Adaptive Test-Time Compute Allocation for Block Diffusion Language Models in Complex Reasoning

Yi Lu, Deyang Kong, Jianing Wang, Linsen Guo, Xue Wang, Qi Guo, Tao Gui, Xuanjing Huang, Wei Ye, Shikun Zhang, Wei Wang


Abstract
Recent advances in block diffusion language models have demonstrated competitive performance and strong scalability on reasoning tasks. However, their test-time compute allocation remains largely unexplored, leaving a critical speed-effectiveness trade-off unresolved in long Chain-of-Thought reasoning. To address this, we propose a unified test-time compute allocation framework that introduces adaptivity in both step-wise decoding and blockwise generation. At the decoding level, we propose Bounded Adaptive Confidence Decoding (BACD), a difficulty-aware sampling strategy that dynamically adjusts denoising based on model confidence, accelerating inference while controlling error accumulation. Beyond step-wise adaptivity, we introduce the Think Coarse, Critic Fine (TCCF) paradigm that allocates large block sizes for exploratory thinking and smaller block sizes for precise refinement. To stabilize training under varying block configurations, we adopt Progressive Block Size Extension, which mitigates quality degradation when scaling up block sizes. Extensive evaluations on six benchmarks show that our TDAR-8B model with BACD and TCCF achieves a 2.38 speedup and +3.4% average accuracy over the strong TraDo-8B baseline, unlocking the potential of block diffusion in complex reasoning.
Anthology ID:
2026.findings-emnlp.1774
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
37952–37967
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URL:
https://aclanthology.org/2026.findings-emnlp.1774/
DOI:
Bibkey:
Cite (ACL):
Yi Lu, Deyang Kong, Jianing Wang, Linsen Guo, Xue Wang, Qi Guo, Tao Gui, Xuanjing Huang, Wei Ye, Shikun Zhang, and Wei Wang. 2026. Adaptive Test-Time Compute Allocation for Block Diffusion Language Models in Complex Reasoning. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 37952–37967, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Adaptive Test-Time Compute Allocation for Block Diffusion Language Models in Complex Reasoning (Lu et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1774.pdf