Collisions

Collision operator in \((v_\parallel,\mu)\) applied to all against all species at the same time. As such, the operator is \(O(N^2)\) in number of species.

It was rewritten from Fortran into C++. The operator's name is KOkkos coLIsion OPerator (KOLIOP) and is provided as a submodule (see /vendor).

While the operator is in C++, the interface with Fortran and other C++ code is made through a C layer. This is also known as the hourglass pattern (conceptually, the narrow neck of the device represent the lowering to C).

To integrate Koliop into Gyselalib++, we wrap its functionalities into a DDC aware operator present in collision_operator.hpp. In Gyselalib++, operator are expected to support multiple if not all kind of geometries. But Koliop expect some data in layout right [sp, phi, theta, r, vpar, mu] instead of the [sp, phi, r, theta, vpar, mu] layout that is going to be favoured in Gyselalib++. We have some machinery that setup input configuration data depending on the geometry. These are in collision_configuration_sprvparmu.hpp, collision_configuration_spvparmu.hpp.

More information can be found in the Gysela collision operator