# Components

This chapter describes how the code is organised. It follows the
*TRACMASS Components* chapter of the Fortran documentation (main program,
main modules, namelist, projects) and maps each Fortran piece onto its JAX
counterpart.

- [Main program](main_program.md): what `tracmass.run` and the integrators
  do, step by step, compared with `TRACMASS.F90` and `mod_loop.F90`.
- [Grid and flux data](grid.md): the C-grid, index conventions, and the
  three-layer split into `GridFields`, `LazyFluxFields` and `FluxFields`.
- [Advection schemes](schemes.md): the equations for the crossing time and
  the new position, for the time-stepping and the time-analytical schemes.
- [Integrators](integrators.md): windows, sub-steps, time interpolation, and
  the full-grid, patched and streaming variants.
- [GCM adapters](adapters.md): the equivalent of the Fortran *projects*
  folder.
- [Main modules](modules.md): a tour of the Python package.
- [Fortran-to-JAX map](fortran.md): every Fortran routine and its
  TRACMASS-JAX equivalent.

```{toctree}
:hidden:

main_program
grid
schemes
integrators
adapters
modules
fortran
```