On 6 September 2011 17:31, Johan Hake <johan.h...@gmail.com> wrote: > On Monday September 5 2011 00:09:58 Anders Logg wrote: >> On Sun, Sep 04, 2011 at 11:23:04PM -0700, Johan Hake wrote: >> > On Friday September 2 2011 23:19:22 Anders Logg wrote: >> > > On Fri, Sep 02, 2011 at 02:35:57PM -0700, Johan Hake wrote: >> > > > What is the different between a MeshMarker and a MeshFunction? Is >> > > > MeshMarker a MeshFunction but instead of storing the values in line >> > > > with its global entity index it stores it wrt the global cell entity >> > > > index together with its local entity index? >> > > >> > > Yes, that and values don't need to be stored on the entire mesh, only >> > > for a subset, so you can mark just 3 facets without needing to store >> > > markers for a million facets. >> > >> > ok, I will see what I can do. >> >> Thanks! >> >> > > Copy paste from the MeshMarker docstring: >> > > /// The MeshMarkers class can be used to store data associated with >> > > /// a subset of the entities of a mesh of a given topological >> > > /// dimension. It differs from the MeshFunction class in two ways. >> > > /// First, data does not need to be associated with all entities >> > > /// (only a subset). Second, data is associated with entities >> > > /// through the corresponding cell index and local entity number >> > > /// (relative to the cell), not by global entity index, which means >> > > /// that data may be stored robustly to file. >> > > >> > > > Also, will this take over for the way we use MeshFunctions in the >> > > > assembler, or will a MeshFunction be generated by a MeshMarker before >> > > > assemble gets called? >> > > >> > > I think we will do that as a first step (convert from MeshMarker to >> > > MeshFunction) since then we don't need to touch the assembler. Then >> > > later we can think about using MeshMarkers directly. >> > >> > Ok. >> > >> > > > I think I also get confused with the naming here. If my explaination >> > > > of what MeshMarker is doing is correct, a MeshMarker and a >> > > > MeshFunction are essentially doing the same thing. What differs is >> > > > the way the data is stored. This is not reflected in the naming of >> > > > the classes >> > > >> > > It was the best I could come up with. Feel free to suggest something >> > > else. SubsetMeshFunction would also be confusing since it's not really >> > > a MeshFunction. >> > > >> > > Either way, I expect the MeshMarkers class to be used mostly >> > > internally by the MeshDomains class. >> > >> > Ok. >> > >> > Not sure these are better, but they might reflect the difference between >> > this guy and a MeshFunction in a slightly more intuitive way. >> > >> > MeshEntityFunction, LocalMeshEntityFunction, LocalMeshFunction, >> > SubMeshFunction >> >> I'm not sure those are much better, and I don't think it would be >> correct to call them something containing "Function" since they are >> not really functions. With a MeshFunction, one can input x (a mesh >> entity) and get y = f(x) (the value of the MeshFunction at that >> entity). That's not possible with MeshMarkers; they are just a >> collection of markers, not really a function since the value is only >> defined on a subset and one would need to loop through the list of >> values to get the value at any entity where the value is actually >> defined. > > What with MeshValueCollection? As it is a templated class I do not think > Marker is an appropriated name.
Agree. > 'Collection' says that the class is not > defined over the whole Mesh. > > Two questions: > > How can the following code work: > > // Get marker data > const std::vector<uint>& marker = _markers[i]; > const uint cell_index = marker[0]; > const uint local_entity = marker[1]; > const T marker_value = marker[2]; > > when _markers is declared as: > > // The markers > std::vector<std::pair<std::pair<uint, uint>, T> > _markers; > The above also permits multiple entries. Perhaps we want boost::unordered_map<std::pair<std::pair<uint, uint>, T> > _markers; > What is the logic behind: > > // Set all value of mesh function to maximum value (not all will > // be set) by markers below > mesh_function.set_all(maxval); > > Isn't it more natural to initiate the values to zero? Also it makes no sense > in conjunction with boundary markers. Then all boundary faces gets marked with > the largest marker value. I cannot see how that could be correct. > I don't get ' mesh_function.set_all(maxval);' or the code comment. >> So MeshMarkers may not be that bad. I'm starting to get used to >> it... :-) > > That's what worries me :) > Me too (worried, that is). Garth > Johan > > >> -- >> Anders > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
