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Welcome to the CLASS public repository wiki!

This is not the same as the CLASS webpage nor the online html documentation.

For simplicity

Please use Anaconda, which is a Python distribution with graphical installer, and a package manager, that will play nicely with Mac OS X, and remove a lot of problems.

Note that you might encounter an error that reads ValueError: unknown locale: UTF-8 when launching ipython. Please paste these two lines:

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

at the end of your file ~/.bash_profile.

If you know what you are doing, and/or are on a Linux, you can of course use the Python distribution you want.

Table of contents

• Detailed instructions on how to install the code, including notes about installing on Mac OS X 10.9+ and the clang compiler.
• You can find more information on the Python wrapper.
• Problems at compilation, and you don't understand the error message? See the frequently asked questions, and search for the error message.

Branches

On this CLASS public repository, you will find only a limited number of branches:

• the master branch contains the latest release (corresponding to a version tag, e.g. v2.7.3)
• the GW_CLASS branch includes the Cosmological Gravitational Wave Background (CGWB) sector: monopole, Cl auto-correlation spectrum at given frequencies, CMBxCGWB cross-correlation spectrum at given frequencies. The code already includes several CGWB production mechanisms, and more can be added. The new features and input parameters of this branch are described and documented in GW_CLASS: Cosmological Gravitational Wave Background in the Cosmic Linear Anisotropy Solving System, by F. Schulze, L. Valbusa Dall'Armi, J. Lesgourgues, A. Ricciardone, N. Bartolo, D. Bertacca, C. Fidler, S. Matarrese, to appear in JCAP, arXiv:2305.01602.
• the classnet branch is accelerated by neural networks. Apart from this, it is kept very close to the master branch, with just a modified python wrapper and additional files located mainly in the python/nn directory. classnet is explained in the CosmicNet II paper by Sven Günther, Julien Lesgourgues, Georgios Samaras, Nils Schöneberg, Florian Stadtmann, Christian Fidler, and Jesus Torrado. It is possible that classnet gets merged into master at some point.
• the ExoCLASS branch contains new modules and features for models with exotic energy injection, including the DarkAges module, as described in Exotic energy injection with ExoCLASS: Application to the Higgs portal model and evaporating black holes, by P. Stöcker, M. Krämer, J. Lesgourgues, V. Poulin, JCAP 1803 (2018) 018, arXiv:1801.01871
• the class_matter branch contains a parallel version computing large scale structure CL's with the FFTlog method of the paper Beyond the traditional Line-of-Sight approach of cosmological angular statistics, by N. Schöneberg, M. Simonovic, J. Lesgourgues, M. Zaldarriaga, JCAP 1810 (2018) 047, arXiv:1807.09540. It incorporates a module for the pre-computation Bessel integrals, and it is provided with an illustrative input file matter.ini. Most new features are located in the new module matter.c
• until the release of v3.0, we were maintaining separate branches for each major release 2.x. They are still accessible. Note that all the tagged version of the master branch can be accessed anyway from the top menu.

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• If you want to contribute to the code, please look at the instructions