dolfin team mailing list archive

[Johan Hake <hake.dev@xxxxxxxxx>]

On 01/28/2013 10:22 PM, Anders Logg wrote:
> On Mon, Jan 28, 2013 at 10:10:40PM +0100, Johan Hake wrote:
>> Hello!
>>
>> I have now added a method to DofMap, which tabulate a map between
>> vertices and dofs. It will only work for DofMaps with dofs on vertices.
>> So basically for any CG 1 FunctionSpaces and will raise error else wise.
>>
>> Usage:
>>
>>   from dolfin import *
>>   import numpy as np
>>   mesh = UnitSquareMesh(10,10)
>>   V = VectorFunctionSpace(mesh, "CG", 1)
>>   u = Function(V)
>>   u.interpolate(Constant((1,2)))
>>   vert_values = np.zeros(mesh.num_vertices()*2)
>>   vert_values[V.dofmap().tabulate_vertex_map(mesh)] = \
>>   u.vector().array()
>>   print vert_values
>>
>> In parallel the map will follow the local dofs. This means that some
>> values in vert_values above will still be 0. The 0 values will then
>> correspond to vertex values which are owned by another process.
>>
>> In C++ the method returns a std::vector<std::size_t>.
>>
>> Questions:
>> Does the name "tabulate_vertex_map" work?
> 
> Sounds ok.
> 
>> Should a version of this method exist in other classes. FunctionSpace,
>> Function (without the mesh argument of course)?
> 
> Yes, would be good to have for convenience.
> 
> What is the relation to Function::compute_vertex_values?

compute_vertex_values works on any GenericFunction. However, for all
Functions from CG 1 families I guess one could use this map to just
tabulate the entries.

Johan