todo

麻省理工的计算光子晶体的程序

Support 3d (r,phi,z) cell, where m is "Bloch wavenumber"
      -- gives 6-fold (and n-fold) symmetry as side effect
      -- allows computation of bended photonic-crystal waveguides

Implement transparent boundary conditions to back PML layers, so that
glancing-angle waves can be absorbed.

Re-entrant functions: foo(vec&) arguments should be foo(vec&, void*)
where the second argument can be used to pass state (instead of global
vars).

Fix bugs: divergence in saturated polarization (tests/symmetry.cpp),
          and problems with nonlinearity + symmetry (idem)

User-specified anisotropic dielectric functions.

Support mu? (i.e. magnetic permeability) (including anisotropic, ideally)

Support non-dispersive conductivities.

Use anisotropic PML rather than split-fields PML (former requires less
memory).  User proper PML for dispersive media and cylindrical.

Use more-stable algorithm for dispersive media.

Field dump/load (i.e. restarting)?

Make sure epsilon and other material properties respect symmetry,
periodic boundaries, etc.?

Remove monitor point class (redundant with HDF5 output, DFT volumes?).

Integrated support for calling MPB mode solver for current distributions.

rename fields::initialize to fields::add_to_fields or something like that,
and allow specifying a geometric_volume.

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Epsilon from file support.

Non-integrated currents.

Give easy way to call various field-integration functions.

Need a way to reset epsilon when restarting, and also phasing support.