\(\renewcommand{\AA}{\text{Å}}\)

3.8. Build the LAMMPS documentation

Depending on how you obtained LAMMPS and whether you have built the manual yourself, this directory has a number of subdirectories and files. Here is a list with descriptions:

README           # brief info about the documentation
src              # content files for LAMMPS documentation
html             # HTML version of the LAMMPS manual (see html/Manual.html)
utils            # tools and settings for building the documentation
lammps.1         # man page for the lammps command
msi2lmp.1        # man page for the msi2lmp command
Manual.pdf       # large PDF version of entire manual
LAMMPS.epub      # Manual in ePUB e-book format
LAMMPS.mobi      # Manual in MOBI e-book format
docenv           # virtualenv folder for processing the manual sources
doctrees         # temporary data from processing the manual
doxygen          # doxygen configuration and output
.gitignore       # list of files and folders to be ignored by git
doxygen-warn.log # logfile with warnings from running doxygen
github-development-workflow.md   # notes on the LAMMPS development workflow

If you downloaded LAMMPS as a tarball from the LAMMPS website, the html folder and the PDF files should be included.

If you downloaded LAMMPS from the public git repository, then the HTML and PDF files are not included. You can build the HTML or PDF files yourself, by typing make html or make pdf in the doc folder. This requires various tools and files. Some of them have to be installed (see below). For the rest the build process will attempt to download and install them into a python virtual environment and local folders.

A current version of the manual (latest feature release, that is the state of the release branch) is is available online at: https://docs.lammps.org/. A version of the manual corresponding to the ongoing development (that is the state of the develop branch) is available online at: https://docs.lammps.org/latest/ A version of the manual corresponding to the latest stable LAMMPS release (that is the state of the stable branch) is available online at: https://docs.lammps.org/stable/

3.8.1. Build using GNU make

The LAMMPS manual is written in reStructuredText format which can be translated to different output format using the Sphinx document generator tool. It also incorporates programmer documentation extracted from the LAMMPS C++ sources through the Doxygen program. Currently the translation to HTML, PDF (via LaTeX), ePUB (for many e-book readers) and MOBI (for Amazon Kindle readers) are supported. For that to work a Python interpreter version 3.8 or later, the doxygen tools and internet access to download additional files and tools are required. This download is usually only required once or after the documentation folder is returned to a pristine state with make clean-all.

For the documentation build a python virtual environment is set up in the folder doc/docenv and various python packages are installed into that virtual environment via the pip tool. For rendering embedded LaTeX code also the MathJax JavaScript engine needs to be downloaded. If you need to pass additional options to the pip commands to work (e.g. to use a web proxy or to point to additional SSL certificates) you can set them via the PIP_OPTIONS environment variable or uncomment and edit the PIP_OPTIONS setting at beginning of the makefile.

The actual translation is then done via make commands in the doc folder. The following make commands are available:

make html          # generate HTML in html dir using Sphinx
make pdf           # generate PDF  as Manual.pdf using Sphinx and PDFLaTeX
make epub          # generate LAMMPS.epub in ePUB format using Sphinx
make mobi          # generate LAMMPS.mobi in MOBI format using ebook-convert

make fasthtml      # generate approximate HTML in fasthtml dir using Sphinx
                   # some Sphinx extensions do not work correctly with this

make clean         # remove intermediate RST files created by HTML build
make clean-all     # remove entire build folder and any cached data

make anchor_check  # check for duplicate anchor labels
make style_check   # check for complete and consistent style lists
make package_check # check for complete and consistent package lists
make link_check    # check for broken or outdated URLs
make spelling      # spell-check the manual

3.8.2. Build using CMake

It is also possible to create the HTML version (and only the HTML version) of the manual within the CMake build directory. The reason for this option is to include the installation of the HTML manual pages into the “install” step when installing LAMMPS after the CMake build via cmake --build . --target install. The documentation build is included in the default build target, but can also be requested independently with cmake --build . --target doc. If you need to pass additional options to the pip commands to work (e.g. to use a web proxy or to point to additional SSL certificates) you can set them via the PIP_OPTIONS environment variable.

