First (?) build on Debian is a success.

[brettviren]

Congrats on first release!

Right on the heels of Heidi's build on gpvm, I built on Debian 12.

In general, it went very smoothly.

Minor Issues

I hit two small issues:

1. I wanted to attempt to avoid any shell environment changes. I was able to build GCC, add the two repos but building the phlex stack fails quickly:

$ ./spack/bin/spack install -j 64 phlex %gcc@14
==> Error: cannot load package 'icaruscode' from the 'fnal_art' repository: 'SPACK_ROOT'

If someone understands this (to me) unexpected behavior, please let me know.

After following phlex's install directions more closely to the letter and building inside a Spack Environment things went smooth until the 2nd minor issue.

2. This probably falls into (my) user error. Building mesa failed due to missing /usr/bin/llvm-config. I had Debian's llvm-14 and llvm-19 packages installed but not the unnumbered llvm package which provides the symlink to one of the versioned llvm-config's. Installing this package and repeating the spack install finished.

Build stats

Some stats

• CPU: AMD 7970X
• GCC stack install: 21m 22s
  • GCC itself: 9m 32s
• Concretization: 12s
• Phlex stack install: 32m 5s
  • Phlex stack itself: 38s
• Final size: 4.4G spack/opt/spack/linux-zen4/

Some observations

Watching top I notice a woefully small amount of parallel building for most packages. The main of culprit of slow serial processing seems to is autoconf's configure. Eg, tar takes 32s to configure and 1.4s to build.

Even when a compilation phase was entered, it was rare to see all 64 cores light up. Peak average load was briefly as high as 12 or 20. The fast majority of compilation was 1 or 2 cores. It tells me 64 cores is not buying all that much compared to phlex's suggested 12.

It would be nice if Spack could execute its graph in parallel.

Some thoughts for future building

The phlex build instructions are good to set us up for success. But, there are two additional Spack config issues we should consider before starting a build

• How to use a Spack configuration "scope" to avoid "polluting" ~/.spack. This matters when one has more than one Spack instance in ones life. Heidi also raised this issue in her build report.

• Configure the Spack target, or add, eg target=x86_64 to spack install command line to avoid building binaries that only work on the build host hardware architecture.