Yifan Song
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2025
The Good, The Bad, and The Greedy: Evaluation of LLMs Should Not Ignore Non-Determinism
Yifan Song | Guoyin Wang | Sujian Li | Bill Yuchen Lin
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Yifan Song | Guoyin Wang | Sujian Li | Bill Yuchen Lin
Proceedings of the 2025 Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics: Human Language Technologies (Volume 1: Long Papers)
Current evaluations of large language models (LLMs) often overlook non-determinism, typically focusing on a single output per example. This limits our understanding of LLM performance variability in real-world applications. Our study addresses this issue by exploring key questions about the performance differences between greedy decoding and sampling, identifying benchmarks’ consistency regarding non-determinism, and examining unique model behaviors. Through extensive experiments, we observe that greedy decoding generally outperforms sampling methods for most evaluated tasks. We also observe consistent performance across different LLM sizes and alignment methods, noting that alignment can reduce sampling variance. Moreover, our best-of-N sampling approach demonstrates that smaller LLMs can match or surpass larger models such as GPT-4-Turbo, highlighting the untapped potential of smaller LLMs. This research shows the importance of considering non-determinism in LLM evaluations and provides insights for future LLM development and evaluation.
More Tokens, Lower Precision: Towards the Optimal Token-Precision Trade-off in KV Cache Compression
Jiebin Zhang | Dawei Zhu | Yifan Song | Wenhao Wu | Chuqiao Kuang | Xiaoguang Li | Lifeng Shang | Qun Liu | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2025
Jiebin Zhang | Dawei Zhu | Yifan Song | Wenhao Wu | Chuqiao Kuang | Xiaoguang Li | Lifeng Shang | Qun Liu | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2025
As large language models (LLMs) process increasing context windows, the memory usage of KV cache has become a critical bottleneck during inference. The mainstream KV compression methods, including KV pruning and KV quantization, primarily focus on either token or precision dimensions separately. However, these works have left the trade-off between these two orthogonal dimensions largely unexplored. In this paper, we leverage the Information Bottleneck principle to formulate KV cache compression within a unified theoretical framework. We demonstrate that a carefully managed token-precision trade-off can achieve an optimal point within the Information Bottleneck compared to standalone KV pruning or KV quantization. Experiments reveal that storing more tokens in the KV cache at lower precision—a strategy we term quantized pruning—can significantly enhance the long-context performance of LLMs. An in-depth analysis of this token-precision trade-off across key aspects shows that quantized pruning achieves substantial improvements in retrieval-related tasks and consistently performs well across varying input lengths. Furthermore, quantized pruning exhibits notable stability and effectiveness across different KV pruning methods, quantization strategies, and model scales. These findings offer valuable insights into optimizing KV cache compression through balanced token-precision trade-off strategies. Our code is available at https://github.com/zhzihao/QPruningKV.
MPO: Boosting LLM Agents with Meta Plan Optimization
Weimin Xiong | Yifan Song | Qingxiu Dong | Bingchan Zhao | Feifan Song | XWang | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2025
Weimin Xiong | Yifan Song | Qingxiu Dong | Bingchan Zhao | Feifan Song | XWang | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2025
Recent advancements in large language models (LLMs) have enabled LLM-based agents to successfully tackle interactive planning tasks. However, despite their successes, existing approaches often suffer from planning hallucinations and require retraining for each new agent. To address these challenges, we propose the Meta Plan Optimization (MPO) framework, , which enhances agent planning capabilities by directly incorporating explicit guidance. Unlike previous methods that rely on complex knowledge, which either require significant human effort or lack quality assurance, MPO leverages high-level general guidance through meta plans to assist agent planning and enables continuous optimization of the meta plans based on feedback from the agent’s task execution. Our experiments conducted on two representative tasks demonstrate that MPO significantly outperforms existing baselines. Moreover, our analysis indicates that MPO provides a plug-and-play solution that enhances both task completion efficiency and generalization capabilities in previous unseen scenarios.
ISR: Self-Refining Referring Expressions for Entity Grounding
Zhuocheng Yu | Bingchan Zhao | Yifan Song | Sujian Li | Zhonghui He
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Zhuocheng Yu | Bingchan Zhao | Yifan Song | Sujian Li | Zhonghui He
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Entity grounding, a crucial task in constructing multimodal knowledge graphs, aims to align entities from knowledge graphs with their corresponding images. Unlike conventional visual grounding tasks that use referring expressions (REs) as inputs, entity grounding relies solely on entity names and types, presenting a significant challenge. To address this, we introduce a novel Iterative Self-Refinement (ISR) scheme to enhance the multimodal large language model’s capability to generate high quality REs for the given entities as explicit contextual clues. This training scheme, inspired by human learning dynamics and human annotation processes, enables the MLLM to iteratively generate and refine REs by learning from successes and failures, guided by outcome rewards from a visual grounding model. This iterative cycle of self-refinement avoids overfitting to fixed annotations and fosters continued improvement in referring expression generation. Extensive experiments demonstrate that our methods surpasses other methods in entity grounding, highlighting its effectiveness, robustness and potential for broader applications.
