arXiv:2505.17813cs.CLcs.AI2025-05被引 75

更短的推理链反而更准,能显著降低计算成本。

Don't Overthink it. Preferring Shorter Thinking Chains for Improved LLM Reasoning

  • 并行生成多个推理链,优先选最早完成的前m条
  • 短链方法在低算力下准确率更高,节省40%思考令牌
  • 训练时用短链效果更好,颠覆长链更优的直觉

推理大模型通常依赖增加测试时计算量,生成冗长的'思考链'来完成复杂任务。然而,这种方法带来高昂的计算开销和延迟。本文挑战了'长思考链=更好推理'的假设,发现单个问题中较短的推理链正确率比最长链高出最多34.5%。基于此,提出short-m@k新推理方法:并行执行k次生成,一旦前m条链完成即停止,用多数投票决定答案。short-1@k在低算力下表现相当或更优,最多减少40%思考令牌消耗;short-3@k在所有算力预算下均超越标准多数投票,且最快可节省33%实际运行时间。进一步微调实验显示,使用短链训练的模型性能更佳。研究表明,测试时过度思考可能适得其反,应重新评估长链推理的有效性。

原文摘要 · Abstract (English)

Reasoning large language models (LLMs) heavily rely on scaling test-time compute to perform complex reasoning tasks by generating extensive "thinking" chains. While demonstrating impressive results, this approach incurs significant computational costs and inference time. In this work, we challenge the assumption that long thinking chains results in better reasoning capabilities. We first demonstrate that shorter reasoning chains within individual questions are significantly more likely to yield correct answers - up to 34.5% more accurate than the longest chain sampled for the same question. Based on these results, we suggest short-m@k, a novel reasoning LLM inference method. Our method executes k independent generations in parallel and halts computation once the first m thinking processes are done. The final answer is chosen using majority voting among these m chains. Basic short-1@k demonstrates similar or even superior performance over standard majority voting in low-compute settings - using up to 40% fewer thinking tokens. short-3@k, while slightly less efficient than short-1@k, consistently surpasses majority voting across all compute budgets, while still being substantially faster (up to 33% wall time reduction). To further validate our findings, we finetune LLMs using short, long, and randomly selected reasoning chains. We then observe that training on the shorter ones leads to better performance. Our findings suggest rethinking current methods of test-time compute in reasoning LLMs, emphasizing that longer "thinking" does not necessarily translate to improved performance and can, counter-intuitively, lead to degraded results.

大模型推理思维链效率优化推理机制

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