Chunk cross_chunk_links/ array by vertex chunk indices

[Andrew-Keenlyside]

Chunk cross_chunk_links array:

cross_chunk_links/level_diff/x.y.z.i.j.k/Zarr Array

• Where xyz and ijk are vertex chunk indexes (6 dimensional zarr array chunking)

Array: Kx2 or ragged array (as per links/) containing the two vertex index of the start and end (from xyz to ijk)

Solution would work intially well for streamlines and graphs, however meshes here may be complicated.

Issues:

• Containing faces where 3+ points each fall in different chunks (only chunking array by 2 chunk IDs)
• Sharding convention as this will increase file number significantly

[Andrew-Keenlyside]

Currently implemented as N dimensional (i.e. a face covering 2 chunks has 6D chunking, a face over 3 chunks has 9D ....). This is not an elegant solution but depending on chunk size, I expect these to be fairly uncommon edge cases. Keeping this approach flattens the access pattern and keeps the fastest approach for the vast majority of cross chunk edges. Happy to change if there's a better alternative, this is just a first working implementation.