About
I am a research assistant at the University of Waterloo, working on
AI for software engineering: I combine
large language models,
multimodal signals (video, execution traces, code), and
formal methods to debug, tutor, evaluate, and verify
block-based programs — 9 first-authored papers, including
VisionScratch (published at FSE 2026) and
ScratchEval (accepted at ISSTA 2026), with recent work on
behavioral equivalence, schedule robustness, certificate-carrying transformation, and
robustness of programming-by-example.
On the side, I work on analytic number theory and probability (4 preprints):
the Collatz affine random model is
under review at Forum of Mathematics, Sigma, and the first of a
three-paper series on rational-distance problems — Guy's
four-corner problem (D19) — is
under review at the Journal of Number Theory.
Previously worked at Microsoft Azure & AI Research.
Publications
Conference Papers
VisionScratch: LLM-Based Automated Feedback Generation using Code-Produced Videos for Scratch Programs
Yuan Si, Daming Li, Hanyuan Shi, Jialu Zhang
Proceedings of the ACM on Software Engineering, Vol. 3 (FSE 2026), pp. 3534–3557 Published
ScratchEval: A Multimodal Evaluation Framework for LLMs in Block-Based Programming
Yuan Si, Simeng Han, Daming Li, Hanyuan Shi, Jialu Zhang
ACM SIGSOFT International Symposium on Software Testing and Analysis (ISSTA) 2026 Accepted
Journal Submissions
A Microcanonical Phase Transition for the Collatz Affine Random Model
Yuan Si
Submitted to Forum of Mathematics, Sigma, 2026 — sharp resonant phase transition at the entropy line for Tao's Syracuse affine model, reducing hard-frequency mixing to a primitive ternary Bernoulli-bridge transform Under Review
Mixed Parity, Diagonal Denominator, and the Pell-Chord Genus-Five Obstruction for the Four-Corner Rational Distance Problem
Yuan Si
Submitted to Journal of Number Theory, 2026 — unconditional necessary conditions on Guy's problem D19 (Pillai's unit-square four-distance) and a reduction of the residual obstruction to a non-fixed Pell-chord involution on a family of arithmetic-genus-five curves Under Review
Preprints
Fixed-Set Robustness in Programming by Example: Example Corruption and Semantic Partition Recovery
Yuan Si, Jialu Zhang
Preprint, 2026
Checked Program Recovery from Execution Video: A Sound Oracle for Untrusted Generators
Yuan Si, Jialu Zhang
Preprint, 2026
SchedCheck: Schedule-Robustness Analysis for Event-Driven Block Programs
Yuan Si, Jialu Zhang
Preprint, 2026
Certificate-Carrying Transformation of Event-Driven Block Programs
Yuan Si, Jialu Zhang
Preprint, 2026 — soundness proof mechanized in Lean; validated on 300 real Scratch projects
ScratchLens: Lens-Parametric Behavioral Equivalence for Scratch Programs
Yuan Si, Jialu Zhang
Preprint, 2026
EcoScratch: Cost-Effective Multimodal Repair for Scratch Using Execution Feedback
Yuan Si, Ming Wang, Daming Li, Hanyuan Shi, Jialu Zhang
Preprint, 2026 Under Review
Stitch: Step-by-step LLM Guided Tutoring for Scratch
Yuan Si, Kyle Qi, Daming Li, Hanyuan Shi, Jialu Zhang
Preprint, 2025 Under Review
Elliptic Decomposition of the Pell-Chord Genus-Five Obstruction for the Four-Corner Rational Distance Problem
Yuan Si
Preprint, 2026 — structural follow-up to Paper I: decomposes the residual genus-five curve into full-2-torsion elliptic pieces via 2-isogeny and Kani–Rosen Jacobian factorization; reduces the four-corner problem to a two-variable Pythagorean-slope exclusion
An Elementary Projection Obstruction for Rational Distances to Regular Polygons
Yuan Si
Preprint, 2026 — an elementary proof that a regular n-gon (n ≥ 5, n ≠ 6) with rational side length admits no point at rational distance from all vertices, via projection identities, the vertex zero-sum relation, and Niven's theorem
Research Reports & Other
Multiplayer Rock-Paper-Scissors: Nash Equilibria via Linear Programming
Yuan Si
Research Report, 2025
Tesla Charging Station Optimization via Independent Dominating Sets
Yuan Si
Research Report, 2025
Public Goods Game: Cooperation Dynamics and Intervention Analysis
Yuan Si
Research Report, 2025
Textbook
A Gentle Introduction to Optimization
Yuan Si
2024 — Adopted as required reading in 3 university courses
