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A Spack environment pairs an abstract manifest ( spack.yaml ) with a concretized lockfile ( spack.lock ); the lockfile is what makes the setup repeatable elsewhere. The open piece is how the concretizer should treat packages already present in the local store. The trade-off Recent releases favor reusing installed specs by default, though the exact default ha
Choosing a unify mode for a multi-root Spack environment I maintain a Spack environment with several root specs that share common dependencies (MPI, BLAS, compression libraries). The documented behavior is that with concretizer: unify: false each root is concretized independently, so the same dependency can appear at multiple concrete versions in one environ
Context A low-traffic HPC site wants to reduce repeated build costs by using Spack binary build caches. The documented --cache-only flag restricts installs to cached binaries and fails on a miss, while the default --use-cache falls back to source builds. Even with cached installs, the concretizer resolves the full dependency DAG, so the cache layout must mat
Integration Boundary Spack provides integration with CDash servers to centralize build reporting via the --cdash-upload-url , --cdash-build , and --cdash-track flags. This allows the Spack client to upload XML reports to a remote dashboard for monitoring build success and failure across different environments. Reporting Consistency and Noise While CDash aggr