Function fft_inplace

src/backend/oneapi/fft.cpp:171–205

template<typename T>
void fft_inplace(Array<T> &in, const int rank, const bool direction) {
    const dim4 idims    = in.dims();
    const dim4 istrides = in.strides();

    constexpr bool is_single = std::is_same_v<T, cfloat>;
    constexpr auto precision = (is_single)
                                   ? ::oneapi::mkl::dft::precision::SINGLE
                                   : ::oneapi::mkl::dft::precision::DOUBLE;
    using desc_ty =
        ::oneapi::mkl::dft::descriptor<precision,
                                       ::oneapi::mkl::dft::domain::COMPLEX>;

    // TODO[STF]: WTF
    // getOffset() for s0 throwing Invalid Descriptor when targeting gpu
    // on CPU, results are wrong but does not throw
    // strides not working? TODO: test standalone oneMKL
    // perhaps in.getDataDims() needed instead of in.dims()?
    std::vector<std::int64_t> fft_input_strides =
        computeStrides(rank, istrides, 0);
    // computeStrides(rank, istrides, in.getOffset()); //TODO[STF]: WTF,
    int batch = 1;
    for (int i = rank; i < 4; i++) { batch *= idims[i]; }

    const bool isInPlace = true;
    PlanType descP = findPlan<precision, ::oneapi::mkl::dft::domain::COMPLEX>(
        rank, isInPlace, idims.get(), fft_input_strides.data(), istrides[rank],
        fft_input_strides.data(), istrides[rank], batch);

    desc_ty *desc = (desc_ty *)descP.get();

    if (direction)
        ::oneapi::mkl::dft::compute_forward(*desc, *in.get());
    else
        ::oneapi::mkl::dft::compute_backward(*desc, *in.get());
}

template<typename Tc, typename Tr>
Array<Tc> fft_r2c(const Array<Tr> &in, const int rank) {