Using FORCES with your Fortran program

Let's assume, you want to write a fortran program using forces, like this example test.f90:

program test
  use mo_message, only : message
  implicit none
  call message("This is working!")
end program test

You should create a minimal CMakeLists.txt file next to the test.f90 file like this:

cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
# get CPM (package manager)
set(CPM_DOWNLOAD_LOCATION "${CMAKE_BINARY_DIR}/cmake/CPM_0.35.0.cmake")
file(DOWNLOAD https://github.com/cpm-cmake/CPM.cmake/releases/download/v0.35.0/CPM.cmake ${CPM_DOWNLOAD_LOCATION})
include(${CPM_DOWNLOAD_LOCATION})
 
# create project
project(MyProject LANGUAGES Fortran)
 
# add executable
add_executable(test test.f90)
 
# add FORCES dependency
CPMAddPackage("https://git.ufz.de/chs/forces.git@0.3.1")
 
# link dependencies
target_link_libraries(test forces)

There, CPM (the cmake package manager) is downloaded on the fly and used to get FORCES to be able to link against it.

Afterwards you only need to do the following to configure, compile and execute your program:

cmake -B build
cmake --build build --parallel
./build/test

And it will happily write:

This is working!

If you have the FORCES sources downloaded and you want to link a local executable against it, you can specify a path to CMake with FORCES_EXE:

cmake -B build -D FORCES_EXE=test.f90
cmake --build build --parallel
./build/main

You can use this with the examples provided in the examples/ directory, e.g. FORCES_EXE=examples/01_grids/01_regridding.f90. The executable will be always called main.

For a more complex project, prepared for unit-tests, documentation and modules, have a look at the Fortran Template.

Dependencies and Requirements

Fortran compiler: We support gfortran, nagfor and ifort
Build system: We support make and ninja
cmake: Software for build automation
NetCDF-Fortran: NetCDF I/O for Fortran
(optional) fypp: Fortran pre-processor written in Python

It is recommended to have a clean installation at a custom location for a C compiler, a Fortran compiler, the NetCDF C library and the NetCDF Fortran library with consistent compilers.

We recommend to use a conda environment by using Miniconda to get all dependencies easily:

conda create -y --prefix ./forces_env
conda activate ./forces_env
conda config --add channels conda-forge
conda config --set channel_priority strict
conda install -y cmake make fortran-compiler netcdf-fortran fypp

With this you could now proceed with the example given above.

Table of Contents

Using FORCES with your Fortran program

Dependencies and Requirements

License