Re: [ublas] Vector of size 3 without the size element

From: Langeland, Stian (GE Healthcare) (Stian.Langeland_at_[hidden])
Date: 2007-05-29 05:03:12

I think I need to clarify what I need to do :-) It is a bit difficult to
explain so I will try to to use some pseudo code:

typedef c_vector<float, 3> point;

double *pp;

point p1(0.0f, 0.1f, 0.2f);
point p2(1.0f, 1.1f, 1.2f); 

std::vector<point> points;

points.push_back(p1);
points.push_back(p2);

pp = &(points[0])(0); //pp should point to p1(0)
pp++;//pp point to p1(1)
pp++;//pp point to p1(2)
pp++;//pp point to p2(0)
pp++;//pp point to p2(1)
...

however as the 
size_type size_;
is a member of c_vector this will not work.

Stian

> -----Original Message-----
> From: ublas-bounces_at_[hidden] 
> [mailto:ublas-bounces_at_[hidden]] On Behalf Of Nico Galoppo
> Sent: 29. mai 2007 10:39
> To: ublas mailing list
> Subject: Re: [ublas] Vector of size 3 without the size element
> 
> Can't you just subclass c_vector and provide an accessor to 
> data_ ? Some pseudo 
> code:
> 
> template <typename T>
> class vector3 : public ublas::c_vector<real_type, 3> {
> ..
> public:
>    array_type::value_type* data() { return data_; }
> ..
> }
> 
> Then you can do
> 
> typedef vector3<float> vector3f;
> vector3f p(0.0f, 1.0f, 1.0f);
> glVector3fv(p.data());
> 
> or, I think you should be able to do the following with a 
> regular c_vector
> 
> c_vector<float, 3> p(0.0f, 1.0f, 1.0f);
> glVector3fv(&p(0));
> 
> HTH,
> 
> --nico
> 
> Langeland, Stian (GE Healthcare) wrote:
> > Thanks for such a quick reply. I have considered the 
> c_vector but when I
> > looked in vector.hpp I see that it has a member size_
> > ....
> >     private:
> >         size_type size_;
> >         array_type data_;
> > .... 
> > I guess this will still come in-between the floats?
> > 
> > Stian
> > 
> >> -----Original Message-----
> >> From: ublas-bounces_at_[hidden] 
> >> [mailto:ublas-bounces_at_[hidden]] On Behalf Of Dima Sorkin
> >> Sent: 29. mai 2007 10:11
> >> To: ublas mailing list
> >> Subject: Re: [ublas] Vector of size 3 without the size element
> >>
> >> Hi.
> >>  It can be c_vector, from
> >> http://www.boost.org/libs/numeric/ublas/doc/types_overview.htm
> >>
> >> I don't sure that if you put an array of c_vector, then all
> >> floating numbers will sit continuously in memory (compiler 
> >> can add some
> >> spaces).
> >>
> >> May be a 3xN matrix fits your needs ?
> >>
> >> Regards,
> >>  Dima.
> >>
> >> Quoting "Langeland, Stian (GE Healthcare)" 
> <Stian.Langeland_at_[hidden]>:
> >>
> >>> Hi,
> >>>
> >>> I have been trying to create a vector of 3 elements (a 
> >> point) without
> >>> the size element stored in the object. The reason for 
> this is that I
> >>> need to be able to have all the elements consecutive in 
> memory when
> >>> gathering several points in a std::vector. In this way all 
> >> points in the
> >>> std::vector can be uploaded to a graphics card using a 
> >> single memcopy.
> >>> Can this be acheived using ublas? I have not been able to 
> >> find a way.
> >>> Thanks,
> >>> Stian
> >>> _______________________________________________
> >>> ublas mailing list
> >>> ublas_at_[hidden]
> >>> http://lists.boost.org/mailman/listinfo.cgi/ublas
> >>>
> >> _______________________________________________
> >> ublas mailing list
> >> ublas_at_[hidden]
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> >>
> > _______________________________________________
> > ublas mailing list
> > ublas_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/ublas
> 
> -- 
> Nico Galoppo        UNC-CH PhD. student        http://www.ngaloppo.org
>                        [phone]
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