Re: [eigen] alpha6!

["Gael Guennebaud" <gael.guennebaud@xxxxxxxxx>]

Hi,

thanks for the feedback. For the same reason than you I usually don't
like the use of such casting operators. However I think here they are
quite safe. Actually the main question is whether or not we want to
allow automatic conversion between each rotation representation or not
? Automatic conversion between Quaternion and AngleAxis also exist by
mean of constructors and operator=(). Here I used the cast operator
because I initially wanted to separate the Core and Geometry module as
much as possible.

Currently you can write:

Matrix3f rotmat;
Quaternionf q;
rotmat = AngleAxisf(alpha,Vector3::UnitX());
q = AngleAxisf(alpha,Vector3::UnitX());
rotmat = q;

I cannot think to any case where this would be dangerous,  and if you
want to be more explicit in your code you can still write:

rotmat = AngleAxisf(alpha,Vector3::UnitX()).toRotationMatrix();
rotmat = Matrix3f(AngleAxisf(alpha,Vector3::UnitX())));
q = Quaternion(AngleAxisf(alpha,Vector3::UnitX()));
rotmat = q.toRotationMatrix();

If someone is still strongly against such automatic conversion then I
agree to remove the cast operators, the operator= and keep only
explicit constructor.


About the operator Rotation2D::operator Scalar(), again I think this
one is really safe since Rotation2D is nothing else than a Scalar with
a function toRotationMatrix() and slerp(). The idea of this cast
operator is to be able to write:

Rotation2D<float> rot = M_PI/2;
rot = rot * 0.25;

without redefining all arithmetic operators in Rotation2D, that's it.


Gael.





On Wed, Aug 13, 2008 at 10:43 AM, Schleimer, Ben <bensch128@xxxxxxxxx> wrote:
> Wow Benoit,
>   I have to say that I am extremely impressed with Eigen2 and the cleanliness of the api. WOW! I'm really looking forward to using it in my next krita plugin, (when I get a break from work...) and am really excited to do so. My only issue is the usage of the operator Matrix3f() in AngleAxis and Quaterion and operator Scalar() and others in Rotation2d. The toMatrix() is clearer and less error prone IMHO.
>
> Also, I hope you add the performance benchmarks as examples to the wiki.
> They would be good examples to work from No?
>
> Cheers
> Ben
>
>
>
>
> --- On Mon, 8/11/08, Benoît Jacob <jacob@xxxxxxxxxxxxxxx> wrote:
>
>> From: Benoît Jacob <jacob@xxxxxxxxxxxxxxx>
>> Subject: [eigen] alpha6!
>> To: eigen@xxxxxxxxxxxxxxxxxxx
>> Date: Monday, August 11, 2008, 9:23 PM
>> Hi List,
>>
>> Eigen 2.0-alpha6 is released!
>>
>> Wiki: http://eigen.tuxfamily.org
>> Tarball:
>> http://download.tuxfamily.org/eigen/eigen-2.0-alpha6.tar.bz2
>> API: http://eigen.tuxfamily.org/api/
>>
>> It is now time for eigen1 apps to port to eigen2, as it now
>> supports
>> essentially all what eigen1 did.
>>
>> The changes since alpha5 are huge, there are 160 commits
>> since alpha5, the
>> sloccount is now 10975 (up from 6143 in alpha5), so I'm
>> not going to list
>> them all here, here is just an overview:
>>
>> - huge benchmarking and optimization effort by Gael. We now
>> often beat the
>> established "big iron" libraries on their own
>> ground, which is, standard
>> algorithms on large matrices:
>> http://eigen.tuxfamily.org/index.php?title=Benchmark
>>
>> - huge vectorization improvements, resulting in much more
>> vectorization, and
>> much cleaner, faster, extensible source code.
>>
>> - Gael made the Geometry module (with homogeneous
>> transforms, rotations,
>> quaternions etc).
>>
>> - Gael started the Sparse module, still experimental and
>> incomplete (probably
>> not for 2.0), but showing amazing performance already.
>>
>> - I made the LU module (in alpha5 it was just a stub).
>>
>> - I reworked the API for cwise ops, and reimplemented Swap
>> so it automatically
>> benefits from the vectorization, unrolling, and traverses
>> arrays only once.
>>
>> - Gael rewrote the partial reduction stuff.
>>
>> - I added a little demo, 'mandelbrot', a fractal
>> viewer, demonstrating how
>> Eigen can be used purely as a vectorization library.
>>
>> - I added a quick and dirty Regression module adapted from
>> eigen1. It will
>> change before 2.0, though.
>>
>> - we worked on reducing significantly compilation times.
>>
>> - many many improvements all over the place by both of us.
>>
>>
>> I surely forgot a ton of things!
>>
>> Now I must make a pause to dedicate myself to my new
>> postdoc position at the
>> University of Toronto. I'll just be doing what is
>> needed for KDE 4.2, KOffice
>> 2.0, Avogadro 1.0, OpenBabel 3.0 (to name a few projects
>> which should be
>> users of eigen2 in the near future). I think that Gael is
>> going to be busy
>> too with his new position and even more so now that
>> he'll be living in the
>> same city as his girlfriend again :)
>>
>> So, to anyone lurking here -- now's a great time to
>> step up and join us! We'd
>> be happy to mentor newcomers. Among the jobs you could
>> start with, you could
>> write SVD decomposition, improve the QR/eigenvalues stuff
>> in some way, help
>> with the Sparse module, revive AltiVec vectorization, help
>> vectorize more
>> parts of the code (such as Redux.h and Visitor.h), and the
>> list goes on...
>> (yes, we should update the TODO).
>>
>> Cheers,
>> Benoit
>
>
>