ship.bits

Policy layer and recipes for building FairShip (the SHiP experiment software) with bits. It is a thin overlay on stacks.bits, the shared base every community builds on: the build environment, the compiler/build-type profiles and the ~1100-recipe lcg.bits pool all come from there. This repository adds only the SHiP CVMFS namespace, the FairRoot/FairShip stack, and the few externals SHiP must build differently from LCG.

Anything not listed under Recipes comes from lcg.bits and hashes like the same package built by any other group on the same base (a group that sets its own env: or package_family, as LHCb currently does, is not on the same base), so it is reused from the store instead of rebuilt.

ship.bits  ──requires──▶  stacks.bits  ──requires──▶  lcg.bits
  defaults-ship.sh          defaults-release.sh          ROOT, Geant4, pythia8,
  FairRoot, FairShip, …     gcc13/14/15, clang, dbg,      evtgen, acts, lhapdf, …
                            cuda, dev3/dev4

bits clones stacks.bits and lcg.bits on demand (repository-provider packages) into sw/REPOS/ and adds them to BITS_PATH. Recipes in ship.bits come first on the path, so a recipe here replaces the lcg.bits one of the same name for the whole SHiP build.

Composed with --defaults ship[::gcc15].

• requires: stacks.bits — the shared base.
• variables: release: "main" plus overrides: lcg.bits/stacks.bits: tag: "%(release)s" — both providers follow the release; main is only the default (see Releases). Identical in every stacks-based overlay.
• overrides: "ROOT:osx" — ROOT v6.40.00 on macOS only, for Apple-clang/Xcode; Linux keeps the recipe default.
• system: — the CVMFS namespace and store policy. Never hashed, so it never affects reuse.

As in ALICE, a package lands once at …/ship/<arch>/Packages/<pkg>/<version>-<revision>, where <arch> is the build arch (e.g. x86_64-el9-gcc15-opt), whatever release it was built for; a package already there is not published again.

The overlay deliberately has no env: and no disable:: both are hashed and would make every SHiP package differ from the shared stacks.

SHiP's own stack:

Externals that replace the lcg.bits recipe, because SHiP needs a different build:

Each replacement changes the hash of that package and of everything above it in the SHiP build, so those are rebuilt for SHiP; everything below them is still reused. lhapdf is taken from lcg.bits.

The single release variable names the lcg.bits (and stacks.bits) branch to build against. SHiP's CVMFS paths have no release level: packages are published once per build arch whatever the release. bits resolves it, highest precedence first:

Pass the release on the command line (--set release=LCG_110); main is only the default. Every stacks-based group (atlas, lhcb, key4hep, ship) follows this rule, because a --set value is also exported into the build environment and enters every package hash: a release chosen any other way (a release: in a profile, or the checkout's branch name) hashes differently, and nothing the other groups built would be reused. Reuse also needs the same lcg.bits and stacks.bits commits and the same compiler/build-type profiles.

The effective release must exist as an lcg.bits and a stacks.bits branch.

bits deps  FairShip --defaults ship::gcc15                         # inspect the tree
bits build FairShip --defaults ship::gcc15                         # main line
bits build FairShip --defaults ship::gcc15 --set release=LCG_110   # on LCG_110
bits build FairShip --defaults ship::gcc15::testbed                # publish to the testbed root

The testbed overlay (from testbed.bits, which must be on BITS_PATH; always last in the chain) replaces only the CVMFS root and user prefix; the layout above is kept.

Explore a local build with bitsenv:

bitsenv q FairShip
bitsenv enter FairShip/26.06

bits cvmfs-path -c . --defaults ship::gcc15 --admin --package <pkg> --version <v> --platform <p> prints where a package would be published, without building.