KLASS: KL-Guided Fast Inference in Masked Diffusion Models
Authors: name: Seo Hyun Kim; name: Sunwoo Hong; name: Hojung Jung; name: Youngrok Park; name: Se-Young Yun
Published: 2025-11-07 19:05:36

Abstract: Masked diffusion models have demonstrated competitive results on various
tasks including language generation. However, due to its iterative refinement
process, the inference is often bottlenecked by slow and static sampling speed.
To overcome this problem, we introduce `KL-Adaptive Stability Sampling'
(KLASS), a fast yet effective sampling method that exploits token-level KL
divergence to identify stable, high-confidence predictions. By unmasking
multiple tokens in each iteration without any additional model training, our
approach speeds up generation significantly while maintaining sample quality.
On reasoning benchmarks, KLASS achieves up to 2.78times wall-clock speedups
while improving performance over standard greedy decoding, attaining
state-of-the-art results among diffusion-based samplers. We further validate
KLASS across diverse domains, including text, image, and molecular generation,
showing its effectiveness as a broadly applicable sampler across different
models.