Update dataset.py

[Shiyu-Sandy-Du]

open_dataset can only get coordinates in single precision. Here in this change, the coordinates can be extracted in double precision

[ashwinvis]

@Shiyu-Sandy-Du if your mesh is so fine, then it might be worthwhile to also modify the precision for np.round call. Have you tested it with your data?

[Shiyu-Sandy-Du]

@Shiyu-Sandy-Du if your mesh is so fine, then it might be worthwhile to also modify the precision for np.round call. Have you tested it with your data?

Hi! My mesh is a spectral element mesh, so at the interface the coordinates of the points is not exactly the same to the precision of e-16 (it somehow to the error of e-14 in the global coordinates), but it could be avoided by identifying them by single precision and extracting them by double precision (just like what is modified in this PR)

[ashwinvis]

Ok. I understand. It is unlikely to have super-fine meshes. Let's merge as it is.