feat(sharding): lift constraint on evenly divisible subchunk shapes

[LDeakin]

xref: zarr-developers/zarr-extensions#34

[normanrz]

Thanks! I can see the rationale of this change for the rectilinear chunk grid. However, I would favor keeping the strict requirement for regular outer chunk grids. That way, implementations that don't implement the rectilinear grid won't need to change.

[LDeakin]

I would favor keeping the strict requirement for regular outer chunk grids. That way, implementations that don't implement the rectilinear grid won't need to change.

I'm interested to hear more perspectives here. Personally, I think this change is very useful with regularly gridded arrays, and irregular grids just make the problem far more apparent. For example, say a chunk shape is constrained by a sensor or data pipeline and must be [997, 997, 997]. Well, the inner chunk shape can only be [1, 1, 1] because 997 is prime.

Would it be sufficient in your view to recommend that implementations that add support for this issue a warning that it will not be supported by impls that only support version 1.0 of the sharding codec?

[d-v-b]

+1 to this change, it seems like a logical extension of how we currently handle the shape / chunk grid relationship for the regular chunk grid.