Memo: an incremental computation library that powers Dune

Andrey Mokhov (Jane Street)

We present Memo, an incremental computation library that supports a new, faster and more scalable, file-watching build mode in Dune 3.0. The requirements from the build systems domain make Memo a unique point in the design space of incremental computation libraries. Specifically, Memo needs to cope with concurrency, dynamic dependencies, dependency cycles, and non-determinism, provide support for efficiently collecting and reporting user-friendly errors, and scale to computation graphs containing tens of millions of incremental nodes.