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Fun OCaml

September 15-16, 2025

Warsaw, Poland

Come join us in-person to learn from our experience using OCaml.

Performance Pitfalls: Tales from a Python/OCaml Codebase (Emma Jin)

Semgrep is a tool that enables developers to search their code for security vulnerabilities, built with an OCaml engine and a Python frontend. This has come with a fair amount of performance pain. In this talk, I'll share some of the worst problems we ran into, how we found them, and how we solved them (mostly, rewriting Python code in OCaml).

OCaml Observability with OpenTelemetry (Austin Theriault)

See how Semgrep uses OpenTelemetry to scale their OCaml-based product, covering implementation of telemetry types and real-world examples from their production system.

You'll learn hands-on techniques for instrumenting OCaml applications with observability tools that have proven essential for scaling complex software systems.

Analyzing Programs with SMT Solvers (Tikhon Jelvis)

In this talk, you'll see how to leverage SMT solvers like Z3 for program analysis by building constraints that can verify code properties, locate errors, and even synthesize programs automatically. You'll see a hands-on walkthrough of an OCaml implementation that generates SMT constraints for a simple imperative language, showcasing how algebraic data types and pattern matching make this type of formal verification both practical and accessible.

From OCaml 4 to 5 and from Parmap to Effects: A legacy code transition story (Nathan Taylor, Nat Mote)

This session tells the story of the migration of a 3 million line OCaml codebase from proess-based Parmap to OCaml 5's shared-memory parallelism with Eio effects.

The speakers will present their incremental migration approach using static and dynamic analysis, the pitfalls encountered during the transition, and practical lessons for developers undertaking similar migrations.


Learn more about the event by visiting: https://fun-ocaml.com/#event

Emma Jin
Austin Theriault
Tikhon Jelvis
Nat Mote
Nathan Taylor