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Attention-Based Sampler for Diffusion Language Models
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Proposes Attn-Sampler, a training-free dLLM sampling-order method that decodes masked tokens in descending attention column-sum order, with dynamic attention thresholding for parallel decoding.
Problem
Choosing the token sampling order in diffusion LLMs to maximize target sequence log-likelihood; existing samplers (confidence, margin, entropy, thresholding, top-k) are token-level greedy heuristics without theoretical grounding.
Approach
Frames order selection as minimizing a permutation dependency gap, shows NP-hardness via weighted linear ordering, replaces it with a rank-based expected approximation, and proves the tractable bound is minimized by decoding in descending total attention (attention column sum) order; adds a dynamic attention threshold for parallel decoding.
Key results
- Attn-Sampler (Sequential) reaches 57.67% average on Fast-dLLM v2 7B, versus 54.66% for the top confidence sampler and 56.57% for the entropy sampler.
- On LLaDA-1.5 8B, Attn-Sampler (Sequential) averages 52.84% versus 50.98% for confidence sampling.
- On GSM8K with Fast-dLLM v2 7B, Attn-Sampler achieves 84.2% accuracy at 95 TPS, while Fast-dLLM gets 82.1% at the same throughput.
Surprising findings
- Static or top-k attention-based parallelization degrades accuracy sharply at higher parallelism (top-k accuracy falls from 81.12 to 65.35 as throughput rises from 67 to 124 TPS).
Limitations
- Cannot be directly extended to uniform diffusion, as the optimal permutation relies on one-pass decoding of masked dLLMs.
- Theoretical bound relies on first-order approximations and assumptions that rarely hold exactly in practice, as the authors acknowledge.
- Evaluated only on four benchmarks and three dLLMs; no error bars reported.
Experimental setup
Datasets: GSM8K MATH HumanEval MBPP
Benchmarks: GSM8K MATH HumanEval MBPP
Metrics: accuracy tokens per second (TPS)
Baselines: top-1 confidence sampler top-1 margin sampler top-1 entropy sampler Fast-dLLM EB-Sampler KLASS
Builds on: Fast-dLLM KLASS EB-Sampler LLaDA
Closest papers by meaning
- Breaking AR’s Sampling Bottleneck: Provable Acceleration via Diffusion Language Models (NeurIPS 2025 · similarity 0.91)
- Attention-Discounted Adaptive Sampler for Masked Diffusion Language Models (NeurIPS 2026 · similarity 0.89)
- Scaling Diffusion Language Models via Adaptation from Autoregressive Models (ICLR 2025 · similarity 0.89)
- Free Lunch for Pass@$k$? Low Cost Diverse Sampling for Diffusion Language Models (NeurIPS 2026 · similarity 0.89)
- Fast and Fluent Diffusion Language Models via Convolutional Decoding and Rejective Fine-tuning (NeurIPS 2025 · similarity 0.88)
- Theoretical Benefit and Limitation of Diffusion Language Model (NeurIPS 2025 · similarity 0.88)
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