Implement an interface that external surface deformation tools can use.

[bangerth]

@tjhei and @gregtucker and I were brainstorming how the interface to external tools for surface deformation should look like. I promised @tjhei a prototype that he could fill in with the MPIRemotePointEvaluation tools he has been writing.

@tjhei Feel free to push to this branch. I think I marked up all the places where you have to put code.

@xlia62, @minerallo, @djneu, @MFraters Once this is finished, it may actually be of interest to you as well. Feedback on the interface, documentation, and implementation of the class here is certainly welcome!

[Minerallo]

This sounds great! Just to clarify, does this mean it will allow interpolation of values at remote points, for example on a higher-resolution mesh used by an external surface model? Im looking forward !

[bangerth]

@Minerallo Yes, exactly. You won't have to do the interpolation yourself any more, just say "I need the solution at these points" and it will be given to you :-)

[gregtucker]

For run-control and data-query functions, consider looking to the Basic Model Interface (BMI) for inspiration. For example, BMI run-control specifications in C++ look like:

      // Model control functions.
      virtual void Initialize(std::string config_file) = 0;
      virtual void Update() = 0;
      virtual void UpdateUntil(double time) = 0;
      virtual void Finalize() = 0;

and variable getters and setters look like:

      // Variable getters
      virtual void GetValue(std::string name, void *dest) = 0;
      virtual void *GetValuePtr(std::string name) = 0;
      virtual void GetValueAtIndices(std::string name, void *dest, int *inds, int count) = 0;

      // Variable setters
      virtual void SetValue(std::string name, void *src) = 0;
      virtual void SetValueAtIndices(std::string name, int *inds, int count, void *src) = 0;

[bangerth]

@tjhei 's current draft of an implementation: https://github.com/landlab-aspect/aspect/pull/9

@danieldouglas92 FYI