Incremental λ-Calculus—Paolo G. Giarrusso

Introduction

This is the homepage for the Incremental λ-Calculus project. Our goal is to extend database technology for low-overhead incremental computation, based on finite differencing, and apply it to higher-order languages.

Papers

A theory of changes for higher-order languages — incrementalizing λ-calculi by static differentiation (updated version). With Yufei Cai, Tillmann Rendel, and Klaus Ostermann. Accepted at PLDI ’14.

Abstract:

If the result of an expensive computation is invalidated by a small change to the input, the old result should be updated incrementally instead of reexecuting the whole computation. We incrementalize programs through their derivative. A derivative maps changes in the program’s input directly to changes in the program’s output, without reexecuting the original program. We present a program transformation taking programs to their derivatives, which is fully static and automatic, supports first-class functions, and produces derivatives amenable to standard optimization.

We prove the program transformation correct in Agda for a family of simply-typed λ-calculi, parameterized by base types and primitives. A precise interface specifies what is required to incrementalize the chosen primitives.

We investigate performance by a case study: We implement in Scala the program transformation, a plugin and improve performance of a nontrivial program by orders of magnitude.

Credits

This project benefited from code and ideas of many different people:

Cai Yufei
Paolo G. Giarrusso
Tillmann Rendel
Klaus Ostermann

Further acknowledgments in the paper itself.

News

2014-05-04: Author’s version of the paper camera-ready finally online.
2014-03-15: The AEC submission was found to “meet or exceed expectations”!
2014-02-21: Link to the AEC submission.
2014-02-10: Submission to the artifact evaluation committee (AEC) evaluation
2014-02-05: Website online
2014-02-03: Our first paper on this project was accepted for PLDI ’14! The author’s version of the camera-ready is available.

Contacts

For any question or suggestion, feel free to contact me, Paolo G. Giarrusso, at pgiarrusso (at) informatik !dot! uni-marburg !dot! de.