Welcome to grackle’s documentation!

Grackle is a chemistry and radiative cooling library for astrophysical simulations and models. The core library provides interfaces for C, C++ and Fortran simulation codes. The project also offers the Pygrackle package to provide Python bindings.

Features

Grackle provides functions to update chemistry species; solve radiative cooling and update internal energy; and calculate cooling time, temperature, pressure, and ratio of specific heats (γ). The library offers

  • two options for primordial chemistry and cooling. It can (i) evolve a non-equilibrium chemistry network OR (ii) use tabulated cooling rates calculated with the photo-ionization code, Cloudy.

  • tabulated metal cooling rates calculated with Cloudy.

  • photo-heating and photo-ionization (with optional self-shielding corrections) from either the Faucher-Giguere et al. (2009) or Haardt & Madau (2012) UV backgrounds.

  • support for user-provided arrays of volumetric and specific heating rates.

Our method paper provides more information.

Getting Grackle

Currently, Grackle must be built from source. If you only need Grackle as a dependency of a simulation code and that code is built with CMake, then that code’s build system might be configured to automatically fetch, build, and link Grackle into the code for you (Enzo-E is an example of a code configured in this manner).

If you contribute to a simulation code, our Integration Guide provides guidance on simplifying the process (for you and your users) of configuring your code to use Grackle.

Building the Core Grackle Library From Source

Grackle requires a C99 compiler, a Fortran compiler, and HDF5 (1.6 or newer). On most platforms, compilation with the CMake build system (3.16 or newer) is as simple as:

cmake -B build          # configure the build-directory
cmake --build ./build   # perform the build

You can run invoke the examples from within the build/examples directory.[1] To build Grackle as a shared lib, replace the first command with cmake -DBUILD_SHARED_LIBS=ON -Bbuild. To install Grackle, invoke cmake --install ./build [--prefix <prefix/path>] (the optional part lets you specify an install-path).

For more details (especially if you encounter any errors), see our comprehensive Installation Guide. It provides more context for inexperienced CMake users, describes additional configuration options (relevant if you encounter issues), and describes Grackle’s “classic” build-system.

Building Pygrackle from Source

Once you have a Fortran compiler and a copy of HDF5 (1.6 or newer), simply invoke the following from the root of the Grackle repository

~/grackle $ pip install .

For more about installation see our Pygrackle installation guide.

Getting Started

To help you start using Grackle, we provide:

Help

Mailing List

If you have any questions, please join the Grackle Users Google Group. Feel free to post any questions or ideas for development.

Slack Channel

We also use Slack for lower latency discussions. If you’d like help in real time, this is the place. Click here for an invitation to our Slack channel.

GitHub Issues

Alternatively you can describe issues or get help or post ideas for development by openning a GitHub Issue

Contributing

Development of Grackle happens in the open on GitHub here. We welcome new contributors. Please, see the Grackle Community Code of Conduct. For a guide to developing Grackle, see How to Develop Grackle.

Citing grackle

The Grackle method paper can be found here.

The Grackle library was born out of the chemistry and cooling routines of the Enzo simulation code. As such, all of those who have contributed to Enzo development, and especially to the chemistry and cooling, have contributed to the Grackle.

If you used the Grackle library in your work, please cite it as “the Grackle chemistry and cooling library (Smith et al. 2017).” Also, please add a footnote to https://grackle.readthedocs.io/.

Footnotes