Xiwen Chen
Author directory2026
CE-GAD: Curriculum-Efficient On-Policy Adversarial Distillation of Large Language Models
Wenhui Zhu | Hejian Sang | Xiwen Chen | Zhipeng Wang | Shayan Mohajer Hamidi | Han Yu | Jingjing Wang | Yuanda Xu | Xuanzhao Dong | Zhengze Zhou | Ran He | Jelena Markovic-Voronov | Kayhan Behdin | Sayan Ghosh | Alborz Geramifard
Findings of the Association for Computational Linguistics: EMNLP 2026
Wenhui Zhu | Hejian Sang | Xiwen Chen | Zhipeng Wang | Shayan Mohajer Hamidi | Han Yu | Jingjing Wang | Yuanda Xu | Xuanzhao Dong | Zhengze Zhou | Ran He | Jelena Markovic-Voronov | Kayhan Behdin | Sayan Ghosh | Alborz Geramifard
Findings of the Association for Computational Linguistics: EMNLP 2026
Generative adversarial distillation (GAD) provides on-policy feedback for black-box distillation by training a discriminator that ranks teacher and student responses to the same prompt. While effective, GAD is also costly: every step pays for a discriminator update, an actor update over the full response, and the indirect cost of recovering whenever the discriminator and the actor progress at incompatible rates. We argue that the right way to make GAD efficient is not to make individual updates cheaper but to decide **when each update is worth its cost**. We introduce **curriculum-efficient GAD (CE-GAD)**, an adaptive recipe that monitors a small set of training signals and uses them to:
- (i) skip discriminator updates that would not change the reward, - (ii) constrain actor updates and prune per-token gradients to the subset that actually carries signal, and - (iii) rescale rewards and normalize advantages to preserve within-batch contrast under saturation.
Evaluations across four models from two open-source families (Qwen2.5 at 3B/7B/14B and Llama-3.2-3B) demonstrate that CE-GAD matches or surpasses vanilla GAD on quality while winning on 12 out of 16 individual benchmark configurations. Specifically, on Qwen2.5-7B, CE-GAD improves the average score by up to **+3%** relative compared to the base model, while reducing per-step wall-clock time by up to **8x** relative to vanilla GAD.
- (i) skip discriminator updates that would not change the reward, - (ii) constrain actor updates and prune per-token gradients to the subset that actually carries signal, and - (iii) rescale rewards and normalize advantages to preserve within-batch contrast under saturation.
Evaluations across four models from two open-source families (Qwen2.5 at 3B/7B/14B and Llama-3.2-3B) demonstrate that CE-GAD matches or surpasses vanilla GAD on quality while winning on 12 out of 16 individual benchmark configurations. Specifically, on Qwen2.5-7B, CE-GAD improves the average score by up to **+3%** relative compared to the base model, while reducing per-step wall-clock time by up to **8x** relative to vanilla GAD.
DRA-GRPO: Your GRPO Needs to Know Diverse Reasoning Paths for Mathematical Reasoning
Xiwen Chen | Wenhui Zhu | Peijie Qiu | Xuanzhao Dong | Hao Wang | Haiyu Wu | Huayu Li | Aris Sotiras | Yalin Wang | Abolfazl Razi
Findings of the Association for Computational Linguistics: ACL 2026
Xiwen Chen | Wenhui Zhu | Peijie Qiu | Xuanzhao Dong | Hao Wang | Haiyu Wu | Huayu Li | Aris Sotiras | Yalin Wang | Abolfazl Razi
Findings of the Association for Computational Linguistics: ACL 2026
Post-training LLMs with Reinforcement Learning, specifically Group Relative Policy Optimization (GRPO), has emerged as a paradigm for enhancing mathematical reasoning. However, standard GRPO relies on scalar correctness rewards that are often non-injective with respect to semantic content: distinct reasoning paths receive identical rewards. This leads to a Diversity-Quality Inconsistency, where the policy collapses into a narrow set of dominant modes while ignoring equally valid but structurally novel strategies.To bridge this gap, we propose Diversity-aware Reward Adjustment (DRA), a theoretically grounded framework that calibrates the reward signal using the semantic density of sampled groups. By leveraging Submodular Mutual Information (SMI), DRA implements an Inverse Propensity Scoring (IPS) mechanism that effectively de-biases the gradient estimation. This creates a repulsive force against redundancy, driving the policy to achieve better coverage of the high-reward landscape.Our method is plug-and-play and integrates seamlessly with GRPO variants. Empirical evaluations on five math benchmarks demonstrate that DRA-GRPO consistently outperforms strong baselines, achieving an average accuracy of 58.2% on DeepSeek-R1-Distill-Qwen-1.5B with only 7,000 training samples and 55 cost, highlighting the critical role of diversity calibration in data-efficient alignment.
AHA: Aligning Large Audio-Language Models for Reasoning Hallucinations via Counterfactual Hard Negatives
Yanxi Chen | Wenhui Zhu | Xiwen Chen | Zhipeng Wang | Xin Li | Peijie Qiu | Hao Wang | Xuanzhao Dong | Yujian Xiong | Anderson Schneider | Yuriy Nevmyvaka | Yalin Wang
Findings of the Association for Computational Linguistics: ACL 2026
Yanxi Chen | Wenhui Zhu | Xiwen Chen | Zhipeng Wang | Xin Li | Peijie Qiu | Hao Wang | Xuanzhao Dong | Yujian Xiong | Anderson Schneider | Yuriy Nevmyvaka | Yalin Wang
Findings of the Association for Computational Linguistics: ACL 2026
Although Large Audio-Language Models (LALMs) deliver state-of-the-art (SOTA) performance, they frequently suffer from hallucinations, e.g., generating text not grounded in the audio input. We analyze these grounding failures and identify a distinct taxonomy: Event Omission, False Event Identity, Temporal Relation Error, and Quantitative Temporal Error. To address this, we introduce the AHA (Audio Hallucination Alignment) framework. By leveraging counterfactual hard negative mining, our pipeline constructs a high-quality preference dataset that forces models to distinguish strict acoustic evidence from linguistically plausible fabrications. Additionally, we establish AHA-Eval, a diagnostic benchmark designed to rigorously test these fine-grained reasoning capabilities. We apply this data to align Qwen2.5-Omni. The resulting model, Qwen-Audio-AHA, achieves a 13.7% improvement on AHA-Eval. Crucially, this benefit generalizes beyond our diagnostic set. Our model shows substantial gains on public benchmarks, including 1.3% on MMAU-Test and 1.6% on MMAR, outperforming latest SOTA methods.