[Dune-devel] [GSoC] Status update

[Oliver Sander]

Hi Xinyun,

> Thanks for your detailed and clear decomposition. Sorry I didn't reply in time because I just moved into a new flat and didn't have Internet last week.
> I have mainly followed your steps and uploaded them to Gitlab. Please check if I did it correctly.

that's all looking very nice so far.

> 
> Now should I create the entity class and complete the leafIterator class? Below are my elementary thoughts.
> 1.For the BSpline entitry class
> template<int codim, typename GridImp>
> class BSplineGridEntiry
> 
> contains a BSplinePatch object pointer and an index indicative of the knot span where it locates. Also, a geometry function should be provided to access the BSpline geometry the entity binds to.

That sounds good.

> 
> 2. The BSpline leaf itertator class
> template<int codim, typename GridImp>
> class BSplineGridLeafIterator
>  
> should contain an gridView object and an index. The operator* method, an operator != method, and an operator++ should be implemented.

Yes.

When implementing iterators, you can save a lot of work by using the iterator facades from

dune/common/iteratorfacades.hh

Please let me know if there are any further questions.

Cheers,
Oliver

> 
> Please kindly correct my ideas. If you agree on them, I will start implementing them.
> 
> Best regards,
> Xinyun
> 
> 
> On 06/29/2016 06:44 AM, Oliver Sander wrote:
>> Hi Xinyun,
>>
>> too bad you didn't write earlier.  You seem to have gone off slightly in a bad direction.
>>
>> This just goes to show that it would be really great if we had a text that describes
>> how to write grids!
>>
>> Namely, you do not have to use the DefaultGridView class, and you do not have to implement
>> all the GridTraits at once.  Here is my proposal for how to proceed in small steps:
>>
>> 1) Write a class
>>
>> template <int dim, int dimworld>
>> class BSplineGrid;
>>
>> with a constructor that accepts all information needed to setup a B-spline patch.
>>
>> 2)  Write a class
>>
>> template <int dim, int dimworld>  // more parameters, if needed
>> class BSplineLeafGridView;
>>
>> with a constructor that accepts all information needed to setup a B-spline patch.
>>
>> 3) The BSplineGrid class gets a data member 'BSplineLeafGridView leafGridView_'.
>>
>> Make the following snippet compile
>>
>> BSplineGrid<2,3> grid;
>> auto gridView = grid.leafGridView();  // returns the BSplineLeafGridView by value
>>
>> 4) Write an empty class
>>
>> template <int codim, int GridImp>  // more parameters, if needed
>> class BSplineGridLeafIterator;
>>
>> 5) Make the BSplineLeafGridView export the type of the iterator:
>>
>> The following typedef should return the type of the new iterator
>>
>> template <int codim>
>> using NewIterator = BSplineLeafGridView::Codim<codim>::Iterator;
>>
>>
>> These should all be reasonably easy to do.  I need to go now, but I can add more steps
>> later today.  If you want we can have another phone call, but that would practically
>> have to be tomorrow between 14:00 and 16:00.  After that I am unavailable until next
>> wednesday.  Or maybe one of the other mentors can step in.
>>
>> Cheers,
>> Oliver
>>
>>
>>
>> On 27.06.2016 16:55, Xinyun wrote:
>>> Hi Oliver,
>>>
>>> Sorry I did not report my latest progress to you as I really feel stuck somehow.
>>>
>>> Last week, I spend quite some time to read and understand the source code of onedgird and vtkwriter as well. I found for most girds they use the defaultGridView which takes the gird type as a template parameter. It means that we don't need to manually implement a specific girdView but we need to implement all the grid traits. It seems that vtkwriter requires all or most gird traits specifications.  So I decided to set the vtkwriter as a long term goal in the very end.
>>>
>>> Then I tried to decompose the long term goal into realistic small ones. Having every trait implemented is not realistic for me in a short time so I picked out three important traits in a priority order: gridentity, gridLeafIterator, gridIndexSet. It doesn't mean the others are not needed, for example, girdintersectioniterator.
>>>
>>> Aftereards, I attempted to imitate the entity implementation of onegrid. But I found the OneDGridEntity is inherited from the EntityDefaultImplementation and wraps the OneDEntityImp object. Another class
>>> OneDGridEntityPointer then wraps a OneDGridEntity object and is the base class for the gridLeafIterator. These relations may be very clear to experienced dune develops but it really took me a while to figure them out. Then I have doubts on how to define a B-Spline entity. In isogemetric analysis, the knot span is considered as the element in finite element analysis. So should I take each knot as a vertex(0-dimension entity) and every possible knot cube(with multiplications) as an element(1-dimension entity)? Or do I just need the element since the vertex doesn't make a lot of sense?
>>>
>>> Please correct me if I made any mistake or I'm going to a total wrong direction. I feel very sorry that I am moving slowly. Now I am still working on the BSplinePatchEntityImp, BSplinePatchEntity and BSplinePatchEntityPointer. I hope very much that I can finish and show you this week.
>>>
>>> Best regards,
>>> Xinyun
>>>
>>> On 06/26/2016 10:04 PM, Oliver Sander wrote:
>>>> Hi Xinyun,
>>>>
>>>> how are you?  I am writing to enquire about the current status of your GSoC project.
>>>> The last time we talked in person we agreed that the next milestone should be a
>>>> spline surface that can be written to a file by the standard VTKWriter class.
>>>> You have shown good results so far, but in your git repo I see no movement at all
>>>> towards the VTK milestone.  Does that all happen on your local machine?  Then please
>>>> share the current status with me, to keep me informed.  Or are you stuck with some
>>>> questions?  In that case, I am here to help.
>>>>
>>>> Cheers,
>>>> Oliver
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Dune-devel mailing list
>>>> Dune-devel at dune-project.org
>>>> http://lists.dune-project.org/mailman/listinfo/dune-devel
> 

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