Anders Logg wrote:
> On Fri, Sep 26, 2008 at 11:35:38AM +0200, Niclas Jansson wrote:
>> Anders Logg wrote:
>>> On Mon, Sep 22, 2008 at 06:17:49PM +0200, Anders Logg wrote:
>>>> On Mon, Sep 22, 2008 at 06:13:34PM +0200, Niclas Jansson wrote:
>>>>> Anders Logg wrote:
>>>>>> On Mon, Sep 22, 2008 at 05:03:59PM +0200, Niclas Jansson wrote:
>>>>>>> Anders Logg wrote:
>>>>>>>> I'm slowly working my way through PXMLMesh.cpp and I need some
>>>>>>>> assistance (from Niclas).
>>>>>>>>
>>>>>>>> It all looks very good and I'm sure it works perfectly, but some work
>>>>>>>> is needed to make it possible to read/understand:
>>>>>>>>
>>>>>>>> 1. PXMLMesh::closeMesh really needs some commenting. It's a large
>>>>>>>> chunk of nontrivial and quite complex code so a whole lot of
>>>>>>>> commenting is needed.
>>>>>>> I'm working on it.
>>>>>> ok, nice.
>>>>>>
>>>>>>>> 2. Why is the mesh editor closed in PXMLMesh::readCells and then
>>>>>>>> opened again later in PXMLMesh::closeMesh?
>>>>>>>>
>>>>>>>> If we can't write to the mesh until everything is read in, then maybe
>>>>>>>> we should wait with initializing anything until closeMesh() and at
>>>>>>>> that point start editing the mesh?
>>>>>>>>
>>>>>>> It's a (ugly) workaround due to the static nature of the MeshEditor
>>>>>>> (number of vertices must be specified a priori). It could of course be
>>>>>>> fixed by moving the geometric partitioner inside the parser, and only
>>>>>>> opening the editor inside closeMesh().
>>>>>>>
>>>>>>> However the nice solution would be to make the MeshEditor more dynamic.
>>>>>>> That would also make life easier when implementing a better refinement
>>>>>>> algorithm (for example, the recursive longest edge bisection (Rivara)
>>>>>>> from unicorn)
>>>>>> I agree it would be better to make MeshEditor dynamic. The problem is
>>>>>> that this is not always needed. Perhaps we should add a new class
>>>>>> DynamicMeshEditor that can be used when one does not know the number
>>>>>> of vertices and cells a priori.
>>>>>>
>>>>>> It could be very simple, just storing the dynamic data in suitable STL
>>>>>> containers and then calling MeshEditor in close().
>>>>>>
>>>>>>>> 3. I don't understand the logic in readTriangle/readTetrahedron.
>>>>>>>> What does the following code do?
>>>>>>>>
>>>>>>>> if (!(is_local(v2) || is_local(v1) || is_local(v0)) || !is_local(v0))
>>>>>>>> return;
>>>>>>>>
>>>>>>>> used_vertex.insert(v0);
>>>>>>>> if (is_local(v1))
>>>>>>>> used_vertex.insert(v1);
>>>>>>>> if (is_local(v2))
>>>>>>>> used_vertex.insert(v2);
>>>>>>>>
>>>>>>>> if (!(is_local(v1) && is_local(v2) && is_local(v0)))
>>>>>>>> {
>>>>>>>> if (!is_local(v1))
>>>>>>>> shared_vertex.insert(v1);
>>>>>>>> if (!is_local(v2))
>>>>>>>> shared_vertex.insert(v2);
>>>>>>>> }
>>>>>>>>
>>>>>>> The idea is to assign the triangle/tetrahedron to the processor who owns
>>>>>>> vertex v0. And, yes the logical could probably be more clearer.
>>>>>> ok, I see.
>>>>>>
>>>>>> It seems that
>>>>>>
>>>>>> !(is_local(v2) || is_local(v1) || is_local(v0)) || !is_local(v0)
>>>>>>
>>>>>> is equivalent to
>>>>>>
>>>>>> (!is_local(v2) && !is_local(v1) && !is_local(v0)) || !is_local(v0)
>>>>>>
>>>>>> which is equivalent to
>>>>>>
>>>>>> !is_local(v0)
>>>>>>
>>>>>> Is this correct, and is this what you have in mind?
>>>>> It looks correct to me. Seems like I should refresh my logic, that was a
>>>>> really simple reduction :)
>>>>>
>>>>> Niclas
>>>> It wasn't very obvious that it could be so much simplified, but it
>>>> should help to clear up the logic.
>>>>
>>>> I'll wait for you to do some more work on PXMLMesh.cpp before I
>>>> continue reading it.
>>>>
>>>> If possible, I'll add DynamicMeshEditor later tonight so you can use
>>>> that to simplify PXMLMesh.cpp further.
>>> I've added DynamicMeshEditor. Try to use this in PXMLMesh.cpp. It may
>>> simplify it a bit.
>>>
>>>
>>>
>> Commenting and bug fixes in PXMLMesh.
>
> Thanks, it looks much better! I'll make a new attempt to get through
> the code (after the suggested changes below).
>
>> I couldn't use DynamicMeshEditor to get rid of the opening and closing
>> of the mesh editor. The problem is that each processor parse (and
>> receive from partitioning) vertices which are not used in the local
>> cells. These must be removed before the final mesh is returned, and this
>> is not supported by the editor.
>>
>> I think the easiest solution to this problem is to move the geometric
>> partitioner inside the XML parser. Since it's produces rather bad
>> partitions I don't see why anyone would like to use it in an application.
>
> That sounds good, especially since you now call the partitionGeom()
> before the mesh is even a mesh (it has only vertices).
>
> Can you make an attempt to do the geometric partitioning inside
> PXMLMesh?
>
> I also suggest that you don't open the mesh editor until you get to
> the closemMesh() function. Just store the vertices in an Array<>
> (which is the same as an std::vector). You don't call editor.addCell()
> until closeMesh() so it's not really a Mesh before then anyway.
>
> It also fits well with how you treat the cells. You already have a
> cell_buffer. You could store a vertex_buffer similarly.
>
> So it would be something like this:
>
> 1. Read vertex coordinates into a simple Array (or similar).
>
> 2. Partition the vertices.
>
> 3. Build the Mesh in closeMesh() using MeshEditor.
>
> Would that work?
>
I think so. I'll try fix this and insert the geometric partitioner as
soon as possible.
Niclas
> --
> Anders
>
_______________________________________________
DOLFIN-dev mailing list
[email protected]
http://www.fenics.org/mailman/listinfo/dolfin-dev
