File-based computations

• electrodes:

  • New source TxMagneticPoint (requires discretize; mainly used as
    adjoint source for magnetic receivers; does not work in the presence of
    magnetic permeabilities in the vicinity of the source).
  • Both receivers (Rx{Electric;Magnetic}Point) can now produce their
    proper adjoint (thanks to @sgkang!).

• Changes in Simulation and parallel execution.

  • Parallel computation is not sharing the simulation any longer.
  • Parallel computation can new be done both file-based or all in memory.
    The new possibility for file-based computation should make it possible
    to compute responses for any amount of source-frequency pairs. See
    parameter file_dir in the Simulation class (or corresponding parameter
    in the CLI parameter file).
  • get_model and get_hfield are now done on the fly, they are not
    stored in a dict; simulation._dict_model and
    simulation._dict_hfield do not exist any longer.
  • New methods jvec (sensitivity times a vector) and jtvec
    (sensitivity transpose times a vector). These methods are currently
    experimental; documentation and examples are lacking behind.

• Various small things:

  • Models and Fields return itself (not a copy) when the grid provided to
    interpolate_to_grid is the same as the current one.