[Ipopt] Linear Solver Loader with MUMPS?

[John Pye]

Hi all

I have downloaded IPOPT 3.4.0 and set about trying to compile it. I'm
very pleased to see the work on the Linear Solver Loader that will make
it much easier to distribute programs that use IPOPT. I just had a few
questions...

   1. BLAS and LAPACK are listed as external code that must be
      downloaded, but I haven't downloaded those as instructed and yet
      IPOPT still compiles. I presume this means that the copies of BLAS
      and LAPACK already on my (Linux) system have been detected. Is
      that true? Should this be added to the online documentation,
      because it can reduce downloading/manual compilation by new users?
   2. It's possible to compile IPOPT without any linear solvers being
      available at build-time. I see that there is a IPOPT Option
      available to allow the linear solver to be selected at runtime.
      But how can I query the list of available linear solvers at
      runtime, such that I can ensure I pick a valid solver? What if I
      have a default build of IPOPT and I have libpardiso.so on my
      system, but not libhsl.so -- will libpardiso.so be selected
      automatically?
   3. Is there documentation available on the API required in the
      dlopenable shared libraries used by the Linear Solver Loader?
   4. If I wanted to add support for a new linear solver, would it
      require changes to libipopt.so, or can it be registered
      dynamically at runtime?
   5. If I downloaded HSL into the ThirdParty directory, can I control,
      using ./configure, whether HSL is statically or dynamically linked
      to IPOPT, or whether the Linear Solver Loader .so file is instead
      generated? How do I do that? Or is it determined just by the
      absence/presence of the ma27ad.f file at configure-time?
   6. Is there any plan to migrate MUMPS to a dlopenable solver, rather
      than it always being statically linked?

Cheers
JP