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Fortran package

This part of the documentation covers the legacy Fortran infrastructure, compilation, driver execution, and how the original reference model is run.

Architecture

The Fortran codebase is located in:

  • src/fortran/: Contains the original Fortran 77/90 source files, a CMake build configuration, and command-line driver/test scripts.

  • src/data/: Centralized .dat and .asc files required to operate the models.

  • Key source files include:

  • irisub.for: Core subroutine (IRI_SUB) that orchestrates all sub-model calculations.

  • irifun.for: Auxiliary mathematical functions, interpolation routines, and profile calculation helpers.
  • iritec.for: Subroutine (IRITEC) for numerical integration of Total Electron Content.
  • igrf.for & cira.for & rocdrift.for: External physical and empirical models (IGRF magnetic field, CIRA/MSIS neutral atmosphere, ROCSAT vertical plasma drift).
  • iridreg.for: Danilov D-region model and lookup table logic.
  • iri_driver.f90 & test.f90: Standalone command-line program drivers to execute the simulation and print outputs.
  • CMakeLists.txt: CMake build configuration to compile the Fortran source code into a static library.

Compiling and Running

To compile the Fortran library and drivers, you need a Fortran compiler (e.g., gfortran) and CMake.

Using CMake

From the repository root:

mkdir -p src/fortran/build
cd src/fortran/build
cmake ..
make

Direct Compilation with gfortran

Alternatively, you can compile the standalone basic test program directly using gfortran:

cd src/fortran
gfortran -o basictest test.f90 irisub.for irifun.for iritec.for iridreg.for iriflip.for igrf.for cira.for rocdrift.for
./basictest

Similarly, the command-line driver iri_driver can be compiled and executed:

gfortran -o iri_driver iri_driver.f90 irisub.for irifun.for iritec.for iridreg.for iriflip.for igrf.for cira.for rocdrift.for
./iri_driver 1980 03 21 12 00 00 0.0 0.0 100.0 500.0 20.0

Arguments are: year, month, day, hour, minute, second, latitude, longitude, min_alt_km, max_alt_km, step_alt_km

Running Tests

The legacy basic test is defined in test.f90. When compiled and executed as shown above, it prints key parameters like \(N_e\) profile, \(N_mF_2\), and \(h_mF_2\) values, verifying that the outputs conform to expected ranges and checking for any output length discrepancies.

Legacy Limitations

  • No Thread Safety: Extensive use of global mutable variables, /COMMON/ blocks, and SAVE statements prevents concurrent execution across threads.
  • Compiler Dependency: Requires a Fortran compiler (gfortran or similar) and build systems like CMake to be installed on the host system.
  • Undefined/Implicit State: Some variables are implicitly saved or left uninitialized, introducing potential state leakage bugs across sequential invocations.