Aaron Orenstein
Software Engineer at Facebook
Billerica, Massachusetts, United States
Summary
🤩
Rockstar🎓
Top SchoolAaron Orenstein is a seasoned software engineer with over a decade of experience building high-performance back-end systems and developer tooling. Currently at Facebook, he has a strong track record modernizing large codebases and improving runtime and build performance—evidenced by performance-focused contributions to major open-source projects like CMake and PyTorch. His background spans finance-grade platform work at Bank of America, cross-platform client and protocol implementations at startups, and deep graphics and systems engineering from early roles at ATI and game studios. Aaron combines low-level C/C++ expertise with practical Python and tooling experience, and he often uncovers and fixes subtle inefficiencies (e.g., replacing recursive algorithms to avoid stack overflows and optimizing data lookups). Based in Billerica, MA, he brings both hands-on implementation skills and architectural judgment to high-impact performance and migration projects.
10 years of coding experience
21 years of employment as a software developer
UMass Lowell
Github Skills (25)
algorithm10
algorithms10
pytorch10
c-language10
python10
build-system10
cmake10
data-structure10
performance-optimization10
data-structures10
cprogramming-language10
test-automation9
compiler-optimization9
cuda8
deep-learning8
Programming languages (9)
Github contributions (5)
facebook/hhvm
Jun 2016 - Sep 2022
A virtual machine for executing programs written in Hack.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:348 commits, 22 PRs, 28 pushes in 6 years 4 months
Contributions summary:Aaron primarily contributed to the Hack virtual machine for the Hack language. They worked on implementing language specifications and test suites. Their work included importing and modifying the Hack language specifications from previous repositories, as well as writing test cases for features such as bitwise shift operators and conversions. The user also addressed code style issues and fixed namespace issues in the test suite.
hacklangphpvirtual-machineprogramshhvm
pytorch/pytorch
Jan 2024 - Apr 2025
Tensors and Dynamic neural networks in Python with strong GPU acceleration
Role in this project:Back-end Developer & Performance Engineer
Back-end Developer & Performance EngineerContributions:368 reviews, 297 PRs, 2685 pushes in 1 year 3 months
Contributions summary:Aaron primarily focused on optimizing the performance of core PyTorch components. They refactored and reimplemented existing code, such as replacing a recursive function call with an iterative one to prevent stack overflows. They addressed performance bottlenecks by modifying code to reduce the overhead, which improved compilation and run times. The contributions also involved fixing bugs and ensuring code correctness by addressing issues related to parameter defaults and memory management.
pythongpu-accelerationdeep-learninggpunumpy
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