Define _localNonOverlappingFaceIDs for Gmsh

[guyer]

Gmsh ghost faces were not properly accounted for.

• Fix FaceVariable does not accumulate properly in parallel #856
• Fix Fix FaceVariable.globalValue method #400

[guyer]

Needs a test

[guyer]

@wd15 & @tkphd, can one of you take a look at this, please?

[wd15]

Looks good with a nice test case.

[wd15]

I guess you could also test the dumb parallel grid 2D if you want to, but probably not necessary. Don't need all the Gmsh setup for that.

[guyer]

I guess you could also test the dumb parallel grid 2D if you want to, but probably not necessary.

Grid2D or GmshGrid2D?

[guyer]

Why would we need to test Grid2D, anyway? It's not like there's any chance that it's broken:

======================================================================
FAIL: _test (fipy.meshes.uniformGrid2D.UniformGrid2D)
Doctest: fipy.meshes.uniformGrid2D.UniformGrid2D._test
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/guyer/mambaforge/envs/fipy3k_again/lib/python3.10/doctest.py", line 2217, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for fipy.meshes.uniformGrid2D.UniformGrid2D._test
  File "/Users/guyer/Documents/research/FiPy/fipy/fipy/meshes/uniformGrid2D.py", line 600, in _test

----------------------------------------------------------------------
File "/Users/guyer/Documents/research/FiPy/fipy/fipy/meshes/uniformGrid2D.py", line 820, in fipy.meshes.uniformGrid2D.UniformGrid2D._test
Failed example:
    print(numerix.allclose(area, 10))
Expected:
    True
Got:
    False
----------------------------------------------------------------------
File "/Users/guyer/Documents/research/FiPy/fipy/fipy/meshes/uniformGrid2D.py", line 822, in fipy.meshes.uniformGrid2D.UniformGrid2D._test
Failed example:
    print(area)
Expected nothing
Got:
    14.0
----------------------------------------------------------------------
File "/Users/guyer/Documents/research/FiPy/fipy/fipy/meshes/uniformGrid2D.py", line 825, in fipy.meshes.uniformGrid2D.UniformGrid2D._test
Failed example:
    print(numerix.allclose(area, 10))
Expected:
    True
Got:
    False
----------------------------------------------------------------------
File "/Users/guyer/Documents/research/FiPy/fipy/fipy/meshes/uniformGrid2D.py", line 827, in fipy.meshes.uniformGrid2D.UniformGrid2D._test
Failed example:
    print(area)
Expected nothing
Got:
    14.0

[guyer]

Ugh. in1d is broken for masked arrays (numpy/numpy#20011).

[guyer]

@wd15 & @tkphd: lots of changes since the last time I asked you to review, but now with tests(tm)!