Fix GridGenerator::merge_triangulations() for simplex meshes

[peterrum]

No description provided.

[drwells]

I'm traveling today so I might not be around to approve this later. This is fine but it would be better if we avoided the double negative.

[drwells]

Suggested change

	if (std::find_if(cells.begin(), cells.end(), [](const auto &cell) {
	return cell.vertices.size() !=
	ReferenceCells::get_hypercube<dim>().n_vertices();
	}) == cells.end())
	GridTools::consistently_order_cells(cells);
	if (std::all_of(cells.begin(), cells.end(), [](const auto &cell) {
	return cell.vertices.size() ==
	ReferenceCells::get_hypercube<dim>().n_vertices();
	}))
	GridTools::consistently_order_cells(cells);

[masterleinad]

I think the condition really rather is that there is something to be done if any of the cells reference is a (generalized) hex, isn't it? Shouldn't it be

Suggested change

	if (std::find_if(cells.begin(), cells.end(), [](const auto &cell) {
	return cell.vertices.size() !=
	ReferenceCells::get_hypercube<dim>().n_vertices();
	}) == cells.end())
	GridTools::consistently_order_cells(cells);
	if (std::any_of(cells.begin(), cells.end(), [](const auto &cell) {
	return cell.vertices.size() ==
	ReferenceCells::get_hypercube<dim>().n_vertices();
	}) == cells.end())
	GridTools::consistently_order_cells(cells);

then?

[peterrum]

The right logic is all_of. GridTools::consistently_order_cells only works if all cells are hypercubes. In all other cases, we store the orientation of faces/edges anyway. I have made the modification. It ready from my side!

[peterrum]

/rebuild