Chang Xu
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2026
Ban&Pick: Enhancing Performance and Efficiency of MoE-LLMs via Smarter Routing
Yuanteng Chen | Peisong Wang | Yuantian Shao | Nanxin Zeng | Chang Xu | Jian Cheng
Findings of the Association for Computational Linguistics: EMNLP 2026
Yuanteng Chen | Peisong Wang | Yuantian Shao | Nanxin Zeng | Chang Xu | Jian Cheng
Findings of the Association for Computational Linguistics: EMNLP 2026
Mixture-of-Experts (MoE) has become a key architecture for scaling large language models. Recent fine-grained MoE designs introduce hundreds of experts per layer, with multiple experts activated per token, enabling stronger specialization. However, during pre-training, routers are optimized mainly for stability and robustness: they converge prematurely and enforce balanced usage, limiting the full potential of model performance and efficiency at inference. In this work, we uncover two overlooked issues: (i) a few highly influential experts are underutilized due to premature and balanced routing decisions; and (ii) enforcing a fixed number of active experts per token introduces substantial redundancy. Instead of retraining or redesigning MoE architectures, we introduce Ban Pick, a training-free, plug-and-play strategy for smarter routing. Pick discovers and reinforces key experts, a small group with outsized impact on performance, leading to notable accuracy gains. Ban further dynamically prunes redundant experts based on layer and token sensitivity, delivering faster inference. Experiments on fine-grained MoE-LLMs (DeepSeek, Qwen3) across math, code, and general reasoning benchmarks demonstrate that Ban Pick delivers free performance gains and inference acceleration. For instance, on Qwen3-30B-A3B, it improves accuracy from 80.67 to 84.66 on AIME2024 and from 65.66 to 68.18 on GPQA-Diamond, while accelerating inference by 1.25× under the vLLM.
Mitigating Legal Hallucinations via Symbolic Constraints and Analogical Precedents
Zixuan Huang | Yanxiang Ma | Luhan Wang | Yunke Wang | Duo Shi | Chang Xu
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Zixuan Huang | Yanxiang Ma | Luhan Wang | Yunke Wang | Duo Shi | Chang Xu
Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
With the growing potential of large language models (LLMs) in the legal domain, domain-specific finetuning and retrieval-augmented generation (RAG) methods have received widespread attention. However, current methods still suffer from hallucination risk and failing to resolve semantic drift and adapt to varying citation numbers. To address this, we propose Authoritative and Accurate Lawyer (AALawyer), a complementary dual-retriever framework based on the Legal Syllogism and the nature of different legal data. First, we introduce Symbolic Constrained Retrieval (SCR) for closed-set article retrieval, by constraining retrieval to the generative prediction. Second, we build Analogical Precedent Retrieval (APR) to retrieve open-set judicial precedents for reasoning with a newly collected large criminal dataset.Extensive experiments, including LawBench, our Hallucination Risk-Benchmark, and comprehensive ablation studies, demonstrate the effectiveness of AALawyer, which mitigates hallucinations while improving the explainability of legal reasoning.
2025
CollagePrompt: A Benchmark for Budget-Friendly Visual Recognition with GPT-4V
Siyu Xu | Yunke Wang | Daochang Liu | Bo Du | Chang Xu
Findings of the Association for Computational Linguistics: NAACL 2025
Siyu Xu | Yunke Wang | Daochang Liu | Bo Du | Chang Xu
Findings of the Association for Computational Linguistics: NAACL 2025
ThoughtProbe: Classifier-Guided LLM Thought Space Exploration via Probing Representations
Zijian Wang | Chang Xu
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
Zijian Wang | Chang Xu
Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
This paper introduces ThoughtProbe, a novel inference-time framework that leverages the hidden reasoning features of Large Language Models (LLMs) to improve their reasoning performance. Unlike previous works that manipulate the hidden representations to steer LLM generation, we harness them as discriminative signals to guide the tree-structured response space exploration. In each node expansion, a classifier serves as a scoring and ranking mechanism that efficiently allocates computational resources by prioritizing higher score candidates for continuation. After completing the tree expansion, we collect answers from all branches to form a candidate answer pool. We then propose a branch-aggregation method that marginalizes over all supporting branches by aggregating their CoT scores, thereby identifying the optimal answer from the pool. Experimental results show that our framework’s comprehensive exploration not only covers valid reasoning chains but also effectively identifies them, achieving significant improvements across multiple arithmetic reasoning benchmarks.
2024
Locating and Extracting Relational Concepts in Large Language Models
Zijian Wang | Britney Whyte | Chang Xu
Findings of the Association for Computational Linguistics: ACL 2024
Zijian Wang | Britney Whyte | Chang Xu
Findings of the Association for Computational Linguistics: ACL 2024
Relational concepts are indeed foundational to the structure of knowledge representation, as they facilitate the association between various entity concepts, allowing us to express and comprehend complex world knowledge.By expressing relational concepts in natural language prompts, people can effortlessly interact with large language models (LLMs) and recall desired factual knowledge. However, the process of knowledge recall lacks interpretability, and representations of relational concepts within LLMs remain unknown to us. In this paper, we identify hidden states that can express entity and relational concepts through causal mediation analysis in fact recall processes. Our finding reveals that at the last token position of the input prompt, there are hidden states that solely express the causal effects of relational concepts. Based on this finding, we assume that these hidden states can be treated as relational representations and we can successfully extract them from LLMs. The experimental results demonstrate high credibility of the relational representations: they can be flexibly transplanted into other fact recall processes, and can also be used as robust entity connectors. Moreover, we also show that the relational representations exhibit significant potential for controllable fact recall through relation rewriting.