On 03/16/2015 07:07 PM, Bård Skaflestad wrote:
> On 16/03/15 18:43, Jørgen Kvalsvik wrote:
>> Right, but isn't this also, I suppose implicitly, reforming the
>> unchanged sparsity structure?
>
> "It depends".
>
> Specifically, it depends specifically on what you mean by the term
> "sparsity structure". If you mean the pattern of non-zeros of the
> mathematical object represented by a particular coefficient matrix, then
> yes assembling new numerical values does (potentially) changes the
> sparsity structure. However, in the context of a packaged software
> implementation, the sparsity structure is the contents of the "ia" and
> "ja" arrays of struct CSRMatrix--or their internal Dune::BCRSMatrix<>
> equivalents. Those are formed once, during initSystemStructure(), and
> not changed during numerical assembly.
>
> In essence, the structural analysis that creates the sparsity structure
> is run once for each call to initSystemStructure() and subsequently used
> only in a read-only capacity. Note that the BCRSMatrix<> produces an
> error if an unknown matrix element is referenced in
>
> S_[i][j]
>
> after its 'endindices()' method has been called (i.e., once its
> build-stage ('ready') is 'built').Splendid. This makes everything clearer, thanks. Appreciate your feedback!
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