Boost uBLAS Matrix Reference

Question

I'm wondering if it's possible to get the address of an individual element of a Boost uBLAS matrix?

That is

boost::numeric::ublas::matrix<char> bob(3,3);
some_function(&bob[2][2]);

Now, of course the second line won't work... but I'd like it to.

Any thoughts?

Thanks!

Anonymous · Accepted Answer · 2012-04-19T18:09:57.413

3

Wouldn't using the address of the return value of the following operator be simpler? And independent of the matrix layout?

reference operator () (size_type i, size_type j)

For example:

some_function(&bob(2,2));

edited Apr 19 '12 at 18:09

answered Mar 30 '12 at 09:05

Anonymous

I'm not sure I follow you? Could you be more explicit or explanatory? Sorry :-( – Richard Apr 19 '12 at 04:56
Fixed the indices in question in the question. – Richard Apr 19 '12 at 15:08

score 1 · Answer 2 · edited Mar 30 '12 at 08:51

1

by default, the inner representation of a matrix is a row major 1D array.

some_function(&bob.data()[i*ncol+j] would work

edited Mar 30 '12 at 08:51

pjumble

answered Mar 30 '12 at 04:59

pem

1

By default in uBLAS? Which part of the Boost uBLAS specification indicates that this will work? – Richard Apr 19 '12 at 04:55
m.data() Returns a reference to the underlying dense storage. http://www.boost.org/doc/libs/1_46_0/libs/numeric/ublas/doc/container_concept.htm#matrix. As for the storage, there are 2 types: row_major or column_major, default is row_major. I forgot where it was specified. I once called lapack routines with ublas matrix, as far as I am concerned, get the pointer of 1D array by m.data() works. – pem May 04 '12 at 08:50

2 Answers2