dolfin team mailing list archive

[kent-and@xxxxxxxxx]

>
>
> Martin Sandve Alnæs wrote:
>> On Wed, Jan 7, 2009 at 3:09 PM, Garth N. Wells <gnw20@xxxxxxxxx> wrote:
>>>
>>> Anders Logg wrote:
>>>> On Wed, Jan 07, 2009 at 02:49:17PM +0100, Johan Hake wrote:
>>>>> On Wednesday 07 January 2009 14:28:09 Kent Andre wrote:
>>>>>> It seems to me that the problem is that I have created two different
>>>>>> FunctionSpaces that are actually the same and that the test
>>>>>> in Function is a pointer check.
>>>>>>
>>>>>> One could of course make a better check based on e.g. a signature.
>>>>>> This should be trivial to do. But I will end up with using
>>>>>> a bit more memory than needed. Is this an acceptable solution ?
>>>>> A check for the signature is not enough. Eventually we have to check
>>>>> for the
>>>>> meshes in the two files being the same too.
>>>> Maybe we should add a signature() function for meshes also that
>>>> returns some kind of checksum for the mesh?
>>>>
>>> What's wrong with the approach that I presented? Just read the function
>>> and extract from the function the FunctionSpace and the mesh?
>>>
>>> Garth
>>
>> Reading ten functions from file gives ten meshes in memory.
>>
>
> This is another issue. Kent's code was reading in one function only.
>
> I have a dislike for reading and writing functions, mainly because of
> the use of signatures and the presence of pre-compiled finite elements
> in DOLFIN (the latter going against the spirit of automated generation).
> The most general approach would be to allow the construction of a
> Function with a FunctionSpace and a GenericVector. The user has to take
> some responsibility in making sure that the DofMap, Mesh, FiniteElement
> and GenericVector match. From a quick look at the code, the only extra
> thing that would be needed is a Function constructor that accepts a
> FunctionSpace and a GenericVector.
>
> Garth
>

In my case I solve a PDE for computing the coefficients in another PDE.
And it is a lot easier to load the coefficient from file than solving the
PDE.
In my case efficiency is not much of an issue (at least not yet).

The only problem I see with signatures is that one can use more memory than
needed, but in many situations simplicity is more 'important' than memory.

Kent