## call fortran routine from C++ function * a FORTRAN90 subroutine is like a C++ void function, and should be declared this way in the C++ code. The qualifier extern should also be used. * a FORTRAN90 subroutine or function expects all its arguments to be passed by reference. This generally means simply that the C++ function must pass scalar variables by reference, not value. * typically, when the FORTRAN90 compiler compiles the FORTRAN90 code, the names of functions and subroutines are stored with an appended underscore. In order for these names to be found by the C++ code, it is necessary that the C++ code declare and invoke the FORTRAN90 functions and subroutines with the underscore explicitly appended to the name. * in many cases, a FORTRAN90 compiler is simply a "front end" to a corresponding C++ compiler, as in the case of the GNU compilers gfortran and g++, or the Intel compilers ifort and icpp. This means that, as long as the corresponding compilers are used to compile the FORTRAN90 and C++ codes, it is probably possible to use either compiler to link and load the object codes; however, the load command may need to specify explicitly certain libraries associated with one of the languages. For instance, if loading using the gcc command, it is necessary to include "-l gfortran" so that the FORTRAN90 I/O libraries, among others, are included in the build. ## use bind(C) in F90 ``` shell gfortran -shared -o math_module.so math_module.f90 g++ hello.cpp -L. -lmath_module -o main g++ hello.cpp /path/to/math_module.so -o main ``` ## install mini-requirements for clm ### netCDF-C ``` shell sudo apt install libhdf5-dev wget https://path/to/netcdf-c.source.zip unzip netCDF.zip cd netcdf mkdir build cd build cmake ../. make sudo make install ``` ### netcdf-fortran ``` shell wget https://github.com/Unidata/netcdf-fortran/archive/refs/tags/v4.6.1.zip unzip netcdf-fortran cd netcdf-fortran ./configure make check sudo make install ``` ### pnetcdf ``` shell git clone https://github.com/Parallel-NetCDF/PnetCDF.git cd PnetCDF autoreconf -i ./configure make sudo make install ``` ### lapack ``` shell wget https://github.com/Reference-LAPACK/lapack/archive/refs/tags/v3.12.0.zip unzip v3.12.0.zip cd v3.12.0 mkdir build cd build cmake .. make sudo make install ```