This documentation is built using Sphinx, and an automatically generated API reference using Doxygen and Breathe.

We always welcome suggestions on how to improve our documentation, as well as pull requests with corrections and additions.


To build the HPX documentation, you need recent versions of the following packages:

  • python3

  • sphinx 3.5.4 (Python package)

  • sphinx_rtd_theme (Python package)

  • breathe 4.16.0 (Python package)

  • doxygen

If the Python dependencies are not available through your system package manager, you can install them using the Python package manager pip:

pip install --user sphinx sphinx_rtd_theme breathe

You may need to set the following CMake variables to make sure CMake can find the required dependencies.


Specifies where to look for the installation of the Doxygen tool.


Specifies where to look for the installation of the Sphinx tool.


Specifies where to look for the installation of the Breathe tool.

Building documentation

Enable building of the documentation by setting HPX_WITH_DOCUMENTATION=ON during CMake configuration. To build the documentation, build the docs target using your build tool. The default output format is HTML documentation. You can choose alternative output formats (single-page HTML, PDF, and man) with the HPX_WITH_DOCUMENTATION_OUTPUT_FORMATS CMake option.


If you add new source files to the Sphinx documentation, you have to run CMake again to have the files included in the build.

Style guide

The documentation is written using reStructuredText. These are the conventions used for formatting the documentation:

  • Use, at most, 80 characters per line.

  • Top-level headings use over- and underlines with =.

  • Sub-headings use only underlines with characters in decreasing level of importance: =, - and ..

  • Use sentence case in headings.

  • Refer to common terminology using :term:`Component`.

  • Indent content of directives (.. directive::) by three spaces.

  • For C++ code samples at the end of paragraphs, use :: and indent the code sample by 4 spaces.

    • For other languages (or if you don’t want a colon at the end of the paragraph), use .. code-block:: language and indent by three spaces as with other directives.

  • Use .. list-table:: to wrap tables with a lot of text in cells.

API documentation

The source code is documented using Doxygen. If you add new API documentation either to existing or new source files, make sure that you add the documented source files to the doxygen_dependencies variable in docs/CMakeLists.txt.