Re: [boost] ublas: matrix views

From: boost (boost_at_[hidden])
Date: 2002-04-16 08:43:00

Salut,
On Tuesday 16 April 2002 11:24, Kresimir Fresl wrote:

> Since Joerg didn't reply, I will quote his earlier comment
> on this topic (thread: `slicing and ranges of matrices', Jan.  24th):
>
> ``I believe, that it's difficult to estimate the complexity of
> operations on such a view for sparse matrices (in other words: they
> could be rather inefficient). May be we currently should be more
> interested in some gather and scatter functionality for sparse
> matrices.''
>

At least you could test a simple class, were you implement the
element look up using your indices. 

T& matrix_view< matrix< double > >::operator( const int index1, const int 
index2 )
{
        return matrix_reference( rows[index1], columns[index2] );
}

where  matrix_view<> has a reference to a matrix, and the desired rows and 
columns vectors a private members. Maybe the performance is sufficient,
since the access of the underlying (sparse) matrix is probably much more 
expensive.

Best wishes,
Peter