Research map / Large language models / Reasoning and chain of thought
A State-Transition Framework for Efficient LLM Reasoning
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Models long CoT as a state-transition process by replacing most softmax attention with a linear-attention reasoning-state module (mixed attention) plus a momentum-based state correction, cutting attention cost and KV-cache while keeping accuracy.
Problem
Long chain-of-thought generation is costly in computation and KV-cache memory, and existing CoT compression methods trade away reasoning accuracy.
Approach
Each reasoning step is generated attending only to the prompt and its own step via softmax attention, while a linear-attention state matrix carries compressed information from completed steps; a momentum-averaged global reasoning direction corrects noisy step updates. Attention cost becomes linear and KV-cache constant per step, without shortening the CoT.
Key results
- On Qwen2.5-1.5B, the method averages 56.2 accuracy across five math benchmarks versus 51.5 for the base model, with average reasoning latency 253.0 vs 300.0 (ms-scale per sample as reported).
- On Qwen2.5-7B, average accuracy rises to 68.3 from 65.9 for the base model, with latency 263.3 vs 314.2.
- Ablation removing the model reasoning state (replaced by a sliding window of 64) yields the largest drop, to 46.8 average accuracy.
Surprising findings
- The method improves accuracy over the full-attention base model while also reducing latency, despite replacing most attention with linear attention.
- Removing low-process-reward steps (under 20%) by a cosine-based score improved performance, suggesting the state carries step-quality signal.
Limitations
- Results reported with greedy decoding; gains shrink or vary under sampling and the authors note hyperparameters tuned mainly on 1.5B.
- Reasoning-step segmentation and thinking-type annotation rely on heuristic high-entropy tokens and K-means clustering rather than human or LLM annotation.
- Efficiency gains are reported only for FlashAttention-2 setting at batch size 1 on a single A100.
Experimental setup
Datasets: OpenR1-Math-220K
Benchmarks: GSM8K MATH-500 AMC23 AIME24 AIME25 GPQA_Diamond HumanEval
Metrics: accuracy token number reasoning latency
Baselines: H2O SepLLM LightThinker INFTYTHINK TAMM SBT-D L1-Max AR
Builds on: Qwen2.5 DeepSeek-R1 linear attention test-time training view of linear attention LightThinker INFTYTHINK LoRA
Closest papers by meaning
- Dynamic Early Exit in Reasoning Models (ICLR 2026 · similarity 0.93)
- Training Language Models to Reason Efficiently (NeurIPS 2025 · similarity 0.91)
- Bag of Tricks for Inference-time Computation of LLM Reasoning (NeurIPS 2025 · similarity 0.91)
- Forest-of-Thought: Scaling Test-Time Compute for Enhancing LLM Reasoning (ICML 2025 · similarity 0.91)
- Towards Thinking-Optimal Scaling of Test-Time Compute for LLM Reasoning (NeurIPS 2025 · similarity 0.90)
- Think Deep, Not Just Long: Measuring LLM Reasoning Effort via Deep-Thinking Tokens (ICML 2026 · similarity 0.90)
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