Grid Utility Functions for Unstructured Grid Conversion into CPG format

[arturcastiel]

Grid Utility Functions for Unstructured Grid Conversion into CPG format

Summary

This pull request introduces a set of utility functions in the GridUtil namespace to facilitate unstructured grid indexing and conversion from an unstructured mesh representation to a corner-point grid (CPG) format. The key functions include:

• pillar_to_flat_array(pillar): Flattens a pillar-based coordinate representation into a linear array.
• convertUnsToCPG(coord_uns, element, nx, ny, nz): Converts an unstructured mesh into a corner-point grid representation, generating coord_cpg and zcorn_cpg arrays.

Changes Introduced

• Introduced convertUnsToCPG, which processes an unstructured mesh into a corner-point grid representation by:
  • Extracting pillar coordinates.
  • Mapping mesh elements to pillar-based coordinates.
  • Computing zcorn indices and assembling the final arrays.

Motivation

This implementation is necessary to convert the LGR refined coordinates given in a Unstructured Grid structured into CPG structure as required by the OUTPUT file format.

[arturcastiel]

jenkins build this please

[arturcastiel]

jenkins build this please

[arturcastiel]

@bska

[bska]

I understand that these are utility functions, but I think we should spend some more time on this before we merge them. In particular, it's not clear to me what guides the choice of input and output data structures here and vector<array<>> isn't what I usually reach for first personally. It might be the correct choice here, but then I'd like to see some more justification.

Other than that, there are minor issues regarding const objects and making too many copies, but those are secondary and can be fixed quickly.