Accessing the same ATLAS data from both C++ and Fortran about atlas HOT 3 CLOSED

OK, I have found the solution for the ATLAS State that I am finally using:

• in C++ :
  • declare a State pointer:

  State * state = new State(...)
  

  • pass it to the Fortran function:

  my_fortran_subroutine_f90(state, ...)
  

• in the C interface: pass the State pointer

extern "C" {
  void my_fortran_subroutine_f90(State * state, ...);
}

• in Fortran: get the State pointer as a type(c_ptr) and use it to initialize a type(atlas_state):

subroutine my_fortran_subroutine_c(state_ptr,...) bind (c,name='my_fortran_function_f90')

type(c_ptr),intent(in),value :: state_ptr
type(atlas_state) :: state

state = atlas_state(state_ptr)

end subroutine my_fortran_subroutine_c

Maybe it would be worth adding an example in the documentation. Not a top priority though...

from atlas.

Hi @benjaminmenetrier I'm happy you figured it out.
Perhaps I could advise to you to use atlas_FieldSet instead of atlas_State?
The State is more of an experimental tryout I once did to show Yannick Tremolet what is possible.
Conceptually it is the same as a FieldSet with the difference that it could be constructed from a configuration as shown experimentally here:
https://github.com/ecmwf/atlas/blob/0.19.0/src/tests/grid/test_state.cc#L137
If you don't need that, then you could probably use FieldSet instead, as that is more widespread used in API's, and maintained.

from atlas.

Thank you for the tip! I'll switch to FieldSet now, before the use of State is too widespread in the code...

from atlas.