Siwen Zhang
  • Projects
  • Skills
  • Bioinformatics
  • Publications
  • Resumé

On this page

  • Planning and Reflection for Agentic LLMs
  • End-to-End Small LLM Development with Nanochat
  • Recommendation Challenge for Amazon Products
  • SASS Robot Cat
  • Reinforcement Learning Algorithms for CartPole Problem
  • Evolutionary Algorithm on Black-box Problems

💻 Projects

Planning and Reflection for Agentic LLMs

Agent Evaluation | Brittleness | Harnessing | BALROG | ReAct | Reflection

  • Built a reproducible BALROG evaluation pipeline for GPT-6.1-sol and Qwen3-4B-Instruct across BabyAI, TextWorld, and BabaIsAI, using seeded multi-episode experiments and automated performance reporting.
  • Designed a ReAct-inspired language agent with dynamic planning, structured action generation, short-term memory, and explicit detection of repeated actions and state loops.
  • Implemented and evaluated a Reflexion-style agent that converts trial outcomes into verbal memory, comparing matched with/without-reflection conditions using trial-level progression.
agent workflow agent comparison

End-to-End Small LLM Development with Nanochat

LLM Training Pipeline | Instruction Fine-tuning | Model Evaluation | Nanochat | Tokenization

  • Trained and compared 8K and 32K BPE tokenizers on 500MB of CLIMBMix data, then pre-trained a 13M-parameter Transformer while monitoring convergence through training and validation BPB.
  • Designed a two-stage post-training pipeline using MMLU and GSM8K for capability-focused mid-training, followed by supervised fine-tuning on SmolTalk with assistant-only loss masking.
  • Evaluated model checkpoints on ARC-Easy, ARC-Challenge, and GSM8K, analyzed domain shift and catastrophic forgetting, and tested temperature sampling and KV caching through a web inference interface.
agent workflow agent comparison

Recommendation Challenge for Amazon Products

Recommendation System | Sequential User Behavior | SASRec | BERT4Rec | LightGCN

  • Built a Top-10 Amazon product recommender for a Kaggle competition, evaluated by Recall@10.
  • Compared SASRec, BERT4Rec, SASRec+, and LightGCN on temporally ordered user sequences.
  • Designed a multi-stage pipeline with metadata-based candidate filtering and SASRec ranking.
  • Ranked 8th/60 on the Kaggle leaderboard with the final SASRec-based recommendation system.

Kaggle Group 58

kaggle amazon

SASS Robot Cat

Robotics | Computer Vision | Speech Recognition | Actuator Control | Human-Robot Interaction

  • Built a ROS 2 robotic cat integrating vision, speech, navigation, and actuator control.
  • Implemented person following, object search, autonomous docking, and state-based behaviors.
  • Added expressive head, ear, and sound responses for interactive human-robot interaction.

Video | Code

cat body cat face YOLO detection

Reinforcement Learning Algorithms for CartPole Problem

Reinforcement Learning | Deep Q-Network | Actor Critic | A2C | Proximal Policy Optimization

  • Implemented Naive DQN, REINFORCE, AC, A2C, and PPO in CartPole environment.
  • Several engineering tricks were applied to improve performance and stability, including mini-batch update, multiple epochs, generalized advantage estimation (GAE), advantage normalization and entropy regularizatio, which are important for stable policy learning.
  • The transition from value-based to policy-based to advanced policy-based methods suggests the evolution of reinforcement learning methods on providing greater flexibility and more expressive decision-making strategies.
algo comparison

Evolutionary Algorithm on Black-box Problems

Genetic Algorithm | Evolutionary Strategy | Optimization | Black-box Problems

  • Implemented Genetic Algorithm (GA) and self-adaptive \((\mu,\lambda)\) Evolution Strategy (ES) from scratch for discrete and continuous optimization.
  • Applied GA to LABS and N-Queens (Doerr et al. 2018; Wang et al. 2022; Nobel et al. 2021), and ES with log-normal step-size adaptation to the Katsuura problem.
  • Designed a budget-aware, step-wise hyperparameter tuning strategy to efficiently identify promising configurations.
  • Evaluated convergence and robustness using EAF, ECDF, and Expected Runtime (ERT) across multiple runs.

References

Doerr, Carola, Hao Wang, Furong Ye, Sander van Rijn, and Thomas Bäck. 2018. “IOHprofiler: A Benchmarking and Profiling Tool for Iterative Optimization Heuristics.” arXiv e-Prints:1810.05281, October. https://arxiv.org/abs/1810.05281.
Nobel, Jacob de, Furong Ye, Diederick Vermetten, Hao Wang, Carola Doerr, and Thomas Bäck. 2021. “IOHexperimenter: Benchmarking Platform for Iterative Optimization Heuristics.” arXiv e-Prints:2111.04077, November. https://arxiv.org/abs/2111.04077.
Wang, Hao, Diederick Vermetten, Furong Ye, Carola Doerr, and Thomas Bäck. 2022. “IOHanalyzer: Detailed Performance Analyses for Iterative Optimization Heuristics.” ACM Transactions on Evolutionary Learning and Optimization 2 (1). https://doi.org/10.1145/3510426.