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Latent Refinement Decoding: Enhancing Diffusion Language Models by Refining Belief States
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Proposes Latent Refinement Decoding (LRD), a two-stage training-free decoding scheme for diffusion LLMs that mixes [MASK] embeddings with entropy-weighted top-p token embeddings, then uses KL-based soft-to-hard scheduling and early stopping.
Problem
Parallel decoding in diffusion language models discards predictive distributions of non-finalized tokens (hard masking), causing information loss, premature commitment, and fixed iteration counts that waste compute.
Approach
Keep uncertain masked positions as soft mixtures of the [MASK] embedding and the top-p expected token embedding (weight set by normalized entropy), first refine these soft beliefs until KL-stable, then progressively commit confident tokens while keeping the rest soft, with KL-based early stopping.
Key results
- HumanEval +6.3 pass@1 for Dream-Base-7B at length 256 over baseline (50.6 to 56.9), with 1.2x speed.
- Dream-Ins-7B at length 1024 reaches 10.6x speedup on MBPP and 9.3x on HumanEval, with HumanEval +5.0 accuracy.
- GSM8K +2.9 (Dream-Base-7B, 256) and MATH500 +3.8 (Dream-Ins-7B, 1024) gains reported.
Surprising findings
- Removing early stopping drops speed far below baseline (e.g., 0.8x) while token counts barely change, so early stopping is the main speed driver.
- Mixing a very small fraction of tokens (top-p up to about 0.2) already yields most of the accuracy gain, and full mixing (r_f=1) collapses the model.
Limitations
- Stability analysis is only local (single self-attention layer) and no global convergence guarantee is provided.
- Speedups vary widely across settings; some configurations (e.g., Dream-Ins MATH500 at 1.1-1.2x) show modest gains, and speed is measured as relative runtime.
- Results rely on hyperparameters (r_f, top-p, thresholds) tuned per setting; evaluation limited to LLaDA and Dream 7-8B models and four benchmarks.
Experimental setup
Datasets: GSM8K MATH500 MBPP HumanEval
Benchmarks: HumanEval MBPP GSM8K MATH500
Metrics: accuracy pass@1 relative speed effective token number
Baselines: LLaDA hard-masking decoding Dream hard-masking decoding
Builds on: LLaDA Dream Fast-dLLM
Closest papers by meaning
- Beyond Confidence: Adaptive and Coherent Decoding for Diffusion Language Models (ICML 2026 · similarity 0.91)
- Fast and Fluent Diffusion Language Models via Convolutional Decoding and Rejective Fine-tuning (NeurIPS 2025 · similarity 0.91)
- Mean-Field Parallel Decoding for Discrete Diffusion Language Models (NeurIPS 2026 · similarity 0.90)
- From Next-Token to Next-Block: A Principled Adaptation Path for Diffusion LLMs (NeurIPS 2026 · similarity 0.90)
- Confidence-Based Decoding is Provably Efficient for Diffusion Language Models (NeurIPS 2026 · similarity 0.89)
- Breaking AR’s Sampling Bottleneck: Provable Acceleration via Diffusion Language Models (NeurIPS 2025 · similarity 0.89)
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