[dune-pdelab] VectorBackend, OnTheFlyOperator and storage

[Christian Engwer]

-------- 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...

I have a conceptual patch for the vector that allows to user the backend without implement the whole istl interface again (where would qr ends, if we have to mimic istl and petsc and eigen and every LA lib we want to support?!). I'll Clea the patch up and send it around for discussion.

Cheers
Christian

>Best,
>
>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/
>
>
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