Ordering of basis functions

Question

When genrating a square mesh (say 100 nodes), as far as I can tell, the nodes are numbered as follows:

mesh = UnitSquareMesh(9,9)

 |    |    |    |          |
11 - 12 - 13 - 14 - ... - 20
 |    |    |    |          |
 1 -  2 -  3 -  4 - ... - 10

However, when I create a function space on this mesh and take a function u in this space. The the index in the underlying vector for u are arranged like this:

V = FunctionSpace(mesh,'CG',1)
u = Function(V)
uv = u.vector().array()

 |    |    |
 6 -  9 - 13 -  .
 |    |    |    |          |
 3 -  5 -  8 - 12 - ... - 56
 |    |    |    |          |
 1 -  2 -  4 -  7 - ... - 46

This affects the structure of my mass and stiffness matrix. Is it possible to select a particular ordering of the basis function in the function space. For instance such that they are ordered as the nodes in the mesh?

KristianE · Answer 1 · Mar 3, 2016

Best answer

do

parameters['reorder_dofs_serial'] = False

answered Mar 3, 2016 by KristianE FEniCS Expert (12,900 points)
selected Mar 3, 2016 by bcsj

Ordering of basis functions

1 Answer