Using Spack on top of EESSI: A Proof of Concept¶

EESSI provides a rich set of software installations, which were built and installed using EasyBuild.

Can we convince Spack to reuse software installed in EESSI, and by doing so make EESSI more attractive to those of you who prefer using Spack over EasyBuild?

Several people have expressed interest in exposing the software installations provided by EESSI to Spack, so they can be used as dependencies when building and installing software with Spack.

Recently, we have explored how this could be achieved through a proof-of-concept with QuantumESPRESSO.

The goal here is to build and install only QuantumESPRESSO with Spack, and leveraging software installations from EESSI for all required dependencies, including the compiler and libraries for MPI, BLAS/LAPACK, FFTW, etc.

Step 1: A Spack database for EESSI¶

To get started, we created an external Spack database using the spack.database.Database class that Spack provides, which exposes software installed in EESSI to Spack.

This was done through a Python script, and only for a small set of hand-picked software installations: those that are build or runtime dependencies of QuantumESPRESSO.

Using spack find, we can check whether Spack is aware of these installations:

Spack database for software installations included in EESSI

Looks good so far...

Step 2: Checking required dependencies for QuantumESPRESSO¶

Spack being aware of software installed in EESSI is not sufficient though. We need to make sure those installations are also actually used by Spack to resolve required dependencies.

For this, we need to provide the necessary metadata for those installations, including which variants they provide. When done correctly, we can see that all required dependencies are indeed resolved using spack spec:

Checking required dependencies with spack spec

Here, we use @7.4.1 to specify the QuantumESPRESSO version we want to install, and ~mpi to ensure that the QuantumESPRESSO installation will have MPI support.

Step 3: Installing QuantumESPRESSO with Spack¶

The real test consist of actually trying to build and install QuantumESPRESSO using Spack, by running spack install quantum-espresso:

Installing QuantumESPRESSO with spack install

That worked like charm!

Step 4: Running QuantumESPRESSO¶

Finally, we try to actually run QuantumESPRESSO as it was installed with Spack.

We set up the environment with spack load quantum-espresso, and feed an input file into the main command pw.x:

Running the pw.x binary

This was just a simple single-core test, but it does seem to work as expected!

When we inspect the pw.x binary a bit more closely, we can see that it (only) links to libraries provided by EESSI:

Inspecting the list of libraries that pw.x binary links to

It's clear that more work needs to be done to further validate the installation and check its performance, but this is a nice first step...

More information & updates¶

This work is being done in collaboration with members of the Spack development team, including Todd Gamblin and Massimiliano Culpo.

For updates, check the dedicated support issue that was opened on using Spack on top of EESSI, or stay tuned for future blog posts!