This package enables installation of Loci/CHEM via Spack.

Setup

First obtain Spack and source the activation script:

git clone -c feature.manyFiles=true https://github.com/spack/spack.git
. spack/share/spack/setup-env.sh

Second, run spack list to pull down the built-in repositories. Next, have Spack search your system for compilers and other software it can reuse. Make sure any software you want it to find is on your path:

spack compiler find
spack external find

Next, add this and the Loci Spack repo as git-based repositories and pull them both down:

spack repo add --name loci_repo https://github.com/TimothyEDawson/loci_spack.git
spack repo add --name chem_repo https://github.com/TimothyEDawson/chem_spack.git
spack repo update loci_repo
spack repo update chem_repo

And you're good to go! You can verify that Spack is able to find the packages with spack info chem and spack info loci. You can also pull in any updates by rerunning the update commands, or update all repos (including built-ins) with:

spack repo update

Obtaining the Source Code:

Loci/CHEM is currently export-controlled, and access is restricted accordingly. This Spack repo is set up to use either tarballs or a git bundle, both of which are distributed via CAVS SimSys. To use the tarballs, first download the encrypted .tgz files and decrypt them. You may then either execute your spack commands from the directory containing them, or set the environment variable CHEM_TARBALL_DIR to their location.

To use the git bundle, likewise download and decrypt the .bundle file, then set the CHEM_GIT_REPO environment variable to point to the file (or to your own hosted mirror of its contents). Note that this will take precedence over the tarball option if set.

Note for Python:

I generally recommend installing your own Python version so that Spack will use that instead of the older system-installed version, making sure it's on your path and running spack external find again. This should add lines like:

packages:
  python:
    externals:
    - spec: python@3.14.0rc1+bz2+ctypes+dbm+lzma+pyexpat+pythoncmd+readline+sqlite3+ssl~tix+tkinter+uuid+zlib
      prefix: /home/tim.dawson/python_venvs/uv-py3p14

to your ~/.spack/packages.yaml file. I highly recommend using uv to manage your Python installation.

Basic Installation (Not Recommended)

You can now install the latest snapshot version directly from the Git repository:

spack install chem@develop

You can also specify the compiler to use, e.g. to install with LLVM compilers:

spack install chem@develop %llvm

Specific tagged releases will be added over time. They will then be installable with the version syntax:

spack install chem@4.1.b7

Environment Setup (Recommended)

We recommend utilizing Spack environments to manage your Spack installations. To create and activate an environment called "chem", execute:

spack env create chem
spack env activate -p chem

Where the -p option will prepend the terminal with the name of the activated environment (highly recommended). To deactivate an active environment, run:

despacktivate

With the environment active, you will need to manually add specs before you will be able to install them. It is also recommended to manually concretize the specs before installation, which performs the dependency analysis and shows which packages will be installed and which already-installed packages will be reused.

spack add chem@develop
spack concretize

You can now install the requested packages via spack install. If you did not manually concretize, it will automatically concretize when you install.

Post-Installation Steps

Spack will not set the CHEMISTRY_DATABASE environment variable, so it will need to be set manually. I recommend creating a copy of the data_base folder in a separate, fixed location, for use with any CHEM installations. This can be easily obtained by cloning or extracting the CHEM source code, e.g.:

cd $HOME/code
git clone chem-4.1-b8.bundle chem
export CHEMISTRY_DATABASE=$HOME/code/chem

Note that $CHEMISTRY_DATABASE must point to folder which contains the data_base folder, not to the data_base folder itself.

Updating

As this repository is updated, you only need to pull the latest version using Spack:

spack repo update

Developing

In order to utilize Spack while actively developing for Loci and CHEM you can follow the instructions for creating an environment, adding the spack develop command before concretizing:

spack add chem@develop
spack develop chem@develop
spack develop loci@develop
spack concretize

By adding these commands, Spack will clone the specified packages into the environment directory instead of a temporary directory, and use these directories as-is during the build and install process. Thus the developer may cd into these directories and make changes to the source code before executing spack install.

To enter the directories, use the convenience function to enter the environment directory and then cd into the code directory:

spack cd -e
cd chem

After making changes you can re-run spack install to rebuild the code, and it should automatically skip unnecessarily rebuilding files in the standard make fashion.