Who are we?

Tweag is a software innovation lab that helps deep tech startups quickly scale their engineering performance and execute on high-risk, high-reward projects with confidence. We find the best wherever they live, to build better software by applying mathematics, computer science and the methods of open source.

Our core engineering mantras: functional, typed, immutable. These are the key technologies for composable software. We build parts as functions, because functions compose where objects do not. We use types to describe functions, because one type is worth a thousand out-of-date comments. We keep data immutable, because immutability lets us focus on the business logic holistically without getting bogged down by hundreds of corner cases.

Project to improve GHC's performance

This internship is all about improving the performance of the Glasgow Haskell Compiler (GHC). You would work directly with Tweager and GHC contributor Richard Eisenberg to contribute to this open source project. Some ideas are explained in the announcement blog post.


  • Timing: We are flexible on this; the successful applicant and Richard will work out a mutually convenient stretch of time. Waiting until summer is an option.
  • Length: Typically 3 months, but a longer internship may be possible.
  • Location: Either on site in Paris or remote.
  • Payment: The stipend is twice the rates specified for the Google Summer of Code projects, as the duration is roughly double the length.
  • Closing date: Thursday, March 4, 2021 (anywhere on Earth). Applications will be collected until this date and reviewed shortly thereafter.

Application requirements

In your cover letter, make sure to describe your Haskell
experience, any experience you already have with working on GHC (though none is
required), and any experience you already have with performance work (in any

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