ALoDLM: Adaptively Looped Diffusion Language Models

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扩散语言模型(DLM)通过并行预测多个词元实现快速生成,但其实际应用仍受限于与同规模自回归(AR)模型相比持续存在的生成质量差距。我们认为,这一差距源于“计算量-预测难度”之间的不匹配:在部分已观测到的序列中,某些待预测词元本身易于推断,而另一些则需要显著更高的计算开销。然而,现有DLM在每次去噪步骤中,对所有待预测位置均施加统一的计算深度。为此,我们提出ALoDLM(Adaptive Latent Diffusion Language Model,自适应隐状态扩散语言模型),以词元自适应的隐状态循环机制取代固定不变的计算分配策略。在每次去噪过程中,ALoDLM迭代地更新隐状态表征,并依据各词元的预测难度动态分配计算资源:对于已具备足够置信度、可确定输出的词元,将其以离散化形式反馈为上下文;而对于尚未充分收敛的词元,则保留其当前隐状态,并通过额外的循环迭代进一步精炼。为联合学习词元预测与计算资源分配策略,我们将逐词元的计算调度建模为隐变量,并推导出一种条件负证据下界(Conditional Negative Evidence Lower Bound, NELBO)作为优化目标。我们在1.7B和8B两种参数规模上训练了ALoDLM。在涵盖十一项基准任务的全面评估中,ALoDLM在两个规模下均超越了所有参与对比的扩散模型以及对应规模的自回归基线模型,在平均基准得分上表现最优。此外,ALoDLM仍保持快速的并行解码能力,在经优化的推理引擎支持下,其在生成质量与推理效率之间的权衡表现,优于所有参与对比的自回归模型与扩散模型。
Diffusion language models (DLMs) enable fast generation by predicting multiple tokens in parallel, but their practical adoption remains limited by a persistent quality gap relative to comparably sized autoregressive (AR) models. We attribute this gap to a computation-difficulty mismatch: within a partially observed sequence, some unknown tokens are easy to predict, while others require substantially more computation. Existing DLMs nevertheless apply uniform computational depth to all unknown positions at each denoising step. We introduce ALoDLM, which replaces uniform computation with token-adaptive latent recurrence. At each denoising step, ALoDLM iteratively refines latent representations and allocates computation according to token difficulty. Tokens ready to commit are fed back as discrete context, while unresolved tokens retain and further refine their latent states through additional recurrent passes. To learn token prediction and computation allocation jointly, we formulate token-wise computation schedules as latent variables and derive a conditional negative evidence lower bound (NELBO). We train ALoDLM at 1.7B and 8B parameter scales. Across eleven benchmarks, ALoDLM outperforms all evaluated DLMs and the corresponding AR baselines in average benchmark score at both scales. ALoDLM also retains fast parallel decoding, yielding a strong quality-efficiency trade-off among evaluated autoregressive and diffusion models under optimized inference engines.