[dune-pdelab] VectorBackend, OnTheFlyOperator and storage

[Peter Bastian]

Am 04.05.2013 um 17:56 schrieb Christian Engwer <christian.engwer at uni-muenster.de>:

> 
> 
> 
> -------- Ursprüngliche Nachricht --------
> Von: Christian Engwer <christian.engwer at uni-muenster.de>
> Gesendet: Sat May 04 17:43:59 MESZ 2013
> An: Peter Bastian <peter.bastian at iwr.uni-heidelberg.de>
> Betreff: Re: [dune-pdelab] VectorBackend, OnTheFlyOperator and storage
> 
> Hi Peter,
> 
>>> c) Oliver asked we, why it is not possible to create an ISTL Matrix
>>>  and then later use PDELab to fill this matrix. While we completely
>>>  stay in the PDELab context one might argue that this is not
>>>  necessary and even the wrong approach, I think in situations where
>>>  we mix different codes Oli has a point. If we implement (b) and
>>>  then don't store the matgrix obect directly in the backend, but use
>>>  a shared_ptr, we could easily allow the user to allocate the matrix
>>>  before hand and then warp this matrix in a backend container.
>> Such a possibility is clearly something one should have. I just
>> committed
>> a constructor on the matrix backend yesterday that allows you to
>> initialize a MatrixContainer with a given ISTL Matrix (instead of
>> a grid operator). In my case this 
>> is the triple product A_C = R A_DG A^T which is constructed using ISTL
>> but is then later to be used within PDELab (e.g. to insert essential
>> boundary
>> conditions). 
> 
> I saw your commit and one thing that striked me, is that the matrix is actually copied... One thing I'd like to avoid…

Thats true, I just copy an empty matrix and then fill this matrix, when it is
in the container. I will change it such that just a MatrixContainer with an
empty ISTL matrix is constructed. That will work for me, but it is clear that
it is only a partial solution.

-- Peter

------------------------------------------------------------
Peter Bastian
Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Universität Heidelberg
Im Neuenheimer Feld 368
D-69120 Heidelberg
Tel: 0049 (0) 6221 548261
Fax: 0049 (0) 6221 548884
email: peter.bastian at iwr.uni-heidelberg.de
web: http://conan.iwr.uni-heidelberg.de/people/peter/