Hierarchical Memory Organization for Wikipedia Generation
Eugene J. Yu | Dawei Zhu | Yifan Song | Xiangyu Wong | Jiebin Zhang | Wenxuan Shi | Xiaoguang Li | Qun Liu | Sujian Li
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Eugene J. Yu | Dawei Zhu | Yifan Song | Xiangyu Wong | Jiebin Zhang | Wenxuan Shi | Xiaoguang Li | Qun Liu | Sujian Li
Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Generating Wikipedia articles autonomously is a challenging task requiring the integration of accurate, comprehensive, and well-structured information from diverse sources. This paper introduces the Memory Organization-based Generation (MOG) framework, a novel approach to address these challenges by leveraging a hierarchical memory architecture. MOG extracts fine-grained memory units from web documents, recursively organizes them into a Wikipedia-style hierarchical structure, and uses this structure to guide the generation process. This ensures alignment between memory and the article outline, improving both informativeness and verifiability while minimizing hallucinations. Additionally, a citation module is implemented to enhance traceability by linking every generated sentence to specific memory units. Evaluations on our newly created WikiStart dataset demonstrate that MOG outperforms baseline methods in producing informative and reliable articles, making it particularly robust in real-world scenarios.
2024
AgentBank: Towards Generalized LLM Agents via Fine-Tuning on 50000+ Interaction Trajectories
Yifan Song | Weimin Xiong | Xiutian Zhao | Dawei Zhu | Wenhao Wu | Ke Wang | Cheng Li | Wei Peng | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2024
Yifan Song | Weimin Xiong | Xiutian Zhao | Dawei Zhu | Wenhao Wu | Ke Wang | Cheng Li | Wei Peng | Sujian Li
Findings of the Association for Computational Linguistics: EMNLP 2024
Fine-tuning on agent-environment interaction trajectory data holds significant promise for surfacing generalized agent capabilities in open-source large language models (LLMs). In this work, we introduce AgentBank, by far the largest trajectory tuning data collection featuring more than 50k diverse high-quality interaction trajectories which comprises 16 tasks covering five distinct agent skill dimensions. Leveraging a novel annotation pipeline, we are able to scale the annotated trajectories and generate a trajectory dataset with minimized difficulty bias. Furthermore, we fine-tune LLMs on AgentBank to get a series of agent models, Samoyed. Our comparative experiments demonstrate the effectiveness of scaling the interaction trajectory data to acquire generalized agent capabilities. Additional studies also reveal some key observations regarding trajectory tuning and agent skill generalization.
Watch Every Step! LLM Agent Learning via Iterative Step-level Process Refinement
Weimin Xiong | Yifan Song | Xiutian Zhao | Wenhao Wu | Xun Wang | Ke Wang | Cheng Li | Wei Peng | Sujian Li
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Weimin Xiong | Yifan Song | Xiutian Zhao | Wenhao Wu | Xun Wang | Ke Wang | Cheng Li | Wei Peng | Sujian Li
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Large language model agents have exhibited exceptional performance across a range of complex interactive tasks. Recent approaches have utilized tuning with expert trajectories to enhance agent performance, yet they primarily concentrate on outcome rewards, which may lead to errors or suboptimal actions due to the absence of process supervision signals. In this paper, we introduce the Iterative step-level Process Refinement (IPR) framework, which provides detailed step-by-step guidance to enhance agent training. Specifically, we adopt the Monte Carlo method to estimate step-level rewards. During each iteration, the agent explores along the expert trajectory and generates new actions. These actions are then evaluated against the corresponding step of expert trajectory using step-level rewards. Such comparison helps identify discrepancies, yielding contrastive action pairs that serve as training data for the agent. Our experiments on three complex agent tasks demonstrate that our framework outperforms a variety of strong baselines. Moreover, our analytical finds highlight the effectiveness of IPR in augmenting action efficiency and its applicability to diverse models.
LongEmbed: Extending Embedding Models for Long Context Retrieval
Dawei Zhu | Liang Wang | Nan Yang | Yifan Song | Wenhao Wu | Furu Wei | Sujian Li
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Dawei Zhu | Liang Wang | Nan Yang | Yifan Song | Wenhao Wu | Furu Wei | Sujian Li
Proceedings of the 2024 Conference on Empirical Methods in Natural Language Processing
Embedding models play a pivotal role in modern NLP applications such as document retrieval. However, existing embedding models are limited to encoding short documents of typically 512 tokens, restrained from application scenarios requiring long inputs. This paper explores context window extension of existing embedding models, pushing their input length to a maximum of 32,768. We begin by evaluating the performance of existing embedding models using our newly constructed LongEmbed benchmark, which includes two synthetic and four real-world tasks, featuring documents of varying lengths and dispersed target information. The benchmarking results highlight huge opportunities for enhancement in current models. Via comprehensive experiments, we demonstrate that training-free context window extension strategies can effectively increase the input length of these models by several folds. Moreover, comparison of models using Absolute Position Encoding (APE) and Rotary Position Encoding (RoPE) reveals the superiority of RoPE-based embedding models in context window extension, offering empirical guidance for future models. Our benchmark, code and trained models will be released to advance the research in long context embedding models.