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Subject: Re: [ublas] fixed size vector in boost::numeric::ublas?
From: Nasos Iliopoulos (nasos_i_at_[hidden])
Date: 2010-08-02 18:31:01
Markus,As for the unit tests: I would certainly like to write unit tests for fixed_vector, but when running "bjam" inhttp://svn.boost.org/svn/boost/trunk/libs/numeric/ublas/test, I get several compilation errors. Is gcc-4.5 supposed to work with these tests, or shall the tests be launched differently?If for some reason bjam is not working, just make a unit test file using your compiler. I think it does not make any important difference for the maintainers (right?).
For the unit test I'd suggest using the test libary as in those (maybe we will need to move to boost.test someday though):http://svn.boost.org/svn/boost/trunk/libs/numeric/ublas/test/size.cpphttp://svn.boost.org/svn/boost/trunk/libs/numeric/ublas/test/test_assignment.cppBestNasosTo: ublas_at_lists.boost.orgFrom: grabner_at_[hidden]
Date: Mon, 2 Aug 2010 20:00:56 +0200
Subject: Re: [ublas] fixed size vector in boost::numeric::ublas?
Nasos Iliopoulos wrote:
>
> All,
>
> The fixed array is a good idea and I think this should be considered to be
> included in ublas. This would allow for small size vectors and matrices to
> work in near optimal state (i.e. something like defining a struct vec3d
> {double data[3]};
>
> I also implemented (among other people as I can see) this in the past and
> it should be somewhere in the list, but if Markus wants to take the task
> to integrate it into uBlas, I find his implementation sufficient.
I slightly modified it to better fit into the existing ublas framework and
also added a fixed_vector template using the fixed_array (similar to
bounded_vector using bounded_array). A patch against revision 64531 is
attached.
> A nice exercise (although I don't know if this is efficient anymore given
> the cpus and compilers we have), is to implement some basic loop unrolling
> algorithms through template metaprogramming to achieve some faster basic
> operations, like tvmet does. This would need some further study, because
> the compilers can nowadays unroll the loops when they detect const
> arguments and therefore getting uBlas to do the unrolling may gain
> nothing.
Indeed, I wasn't able to make gcc-4.5 unroll the loop in a simple vector
addition. However, this is an issue which affects the existing vector
implementations as well and should IMO be dealt with separately.
> Furthermore in order for this addition to be complete, fixed_vector and
> fixed_matrix classes should be implemented, that would be similar to
> bounded_vector and bounded_matrix (without the size member variables).
> IMHO If this is done (and given a few unit tests), the implementation
> would be at an excellent stage to be included into uBlas.
As I said above, fixed_vector was an easy exercise. However, a fixed_matrix
is much more complicated (I will give some thoughts on this in a separate
message to keep this one to the point). Still I believe if fixed_vector is
easy and fixed_matrix is hard, then fixed_vector could be a useful addition
to boost even if fixed_matrix is not yet available. Do you agree with this?
As for the unit tests: I would certainly like to write unit tests for
fixed_vector, but when running "bjam" in
http://svn.boost.org/svn/boost/trunk/libs/numeric/ublas/test, I get several
compilation errors. Is gcc-4.5 supposed to work with these tests, or shall
the tests be launched differently?
> If I remember well from my implelentation the major decision that has to
> be made relates to the resize(..) member function. Since the fixed types
> cannot resize it would seem obvious that those functions should not be
> implemented at all, but I think uBlas is using it in some algorithms, so
> either the algorithms need to be specialized, or the the fixed type
> resize function needs to be implements as an empty function. I think the
> first option is the best.
I prefer an exception to be thrown on an attempt to resize a fixed_vector to
some different size (I'll give some more comments to the following posts).
> Nice work Markus and I hope this will make it in soon!
Thanks :-)
Kind regards,
Markus
-- Markus Grabner Institute for Computer Graphics and Vision Graz University of Technology, Inffeldgasse 16a/II, 8010 Graz, Austria WWW: http://www.icg.tugraz.at/Members/grabner _______________________________________________ ublas mailing list ublas_at_[hidden] http://lists.boost.org/mailman/listinfo.cgi/ublas Sent to: nasos_i_at_[hidden]