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Ublas : |
Subject: Re: [ublas] Matrix 'View' class
From: Jörn Ungermann (j.ungermann_at_[hidden])
Date: 2010-08-02 04:59:44
Hi,
I'd like to have something like that within the library and not (only)
on Gunther Winklers Website. In addition, the version on the website
does not offer write access.
Regards,
Joern
On Tue, 2010-07-27 at 18:24 +0200, Andrey Asadchev wrote:
>
>
> On Tue, Jul 27, 2010 at 11:11 AM, Andy Somogyi <somogyie_at_[hidden]>
> wrote:
> Hello All
>
> I frequently work where an external routine gives me a block
> of memory that I need to access as a 2 dimensional matrix
> (row-major).
>
> I've written a 'matrix-view' class attached below. I plan on
> just reading and writing to the memory block (that I don't
> own) using this view class. I've tested it with a variety of
> test cases (reading, writing, assigning to and from other
> matrices), and have not come into any problems. Would you guys
> care to take a look at this class, and let me know if there
> are any potential problems with this design, and I think a
> class like this would be of great utility to boost, any
> possibilities of submitting it?
>
> thanks.
>
>
>
> namespace boost { namespace numeric { namespace ublas {
>
> template<class T, class L=row_major >
> /**
> * a temporary 'view' of an existing 2-dimensional block of
> * memory.
> */
> class matrix_view : public matrix<T, L,
> shallow_array_adaptor<T> > {
> typedef typename shallow_array_adaptor<T>::size_type
> size_type;
> typedef matrix<T, L, shallow_array_adaptor<T> > base_type;
> public:
> /**
> * create a matrix_view that is a view of an existing block of
> data.
> * the matrix_view does NOT own the given pointer, user is
> responsible
> * for making sure that this class is not used after the
> p_data
> * block has been freed.
> */
> matrix_view (size_type size1, size_type size2, T* p_data) :
> base_type(size1, size2, shallow_array_adaptor<T>(size1*size2,
> p_data)) {};
>
> private:
> /**
> * hide ctors of base class, can only have a matrix_view that
> is attached to
> * an existing block of data.
> */
> matrix_view() {};
> matrix_view(size_type size1, size_type size2) {};
> };
> }}};
>
> // example of use, assign identity matrix to given data
> block,
> // assuming rows == columns.
> void myFunc(int rows, int columns, double* pData) {
> matrix_view<double> mv(rows,colums,pData);
> identity_matrix<double> i(rows);
> mv = i; // the data block referenced by pData is now
> initialized to the identity matrix.
> }
>
>
>
>
>
> _______________________________________________
> ublas mailing list
> ublas_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/ublas
> Sent to: asadchev_at_[hidden]
>
> looks very similar to:
> http://www.guwi17.de/ublas/examples/storage_adaptors.hpp
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