shore grd-merge

Concatenate multiple .grd files into one for an Xall multi-mesh run.

shore grd-merge INPUT1.grd INPUT2.grd ... -o OUTPUT.grd

Motivation

When an Xall job combines several independent Chimera components — for example a near-body wall mesh plus a far-field background — each component is generated as its own .grd + cc.par pair. Running them through Xall as one job needs both pairs concatenated into a single assembly.grd and a single assembly.cc.par whose patch indices are shifted to refer to the merged block list.

shore grd-merge does the file half:

shore grd-merge background.grd wall.grd -o assembly.grd

The merged file lists every block from inputs[0] first, then inputs[1], etc. The header block count is rewritten to the sum; shape and coordinate records are passed through byte-for-byte (no node values are touched). Order is the caller's choice — it matters because Xall's overset solver uses block ordering to break level / priority ties — but it must match the order used for the companion shore cc-par-merge.

Coordinated invocation

grd-merge and cc-par-merge are a pair. The cc.par patch block and box associated_block fields are 1-based indices into the .grd block list, so the merged cc.par only makes sense if its block ordering matches the merged .grd. Always invoke them with the same input ordering:

shore grd-merge    background.grd    wall.grd    -o assembly.grd
shore cc-par-merge background.cc.par wall.cc.par -o assembly.cc.par \
                   --grd assembly.grd

The example at examples/05-chimera-assembly/chimera_assembly.py runs both halves in sequence; the bash sibling examples/05-chimera-assembly/chimera_assembly.sh does the same through shore CLI calls only. See the cc.par + boxes pipeline walkthrough for the end-to-end flow.

Python API

from shore.io.grd import merge_grd

merge_grd(
    ["background.grd", "wall.grd"],
    "assembly.grd",
)

Raises ValueError for fewer than 2 inputs or a malformed .grd file.

See also

• shore grd — generate one .grd per Chimera component.
• shore cc-par-merge — companion cc.par merger; invoke as a pair.
• shore cc-par — generate one cc.par per component.