[Dune] [Fwd: Re: [Dune-Commit] dune-istl r929 - trunk/istl]

[Markus Blatt]

On Wed, Jul 30, 2008 at 05:23:10PM +0200, Carsten Graeser wrote:
> Although I don't recognize why non-existence of a feature is better
> than a slow implementation of it I would suggest to remove the
> cast to avoid repeating the same arguments again and again.
> 
> Probably we're the only ones using this class, but if we really need
> the cast we can keep in in our working copies.
> 

Probably there is a misunderstanding. I never told you to remove it,
did I? I am just concerned about performance.

As the implicite conversion operator is not needed if we have
corresponding constructors and assignment operators in FieldMatrix I
propose the following:

1. We add an (explicit) conversion constructor and an assignment
constructor to FieldMatrix. Both will have a template parameter for
the other type and both call the method istl_assign_to_fmatrix which
does the assignment in an efficient way.

class FieldMatrix{
 ...
 template<class T>
  FieldMatrix(const T& other){
    istl_asssign_to_fmatrix(*this, other)
  }
 ...
};

2. You overload istl_assign_to_fmatrix for ScaledIdMatrix.

   template<class T, int n>
   inline void istl_assign_to_fmatrix(ScaledIdentityMatrix<T,n> s,
                                      const FieldMatrix<T,n,n>&
				      other){
     ...
   }

This should do the trick and make everybody happy because
ScaledIdMatrix stays in ISTL.

Objections?

Cheers,

Markus