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Concise Thoughts: Impact of Output Length on LLM Reasoning and Cost

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arxiv 2407.19825 v2 pith:3E4QNBUH submitted 2024-07-29 cs.CL cs.AI

classification cs.CLcs.AI
keywords concisenessimpactmodelsoutputprompttechniquesanswersccot
verification ladder T0 review T1 audit T2 compute T3 formal

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Today's large language models (LLMs) can solve challenging question-answering tasks, and prompt engineering techniques, such as chain-of-thought (CoT), have gained attention for enhancing the explanation and correctness of outputs. However, many models and techniques tend to produce excessively verbose and lengthy answers, leading to issues with both conciseness and generation time. To address this, this paper analyzes the impact of output lengths on LLM inference pipelines by introducing and proposing novel metrics to evaluate the \textit{correct conciseness} of a model and related prompting techniques. Then, we examine the impact of controlling output length through a refined prompt engineering strategy, Constrained-CoT (CCoT), which encourages the model to produce more concise outputs. To better understand the effects of such a prompt, we also introduce two additional scores for analyzing the conciseness, measured in terms of redundancy and information flow in generated answers. Experiments on pretrained LLMs and multiple datasets demonstrate the benefits of the proposed metrics and the effectiveness of CCoT across different models.

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Cited by 30 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

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  2. Shorter Reasoning, Earlier Answers? An Evaluation of Reasoning Interfaces

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    Matched-horizon comparisons show that a numeric/concision prompt shortens Qwen3 reasoning without consistent accuracy gains, while lower gpt-oss effort wins early mainly by finishing sooner, not by reasoning better.

  3. NELSSA: A GPU-PNM Heterogeneous System for Mixed-Length LLM Serving via Length-based Request Placement

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  4. Contrastive On-Policy Distillation

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    Contrasting a teacher's token scores under light- and heavy-thinking prompts yields a training signal that cuts reasoning length roughly in half without hurting accuracy.

  5. R2-Router: A New Paradigm for LLM Routing with Reasoning

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    R2-Router jointly selects the LLM and an output-token budget, modeling each model as a quality-cost curve rather than a fixed point, and reports 4-5x cost savings on its new R2-Bench.

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    Interrupting large reasoning models or changing the problem mid-thought sharply degrades accuracy, with up to 60% drops and distinct failure modes: reasoning leakage, panic, and self-doubt.

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  10. AALC: Large Language Model Efficient Reasoning via Adaptive Accuracy-Length Control

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    AALC, an accuracy-aware length reward, reduces reasoning-model response length by over 50% on math benchmarks while preserving or improving accuracy.

  11. AdapThink: Adaptive Thinking Preferences for Reasoning Language Model

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  17. An Empirical Study of LLM Reasoning Ability Under Strict Output Length Constraint

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  19. Rethinking Chain-of-Thought from the Perspective of Self-Training

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  22. LISA: Linear-Indexed Sparse Attention for Efficient Long-Context Reasoning

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  23. REST: Stress Testing Large Reasoning Models by Asking Multiple Problems at Once

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    Asking a reasoning model several problems at once reveals large accuracy drops and exposes differences that single-question benchmarks miss.

  24. Reasoning on a Budget: A Survey of Adaptive and Controllable Test-Time Compute in LLMs

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  25. Prolonged Reasoning Is Not All You Need: Certainty-Based Adaptive Routing for Efficient LLM/MLLM Reasoning

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  26. Incorporating Token Usage into Prompting Strategy Evaluation

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  27. Towards Concise and Adaptive Thinking in Large Reasoning Models: A Survey

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