[eigen] What happens inside Eigen

["Benoit Jacob" <jacob.benoit.1@xxxxxxxxx>]

Hi List,

As you know, we're really serious about getting more hackers involved
in Eigen and making sure that it's possible for newcomers to
understand Eigen internals...

So I wrote a new dox page where we study a trivial example program
doing one vector addition "u = v + w" and we follow Eigen as is
complex logic expands, all the way down to the emitted assembly
intructions. Along the way we get to learn how expression templates
work, and we explain some aspects of the design of Eigen.

I uploaded it here for your reading pleasure (note that the rest of
the online dox is not yet updated since beta1):

http://eigen.tuxfamily.org/api/InsideEigenExample.html

Cheers,
Benoit

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