Apple Machine Learning Research1 min readpaperadvanced
DACA-GRPO: Denoising-Aware Credit Assignment for Reinforcement Learning in Diffusion Language Models
Summary
DACA‑GRPO adds denoising‑aware credit assignment to GRPO‑style RL trainers for diffusion LLMs. It computes per‑token importance scores from intermediate denoising steps and uses stratified masking to reduce mean‑field bias in likelihood estimates. Plug‑and‑play on three existing GRPO methods, it yields consistent gains on seven downstream tasks (up to +5.6 pp math, +7.4 pp code, +36.3 pp constrai…
- Existing RL for diffusion LLMs treats every denoising step equally and relies on biased, high‑variance mean‑field likelihood estimates.
- DACA‑GRPO introduces two orthogonal mechanisms:
- • Denoising Progress Scores: extract token‑level importance weights from intermediate predictions without extra forward passes.
- • Stratified Masking Likelihood: partition token positions into strata so each token sees most of the sequence as context, cutting the mean‑field bias.
Temporal credit assignment is a known gap in diffusion‑based RL; DACA‑GRPO provides a practical, low‑overhead solution that directly improves downstream task performance, suggesting a new direction for training diffusion LLMs with RL.
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