2.5. Download source via 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 communicate with the public Git server for LAMMPS.

Warning

As of Oct 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, may not be up-to-date, and may go away at any time.

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 <branchname>”.)

Once the command completes, your directory will contain the same files as if you unpacked a current LAMMPS tarball, with two exceptions:

1) No LAMMPS packages are initially installed in the src dir (a few packages are installed by default in the tarball src dir). You can install whichever packages you wish before building LAMMPS; type “make package” from the src dir to see the options, and the Packages doc page for a discussion of packages.

2) 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 the doc directory.

After initial cloning, as bug fixes and new features are added to LAMMPS, as listed on this page, 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 the 3 checkout commands
git checkout master
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 “checkout” 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 first will need to first type “git checkout unstable” (or check out any other desired branch).

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. To do this, you should cd 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)

just as described on the Install patch doc page, after a patch has been installed.

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 src dir is merely a copy and will be wiped out if you type “make package-update”.

Warning

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

The LAMMPS GitHub project is managed by Christoph Junghans (LANL, junghans at lanl.gov), Axel Kohlmeyer (Temple U, akohlmey at gmail.com) and Richard Berger (Temple U, richard.berger at temple.edu).