Dayiheng Liu

Structured pruning and knowledge distillation (KD) are typical techniques for compressing large language models, but it remains unclear how they should be applied at pretraining scale, especially to recent mixture-of-experts (MoE) models. In this work, we systematically study MoE compression in large-scale pretraining, focusing on three key questions: whether pruning provides a better initialization than training from scratch, how expert compression choices affect the final model after continued training, and which training strategy is most effective. We have the following findings: First, across depth, width, and expert compression, pruning a pretrained MoE consistently outperforms training the target architecture from scratch under the same training budget. Second, different one-shot expert compression methods converge to similar final performance after large-scale continual pretraining. Motivated by this, we introduce a simple partial-preservation expert merging strategy that improves downstream performance across most benchmarks. Third, combining KD with the language modeling loss outperforms KD alone, particularly on knowledge-intensive tasks. We further propose multi-token prediction (MTP) distillation, which yields consistent gains. Finally, given the same training tokens, progressive pruning schedules outperform one-shot compression, suggesting that gradual architecture transitions lead to better optimization trajectories. Putting it all together, we compress Qwen3-Next-80A3B to a 23A2B model that retains competitive performance. These results offer practical guidance for efficient MoE compression at scale.

We investigate the functional role of emergent outliers in large language models, specifically attention sinks (a few tokens that consistently receive large attention logits) and residual sinks (a few fixed dimensions with persistently large activations across most tokens). We hypothesize that these outliers, in conjunction with the corresponding normalizations (\textit{e.g.}, softmax attention and RMSNorm), effectively rescale other non-outlier components. We term this phenomenon \textit{outlier-driven rescaling} and validate this hypothesis across different model architectures and training token counts. This view unifies the origin and mitigation of both sink types. Our main conclusions and observations include: (1) Outliers function jointly with normalization: removing normalization eliminates the corresponding outliers but degrades training stability and performance; directly clipping outliers while retaining normalization leads to degradation, indicating that outlier-driven rescaling contributes to training stability. (2) Outliers serve more as rescale factors rather than contributors, as the final contributions of attention and residual sinks are significantly smaller than those of non-outliers. (3) Outliers can be absorbed into parameters or reduced by explicit gated rescaling, which in turn yield better training and quantization performance.

Inspired by the success of scaling language modeling through massive real-world corpora, we demonstrate that similar power-law patterns exist in preference modeling. We propose \textbf{World Preference Modeling (WorldPM)}, which model a robust consensus on intrinsic utility from real-world user interactions. We curate a 15M-scale preference dataset from online forum data and conduct large-scale experiments on models from 1.5B to 72B parameters. Across 10 objective preference test sets with consensus-based labels, we observe two distinct scaling patterns: (1) common-sense preference (e.g., identifying factual errors) exhibits stable log-linear improvement across all model sizes, while (2) domain preference (e.g., coding, math, knowledge QA) reveals an emergent phenomenon where only sufficiently large models achieve meaningful scaling. Through training dynamics analysis, we reveal the learning mechanism behind preference scaling: the model first learns to discriminate using surface preferences, but counter-surface examples progressively compel it to discover intrinsic utility beyond surface features as training scales. Further experiments validate WorldPM as an effective foundation for preference fine-tuning, broadly improving generalization across human preference datasets of varying sizes (7K, 100K, and 800K), with gains exceeding 5\% on many key subtasks.