The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview

TL;DR

CLASS is a new, flexible, and accurate Boltzmann code designed for cosmologists, emphasizing user-friendliness, ease of modification, and controlled accuracy, with better performance than existing codes.

Contribution

This paper introduces CLASS, a novel Boltzmann code that improves flexibility, usability, and accuracy control for cosmological computations.

Findings

CLASS is faster than comparable codes.

It offers a highly structured and modifiable framework.

The code emphasizes user-friendliness and accuracy management.

Abstract

The Cosmic Linear Anisotropy Solving System (CLASS) is a new accurate Boltzmann code, designed to offer a more user-friendly and flexible coding environment to cosmologists. CLASS is very structured, easy to modify, and offers a rigorous way to control the accuracy of output quantities. It is also incidentally a bit faster than other codes. In this overview, we present the general principles of CLASS and its basic structure. We insist on the friendliness and flexibility aspects, while accuracy, physical approximations and performances are discussed in a series of companion papers.