Re: [Boost-Users] ublas::matrix sharing storage with ublas::vecto r

From: Stephen Crowley (stephenc_at_[hidden])
Date: 2002-11-27 20:46:22

What do you mean by "just use it as" ?

For example.. I have a matrix<double> m(5,5);

In some code I actually need to use it as a 5x5 matrix.. but other parts
must reference it as a vector (to pass to another library).

Currently I am doing something like this

matrix<double> m(5,5);
// do stuff to m
vector<double> v(25);
v.data() = m.data();
// pass v to library
// get results back
m.data() = v.data();

This is obviously not optimal.. and if both m.data() and v.data() pointed to
the same location in memory the problem would be solved. 

I suppose I might be able to get around it by making my own storage class
that allows you to specify a location and size instead of allocating one
itself.

--Stephen

On Wed, Nov 27, 2002 at 08:31:37AM +0200, Scott Sinclair wrote:
> 
> Hi Stephen
> 
> Yes, just use a (1, n) or (n, 1) matrix as appropriate and do matrix
> operations instead of vector ops. The results will be correct as long as you
> make sure you have a correctly dimensioned matrix in place of your vector
> (i.e one that matches your vectors size and orientation). After all a matrix
> is just a collection of vectors ;-)
> 
> cheers,
> Scott
> 
> On 27/11/2002 05:10, Stephen Crowley wrote
> > It is possible for a vector and a matrix to share the same storage, as
> > long as the dimensions agree?
> > 
> > Some of the algorithms I am implementing require some objects 
> > to be treated
> > as an arbitrarily sized matrix, and sometimes as a vector, 
> > and it would be
> > convient to have a matrix and a vector share the same memory.
> > 
> > -- 
> > Stephen
> 
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-- 
Stephen