrastive Decoding for Reasoning
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Paper summary
Shows that contrastive decoding, a simple inference-time technique, substantially improves reasoning in large LLMs.
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Contrastive decoding: Subtracts the log-probabilities of a smaller "expert" model from those of the target LLM, boosting tokens where the larger model confidently differs from the smaller one.
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Llama 65B beats Llama 2: Contrastive decoding lets Llama 65B outperform Llama 2 and other strong baselines on commonsense and reasoning benchmarks.
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Training-free: Requires no additional training - just a smaller model available at inference time and a modified decoding rule.
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Generalizable lever: Positions contrastive decoding as a simple, cheap lever for reasoning improvement that can complement other prompting or fine-tuning techniques.