通过一致性强制提升扩散语言模型并行解码的可靠性
CForce: Boosting Parallel Decoding for dLLMs via Consistency Forcing

- 用早期与后期预测对齐的方法强制模型生成一致结果
- 在高并行解码下速度提升30%且生成质量不降
- 适用于普通生成和可编辑生成,适合追求高效推理的场景
扩散大语言模型(dLLMs)通过单次前向传播预测多个掩码来加速语言生成。然而,在激进的并行解码策略下,早期去噪阶段的预测可能不可靠,导致错误传播至后续阶段。为此,我们提出一致性强制(CForce),一种蒸馏方法,使早期阶段的掩码预测与后期阶段对齐。CForce 在预收集的自回滚轨迹上训练模型,增强训练与推理的一致性。我们引入置信度自适应KL散度作为蒸馏目标,结合正向与反向KL的优点。进一步提供理论分析说明为何CForce能近似最小化早期预测误差。该方法同时适用于掩码到词和可编辑解码;在可编辑场景中,后期的词到词精修为早期掩码状态提供额外监督。在非编辑与可编辑的LLaDA模型上的实验表明,该方法在高并行解码预算下显著改善了速度-质量权衡。代码已开源:https://github.com/inclusionAI/dFactory。
原文摘要 · Abstract (English)
Diffusion large language models (dLLMs) accelerate language generation by predicting multiple masks in a single forward pass. However, existing dLLMs can suffer from unreliable predictions in early denoising stages under aggressive parallelism strategies, leading to errors that can propagate to later stages. To tackle this issue, we present Consistency Forcing (CForce) for dLLMs, a distillation method to force the mask predictions of early stages to align with those of later stages. CForce trains the model on pre-collected self-rollout trajectories, thereby improving training-inference alignment. We introduce Confidence Adaptive KL Divergence as a distillation objective to conjoin the merits of forward and reverse KL. We further provide a theoretical analysis for the consistency objective to explain why CForce can approximately minimize the prediction error of early stages. Critically, the same formulation applies to both mask-to-token decoding and edit-capable decoding; in the edit-capable case, later token-to-token refinements provide additional supervision for earlier masked-state predictions. Experiments on non-edit and edit-capable LLaDA models show improved speed-quality trade-offs, especially under high-parallelism decoding budgets. Code is available at: https://github.com/inclusionAI/dFactory.
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