2.6. Download the LAMMPS source with git¶

All LAMMPS development is coordinated through the “LAMMPS GitHub site”. If you clone the LAMMPS repository onto your local machine, it has several advantages:

You can stay current with changes to LAMMPS with a single git command.
You can create your own development branches to add code to LAMMPS.
You can submit your new features back to GitHub for inclusion in LAMMPS.

You must have git installed on your system to use the commands explained below to communicate with the git servers on GitHub. For people still using subversion (svn), GitHub also provides limited support for subversion clients.

Note

As of October 2016, the official home of public LAMMPS development is on GitHub. The previously advertised LAMMPS git repositories on git.lammps.org and bitbucket.org are now deprecated or offline.

You can follow LAMMPS development on 3 different git branches:

stable : this branch is updated with every stable release
unstable : this branch is updated with every patch release
master : this branch continuously follows ongoing development

To access the git repositories on your box, use the clone command to create a local copy of the LAMMPS repository with a command like:

$ git clone -b unstable https://github.com/lammps/lammps.git mylammps

where “mylammps” is the name of the directory you wish to create on your machine and “unstable” is one of the 3 branches listed above. (Note that you actually download all 3 branches; you can switch between them at any time using “git checkout <branch name>”.)

Once the command completes, your directory will contain the same files as if you unpacked a current LAMMPS tarball, with the exception, that the HTML documentation files are not included. They can be fetched from the LAMMPS website by typing make fetch in the doc directory. Or they can be generated from the content provided in doc/src by typing make html from the doc directory.

After initial cloning, as bug fixes and new features are added to LAMMPS you can stay up-to-date by typing the following git commands from within the “mylammps” directory:

$ git checkout unstable      # not needed if you always stay in this branch
$ git checkout stable        # use one of these 3 checkout commands
$ git checkout master        # to choose the branch to follow
$ git pull

Doing a “pull” will not change any files you have added to the LAMMPS directory structure. It will also not change any existing LAMMPS files you have edited, unless those files have changed in the repository. In that case, git will attempt to merge the new repository file with your version of the file and tell you if there are any conflicts. See the git documentation for details.

If you want to access a particular previous release version of LAMMPS, you can instead “check out” any version with a published tag. See the output of git tag -l for the list of tags. The git command to do this is as follows.

$ git checkout tagID

Stable versions and what tagID to use for a particular stable version are discussed on this page. Note that this command will print some warnings, because in order to get back to the latest revision and to be able to update with git pull again, you will need to do git checkout unstable (or check out any other desired branch) first.

Once you have updated your local files with a git pull (or git checkout), you still need to re-build LAMMPS if any source files have changed. How to do this depends on the build system you are using.

Change to your build folder and type:

cmake . --build

CMake should auto-detect whether it needs to re-run the CMake configuration step and otherwise redo the build for all files that have been changed or files that depend on changed files. In case some build options have been changed or renamed, you may have to update those by running:

cmake .

and then rebuild.

Switch to the src directory and type:

$ make purge             # remove any deprecated src files
$ make package-update    # sync package files with src files
$ make foo               # re-build for your machine (mpi, serial, etc)

to enforce consistency of the source between the src folder and package directories. This is OK to do even if you don’t use any packages. The “make purge” command removes any deprecated src files if they were removed by the patch from a package sub-directory.

Warning

If you wish to edit/change a src file that is from a package, you should edit the version of the file inside the package sub-directory with src, then re-install the package. The version in the source directory is merely a copy and will be wiped out if you type “make package-update”.

Git protocols

The servers at github.com support the “git://” and “https://” access protocols for anonymous, read-only access. If you have a suitably configured GitHub account, you may also use SSH protocol with the URL “git@github.com:lammps/lammps.git”.

The LAMMPS GitHub project is currently managed by Axel Kohlmeyer (Temple U, akohlmey at gmail.com) and Richard Berger (Temple U, richard.berger at temple.edu).