Building Kokkos-FFT

This section describes how to build Kokkos-FFT with some advanced options. In order to build Kokkos-FFT, we use CMake with following compilers. Kokkos and backend FFT libraries are also necessary. Available CMake options for Kokkos-FFT are listed.

Compiler versions

Kokkos-FFT relies on quite basic functionalities of Kokkos, and thus it is supposed to work with compilers used for Kokkos. However, we have not tested all the listed compilers there and thus recommend the following compilers which we use frequently for testing.

gcc 10.4.0+ - CPUs
IntelLLVM 2024.2.1+ - CPUs, Intel GPUs
nvcc 12.2.0+ - NVIDIA GPUs
rocm 6.3.0+ - AMD GPUs

Note

A compatible C++ compiler that supports at least C++20 is necessary.

Install Kokkos-FFT with CMake

Let’s assume Kokkos is installed under <path/to/kokkos> with OpenMP backend. We build and install Kokkos-FFT under <path/to/Kokkos-FFT>.

export KOKKOSFFT_INSTALL_PREFIX=<path/to/Kokkos-FFT>

cmake -B build_KokkosFFT \
      -DCMAKE_CXX_COMPILER=<your c++ compiler> \
      -DCMAKE_PREFIX_PATH=<path/to/kokkos> \
      -DCMAKE_INSTALL_PREFIX=${KOKKOSFFT_INSTALL_PREFIX}
cmake --build build_KokkosFFT -j 8
cmake --install build_KokkosFFT

Here is an example to use Kokkos-FFT in the following CMake project.

---/
 |
 └──<project_directory>/
    |--CMakeLists.txt
    └──hello.cpp

The CMakeLists.txt would be

cmake_minimum_required(VERSION 3.23)
project(kokkos-fft-as-library LANGUAGES CXX)

find_package(Kokkos CONFIG REQUIRED)
find_package(KokkosFFT CONFIG REQUIRED)

add_executable(hello-kokkos-fft hello.cpp)
target_link_libraries(hello-kokkos-fft PUBLIC Kokkos::kokkos KokkosFFT::fft)

The code can be built as

cmake -B build \
      -DCMAKE_CXX_COMPILER=<your c++ compiler> \
      -DCMAKE_PREFIX_PATH="<path/to/kokkos>;<path/to/Kokkos-FFT>"
cmake --build build -j 8

Install Kokkos-FFT with Spack

Kokkos-FFT can also be installed with [spack](https://spack.io). For example, the recipe for H100 GPU with cufft is as follows:

git clone --depth=2 --branch=v1.1.0 https://github.com/spack/spack.git
source spack/share/spack/setup-env.sh # For bash

spack install kokkos-fft device_backend=cufft ^kokkos +cuda +wrapper cuda_arch=90

We have two main parameters to configure Spack:

host_backend: Enable device backend FFT library (fftw-serial or fftw-openmp)
device_backend: Enable device backend FFT library (cufft, hipfft, or onemkl)

The code can be built as

spack load kokkos kokkos-fft
cmake -B build
cmake --build build -j 8

CMake options

We rely on CMake to build Kokkos-FFT, more specifically CMake 3.22+. Here is the list of CMake options. For FFTs on Kokkos device only, we do not need to add extra compile options but for Kokkos ones. In order to use Kokkos-FFT from both host and device, it is necessary to add KokkosFFT_ENABLE_FFTW=ON. This option may be useful, for example FFT is used for initialization at host. However, to enable this option, we need a pre-installed FFTW for FFT on host, so it is disabled in default if one of the device backend is enabled. (see minimum working example).

CMake options
	Description	Default
`KokkosFFT_ENABLE_INTERNAL_KOKKOS`	Build internal Kokkos instead of relying on external one.	OFF
`KokkosFFT_ENABLE_EXAMPLES`	Build Kokkos-FFT examples	OFF
`KokkosFFT_ENABLE_TESTS`	Build Kokkos-FFT tests	OFF
`KokkosFFT_ENABLE_BENCHMARK`	Build benchmarks for Kokkos-FFT	OFF
`KokkosFFT_ENABLE_FFTW`	Use FFTW for Host backend	ON (if none of Kokkos devices is enabled, otherwise OFF)
`KokkosFFT_ENABLE_CUFFT`	Use cufft for CUDA backend	ON (if `Kokkos_ENABLE_CUDA` is ON, otherwise OFF)
`KokkosFFT_ENABLE_ROCFFT`	Use rocfft for HIP backend	OFF
`KokkosFFT_ENABLE_HIPFFT`	Use hipfft for HIP backend	ON (if `Kokkos_ENABLE_HIP` is ON, otherwise OFF)
`KokkosFFT_ENABLE_ONEMKL`	Use oneMKL for SYCL backend	ON (if `Kokkos_ENABLE_SYCL` is ON, otherwise OFF)

Note

To enable Kokkos-FFT on both host and device, set KokkosFFT_ENABLE_FFTW=ON. Multiple device tpls cannot be enabled at the same time. In addition, at least one tpl must be enabled to configure. For example, it is allowed to set KokkosFFT_ENABLE_CUFFT=OFF even if Kokkos_ENABLE_CUDA=ON as long as KokkosFFT_ENABLE_FFTW=ON.

Kokkos backends

Kokkos-FFT requires Kokkos 4.7+. For the moment, we support following backends for CPUs and GPUs. A FFT library dedicated to Kokkos Device backend (e.g. cufft for CUDA backend) is automatically used. If CMake fails to find a backend FFT library, see How to find fft libraries?. We may support experimental backends like OPENACC in the future.

`Host backend`
CMake option	Description	Backend FFT library
`Kokkos_ENABLE_SERIAL`	Serial backend targeting CPUs	`FFTW (Serial)`
`Kokkos_ENABLE_THREADS`	C++ threads backend targeting CPUs	`FFTW (Threads)`
`Kokkos_ENABLE_OPENMP`	OpenMP backend targeting CPUs	`FFTW (OpenMP)`

`Device backend`
CMake option	Description	Backend FFT library
`Kokkos_ENABLE_CUDA`	CUDA backend targeting NVIDIA GPUs	`cufft`
`Kokkos_ENABLE_HIP`	HIP backend targeting AMD GPUs	`hipfft` or `rocfft`
`Kokkos_ENABLE_SYCL`	SYCL backend targeting Intel GPUs	`oneMKL`