pub fn read_active(root: &Path) -> Option<LibtorchInfo>Expand description
Read the active libtorch variant from <root>/libtorch/.active and
parse its .arch metadata.
On heterogeneous rigs (multiple hosts sharing the same checkout via
NFS / virtiofs / S3-FUSE) a single .active file can’t represent
“PT 2.10 on the Blackwell host AND PT 2.7 on the Pascal host” at
the same time. The FDL_LIBTORCH_CASE env var selects an
alternative pointer file libtorch/.active.<case>; the file’s
content is read identically to .active.
Setting FDL_LIBTORCH_CASE=<case> with no corresponding pointer
file is a hard misconfiguration: this function logs the missing
file to stderr and returns None (callers surface this as “libtorch
not configured”) rather than silently falling back to .active,
which would otherwise mask the user’s explicit selection.