Yarrow Diagrams

⚠️ yarrow is still early in development ⚠️: it's missing some features, and not everything is documented. Consider yourself warned!

yarrow is a Python library implementing the datastructures and algorithms for string diagrams described in the paper Data-Parallel Algorithms for String Diagrams.

What is yarrow?

For a programmer's overview of what yarrow is for, see the documentation. In short, the main datastructure of yarrow is the Diagram, which can be thought of a generalisation of syntax trees to syntax graphs.

Here's an example of a string diagram depicted graphically:

You could think of this as representing the syntax of the following python program:

def compute_mean(numbers: List[int]):
    count, sum = summary(numbers)
    return divide(sum, count)

String diagrams are different from directed graphs in two important ways:

• The boxes (operations) in a string diagram have multiple ordered inputs and outputs in the same way a python function has ordered input arguments.
• The diagram itself has inputs and outputs depicted as "dangling" wires on the left and right

Other examples of structures which can be represented by string diagrams are electronic circuits, quantum circuits, neural networks, and many more. For a more formal introduction to string diagrams aimed at computer scientists, try this recent paper.

Installation

pip install yarrow-diagrams

Running tests

Install test dependencies

pip install hypothesis

Run test with your test runner, e.g.

pytest

Yarrow as a Reference Implementation

Yarrow is intended as a reference implementation for the paper. It has the following goals:

• Fast, data-parallel, and runs on the GPU
• Minimal primitives/dependencies required
• Simple to implement correctly

The aim is to serve as a general-purpose datastructure in many languages by making it simple to implement fast algorithms while relying on few external dependencies.

To port yarrow to your language, the only things needed are:

• Arrays and simple array subroutines (see the numpy backend or Section 2.2.2 of the paper.)
• An algorithm for computing connected components.

Porting Yarrow

If you want to port Yarrow to a different language and you would like help, please reach out. Here are some places you could do that:

• discord
• ##yarrow on irc.libera.chat
• email the author