Float data precision issue

[changliao1025]

When the mesh was saved during the simulation, the precision was lost partially; this causes a vertex comparison function to fail in some steps:

[changliao1025]

The above pVertex_end is actually the point with the cell center. But during the transfer, a slight difference was introduced and the program will miss it.
In this case, we will use a distance to check whether they are the same or not.