Greta

Last updated: 2022-02-15
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🌱 Python library for Green Computing: Execute code at low carbon intensity. 🌱

Green computing is a set of principles to develop software which is as good for the environment as possible. Carbon intensity is a measure of how much carbon is involved in the energy you use at any particular time. This depends on energy demand and the mix of supply from renewable and non-renewable sources. Greta provides function decorators and functions which change the behaviour of your code based on the carbon intensity: skip heavy functions, run more function iterations if the carbon intensity is low, and much, much more.

Getting Started

• The codebase has a flat structure, with 6 code files
• Makes API requests (GET) (no other key dependencies)

Installation

• The codebase is compatible with Python 3.6 and above (f-string 3.6 in greta/checks.py)
• Run pip install -e . in top-level directory to install package in local directory
• Alternatively, install from pypi with

pip install greta

Developers

• Install developer requirements with pip install -r requirements-dev.txt
• Tests are present in tests/ (using pytest)

The project uses GitHub Actions for CI/CD.

CI File	Purpose
test	Executes on push for any branch, pull request for any branch. Linting (with black, isort). Runs unit tests (with pytest)

Code Overview

• The codebase has a flat structure, with 5 files, a few functions and no key classes
• There are 3 source code objects in top-level __main__/__init__:

condition_function from greta/conditionals.py

condition_function(low_func: Callable, high_func: Callable, limit: str, *args, **kwargs)

The function takes two functions and an intensity limit. A limit, and arguments to give to a function.
It executes a the high or low function based on the carbon intensity.

condition_variable from greta/conditionals.py

condition_variable(low_value, high_value, limit: str)

It takes a low_value, high_value, and limit.
Turns the limit into an intensity enum and gets the carbon intensity.
If the carbon intensity is less than or equal to the limit,
it return the low value,
otherwise it returns the high value.
Calls query.get_current_intensity and utils.str_to_intensity_enum.

get_current_intensity from greta/query.py

get_current_intensity() -> str

Gets the current UK carbon intensity.
Converts the intensity from a string to an intensity enum.
Makes a REST GET request (from https://api.carbonintensity.org.uk/intensity).

These entrypoints are broken down into the following modules:

• greta.conditionals has 2 entrypoints
• greta.query has 1 entrypoints

Contributing

Pull requests, issues and feature requests are welcome! Please refer to the contributing guide for more information.

License

Distributed under GNU GPL-3 license. Read the license for full terms.

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