egg: e-graphs good

The egg project uses e-graphs to provide a new way to build program optimizers and synthesizers.

An e-graph compactly represents many equivalent programs. These four e-graphs represent more and more (even infinite!) ways to write (a × 2) / 2. egg makes e-graphs fast and flexible enough for use in program optimization and synthesis.

The core egg library provides high-performance, flexible e-graphs implemented in Rust. It is packaged on crates.io and documented on docs.rs, including a tutorial that provides an introduction to e-graphs and their use cases.

The newer egglog system provides an alternative approach to equality saturation based on Datalog. It features a language-based design, incremental execution, and composable analyses. Check out the paper and the web demo.

BibTeX
@article{2021-egg,
    author = {Willsey, Max and Nandi, Chandrakana and Wang, Yisu Remy and Flatt, Oliver and Tatlock, Zachary and Panchekha, Pavel},
    title = {egg: Fast and Extensible Equality Saturation},
    year = {2021},
    issue_date = {January 2021},
    publisher = {Association for Computing Machinery},
    address = {New York, NY, USA},
    volume = {5},
    number = {POPL},
    url = {https://doi.org/10.1145/3434304},
    doi = {10.1145/3434304},
    abstract = {An e-graph efficiently represents a congruence relation over many expressions. Although they were originally developed in the late 1970s for use in automated theorem provers, a more recent technique known as equality saturation repurposes e-graphs to implement state-of-the-art, rewrite-driven compiler optimizations and program synthesizers. However, e-graphs remain unspecialized for this newer use case. Equality saturation workloads exhibit distinct characteristics and often require ad-hoc e-graph extensions to incorporate transformations beyond purely syntactic rewrites.  This work contributes two techniques that make e-graphs fast and extensible, specializing them to equality saturation. A new amortized invariant restoration technique called rebuilding takes advantage of equality saturation's distinct workload, providing asymptotic speedups over current techniques in practice. A general mechanism called e-class analyses integrates domain-specific analyses into the e-graph, reducing the need for ad hoc manipulation.  We implemented these techniques in a new open-source library called egg. Our case studies on three previously published applications of equality saturation highlight how egg's performance and flexibility enable state-of-the-art results across diverse domains.},
    journal = {Proc. ACM Program. Lang.},
    month = jan,
    articleno = {23},
    numpages = {29},
    keywords = {equality saturation, e-graphs}
  }

EGRAPHS Community

The egg project is part of the larger EGRAPHS Community, which aims to bring together researchers and practitioners interested in e-graphs and related techniques. Check out the EGRAPHS Community resources, including:

News

For updates on egg itself, see the changelog.

Projects using egg and e-graphs

Check out Philip Zucker’s page on Awesome E-graphs for a list of egg and e-graph related projects. PRs are welcome to add your project to the list!

You can also see who's using egg on GitHub and Google Scholar.


View or edit this site on GitHub.