Setting up Spack

Downloading a spack instance

Spack is easy to set up: simply clone the key4hep fork, and use one of the provided spack “environments”, that is spack configuration that is created automatically from the current key4hep/key4hep-spack repository.

git clone https://github.com/spack/spack
git clone https://github.com/key4hep/key4hep-spack
source spack/share/spack/setup-env.sh
source key4hep-spack/environments/key4hep-release-user/setup_clingo_centos7.sh # NOTE: only needed on centos7
spack env activate key4hep-spack/environments/key4hep-release-user # or other environment, see below

These instructions assume that a Centos7 machine with a running CVMFS client is used (for other OSs see below). Since Spack cannot bootstrap with the system compiler on Centos7, a setup script for Clingo ( a spack dependency ) is provided.

Using Spack Environments

The spack environments available in key4hep-spack/environments bundle the spack configuration, setting up a suitable compiler from cvmfs, the key4hep package recipes, whether to create a view, etc. It is recommended to always use spack in an environment. New environments can be easily created by copying and modifying existing ones, but some use relative links to common configuration files in key4hep-spack/environments/key4hep-common, so they should be kept in the key4hep/environments directory.

The basic environment is key4hep-release, which is used for the central installations and therefore uses /cvmfs as install area. key4hep-debug is a variation for debug builds. The default compiler is gcc, but an environment that uses clang is provided under key4hep-release-clang. For local builds that use cvmfs read-only, key4hep-release-user can be used.

Using the key4hep-release-user environment

The key4hep user environment has the key4hep-stack bundle package in its spec list. By concretizing it, spack selects the latest compatible versions, re-using installations from cvmfs

spack concretize -f
spack find # lists the available concretized packages

The environment can be installed as is, although this will just install the bundle packages. However, this will create a setup script that can be used to load the software.

spack install

Custom builds can now be realized, by adding specs to the environment and concretizing together. For example, to build the stack with a local version of EDM4hep:

spack add edm4hep@master
git clone https://github.com/key4hep/edm4hep
# make some local changes to edm4hep
spack develop -p $PWD/edm4hep edm4hep@master
spack concretize -f
spack install

Configuring Spack

Alternatively, and for other platforms, spack can be configured in a few steps. These steps are essentially what is used to create the pre-configured spack instance in this script: https://github.com/key4hep/key4hep-spack/blob/master/scripts/ci_setup_spack.sh

While this still puts the configuration files in the global scope of spack, it is recommended to use them in an environment, as provided by key4hep-spack.

Installing Spack

Spack itself is very easy to install - simply clone the repository with git.

git clone https://github.com/spack/spack.git
source spack/share/spack/setup-env.sh

Installing the key4hep package recipes

The spack repository for key4hep packages is installed the same way:

git clone https://github.com/key4hep/key4hep-spack.git
spack repo add key4hep-spack

Configuring `packages.yaml`

In order to choose the right package versions and build options, spack sometimes needs a few hints and nudges. With the new concretizer (default as of spack version 0.17) this should be mostly obsolete. key4hep-spack ships a spack config file that should give a good build customization out of the box, but can also be customized further. It just needs to be copied to the configuration where spack searches for configurations:

cp key4hep-spack/environments/key4hep-common/packages.yaml spack/etc/spack/

Configuring `upstreams.yaml`

The cvmfs installation can be used as an “upstream installation”, by adding the following configuration:

cat <<EOT >> spack/etc/spack/upstreams.yaml
upstreams:
  spack-instance-1:
      install_tree: /cvmfs/sw.hsf.org/spackages6/
EOT

Setting up additional compilers

Often it is practical to use a compiler already installed upstream. Spack provides the spack compiler find command for this, but the compiler needs to be loaded into the PATH:

# loading the compiler from upstream
source /cvmfs/sft.cern.ch/lcg/contrib/gcc/11.2.0/x86_64-centos7/setup.sh
spack compiler find --scope site