def __init__(self, dx = 1., dy = 1., nx = None, ny = None):
Grid2D.__init__(self, dx = dx, dy = dy, nx = nx, ny = ny)
self.nonPeriodicCellVertexIDs = Grid2D._getCellVertexIDs(self)
self.nonPeriodicOrderedCellVertexIDs = Grid2D._getOrderedCellVertexIDs(self)
from fipy.tools import numerix
self._connectFaces(numerix.nonzero(self.getFacesBottom()),
numerix.nonzero(self.getFacesTop()))
