ffc team mailing list archive

[Kristian Oelgaard <k.b.oelgaard@xxxxxxxxx>]

On 8 July 2010 14:36, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>
>
> On 08/07/10 13:13, Anders Logg wrote:
>>
>> On Thu, Jul 08, 2010 at 01:02:43PM +0100, Garth N. Wells wrote:
>>>
>>>
>>> On 08/07/10 12:59, Anders Logg wrote:
>>>>
>>>> On Thu, Jul 08, 2010 at 12:00:38PM +0100, Garth N. Wells wrote:
>>>>>
>>>>>
>>>>> On 08/07/10 11:49, Kristian Oelgaard wrote:
>>>>>>
>>>>>> On 8 July 2010 08:22, Garth N. Wells<gnw20@xxxxxxxxx>    wrote:
>>>>>>>
>>>>>>> On Jul 8 2010, Anders Logg wrote:
>>>>>>>
>>>>>>>> On Wed, Jul 07, 2010 at 10:34:39PM +0100, Kristian Oelgaard wrote:
>>>>>>>>>
>>>>>>>>> On 7 July 2010 20:22, Garth N. Wells<gnw20@xxxxxxxxx>    wrote:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> On 07/07/10 20:14, Anders Logg wrote:
>>>>>>>>>>>
>>>>>>>>>>> On Wed, Jul 07, 2010 at 06:26:20PM +0100, Kristian Oelgaard
>>>>>>>>>>> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Supporting CellVolume makes it possible to do:
>>>>>>>>>>>>
>>>>>>>>>>>> CG = FiniteElement("Lagrange", triangle, 2)
>>>>>>>>>>>> DG = FiniteElement("DG", triangle, 0)
>>>>>>>>>>>> v = TestFunction(DG)
>>>>>>>>>>>> f = Coefficient(CG)
>>>>>>>>>>>> vol = triangle.v
>>>>>>>>>>>
>>>>>>>>>>> Would it be better to call it vol or volume instead of v? Or does
>>>>>>>>>>> it
>>>>>>>>>>> have to be a one-letter word?
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> . . . or call it 'volume'.
>>>>>>>>>
>>>>>>>>> It can be whatever we want, I just followed what was already there.
>>>>>>>>> Should we then rename 'd', 'n' and 'x' to 'geometric_dimension',
>>>>>>>>> 'facet_normal', and 'spatial_coordinate' while we're at it?
>>>>>>>>
>>>>>>>> I think d, n, x are fine, but v does not necessarily look like a
>>>>>>>> volume to me (it looks like a test function).
>>>>>>>>
>>>>>>>
>>>>>>> I agree - d, n and x are all commonly used, but v for volume isn't.
>>>>>>
>>>>>> I changed 'v' to 'volume' and fixed a few bugs along the way.
>>>>>>
>>>>>> On a related note, should we implement CellDiagonal too?
>>>>>> We use cell.diagonal() for MeshSize in SpecialFunctions.h of DOLFIN
>>>>>> and since we often use MeshSize for the 'h' coefficient in DG forms
>>>>>> e.g., PoissonDG we could remove the need for this function evaluation.
>>>>>> The code to compute the CellDiagonal could just be copied from
>>>>>> IntervalCell, TriangleCell and TetrahedronCell of DOLFIN and dumped in
>>>>>> codesnippets.py.
>>>>>>
>>>>>
>>>>> What if we call it 'Circumradius'?
>>>>>
>>>>> I recall that the agreed not have have CellSize because of the
>>>>> ambiguity in its definition, but circumradius is unambiguous, so I
>>>>> vote to add it.
>>>>
>>>> Isn't 'diameter' better? It is shorter and well-defined
>>>> (2*circumradius).
>>>>
>>>
>>> 'diameter' isn't well defined. We can use it, but we would need to
>>> define it as being 2*circumradius.
>>>
>>> Garth
>>
>> Why isn't it well-defined? The diameter of a set T is
>>
>>   d = sup_{x,y \in T} ||x - y||
>>
>> and that should be the same as 2*circumradius unless I'm mistaken.
>>
>
> What's the set T? At a glance, the above is true if T is not the polygon,
> but the set of all points inside the circle inside which the polygonal can
> be inscribed.

I added cell.circumradius, if we want cell.diameter too we can easily add it.

Kristian

> Garth
>
>> --
>> Anders
>
>