I am an associate professor in the [Department of Computer
Science](https://www.cs.cornell.edu/) at [Cornell
University](https://www.cornell.edu).


**I am always looking for good students!**


Previously, I was an assistant professor in the [Department of Computer
Sciences](https://www.cs.wisc.edu/) at the [University of
Wisconsin--Madison](https://www.wisc.edu), and a postdoc at the [Department of
Computer Science](https://www.cs.cornell.edu/) at [Cornell
University](https://www.cornell.edu/), and in the [Programming Principles,
Logic, and Verification Group](http://pplv.cs.ucl.ac.uk/welcome/) at the
[University College London](https://www.ucl.ac.uk/). I obtained my PhD from the
[Department of Computer Science](https://cis.upenn.edu) at the [University of
Pennsylvania](https://www.upenn.edu).

I am funded by the National Science Foundation, the Office of Naval Research,
and Facebook Research.

## Research Interests ##
I design methods to **formally verify** that **algorithms** are correct. I am
especially interested in programs satisfying quantitative guarantees, or
properties from mathematical or scientific applications.

A particular focus of my work has been verifying programs that use
**randomization**. Such programs can be easy to show correct on paper, but
surprisingly challenging for computers to analyze. Drawing inspiration from how
humans reason about randomized algorithms, we can build simpler and more
automated verification techniques. In the past, I've applied this approach to
properties like **accuracy**, **incentive compatibility**, Markov chain
**mixing**, various notions of **algorithmic stability**, and [**differential
privacy**](https://en.wikipedia.org/wiki/Differential_privacy), a rigorous
definition of privacy. I have developed a variety of [**type
systems**](https://en.wikipedia.org/wiki/Type_system) and [**program
logics**](https://en.wikipedia.org/wiki/Hoare_logic) to verify that programs are
differentially private.

More broadly, I am interested in verifying all kinds of programs and properties
with rich mathematical structure, such as continuous-time systems, programs with
symmetries, economic mechanisms, and most recently, algorithms from numerical
analysis and applied mathematics.

## Teaching ##
- **Data Structures and Functional Programming (CS 3110)**: [F23](https://www.cs.cornell.edu/courses/cs3110/2023fa/) [S23](https://www.cs.cornell.edu/courses/cs3110/2023sp/) [S22](https://www.cs.cornell.edu/courses/cs3110/2022sp/)
- **Category Theory for Computer Scientists (CS 6117)**: [F22](teaching/f22/cs6117)
- **Foundations of Probabilistic Programming (CS 6182)**: [F21](teaching/f21/cs6182)
- **Reasoning about Probabilistic Programs** <br>
  **Invited Course at [OPLSS 2021](https://www.cs.uoregon.edu/research/summerschool/summer21/index.php)**: 
  [[slides](https://justinhsu.net/files/slides/oplss21.pdf)] [[recordings](https://www.cs.uoregon.edu/research/summerschool/summer21/topics.php)]
- **Security and Privacy in Data Science (CS 763)**: [F20](teaching/f20/cs763/) [F19](teaching/f19/cs763/)
- **Introduction to the Theory and Design of PL (CS 538)**: [S20](teaching/s20/cs538/) [S19](teaching/s19/cs538/)
- **Topics in Security and Privacy Technologies (CS 839)**: [F18](teaching/f18/cs839/)

## Awards and Honors ##

- **2024** EATCS [Presburger Award](https://www.eatcs.org/index.php/presburger)
- **2024** Royal Society [Wolfson Visiting Fellowship](https://royalsociety.org/grants/royal-society-wolfson-visiting-fellowship/)
- **2022** CAV Distinguished Paper Award
- **2021** POPL Distinguished Paper Award
- **2020** POPL Distinguished Paper Award
- **2020** NSF CAREER award
- **2018** ACM SIGPLAN [John C. Reynolds Doctoral Dissertation Award](https://www.sigplan.org/Awards/Dissertation/)
- **2015** Simons Award for Graduate Students in Theoretical Computer Science

## Service ##
- **2024** OOPSLA, CSF, CCS, MFPS
- **2023** CSF, ICALP-B, LICS, OOPSLA, MFPS
- **2022** POPL, PLDI, MFPS (co-chair)
- **2021** ESOP, PLMW@POPL, CSF, AAAI, COLT, WoLLIC, MFPS
- **2020** AAAI, CSF, LAFI, WoLLIC, PLMW@POPL, OOPSLA (ERC)
- **2019** POPL, PLMW@POPL, POST, CSF, DARS (co-chair)
- **2018** LICS, WWW
- **2017** FCS, TPDP, MFPS
- **2016** PLDI (ERC)

## Blogging ##
I've greatly enjoyed blogging for [PL Perspectives](https://blog.sigplan.org/blog/)!

- [**Teaching Category Theory to Computer Scientists**](https://blog.sigplan.org/2023/04/04/teaching-category-theory-to-computer-scientists/)
- [**Programming Languages Mentoring Workshop: Ten Years Later**](https://blog.sigplan.org/2021/05/11/programming-languages-mentoring-workshop-ten-years-later/)
- [**Re-Imagining the “Programming Paradigms” Course**](https://blog.sigplan.org/2021/01/28/re-imagining-the-programming-paradigms-course/)
- [**Verifying Randomized Algorithms: Why and How?**](https://blog.sigplan.org/2020/10/20/verifying-randomized-algorithms-why-and-how/)