What's the rule for the global DOFs in [https://ferrite-fem.github.io/Ferrite.jl/stable/examples/incompressible_elasticity/](url)

[zyhsjtu]

in this example https://ferrite-fem.github.io/Ferrite.jl/stable/examples/incompressible_elasticity/,
if my mesh is generated as
grid = generate_grid(Triangle, (nx, ny), Vec((0.0, 0.0)), Vec((2.0, 1.0)))
the elements is (1, 2, 4), (2, 5, 4), ( 2, 3, 5) and ( 3, 6, 5)
then, the global DOFs should be {1, 2, 3, 4, 5, 6,10,11,12}, {4, 5, 6,13,14,15, 10,11,12}, { 4, 5, 6,7,8,9,13,14,15} and {7,8,9,16,17,18,13,14,15}
but in the example https://ferrite-fem.github.io/Ferrite.jl/stable/examples/incompressible_elasticity/, the global DOFs are [1, 2, 3, 4, 5, 6, 7, 8, 9], [3, 4, 10, 11, 5, 6, 8, 12, 9], [3, 4, 13, 14, 10, 11, 8, 15, 12] and [13, 14, 16, 17, 10, 11, 15, 18, 12].
What's the rule for the global DOFs?
and How can I get the global DOFs as this order {1, 2, 3, 4, 5, 6,10,11,12}, {4, 5, 6,13,14,15, 10,11,12}, { 4, 5, 6,7,8,9,13,14,15} and {7,8,9,16,17,18,13,14,15}?

[KnutAM]

In Ferrite, the DoFs are not ordered according to the node numbers. We are working on making this clearer in the docs, see #875

The distribution algorithm is described in the devdocs here (note, this refers to the current master branch of Ferrite, so some vocabulary is slightly different). There is a method to reorder! the dofs as we discussed here, but I think getting the permutation you ask for might be somewhat challenging to implement, and I'm not sure if it will break some used to enforce periodic constraints.

[zyhsjtu]

Thanks for your response, I had understood the rule and know how to deal with it.