Re: [Vxl-maintainers] vector + matrix fixed reference classes

[Gehua Y. <ya...@cs...>]

To make it a little clearer, I meant Paul's new design of
vnl_matrix_fixed_ref & vnl_vector_fixed_ref (I copied his message in the
following). I think this design would make it possible for the class to be
transparent to operations such as transpose, retrieving a row or a column
from a matrix.

I looked at the code of current vnl_matrix_fixed_ref implementation. The
features Paul suggested aren't there. Right now vnl_matrix_fixed_ref is
inherited from vnl_matrix<T>. Compared with the way vnl_matrix_fixed is
implemented, it is not very efficient.

Please correct me if I am wrong.

Gehua

================================================
> A fancier scheme might take the form of:
>
> template <typename T, unsigned n, int element_stride>
> class vnl_vector_fixed_ref;
>
> template <typename T, unsigned n, int row_stride, int col_stride>
> class vnl_matrix_fixed_ref;
>
> which would enable references to be taken to non-contiguous memory.
> e.g.
>
> template <typename T, unsigned rows, unsigned cols>
> vnl_vector_fixed_ref<T,cols,1>
> vnl_matrix_fixed<T,rows,cols>::row_reference(unsigned col_index);
> // take reference to contiguous block of memory for a row
>
> template <typename T, unsigned rows, unsigned cols>
> vnl_vector_fixed_ref<T,rows,cols>
> vnl_matrix_fixed<T,rows,cols>::col_reference(unsigned col_index);
> // take reference to 'spliced' memory for a column
>
> template <typename T, unsigned rows, unsigned cols>
> vnl_matrix_fixed_ref<T,cols,rows,cols,1>
> vnl_matrix_fixed<T,rows,cols>::transpose_reference();
> // view fixed matrix as its transpose
>
> This would enable a function like:
>
> template <typename T, unsigned r, unsigned c, int r_s, int c_s, int el_s1,
> int el_s2>
> void mat_vec_mult(matrix_fixed_ref_const<T,r,c,r_s,c_s> A,
> vector_fixed_ref_const<T,c,el_s1> x, vector_fixed_ref<T,c,el_s2> y)
> // perform y = A x: could be used to perform mulitplication of matrix
> transposed as well
> etc. etc.

----- Original Message ----- 
From: "Peter Vanroose" <Pet...@es...>
To: "Gehua Yang" <ya...@cs...>
Cc: "Paul Smyth" <pau...@vi...>; "Vxl-maintainers (E-mail)"
<vxl...@li...>
Sent: Wednesday, June 18, 2003 3:19 AM
Subject: Re: [Vxl-maintainers] vector + matrix fixed reference classes


> > ... Intuitively, it will benefit computation
> > of large matrices and large vectors ...
>
> As far as large vectors/matrices are concerned, there is already an
> interface for this:  the classes vnl_matrix_ref and vnl_vector_ref.
>
> vnl_vector_fixed_ref is mainly useful for small size vectors, up to
> size 6 say, since it has to be instantiated for all sizes being used.
>
>
> -- Peter.
>
>
>