kml_fft(f/h)_mpi_plan_dft_r2c

Create a plan for the n-dimensional R2C transform of a single contiguous data sequence.

Interface Definition

C interface:

kml_fft_plan kml_fft_mpi_plan_dft_r2c(int rank, const int *n, double *in, kml_fft_complex *out, MPI_Comm comm, unsigned flags);

kml_fftf_plan kml_fftf_mpi_plan_dft_r2c(int rank, const int *n, float *in, kml_fftf_complex *out, MPI_Comm comm, unsigned flags);

kml_ffth_plan kml_ffth_mpi_plan_dft_r2c(int rank, const int *n, __fp16 *in, kml_ffth_complex *out, MPI_Comm comm, unsigned flags);

Return Value

The function returns a structure pointer of the kml_fft(f)_plan type. This object can be passed to the kml_fft(f/h)_execute function as a parameter to perform FFT on the current input and output. This object can also be passed to the kml_fft(f/h)_execute_dft_r2c function as a parameter to perform FFT on new input and output.

If this function returns a non-null pointer, the plan has been successfully created. Otherwise, the plan fails to be created.

Parameters

Parameter	Data Type	Description	Input/Output
rank	int	Dimension of FFT. The constraint is 1 ≤ rank ≤ 3.	Input
n	const int*	Indicates an array whose dimension is rank, including the size of each dimension in the FFT sequence. The constraint is n[i] ≥ 1, for i in 0 to rank - 1.	Input
in	Double precision: double* Single precision: float* Half precision: __fp16*	Inputs the data to be transformed.	Input
out	Double precision: kml_fft_complex* Single precision: kml_fftf_complex* Half precision: kml_ffth_complex*	Outputs the data generated using FFT.	Output
comm	MPI_Comm	MPI communicator handle	Input
flags	unsigned int	Planning option, which can be set to: KML_FFT_ESTIMATE: ESTIMATE mode KML_FFT_PATIENT: PATIENT mode KML_FFT_MPI_SCRAMBLED_[IN\|OUT]: The input/output is in scrambled format. This option takes effect only for one-dimensional transform. KML_FFT_MPI_TRANSPOSED_[IN\|OUT]: The input/output is transposed from n₀ × n₁ × n₂ ×... × n_d-1 to n₁ × n₀ × n₂ ×…× n_d-1.	Input

Dependencies

C: "kfft-mpi.h"

Examples

C interface:

    const ptrdiff_t N0 = 4, N1 = 4;
    kml_fft_plan plan;
    ptrdiff_t alloc_local, local_n0, local_0_start;
 
    MPI_Init(&argc, &argv);
    MPI_Comm comm = MPI_COMM_WORLD;
    kml_fft_mpi_init();
    double *in = NULL;
    kml_fft_complex *out = NULL;
    ptrdiff_t rank = 2;
    ptrdiff_t *n = (ptrdiff_t *)kml_fft_malloc(sizeof(ptrdiff_t) * rank);
    
    n[0] = N0;
    n[1] = N1;
 
    /* get local data size and allocate */
    alloc_local = kml_fft_mpi_local_size(rank, n, comm, &local_n0, &local_0_start);
    if (alloc_local == -1) {
        printf("[%s][%d] allocate size fail.\n", __func__, __LINE__);
    }
    in = (double *)kml_fft_malloc(sizeof(double) * alloc_local * 2);
    if (in == NULL) {
        printf("[%s][%d] malloc memory fail.\n", __func__, __LINE__);
    }
    out = (kml_fft_complex *)kml_fft_malloc(sizeof(kml_fft_complex) * alloc_local);
    if (out == NULL) {
        printf("[%s][%d] malloc memory fail.\n", __func__, __LINE__);
    }
 
    /* create plan for in-place forward DFT */
    plan = kml_fft_mpi_plan_dft_r2c(rank, n, in, out, comm, KML_FFT_ESTIMATE);    
            
    /* compute transforms, in-place, as many times as desired */
    kml_fft_execute_dft_r2c(plan, in, out);
 
    kml_fft_destroy_plan(plan);
    kml_fft_mpi_cleanup();
    MPI_Finalize();

Parent topic: R2C Transforms