-D BUILD_DOC=value       # yes or no (default)

3.8.3. Prerequisites for HTML

To run the HTML documentation build toolchain, python 3, git, doxygen, and virtualenv have to be installed locally. Here are instructions for common setups:

sudo apt-get install git doxygen

sudo yum install git doxygen

sudo dnf install git doxygen

3.8.4. Prerequisites for PDF

In addition to the tools needed for building the HTML format manual, a working LaTeX installation with support for PDFLaTeX and a selection of LaTeX styles/packages are required. To run the PDFLaTeX translation the latexmk script needs to be installed as well.

3.8.5. Prerequisites for ePUB and MOBI

In addition to the tools needed for building the HTML format manual, a working LaTeX installation with a few add-on LaTeX packages as well as the dvipng tool are required to convert embedded math expressions transparently into embedded images.

For converting the generated ePUB file to a MOBI format file (for e-book readers, like Kindle, that cannot read ePUB), you also need to have the ebook-convert tool from the “calibre” software installed. https://calibre-ebook.com/ Typing make mobi will first create the ePUB file and then convert it. On the Kindle readers in particular, you also have support for PDF files, so you could download and view the PDF version as an alternative.

3.8.6. Instructions for Developers

When adding new styles or options to the LAMMPS code, corresponding documentation is required and either existing files in the src folder need to be updated or new files added. These files are written in reStructuredText markup for translation with the Sphinx tool.

Before contributing any documentation, please check that both the HTML and the PDF format documentation can translate without errors. During testing the html translation, you may use the make fasthtml command which does an approximate translation (i.e. not all Sphinx features and extensions will work), but runs very fast because it will only translate files that have been changed since the last make fasthtml command.

Please also check the output to the console for any warnings or problems. There will be multiple tests run automatically:

A test for correctness of all anchor labels and their references
A test that all LAMMPS packages (= folders with sources in lammps/src) are documented and listed. A typical warning shows the name of the folder with the suspected new package code and the documentation files where they need to be listed:
```
Found 88 packages
Package NEWPACKAGE missing in Packages_list.rst
Package NEWPACKAGE missing in Packages_details.rst
```
A test that only standard, printable ASCII text characters are used. This runs the command env LC_ALL=C grep -n '[^ -~]' src/*.rst and thus prints all offending lines with filename and line number prepended to the screen. Special characters like Greek letters (\(\alpha~~\sigma~~\epsilon\)), super- or subscripts (\(x^2~~\mathrm{U}_{LJ}\)), mathematical expressions (\(\frac{1}{2}\mathrm{N}~~x\to\infty\)), or the Angstrom symbol (\(\AA\)) should be typeset with embedded LaTeX (like this :math:`\alpha \sigma \epsilon`, :math:`x^2 \mathrm{E}_{LJ}`, :math:`\frac{1}{2}\mathrm{N} x\to\infty`, or :math:`\AA`).
Embedded LaTeX is rendered in HTML output with MathJax and in PDF output by passing the embedded text to LaTeX. Some care has to be taken, though, since there are limitations which macros and features can be used in either mode, so it is recommended to always check whether any new or changed documentation does translate and render correctly with either output.

A test whether all styles are documented and listed in their respective overview pages. A typical output with warnings looks like this:

Parsed style names w/o suffixes from C++ tree in ../src:
   Angle styles:      21    Atom styles:       24
   Body styles:        3    Bond styles:       17
   Command styles:    41    Compute styles:   143
   Dihedral styles:   16    Dump styles:       26
   Fix styles:       223    Improper styles:   13
   Integrate styles:   4    Kspace styles:     15
   Minimize styles:    9    Pair styles:      234
   Reader styles:      4    Region styles:      8
Compute style entry newcomp is missing or incomplete in Commands_compute.rst
Compute style entry newcomp is missing or incomplete in compute.rst
Fix style entry newfix is missing or incomplete in Commands_fix.rst
Fix style entry newfix is missing or incomplete in fix.rst
Pair style entry new is missing or incomplete in Commands_pair.rst
Pair style entry new is missing or incomplete in pair_style.rst
Found 6 issue(s) with style lists

In addition, there is the option to run a spellcheck on the entire manual with make spelling. This requires a library called enchant. To avoid printing out false positives (e.g. keywords, names, abbreviations) those can be added to the file lammps/doc/utils/sphinx-config/false_positives.txt.