Wrong vertex classification on partitioned mesh reading a gmsh generated mesh

[zhangchonglin]

This is a summary of issue #418 as it is more appropriate here.

For a simple partitioned mesh: rectangular domain with 4 mesh parts, the vertex classification on some mesh parts are incorrect. Below is a mesh part with wrong vertex classification.

• All non-boundary vertices in this mesh part are inside the domain, so they should be classified on the model face. This corresponds to a class_dim of 2.
• But in the figure, many of the vertices have class_id=0.
  

It is confirmed that:

• When using full full buffer and safe methods, the classification looks fine.
• When using full bfs buffer and safe methods, the classification looks fine.
• Only when using bfs bfs buffer and safe methods, the classification does not look correct for some PICparts (the classification for top PICpart is fine, but is incorrect for bottom PICpart).