Simon Marlow
Software Engineer at Meta
Cambridge, England, United Kingdom
Summary
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Rockstar🎓
Top SchoolSimon Marlow is a veteran software engineer and one of the principal architects behind the Glasgow Haskell Compiler (GHC), with over 30 years of experience building high-performance compilers, runtimes, and concurrent systems. He authored GHC’s parallel runtime, chaired the Haskell 2010 committee, and co-won the 2011 ACM PL Software Award for GHC, underscoring his influence on functional language design. At Meta he designed Haxl, a concise concurrent-data-access framework that powers large-scale abuse detection across Facebook, WhatsApp and Instagram, and he’s a lead developer on Glean, an open-source semantic code-indexing system. His open-source footprint includes foundational Haskell tools like Happy, Alex, Haddock, ThreadScope, monad-par and async, and contributions to bytestring, Cabal and Cloud Haskell libraries. Equally at home in research and production, he blends deep PL research (parallel GC, language design) with pragmatic engineering that improves real-world systems. Based in Cambridge with a PhD from Glasgow, he continues to shape large-scale developer tooling and concurrent infrastructure.
30 years of coding experience
16 years of employment as a software developer
PhD, PhD at The University of GlasgowBSc, BSc at University of Bristol
Stackoverflow
12,785reputation
183kreached
45answers
1question
haskell
top-1%
concurrency
top-1%
garbage-collection
top-1%
parallel-processing
top-5%
multithreading
top-1%
functional-programming
top-5%
Github Skills (43)
caching10
back-end-development10
multithreading10
process-management10
build-system10
cab10
distributed-systems10
internals10
semantics10
indexing10
data-structure10
bytestring10
compiler-design10
sys10
ghc10
Programming languages (7)
Github contributions (5)
facebook/Haxl
Jun 2014 - Apr 2022
A Haskell library that simplifies access to remote data, such as databases or web-based services.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:21 commits, 12 PRs, 15 pushes in 7 years 11 months
Contributions summary:Simon contributed to the Haxl Haskell library by implementing and refactoring core backend functionalities. This included modifications to data fetching mechanisms, caching strategies, and the build system. The user also fixed build issues related to specific GHC versions and refactored the codebase for improved organization and maintainability. Additionally, they bumped the version number and made updates to the library's dependencies.
databasedatabaseshaskell
ghc/ghc
Mar 1996 - Jun 2019
Mirror of the Glasgow Haskell Compiler. Please submit issues and patches to GHC's Gitlab instance (https://gitlab.haskell.org/ghc/ghc). First time contributors are encouraged to get started with the newcomers info (https://gitlab.haskell.org/ghc/ghc/wikis/contributing).
Role in this project:Back-end Developer
Back-end DeveloperContributions:11753 commits, 3 comments in 23 years 7 months
Contributions summary:Simon primarily worked on enhancing the Glasgow Haskell Compiler (GHC) by implementing core features and fixing bugs. Their contributions involved modifying core Haskell language constructs, and improving its functional capabilities and stability. The user's commits demonstrate proficiency in compiler design, language semantics, and the underlying mechanisms of a functional programming language implementation.
compilerghcgitlabhaskell
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