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

From: jhr.walter_at_[hidden]
Date: 2002-11-28 16:01:58

Stephen Crowley wrote:

> On Thu, Nov 28, 2002 at 09:12:53AM -0500, Toon Knapen wrote:
> > On Wednesday 27 November 2002 20:46, Stephen Crowley wrote:
> > > 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).
> >
> > OK, So as to get to the bottom of this. Do you really want to perform
vector
> > operations on a vector that consists of a concatenation of all rows (or
> > columns) of the matrix do you want to get access to the storage to pass
your
> > information to another library.
> >
> > The latter case is dealt with in the
boost-sandbox/boost/numeric/bindings.
> > There we've spend effort to be able to extract the begin- and
end-pointer
> > (not iterator) from any vector or matrix. (In the bindings it's used to
pass
> > these pointers to e.g. BLAS)
> >
> > In the former case, could you enlighten me what kind of numeric
operations
> > you're dealing with ?
>
> The matrix I am working with is a set of weights for a neural net. I am
> using a kalman filtering library
> (http://www.acfr.usyd.edu.au/technology/bayesianfilter/Bayes++.htm) that
> treats the weights as a vector.

This looks more like a conceptual than an integration problem. Maybe Bayes++
should support a corresponding matrix signature, too?

OTOH it seems valid to look at the vector space of linear operators. If this
is a recurring use case, we should consider to add new proxy classes
matrix_as_vector<> (and vector_as_matrix<>) to uBLAS.

> So, I'm not really sure how to answer your
> question. I guess I would say that I need to access a vector as a
> concatenation of the rows or columns of the matirx (for this purpose it
> does not matter as long as it is consistent). However, copying undering
data()
> member is working for now, although not as quickly as I would like.

I'm not sure if this (or array_adaptor) should be the final solution.

Regards

Joerg