Research map / Large language models / Reasoning and chain of thought
Re-FORC: Adaptive Reward Prediction for Efficient Chain-of-Thought Reasoning
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Re-FORC trains lightweight Beta-distribution adapters on frozen Qwen3 reasoning models to forecast expected reward as a function of additional thinking tokens, and uses a Gittins-index / Pandora's box greedy policy for early stopping, model selection, and test-time scaling.
Problem
Determining how much inference-time reasoning compute to spend on a given query, and when to stop or switch models, requires knowing the marginal reward gain from additional thinking tokens, which current models do not predict.
Approach
Learn a forecaster on frozen reasoning-model hidden states that outputs Beta distributions over expected reward for a grid of future thinking-token budgets, then plug these forecasts into a Gittins-index / Pandora's box greedy policy with a per-token cost λ to decide when to stop, which model to use, and whether to sample again.
Key results
- Early stopping reduces compute by 26% on average vs. S1 for the Qwen3 4B model while preserving accuracy (abstract states up to 24-26% depending on version).
- Model selection with Re-FORC Pandora reaches 1.7 pp higher peak accuracy than All-8B while needing up to 12% less compute to match its accuracy.
- At peak compute, Re-FORC improves over the strongest DeepConf variant by 13.9 pp on 1.7B, 8.4 pp on 4B, and 7.5 pp on 8B.
Surprising findings
- The forecaster is occasionally overconfident, predicting higher rewards than the base model achieves, which leads to wasteful continued sampling.
Limitations
- Collecting forecaster training data is computationally expensive, requiring multiple trajectories per query at many length intervals.
- Forecaster occasionally overconfident, causing wasteful sampling instead of early termination.
- Evaluated only on math reasoning benchmarks with Qwen3 models up to 8B.
Experimental setup
Datasets: DeepScaleR-Preview AMC 2024 MATH500 AIME 2024 AIME 2025
Benchmarks: AMC 2024 MATH500 AIME 2024 AIME 2025
Metrics: Pearson correlation mean squared error mean absolute error accuracy vs. tokens accuracy vs. compute (TFLOPs)
Baselines: S1 DeepConf majority voting Avg-of-k Pass@k All 1.7B All 4B All 8B
Builds on: Pandora's box problem Gittins index policy S1 DeepConf
Closest papers by meaning
- DeepCompress: A Dual Reward Strategy for Dynamically Exploring and Compressing Reasoning Chains (ICLR 2026 · similarity 0.89)
- Reward Reasoning Models (NeurIPS 2025 · similarity 0.88)
- Fixing the Broken Compass: Diagnosing and Improving Inference-Time Reward Modeling (ICLR 2026 · similarity 0.88)
- RM-R1: Reward Modeling as Reasoning (ICLR 2026 · similarity 0.87)
- What If We Allocate Test-Time Compute Adaptively? (ICML 2026 · similarity 0.87)
- PEAR: Phase Entropy Aware Reward for Efficient Reasoning (ICLR 2026 · similarity 0.87)
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