Feature Request: Ubuntu/WSL2 Intel LLVM Site Config Example and Documentation

[BenjaminTJohnson]

Summary

Update the spack-stack “New Site Configs” documentation to include a clear, Ubuntu-focused example for using Intel LLVM compilers (icx/ifx/icpx) with a local site configuration, including relevant guidance for Ubuntu under WSL2.

This request does not ask for first-class platform support or new spack logic. It asks for a documented example and explicit notes because the current docs focus on GCC and reference GitHub Actions for other compilers, but do not yet provide an accessible worked example for Ubuntu + Intel LLVM.

Motivation

The current “New Site Configs” page:

• describes how to generate a site config from linux.default or macos.default, primarily with GCC examples, and
• recommends looking at GitHub Action workflows for non-GCC compilers.

While that framework is correct, in practice users following those general instructions on Ubuntu (especially under WSL2) frequently run into predictable issues when using Intel LLVM compilers, including:

• Intel runtime library discovery and RPATH handling
• reliance on environment initialization (setvars.sh)
• NetCDF family and other external component detection mismatches

Providing a documented, concrete example for this specific setup would close this practical gap.

Proposed Documentation Enhancements

1. Add an Ubuntu + Intel LLVM site config example

   • Comprehensive site/packages.yaml and site/compilers.yaml snippets
   • Source paths and runtime considerations for Intel oneAPI
   • Intel LLVM versions known to work on Ubuntu

2. Integrate this example into the “New Site Configs” page

   • Under the Linux section, with explicit reference to Ubuntu
   • Show how to start from linux.default and evolve to an Intel LLVM config

3. Add WSL2 Ubuntu notes

   • Recommended filesystem placement (ext4 vs /mnt/c)
   • Environment consistency (interactive vs build shells)
   • Scoped limitations or caveats (e.g., MPI variants under WSL2)

4. Link to CI examples and any Intel LLVM test workflows

   • Connect the example to the existing GitHub Actions use of Intel LLVM

Why This Matters

• Ubuntu is the most common WSL2 distro used by contributors
• Intel LLVM is the modern Intel compiler strategy used in JCSDA stacks
• The current documentation assumes competence with compilers other than GCC, but practical examples significantly reduce trial-and-error ...
• This update fits squarely within the site config model the docs describe: no new code paths, just better examples and clarity for a common use case.

Thanks for considering this enhancement: it would make the “new site configs” workflow more approachable for a broad group of contributors. It could also be extended (or genericized) to support LLVM Flang/Clang. Ideally, I'd like to be able to have a GCC stack, Intel LLVM stack, and LLVM Flang/Clang stack in the same Ubuntu instance, so I could test on multiple compilers + configurations.

[climbfuji]

I'll add this to the spack-stack-2.1 release project.

[eap]

The existing tier-2 ec2 ubuntu config includes a readme that has most of this information except the WLS2 notes.... Agree with dom on keeping this around for possible inclusion in 2.1.