TODO list before 1.0 release

• Tests!
• Docs!
• Cross section calculations. (Done in some Python scripts.)
• Field calculations. (Partly done, needs more testing.)
  • Also test periodic vs. nonperiodic consistence (big finite lattice + absorbing medium vs. infinite lattice + absorbing medium).
• Complex frequencies, n's, k's. (Mostly done.)
• Transforming point (meta)generators.
• Check whether moble's quaternions and my quaternions give the same results in tmatrices.py
• Ewald summations of all types of lattices (dimensionality-wise).
• Split lattices.h into separate point generator and lattice vector manipulation parts.
  • Maybe move something from the .h to .c file.
• Check exact normalisation convention of scuff-tmatrix output.
• Check whether the Condon-Shortley phase affects the form of Wigner matrices.
• The xflip, yflip and possible i-factor problem.
• General 3D point group symmetries.
  • Instead the current hard-coded limited set.
  • The generation, finding subgroups etc. should be "easy" with quaternions and stuff, as the set is quite limited, see Wikipedia.
  • Not sure about the representations, though.
  • As a description of a T-matrix / particle metadata.
• Nice CLI for all general enough utilities.
• Remove legacy code.
• Split qpms_c.pyx.
• Reduce compiler warnings.
• Serialisation (saving, loading) of ScatteringSystem and other structures.
• Python exceptions instead of hard crashes in the C library where possible.
• Scatsystem init sometimes fail due to rounding errors and hardcoded absolute tolerance in the qpms_tmatrix_isclose() call.
• Prefix all identifiers. Maybe think about a different prefix than qpms?
• Consistent indentation and style overall.
• Rewrite the parallelized translation matrix, mode problem matrix generators in a way that reuses as much code as possible without copypasting

Nice but less important features

• Static, thread-safe caches of constant coefficients + API without the current "calculators".

Optimisations

• Leaving out the irrelevant elements if a "rectangular" block of the translations matrix is needed.
• Ewald sums with "non-parallel" shifts (are about 20 times slower than the purely parallel ones).
• Reusing intermediate results (profiling needed)
  • Bessel, Legendre functions (see also branch finite_lattice_speedup)
  • Lattice points (sorting and scaling)
  • Γ/Δ functions (for periodic lattices)
• More parallelisation.
• Possibly pre-calculation of the (precise) coefficients in Bessel and Legendre functions (using gmp)
• Asymptotic approximations of the Bessel functions for far fields.