Ublas :

rrossi_at_[hidden]

-- 
On Fri, 2010-07-23 at 09:25 +0200, David Bellot wrote:
> Hi Markus,
> 
> sounds a good idea. Let me investigate this. It's in fact on the todo
> list so it's very welcome.
> 
> Cheers,
> David
> 
> On Fri, Jul 23, 2010 at 00:16, Markus Grabner <grabner_at_[hidden]>
> wrote:
>         
>                Hi all!
>         
>            In boost::numeric::ublas, there exist different vector
>         variants
>         (unbounded and bounded). All of them can be resized
>         dynamically (up to a
>         maximum size defined at compile time in the case of the
>         bounded vector).
>         Therefore the vector class (or the underlying storage array)
>         have a size
>         member which indicates the current size of the vector.
>         
>         However, it would be extremely useful to have a vector of
>         fixed size, i.e.,
>         one which can't be resized dynamically, but has its size
>         statically defined
>         at compile time. Such a vector does not require a size member
>         and only
>         consumes N*sizeof(T) bytes of storage, where N is the (static)
>         vector size
>         and T the value type. Many libraries dealing with geometric
>         data (OpenGL and
>         OpenInventor being prominent examples) store their data in
>         compact arrays in
>         their native data types, e.g., the values
>         (x0,y0,z0,x1,y1,z1,x2,y2,z2)
>         stored in consecutive memory locations define three points in
>         3D space. By
>         means of a fixed size vector, the entire boost::numeric::ublas
>         functionality
>         could be applied to such arrays by a simple reinterpret_cast
>         on each
>         element. This is not possible with the bounded or unbounded
>         vectors since
>         the vector must be constructed before with its size member
>         properly
>         initialized, and the actual vector data must therefore be
>         copied explicitly
>         before use.
>         
>         I tried to create a fixed_array class to implement this
>         proposal (see
>         attachment), it can be used, e.g., to create the equivalent of
>         the
>         OpenInventor "SbVec3f" data type as follows:
>         
>         typedef
>         boost::numeric::ublas::vector<float,fixed_array<float,3> >
>         vec3d_t;
>         
>         It is probably not the cleanest solution, and I skipped the
>         serialization
>         stuff altogether, but it demonstrates an approach how this can
>         be done.
>         
>         Is such a feature already available in ublas and did I just
>         miss it? If not,
>         what do you think about adding it to improve boost's
>         interoperability with
>         other libraries?
>         
>                Thanks & kind regards,
>                        Markus
>         
>         
>         --
>         Markus Grabner
>         Institute for Computer Graphics and Vision
>         Graz University of Technology, Inffeldgasse 16a/II, 8010 Graz,
>         Austria
>         WWW: http://www.icg.tugraz.at/Members/grabner
>         
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> 
> 
> 
> -- 
> David Bellot, PhD
> david.bellot_at_[hidden]
> http://david.bellot.free.fr
> 
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