About

L2G_cpp is a C++ library used for running FLT runs in a tokamak-type geometry. FLT is performed by following FLs from a desired mesh, in an axisymmetric magnetic field provided in the form of the poloidal magnetic flux and the poloidal current function and performing intersecting tests on neighboring or shadowing geometry.

The equilibrium data is provided to the library via function calls and is not limited by I/O, meaning that an application can get it's equilibrium data from an arbitrary source and feed it to the library via function calls.

For interpolating the input equilibrium data the implementation of 2D Bicubic Spline interpolation method is used.

FLs are followed with the Runge-Kutta-Fehlberg Method (RKF45) method to ensure good precision and stability when traveling along a FL on a magnetic surface.

Intersection tests on the FLs are performed by using the Intersect method from the MIT licensed, single-header only tinybvh project (https://github.com/jbikker/tinybvh). See src/tiny_bvh.h for more information.

Building the software

In order to build the software the following build dependencies are required:

• CMake >= 3.12
• OpenMP support
• Doxygen (optional)
• Ninja (optional)

Linux:

• GCC
• build tools

Windows:

• Visual Studio 17 2022 (use the x64 Native Tools Command Prompt)
• Visual Studio CMake support

Doxygen is optional. It is used for generating a html version of the documentation.

Ninja is optional. It is used for building the software.

Building with CMake

Ensure that dependencies can be found with CMake. Otherwise edit the CMAKE_PREFIX_PATH in order to point to the CMake directories of the dependencies.

# Clone or extract the code
mkdir build

# Generate the build system
cmake -S <path-to-source> -B <path-to-build> -GNinja -DCMAKE_INSTALL_PREFIX=<path-to-install> -DCMAKE_BUILD_TYPE=Release

# Build the project
cmake --build <path-to-build>

# Test the build
cmake -E chdir <path-to-build> ctest

# Install the project
cmake --install <path-to-build>

Debug build CMake for IDE editor

In case you are using an editor with LSP plugins or functionality and you have installed the LSP-clangd plugin, the following steps has to be performed in order to have the LSP-clangd enhanced experience.

Generate the compile build JSON file

When compiling pass the the flag -DCMAKE_EXPORT_COMPILE_COMMANDS=ON. This will generate a JSON file that gives the LSP-clangd compilation information

cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_BUILD_TYPE=Debug <path-to-source>

Now from the build directory copy the compile_commands.json to the root of the source directory.

Usage of the code in other CMake projects

The software can be imported in other CMake projects. The CMake directory has to be appended to the CMAKE_PREFIX_PATH:

export CMAKE_PREFIX_PATH=<path-to-installed-cmake-files>:${CMAKE_PREFIX_PATH}

and then can be used in CMake as following:

find_package(FLT REQUIRED)
find_package(OpenMP)

add_executable(<TARGET> <TARGET_CONFIGURATION>)
target_link_libraries(<TARGET> flt)
target_include_directories(<TARGET> PUBLIC ${FLT_INCLUDE_DIRS})
target_compile_definitions(<TARGET> PUBLIC ${FLT_COMPILE_DEFINITIONS})