The GKC++ code

Description

GKC++ (GyroKinetic Code++) is a δf gyro-kinetic code. Currently features are :

• Various geometries (sheared, shearless, toroidal)
• multiple species support
• fully electromagnetic code
• Interfaces for various field and Vlasov solvers
• Eigensolver interface using SLEPc/PETSc
• Decomposition into eigenvectors using elemental
• Preliminary support for global simulations
• 3-stage parallelization (Vectorization, OpenMP and MPI)
• Data output using HDF-5.
• Data analysis using ipython/matplotlib/ scipy/pytables

However, this code is still considered experimental and benchmark to other codes is pending. You may want to consider using other gyro-kinetic codes such as GENE, gkw or gs2 for production usage.

GKC++ is programmed in C++-11/Cilk+ which (for our opinion) greatly simplifies readability and handling of multi-dimensional arrays. However, note that only a limited subset of compilers support the Cilk+ extensions such as

• Intel Compiler
• [GCC-4.9] (http://gcc.gnu.org/wiki/cilkplus-merge)
• Cilkplus/LLVM

Why C++ but not Fortran

Fortran is popular in numerical science communities due to it's power of handling multi-dimensional arrays. However, the lack of templates, function overloading, pointers and classes (although some of these features are now supported by the Fortran-03 standard) makes Fortran code difficult to read and extend as well as accessing other 3rd party libraries.

To handle multiple dimension in C++, we make use of CEAN (C/C++ Extension for Array Notation) as provided by Cilk+. Additionally, Cilk+ allows to use C99 complex numbers within C++, which facilitates vectorization. Although the code is non-standard, the authors believe that Cilk+ will establish as a new-standard such as OpenMP did (e.g. array sections in Section 2.6 OpenMP 4.0rc2).

License

The code is license under the GNU Public License Version 3 (or at your opinion any later version).