Benjamin Sepanski

Benjamin Sepanski

I am a Staff Compiler Engineer at Mythic, where I work on compilers.

Posts by Collection

portfolio

Bricks

Generate portable, high-performance code in high-dimensional settings via data layout transformations

Cortado

Automatic implicit monitor synchronization

publications

Augmented Hilbert series of numerical semigroups

Published in Integers, 2019

Several new explicit formulas for certain augmented Hilbert Series measuring maximal and minimal factorization lengths for all numerical semigroups.

Recommended citation: Glenn, Jeske and O'Neill Christopher and Ponomarenko, Vadim and Sepanski, Benjamin (June 3, 2019). "Augmented Hilbert series of numerical semigroups." Integers 19 #A32.

Finite Elements for Helmholtz equations with a nonlocal boundary condition

Published in SIAM Journal on Scientific Computing, 2021

A new nonlocal boundary condition for exterior Helmholtz problems along with the software infrastructure to express these boundary conditions in Unified Form Language

Recommended citation: Kirby, Robert C. and Klöckner, Andreas and Sepanski, Benjamin.(2021). "Finite Elements for Helmholtz Equations with a Nonlocal Boundary Condition." SIAM Journal on Scientific Computing, 43(3), A1671-A1691.

Maximizing Performance Through Memory-Hierarchy Driven Data Layout Transformations

Published in MCHPC 2022: Workshop on Memory Centric High Performance Computing at SC22, 2022

Extend the Bricks framework to optimize high-dimensional code through data layout transformation

Recommended citation: B. Sepanski, T. Zhao, H. Johansen and S. Williams, "Maximizing Performance Through Memory Hierarchy-Driven Data Layout Transformations," in 2022 IEEE/ACM Workshop on Memory Centric High Performance Computing (MCHPC), Dallas, TX, USA, 2022 pp. 1-10. doi: 10.1109/MCHPC56545.2022.00006

Synthesizing fine-grained synchronization protocols for implicit monitors

Published in Proc. ACM Program. Lang. 6, OOPSLA1, 2022

Automatatically implementing fine-grained explicit synchronization protocols from an implicit monitor specification using formal methods

Recommended citation: Kostas Ferles, Benjamin Sepanski, Rahul Krishnan, James Bornholt, and Işil Dillig. 2022. "Synthesizing fine-grained synchronization protocols for implicit monitors." Proc. ACM Program. Lang. 6, OOPSLA1, Article 67 (December 2022), 26 pages. https://doi.org/10.1145/3527311

talks

Augmented Hilbert series of numerical semigroups

Published:

Presented at the AMS-MAA-SIAM Special Session on Undergraduate Research at the 2018 Joint Mathematics Meetings in San Diego, California, funded by an MAA Travel Grant for Undergraduates. This was joint work with Christopher O’Neill, Jeske Glenn, and Vadim Ponomarenko from the 2017 SDSU REU, presenting new explicit formulas for augmented Hilbert series that measure factorization lengths in numerical semigroups. A weighted Euler characteristic of an associated simplicial complex is a key ingredient in several of the formulas.

Nonlocal UFL: Finite elements for Helmholtz equations with a nonlocal boundary condition

Published:

Presented at the FEniCS 2021 Conference (slides, abstract, and recording), joint work with Dr. Robert Kirby and Dr. Andreas Klöckner. This work introduces nonlocal boundary conditions for exterior Helmholtz problems that are exact (rather than approximate), relying on layer potentials evaluated via fast multipole methods. Integration of the layer potential library pytential with Firedrake allows these boundary conditions to be expressed naturally in UFL.

Maximizing Performance Through Memory Hierarchy-Driven Data Layout Transformations

Published:

Presented at MCHPC 2022 at SC22 in Dallas, Texas. High-performance stencil codes are typically tuned by transforming loop structure, but this work takes a different approach: the Bricks library improves performance by transforming data layouts to match the memory hierarchy instead, enabling significant speedups for structured-grid computations without manual code restructuring. This was joint work with Dr. Tuowen Zhao, Dr. Hans Johansen, and Dr. Samuel Williams at Lawrence Berkeley National Laboratory; slides here.

Synthesizing Fine-Grained Synchronization Protocols for Implicit Monitors

Published:

Presented at OOPSLA 2022 at SPLASH 2022 in Auckland, New Zealand. Writing correct fine-grained synchronization code for concurrent programs is notoriously hard and error-prone; this work presents a synthesis approach where, given a declarative specification of a monitor’s intended behavior, we automatically synthesize the correct synchronization protocol, eliminating a whole class of subtle concurrency bugs. This was joint work with Dr. Kostas Ferles, Rahul Krishnan, Dr. James Bornholt, and Dr. Işil Dillig.

ZK 360 Panel – Future of ZK

Published:

Panelist on the “Future of ZK” panel at ZK 360 during Consensus 2023 in Austin, Texas. The panel brought together builders and researchers to discuss where zero-knowledge proof technology is headed, and I represented the security and auditing perspective — speaking to practical challenges and risks in real-world ZK deployments. See the recorded video here.

AuditHub: A Platform for Professional Blockchain Audit Firms

Published:

Presented at DeFi Security Summit 2025 in Buenos Aires, Argentina. AuditHub is a platform for professional blockchain security audit firms that provides clients with transparency into the audit process while automating common audit workflows — managing findings, reports, and communications in one place to raise the overall quality bar for blockchain security engagements. This was joint work with Dr. Kostas Ferles and the Veridise team.

Who Pays for Security Audits, Bounties, and Incentives

Published:

Presented at ETHDenver 2026 in Denver, Colorado. Security audits and bug bounties are essential to blockchain safety, but who actually pays for them, and do the incentives align? This talk examines the economics behind security reviews: who bears the cost, how protocol teams decide what to spend, and how misaligned incentives between projects, auditors, and whitehats can leave critical vulnerabilities unfound — and what better incentive structures could look like. See the recorded video here.

teaching

Upward Bound Program

Mathematics Tutoring for the Upward Bound Program, Waco/University High Schools through the Waco ISD and ESC Region 12, 2019

The Upward Bound Program is an initiative by the U.S. Department of Education for “high school students from low-income families; and high school students from families in which neither parent holds a bachelor’s degree.” The goal of this program is “increase the rate at which participants complete secondary education and enroll in and graduate from institutions of postsecondary education.” I worked as a paid tutor in general mathematics/physics as well as for the math/science portion of the ACT and SAT tests.