What is Fern?

Fern optimizes pipelines built from sequences of function calls. In particular, Fern fuses function calls, and produces code that evaluates operations back-to-back on small chunks of data as opposed to entire outputs. Fern accomplishes this by requiring functions to declare how they produce and consume data.

Fern's core idea is that that fused code naturally separates concerns: inner loops handle computation and hardware-specific logic, while outer loops manage data movement. Fern uses black-box subroutines to perform computations and uses simple dataflow analysis to generate outer loops.

Our paper on Lightweight and Locality-Aware Composition of Black-Box Subroutines discusses Fern's design philosophy in detail.

Getting Started

To get started with Fern, take a look at the installation instructions.

The tutorial walks through several example Fern programs to help you understand how it works in practice.

Talk

You can also watch our CppCon talk about Fern. Fern has evolved quite a bit since then, but the design philosophy at its core has remained the same.