Infrastructure

The legs of this group verify the machinery under every FLUME case rather than a flow: what the ghost cells hold on every fill path, whether the scheme carries absolute constants that break the scaling of the equations, and whether a rank that owns no block changes the result. Each oracle is an exact identity (a linear field reproduced, a rescaled run equal bit for bit, np 2 equal to np 1 bit for bit), so the bounds sit at round-off or at zero.

Case	ID	What it verifies
Ghost probe	GP	every face and edge ghost, on every fill path (copy, MPI, 2:1, inter-realm seams, physical boundaries), holds the value a stencil must read; a poison exposes reads before the fill
Scaling covariance and the reference layer	NV-0, NV-4, NV-5, NV-6, NV-8, NV-9	rescaled inputs reproduce the base run bit for bit; dimensional input, restart and output through [reference]
Ranks without blocks	DV-1	a rank that owns no block runs every model and option, and np 2 equals np 1 bit for bit
Non-finite state guard	— (nonfinite)	a NaN planted in the Sod state stops the run at step 1 on the guard's message, on every rank, with the first non-finite value located

The two figures of the group are regenerated from kept runs:

cd src/tests/flume/verification
(cd ghosts && ./check.sh --legs step --np 2 --keep)       # the "after" run; the "before" run is ghosts/work-before-p0-np2-step
./make_doc_runs.sh <dir> ranks
python3 make_doc_figures.py --out ../../../../docs/public/flume --runs <dir> --only ghosts ranks