ufl team mailing list archive

[Harish Narayanan <harish.mlists@xxxxxxxxx>]

Anders Logg wrote:
> On Mon, Nov 09, 2009 at 02:05:29PM +0100, Anders Logg wrote:
>> On Mon, Nov 09, 2009 at 12:58:32PM +0000, Garth N. Wells wrote:
>>>
>>> Marie Rognes wrote:
>>>> Kristian Oelgaard wrote:
>>>>> Quoting Anders Logg <logg@xxxxxxxxx>:
>>>>>
>>>>>
>>>>>> This is something we've discussed before, but I want to discuss it
>>>>>> again.
>>>>>>
>>>>>> Could we change the definition of the gradient of a vector to be the
>>>>>> "normal" definition:
>>>>>>
>>>>>>   grad(u) = du_i / dx_j
>>>>>>
>>>>>> ?
>>>>>>
>>>>> I think this sounds like an excellent idea.
>>>>>
>>>>>
>>>> Me too.
>>>>
>>> Cowards!  ;)  You wait for Martin the leave and then jump on the bandwagon.
>>>
>>> I suggested this March/April, and Martin's argument against was for
>>> consistency with other operations. I think that it's fine to change so
>>> long that other operations do not break or lead to
>>> unexpected/inconsistent results.
>> :-)
>>
>> I've had this discussion with Martin at least twice and both times he
>> managed to convince me of his definition. But I keep forgetting the
>> arguments in favor of the current definition (and more so when it
>> gets me into trouble).
> 
> I've created a blueprint:
> 
> https://blueprints.launchpad.net/ufl/+spec/redine-grad
> 
> Add your comments there. (Harish, add comments on div.)

I will. And there might be something similar with curl too, but who uses
curl anyway! :)

I'd just like to point out that in future discussion, I think it will be
clearer if you used the following notation grad(u)_ij = du_i / dx_j.

Harish