Zhengji Zhang

Computer Science & Mathematics
University of Wisconsin–Madison

I build machine learning systems and applied modeling tools, with an emphasis on reproducible evaluation, clear system boundaries, and measured results.

Most of my work follows the same shape: take a method that is supposed to help, build the harness that can actually tell whether it did, and report the number that comes back — including when it is smaller than expected. The two projects below are written that way, and both state the limits of what their measurements support.

Selected work

MiniMind Systems

Systems extensions on top of MiniMind: a preallocated static KV cache, request batching, and an observable FastAPI serving path with Prometheus metrics. Equivalence tests pin the cache to the reference implementation; the benchmark harness emits JSON reports rather than screenshots.

Exploratory runs · Apple Silicon CPU · 532,864-parameter model
Static cache vs. no cache +74.10% tokens/s
Static cache vs. existing dynamic cache +0.11% tokens/s
Batched serving batch 8 vs. batch 1 +155.20% requests/s

Short local runs on a CPU micro-model — not GPU results, statistical guarantees, or model-quality claims. The +0.11% row is reported precisely because it is not evidence of a robust speedup.

  • PyTorch
  • FastAPI
  • Static KV cache
  • Dynamic batching
  • Prometheus

Explainable ESG Risk & Reporting

Live demo three precomputed companies — Pages cannot run the model

A leakage-aware modeling benchmark, a SHAP evidence bundle, and a FastAPI service that returns a risk estimate alongside the strongest positive and negative contributions behind it. Encoding, imputation, and scaling are fitted inside each training fold, so the comparison below is not flattered by the validation split.

430 eligible companies · 5 shared folds · seed 42 · lower is better
ModelOOF RMSEOOF MAE
Training-fold mean (baseline)6.8905.615
CatBoost4.8703.728
ElasticNet5.9134.812
LightGBM6.0034.709
Equal-weight blend5.3314.232

Internal cross-validation estimates on a historical cross-sectional dataset — not future-period or external validation. The blend did not beat CatBoost in this run.

Grand Prize 2025 Zhixiang Cup — national university economics and management case competition. The award applies to the original competition case; the repository documents the later engineering release.

  • CatBoost
  • SHAP
  • scikit-learn
  • FastAPI

Interests

Machine learning systems · applied mathematics · interpretable modeling · quantitative research.

Currently reading into inference-time efficiency and evaluation design — the question of what a benchmark is actually licensed to conclude.

Contact

Open to research collaborations and internships. Email is the fastest way to reach me: zhengji.zhang@wisc.edu. Code and ongoing work live on GitHub.