The discrete domain computation library (DDC)

See https://ddc.mdls.fr/

DDC, is a C++-17 library that aims to offer to the C++/MPI world an equivalent to the xarray.DataArray/dask.Array python environment. Where these two libraries are based on numpy, DDC relies on Kokkos and mdspan to offer CPU/GPU performance-portable multi-dimensional arrays and iterators.

DDC aims to offer abstractions to represent:

• tagged continuous dimensions,
• discretizations of these (multiple kinds of meshes, function spaces, Fourier, etc.),
• domains in these discretized dimensions,
• associating data to the elements of these discrete domains,
• efficient distribution and iteration over this data.

All these abstractions are handled at compilation using C++ template meta-programming to ensure zero overhead at execution and enable developers to change their design choices (e.g. from a regular mesh to a non-uniform one) with performance portability.

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Prerequisites

To use DDC core, one needs the following dependencies:

• a C++17-compliant compiler
• CMake 3.22...<4
• Kokkos 4.4...<5
• (optional, micro benchmarking) Benchmark 1.8...<2
• (optional, documentation) Doxygen 1.8.13...<2
• (optional, unit-testing) GoogleTest 1.14...<2

To use DDC components, one needs the following dependencies:

• (optional, fft interface) DDC::fft
  • Kokkos-fft 0.2.1...<1
• (optional, IO interface) DDC::pdi
  • PDI 1.6...<2
• (optional, spline interpolation) DDC::splines
  • Ginkgo 1.8...<2
  • Kokkos Kernels 4.5.1...<5

Getting the code and basic configuration

git clone --recurse-submodules -j4 https://github.com/CExA-project/ddc.git
cd ddc
cmake -B build -D DDC_BUILD_KERNELS_FFT=OFF -D DDC_BUILD_KERNELS_SPLINES=OFF -D DDC_BUILD_PDI_WRAPPER=OFF
cmake --build build

Contributing

Formatting

The project makes use of formatting tools for the C++ (clang-format) and cmake (gersemi) files. The formatting must be applied for a PR to be accepted.

To format a cmake file, please apply the command

gersemi -i the-cmake-file

One can find the formatting style in the file .gersemirc.

To format a C++ file, please apply the command

clang-format -i the-cpp-file

One can find the formatting style in the file .clang-format.

Warning

The formatting might not give the same result with different versions of a tool.

Known issues

• Kokkos 4.5.0 embeds a version of mdspan that is not compatible with DDC, see kokkos/mdspan#368. This issue has been fixed in Kokkos 4.5.1.