[Marble-devel] Eigen

[Benoit Jacob]

2009/1/16 Torsten Rahn <rahn at kde.org>:
> Not at the moment. This could however very well change at some point after we
> introduce OpenGL. So I don't expect that it's very likely that we introduce
> Eigen as a dependency before KDE 4.3.
> Currently all we need is already in our Quaternion class.

OK then indeed, i understand Eigen is not necessarry... :)

> Well, I looked at the Eigen version of the Quaternion class recently (in the
> hope that I'd maybe be able to copy the class itself over). However it seems
> to be deeply interwoven already with the rest of Eigen,

indeed it is, the coefficients are stored as a Eigen:: vector.

> Well, I feel reluctant to introduce a dependency

Remember, Eigen is a pure template library, so this would be only a
build-time dependency.

> transfer maintainance of a class that we have barely changed recently.

sure, i see your point.

> The only thing that I'm interested in is getting an SSE/Altivec acceleration
> of the method:
>
>    void        Quaternion::rotateAroundAxis(const matrix &m);

OK, I'll tell you if we eventually vectorize that.
In any case it doesn't look like the perfect candidate for
vectorization so I wouldn't expect more than +50% speed improvements
(assuming qreal==double) in the best case.

> However even for that one I'd rather like to copy over 2-5 classes than
> linking against a whole new library.

There is no linking, there is no binary library, it's only headers and
only the code that you actually use gets compiled into marble. "You
don't pay for what you don't use".

Cheers,
Benoit