Regarding to the triangle bisection scheme used in fenics in adaptivity

General
1

Hello everyone

The triangle bisection in the adaptive process used in FEniCS is a new vertex bisection scheme or an RGB scheme?

2

Hi.

I think you refer to the refinement algorithm used by FEniCS rather than an adaptive process. In this case, the old Dolfin can be configured trough

parameters["refinement_algorithm"]

which has the options

[plaza,plaza_with_parent_facets,regular_cut]

The most popular one is plaza which preserve parent-child information. See for example https://fenicsproject.discourse.group/t/controling-the-refinement-of-an-element/5687/2. The new Dolfinx has plaza by default.

On the other hand, if you are referring explicitly to the marking step in an adaptive process, they are independent of FEniCS, and there is plenty of marking strategies hanging around in the FEniCS discussions and Github repos. You have goal-oriented, RGB, Dörfler, etc (see for example https://github.com/rbulle/fenics-error-estimation/blob/master/fenics_error_estimation/mark.py)

Cheers.

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3

Is Fenics supports New vertex bisection rule ?

4

As far as I can tell the new vertex bisection rule only works for triangles (Ref Local refinement of simplicial grids based on the skeleton , https://www.sciencedirect.com/science/article/abs/pii/S0168927499000227). I think this paper is also the source of the plaza algorithm.

There seems to be certain cases were new bisection rule is equivalent to plaza, see referenced paper above)

Please note that it is possible to implement algorithms on top of dolfinx. The trickiest thing is to get the mpi communication right.

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