PatchToroid is a subclass of PatchGrid in which the patch neighbors are initialized in a toroidal fashion, such that patches on the edge of the grid are "connected" (via neighbor relationships) to patches on the opposite edge.

Note that since PatchGrid objects can already be 3 dimensional, that a 3D toroidal PatchGrid is actually not the traditional donut shaped toroidal topology--it's the corresponding topology in 4 dimensions. Now I don't know about you, but I get a headache thinking about this stuff, so let's just agree that "toroid" is not the totally accurate term, but that it's the easiest way to describe what's going on here.