[Ipopt] Dependency of IPOPT on METIS

[Dominique Orban]

When configuring IPOPT, it's possible to specify where METIS is installed. I'm wondering if METIS is really a (optional) dependency of core IPOPT, or just a dependency of the linear solver.

It turns out that it's perfectly possible to build IPOPT to completion without specifying any linear solver (which seems odd to me), and this raises my question about METIS: what is METIS used for in core IPOPT when it is passed to `configure`?

Thanks.

-- 
Dominique