On 01/28/2013 11:27 PM, Anders Logg wrote: > On Mon, Jan 28, 2013 at 11:19:13PM +0100, Johan Hake wrote: >> On 01/28/2013 11:08 PM, Anders Logg wrote: >>> On Mon, Jan 28, 2013 at 10:37:46PM +0100, Johan Hake wrote: >>>> 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. >>> >>> What does the tabulate_vertex_map method do which >>> compute_vertex_values doesn't? Enable writing to dofs? >> >> RTFC! ;) >> >> tabulate_vertex_map only computes a map based on the prior knowledge of >> the dofs coinciding with the vertices. compute_vertex_values are much >> more general and used >> >> element.interpolate_vertex_values >> >> to do the heavy lifting. > > Yes, so why is tabulate_vertex_map needed, if compute_vertex_values > already computes the vertex values and is much more general? > >> I see tabulate_vertex_map as a convenience mapping for users who want >> their data on a vertex based format, or users who want data which >> resides on vertices into dolfin la structures. > > What is the use case? If it is for plotting or postprocessing, then > compute_vertex_values should be enough.
Yes, but that will only give the mapping from a dolfin::Function to vertex data. Not the other way around. I guess the mapping would be also be faster for CG 1 family Functions as it just tabulate dofs. > Or is the intention to use it for modifying values of CG1 functions > from the outside? Yes. I have use cases where I need vertex based data into my dolfin::Functions. Johan > -- > Anders > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : [email protected] Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
