20.1. Introduction

An interface module can be accessed with the use statement, e.g.

use fsundials_core_mod   ! this is needed to access core SUNDIALS types, utilities, and data structures
use fcvode_mod           ! this is needed to access CVODE functions and types
use fnvector_openmp_mod  ! this is needed to access the OpenMP implementation of the N_Vector class

and by linking to the Fortran 2003 library in addition to the C library, e.g. libsundials_fcore_mod.<so|a>, libsundials_core.<so|a>, libsundials_fnvecpenmp_mod.<so|a>, libsundials_nvecopenmp.<so|a>, libsundials_fcvode_mod.<so|a> and libsundials_cvode.<so|a>. The use statements mirror the #include statements needed when using the C API.

The Fortran 2003 interfaces leverage the iso_c_binding module and the bind(C) attribute to closely follow the SUNDIALS C API (modulo language differences). The SUNDIALS classes, e.g. N_Vector, are interfaced as Fortran derived types, and function signatures are matched but with an F prepending the name, e.g. FN_VConst instead of N_VConst() or FCVodeCreate instead of CVodeCreate. Constants are named exactly as they are in the C API. Accordingly, using SUNDIALS via the Fortran 2003 interfaces looks just like using it in C. Some caveats stemming from the language differences are discussed in §20.3. A discussion on the topic of equivalent data types in C and Fortran 2003 is presented in §20.2.

Further information on the Fortran 2003 interfaces specific to the N_Vector, SUNMatrix, SUNLinearSolver, and SUNNonlinearSolver classes is given alongside the C documentation. For details on where the Fortran 2003 module (.mod) files and libraries are installed see §1.1.

The Fortran 2003 interface modules were generated with SWIG Fortran [90], a fork of SWIG. Users who are interested in the SWIG code used in the generation process should contact the SUNDIALS development team.

Table 20.1 List of SUNDIALS Fortran 2003 interface modules

Class/Module	Fortran 2003 Module Name
SUNDIALS core	fsundials_core_mod
ARKODE	farkode_mod
ARKODE::ARKSTEP	farkode_arkstep_mod
ARKODE::ERKSTEP	farkode_erkstep_mod
ARKODE::MRISTEP	farkode_mristep_mod
ARKODE::SPRKSTEP	farkode_sprkstep_mod
ARKODE::LSRKSTEP	farkode_lsrkstep_mod
ARKODE::SPLITTINGSTEP	farkode_splittingstep_mod
ARKODE::FORCINGSTEP	farkode_forcingstep_mod
CVODE	fcvode_mod
CVODES	fcvodes_mod
IDA	fida_mod
IDAS	fidas_mod
KINSOL	fkinsol_mod
NVECTOR_CUDA	Not interfaced
NVECTOR_MANVECTOR	fnvector_manyvector_mod
NVECTOR_MPIMANVECTOR	fnvector_mpimanyvector_mod
NVECTOR_MPIPLUSX	fnvector_mpiplusx_mod
NVECTOR_OPENMP	fnvector_openmp_mod
NVECTOR_PARALLEL	fnvector_parallel_mod
NVECTOR_PARHYP	Not interfaced
NVECTOR_PETSC	Not interfaced
NVECTOR_PTHREADS	fnvector_pthreads_mod
NVECTOR_RAJA	Not interfaced
NVECTOR_SERIAL	fnvector_serial_mod
NVECTOR_SYCL	Not interfaced
SUNADAPTCONTROLLER_IMEXGUS	fsunadaptcontroller_imexgus_mod
SUNADAPTCONTROLLER_SODERLIND	fsunadaptcontroller_soderlind_mod
SUNADAPTCONTROLLER_MRIHTOL	fsunadaptcontroller_mrihtol_mod
SUNADJOINTCHECKPOINTSCHEME_FIXED	fsunadjointcheckpointscheme_fixed_mod
SUNDOMEIGEST_ARNOLDI	fsundomeigest_arnoldi_mod
SUNDOMEIGEST_POWER	fsundomeigest_power_mod
SUNLINSOL_BAND	fsunlinsol_band_mod
SUNLINSOL_DENSE	fsunlinsol_dense_mod
SUNLINSOL_KLU	fsunlinsol_klu_mod
SUNLINSOL_LAPACKBAND	Not interfaced
SUNLINSOL_LAPACKDENSE	Not interfaced
SUNLINSOL_MAGMADENSE	Not interfaced
SUNLINSOL_ONEMKLDENSE	Not interfaced
SUNLINSOL_PCG	fsunlinsol_pcg_mod
SUNLINSOL_SLUDIST	Not interfaced
SUNLINSOL_SLUMT	Not interfaced
SUNLINSOL_SPBCGS	fsunlinsol_spbcgs_mod
SUNLINSOL_SPFGMR	fsunlinsol_spfgmr_mod
SUNLINSOL_SPGMR	fsunlinsol_spgmr_mod
SUNLINSOL_SPTFQMR	fsunlinsol_sptfqmr_mod
SUNMATRIX_BAND	fsunmatrix_band_mod
SUNMATRIX_DENSE	fsunmatrix_dense_mod
SUNMATRIX_MAGMADENSE	Not interfaced
SUNMATRIX_ONEMKLDENSE	Not interfaced
SUNMATRIX_SPARSE	fsunmatrix_sparse_mod
SUNNONLINSOL_FIXEDPOINT	fsunnonlinsol_fixedpoint_mod
SUNNONLINSOL_NEWTON	fsunnonlinsol_newton_mod
SUNNONLINSOL_PETSCSNES	Not interfaced

20.1.1. Installation

The installation procedure for the Fortran interfaces is the same as for the C/C++ core of SUNDIALS, refer to §1.1. The CMake option to turn on the Fortran interfaces in a SUNDIALS build is BUILD_FORTRAN_MODULE_INTERFACE. The Spack variant is +fortran.

20.1.2. Important notes on portability

The SUNDIALS Fortran 2003 interface should be compatible with any compiler supporting the Fortran 2003 ISO standard.

Upon compilation of SUNDIALS, Fortran module (.mod) files are generated for each Fortran 2003 interface. These files are highly compiler specific, and thus it is almost always necessary to compile a consuming application with the same compiler that was used to generate the modules.