Token-Budget-Aware LLM Reasoning
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "arXiv — non-exclusive license to distribute" does not allow redistributing the text itself. Original — arxiv.org/pdf/2412.18547
Summary
Chain-of-Thought prompting improves LLM accuracy, but the long intermediate reasoning it produces raises inference cost and latency. The authors show that much of this text is redundant: a CoT prompt can state a token limit, and the model shortens its answer accordingly. The size of that limit matters, though. When the budget is very tight, models tend to ignore it and can produce more tokens than they would under a looser one. The authors call this effect "Token Elasticity."
To address it, they first search for the smallest budget that still gives a correct and short answer. They then build TALE, which has two variants:
- TALE-EP has the model estimate a suitable budget for each question with zero-shot prompting.
- TALE-PT uses post-training (SFT or DPO) so the model writes compact reasoning without an explicit limit in the prompt.
Across seven benchmarks, TALE-EP cuts output tokens by roughly two thirds with only a small loss in accuracy. TALE-PT roughly halves token use on Llama-3.1-8B-Instruct. Together, the results offer a practical way to make LLM reasoning cheaper.
Key points
- On a GPT-4o-mini example, vanilla CoT used 258 output tokens. A 50-token budget brought this down to 86, while a 10-token budget produced 157. This is the "Token Elasticity" effect.
- TALE-EP averaged 81.03% accuracy against 83.75% for Vanilla CoT. It reduced output tokens to about 32% and expense to about 41% of the CoT level. On GSM8K it reached 84.46%, slightly above CoT.
- On MathBench-College, TALE-EP was tested with Yi-lightning, GPT-4o-mini, GPT-4o and o3-mini. It lowered output tokens by about 64.6% and costs by about 45.3% on average. GPT-4o-mini lost the most accuracy.
- TALE-PT on Llama-3.1-8B-Instruct, GSM8K: the SFT variant scored 78.57% with about 140 tokens, compared with 77.56% and about 242 tokens for Vanilla CoT. On GSM8K-Zero, the DPO variant used over 50% fewer tokens than CoT.
- Code is released as TALE on GitHub (GeniusHTX/TALE). The method is currently limited to text-only models.
Cited by
- Do NOT Think That Much for 2+3=? On the Overthinking of o1-Like LLMs
- Towards Reasoning Era: A Survey of Long Chain-of-Thought for Reasoning Large Language Models
- Stop Overthinking: A Survey on Efficient Reasoning for Large Language Models
Cite
@misc{han2024token,
title = {{Token-Budget-Aware LLM Reasoning}},
author = {Han, Tingxu and Wang, Zhenting and Fang, Chunrong and Zhao, Shiyu and Ma, Shiqing and Chen, Zhenyu},
year = {2024},
doi = {10.48550/arxiv.2412.18547},
eprint = {2412.18547},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.2412.18547}
}References
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