Re: vector view of a matrix

Hello again 

So it might be this :

int n ; // size of square matrix
double *a ;  //pointer to memory of a row matrix 
 
typedef mtl::external_vec<double > mvec;
 
mvec b(a,n*n); 
// b - vector view

typedef matrix< double, rectangle<>, dense<external>
>::type Matrix;   

  Matrix B(a, n,n);   
   // B -  matrix view

// also check in contrib\examples\external_matrix.cc

Cheers
Janusz



 --- Hugues Demers <[email protected]> wrote:
> On Tue, Feb 03, 2004 at 05:44:52AM +0000, Janusz
> opechowski wrote:
> > hello !
> > 
> > Say :
> > 
> > int n ; // size of square matrix
> > double *a ;  //pointer to memory of a row matrix 
> > 
> > typedef mtl::external_vec<double > mvec;
> > 
> > mvec b(a,n*n); // b is all you need
> > 
> > cheers
> > Janusz
> >
> 
> Yes, I thought about that, but (I did not state that
> clearly) I want to
> have two mtl objects, an mtl::matrix and an
> mtl::dense1D. I want to
> operate differently on those two using mtl
> algorithms. Is there such a
> thing as having a vector view of a matrix as you can
> have a blocked view
> of a matrix? Maybe if I could get a pointer to the
> allocated memory of a
> mtl::matrix and initialized a mtl::vector with it.
> But that would be
> against the point of using the mtl I suppose.
> 
> Hugues
> 
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> >  --- Hugues Demers <[email protected]>
> wrote:
> > > Hi,
> > > 
> > > I just discovered the MTL and I think it would
> fit
> > > my needs perfectly.
> > > Now I would like to know if it's possible to
> have a
> > > vector view of a
> > > matrix. Suppose a have this matrix:
> > > 
> > > M = [1 2]
> > >     [3 4]
> > > 
> > > I want to have this view on it 
> > > 
> > > V = [1 2 3 4]. 
> > > 
> > > I don't want to duplicate the memory. Iterators
> > > won't do, because I want
> > > to be able to do something like:
> > > 
> > > dot( V, V ). 
> > > 
> > > Is it possible to have those two
> representations?
> > > 
> > > Sorry, if I missed this in the doc, but it's
> rather
> > > poor on the subject.
> > > 
> > > Thank you,
> > > Hugues Demers
> > > _______________________________________________
> > > This list is archived at
> > http://www.osl.iu.edu/MailArchives/mtl-devel/ 
> > 
> >
>
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