[Rivet] Eigen2

[Frank Siegert]

Andy Buckley, Tuesday 03 November 2009:
> Holger Schulz wrote:
> > I just stumbled upon the same problem, adding a
> > "-I/rivet/include/eigen2" to the compiler solved the problem.
> >
> > I found the Eigen include files in the Rivet source directory in
> > include/eigen2,
> > so I think they are shipped with Rivet, right?

But not installed.

> We can certainly install these headers... I'd forgotten that we were
> previously installing the eigen headers. I'll add something equivalent
> for eigen2.

Is that really something that should live in the Rivet source tree? Most 
distributions do or will have packages of this, and for the other ones it 
could be something that we add to rivet-bootstrap. I don't have a really 
strong opinion on it, but it weighs in with 4MB (of 16MB total in Rivet 
trunk) and a lot of files to checkout (584 of 1288).

If we were to make it external: Which Rivet features depend on it? I have 
to admit that I wasn't aware of eigen being used in and part of Rivet 
before this change.

While talking about not finding headers needed to compile with Rivet... 
shouldn't we add the -I/path/to/boost/include and -I/path/to/eigen2 to 
rivet-config --cppflags? At least this was one of the most common pitfalls 
for people wanting to compile Sherpa with Rivet support.

Frank