Hello everyone, my name is Siheng Xiong. I am currently a final-year Ph.D. student in Machine Learning at the Georgia Institute of Technology, advised by Prof. Faramarz Fekri. Prior to this, I earned my Bachelor’s degree from Xi’an Jiaotong University and my Master’s degree from Shanghai Jiao Tong University.

My research focuses on post-training large language models for deliberate reasoning and planning, emphasizing model-based reasoning, long-context modelling, and process-level supervision.

🚀 Featured Projects

Large Language Models for Reasoning and Planning

Preprint 2026
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Scaling Search-Augmented Reasoning Agents via Adaptive Information Control
Siheng Xiong, Oguzhan Gungordu, Blair Johnson, James C. Kerce, Faramarz Fekri

Project

DeepControl is an adaptive framework that optimizes information retrieval and expansion based on an agent’s reasoning state, enhancing performance across various benchmarks.

Preprint 2026
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Planning through World Model for Automated Heuristic Design via Self-Evolving LLMs
Oguzhan Gungordu, Siheng Xiong, Faramarz Fekri

Project

PathWise is a multi-agent framework that uses stateful memory and evolutionary actions to guide automated heuristic design, enabling structured reasoning, reuse of prior derivations, and controlled self-evolution of LLM-generated heuristics.

ICLR 2026
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Enhancing Language Model Reasoning with Structured Multi-Level Modeling
Siheng Xiong, Ali Payani, Faramarz Fekri

Project

Multi-Level Reasoning (MLR) is a lightweight planner-executor loop that improves long-horizon reasoning, using iterative Step-DPO for scalable supervision to enhance accuracy and stability.

ACL 2025
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Deliberate Reasoning in Language Models as Structure-Aware Planning with an Accurate World Model
Siheng Xiong, Ali Payani, Yuan Yang, Faramarz Fekri

Project

SWAP (Structure-Aware Planning) is a framework for multi-step reasoning with LMs, where the world model predicts the next state as a graph, guiding the policy model to propose the next action.

NAACL 2025
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CausalEval: Towards Better Causal Reasoning in Language Models
Longxuan Yu*, Delin Chen*, Siheng Xiong*, Qingyang Wu, Dawei Li, Zhikai Chen, Xiaoze Liu, Liangming Pan

Project

We provide a comprehensive review of research aimed at enhancing LMs for causal reasoning. We evaluate the performance of different LMs and methods on various causal reasoning tasks, providing key findings and in-depth analysis.

EMNLP 2024
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Can LLMs Reason in the Wild with Programs?
Yuan Yang, Siheng Xiong, Ali Payani, Ehsan Shareghi, Faramarz Fekri

Project

Tiger is a TactIc-Guided ReasonER designed to tackle reasoning-in-the-wild tasks by generating and refining programs. It learns from previous trajectories to iteratively improve program generation, enabling more effective reasoning (like OpenAI o1).

ACL 2024
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Large Language Models Can Learn Temporal Reasoning
Siheng Xiong, Ali Payani, Ramana Kompella, Faramarz Fekri

Project

TG-LLM performs temporal reasoning in two steps: 1) Text-to-Temporal Graph translation: generate temporal graph given the context and keyword; 2) Temporal Graph Reasoning: perform deliberate CoT reasoning over the temporal graph.

ACL 2024
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Harnessing the power of large language models for natural language to first-order logic translation
Yuan Yang, Siheng Xiong, Ali Payani, Ehsan Shareghi, Faramarz Fekri

Project

LogicLLaMA can be used standalone or to correct previously generated rules by other models for the NL-FOL translation task.

Long Context Language Modelling

NeurIPS 2025
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Long-Context Modeling with Dynamic Hierarchical Sparse Attention for On-Device LLMs
Siheng Xiong, Joe Zou, Faramarz Fekri, Yae Jee Cho

Project

We introduce Dynamic Hierarchical Sparse Attention (DHSA), a plug-in module for Transformers that improves efficiency by predicting token-level sparsity using chunk-level similarity, reducing latency and memory usage while maintaining performance.

Preprint 2024
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The Compressor-Retriever Architecture for Language Model OS
Yuan Yang, Siheng Xiong, Ehsan Shareghi, Faramarz Fekri

Project

We introduce compressor-retriever, a model-agnostic architecture designed for life-long context management. Our approach exclusively uses the base model’s forward function to compress and retrieve context, ensuring end-to-end differentiability.

Temporal Knowledge Graph Reasoning

IJCAI 2024
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TILR: Temporal Inductive Logic Reasoning over Hypergraphs
Yuan Yang, Siheng Xiong, Ali Payani, James C Kerce, Faramarz Fekri

Project

TILR is a reasoning framework that detects inductive patterns in temporal data via neural-logic methodology. The framework aims to assist the training of modern ML models by inducing patterns for accurate grounding with fewer data.

AAAI 2024
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TEILP: Time prediction over knowledge graphs via logical reasoning
Siheng Xiong, Yuan Yang, Ali Payani, James C Kerce, Faramarz Fekri

Project

TEILP extends TILP by converting TKGs into temporal event knowledge graphs (TEKGs) and developing a differentiable random walk approach with conditional probability density functions for time prediction based on query intervals.

ICLR 2023
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TILP: Differentiable learning of temporal logical rules on knowledge graphs
Siheng Xiong, Yuan Yang, Faramarz Fekri, James Clayton Kerce

Project

TILP is the first differentiable framework for learning temporal logical rules, using a constrained random walk mechanism and temporal operators to model key temporal features.

📝 Selected Publications

📝 Preprints

📝 Published

🎖 Honors and Awards

  • China National Scholarship (Top 1% Rank)
  • China UHV Scholarship (Top 1% Rank)
  • Kaggle Santander Value Prediction Challenge, Silver Medal (Top 3.4% Rank)

📖 Education

  • Georgia Institute of Technology, Ph.D. in Machine Learning
  • Shanghai Jiao Tong University, M.S. in Electrical and Computer Engineering
  • Xi’an Jiaotong University, B.S. in Electrical and Computer Engineering

💻 Experience

  • 2025.05 - 2025.08, Applied Research Intern, Google, Sunnyvale, California
  • 2023.09 - 2024.04, Research Intern, Cisco Research, San Jose, California
  • 2020.05 - 2021.01, Research Student Assistant, Rutgers University (Mentor: Dimitris N. Metaxas), New Brunswick, New Jersey

📄 Services

  • Program Committee for AAAI
  • Conference Reviewer for NeurIPS, ICML, ICLR, ACL, EMNLP, NAACL, EACL, KDD, AAAI
  • Journal Reviewer for ACM TIST