  SpFFT - A 3D FFT library for sparse frequency domain data written
in C++ with support for MPI, OpenMP, CUDA and ROCm.

  Inspired by the need of some computational material science
applications with spherical cutoff data in frequency domain, SpFFT
provides Fast Fourier Transformations of sparse frequency domain data.
For distributed computations with MPI, slab decomposition in space
domain and pencil decomposition in frequency domain (sparse data
within a pencil / column must be on one rank) is used.


  By default the package is compiled with single-precision float-point
operations and a sequential version. If you want to change it use the
following environment variable options:
 - DP=yes, use double-precision.
 - OMP=yes, use openmp.

  Options that requires extra packages:
 - MPI=yes, use MPI (requires a MPI implementation either mpich or
 openmpi).
 - CUDA=yes, requires CUDA Toolkit
