Title: ProcessLID: Step-wise Internal Reward in LLM Reasoning via Local Intrinsic Dimension
Primary area: foundation or frontier models, including LLMs
Keywords: Large Language Model, Mathematical Reasoning, Intrinsic Dimension

Abstract: Accurate step-level correctness signals are key to reliable LLM mathematical reasoning. Prior work either invokes external judges or Process Reward Models at inference time, incurring heavy compute, or leverages internal representations but yields outcome-level signals without step-wise granularity. We introduce $\mathbf{ProcessLID}$, a training-free, representation-based method grounded in local intrinsic dimension that produces step-level correctness signals. Across six models on four math benchmarks, ProcessLID attains the state-of-the-art step-level and outcome-level performance and remains competitive in inference-time settings. Lastly, we provide analyses explaining the effectiveness of our methodology.

TL;DR: We propose a process-level, internal signal to detect correctness in LLM reasoning trajectory. The method achieved state-of-the-art performance across six models and four mathematical datasets compared to existing methods.