Research map / Reinforcement learning / Policy gradient and actor-critic
FASTER: Value-Guided Sampling for Fast RL
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Proposes FASTER, which models filtering of diffusion-policy action candidates during denoising as an MDP and learns a noise-level critic to pick one seed to denoise, recovering best-of-N gains at roughly single-rollout cost.
Problem
Best-of-N test-time scaling for diffusion/flow RL policies is effective but requires denoising all N action candidates, making training and inference prohibitively expensive, especially for large VLAs.
Approach
Model denoising of multiple action candidates plus selection as a filtering MDP over noise seeds; learn a noise-level critic Q^dn(s, eps) regressed to the action-level critic so only the top-scoring initial noise is denoised, collapsing the MDP to one step in practice.
Key results
- On the pi05_libero VLA, FASTER-EXPO cuts update step time from 11.6 s to 2.5 s (about 4.5x) and inference latency from 566 ms to 335 ms (1.7x) while matching EXPO success on most tasks.
- Inference FLOPs per step drop from 3.75e13 for EXPO to 4.70e12 for FASTER-EXPO, an 8x reduction.
- FASTER-EXPO and FASTER-IDQL achieve success rates within the margin of error of EXPO and IDQL with best-of-N sampling in the online setting on Robomimic tasks.
Surprising findings
- Filtering at the initial noise seed performs comparably to learning the full adaptive filtering MDP, suggesting the one-step simplification is a good proxy.
- Distilling the value-maximizing action into a single policy performs substantially worse than FASTER, attributed to non-stationary distillation targets.
Limitations
- Not designed to improve sample efficiency; FASTER-EXPO does not surpass EXPO in sample efficiency.
- Applies only to policy classes that use initial noise seeds, excluding policies without seed structure.
- VLA experiments use only 5 held-out LIBERO-90 tasks.
Experimental setup
Datasets: Robomimic LIBERO-90 LIBERO
Benchmarks: Robomimic Lift Robomimic Can Robomimic Square Robomimic Tool Hang LIBERO-90 held-out tasks
Metrics: success rate update step time inference latency FLOPs
Baselines: EXPO IDQL RLPD QSM DSRL QAM FQL pi05_libero
Builds on: EXPO IDQL DSRL
Closest papers by meaning
- Score Regularized Policy Optimization through Diffusion Behavior (ICLR 2024 · similarity 0.89)
- PRECISE: SDE-Consistent Stochastic Sampling for RL Post-Training of Flow-Matching Models (NeurIPS 2026 · similarity 0.88)
- Diffusion Policies Creating a Trust Region for Offline Reinforcement Learning (NeurIPS 2024 · similarity 0.88)
- Prior-Guided Diffusion Planning for Offline Reinforcement Learning (NeurIPS 2025 · similarity 0.88)
- Learning to Sample From Diffusion Models via Inverse Reinforcement Learning (NeurIPS 2026 · similarity 0.88)
- Efficient Online Reinforcement Learning for Diffusion Policy (ICML 2025 · similarity 0.88)
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