kml_fft(f)_plan_guru_dft_r2c

Create a plan for the n-dimensional R2C transform of multiple data sequences. The data sequence of a single FFT does not need to be contiguous and can cross steps.

Interface Definition

C interface:

kml_fft_plan kml_fft_plan_guru_dft_r2c(int rank,

const kml_fft_iodim *dims,

int howmany_rank,

const kml_fft_iodim *howmany_dims,

double *in,

kml_fft_complex *out,

unsigned flags);

kml_fftf_plan kml_fftf_plan_guru_dft_r2c(int rank,

const kml_fftf_iodim *dims,

int howmany_rank,

const kml_fftf_iodim *howmany_dims,

float *in,

kml_fftf_complex *out,

unsigned flags);

Fortran interface:

RES = KML_FFT_PLAN_GURU_DFT_R2C(RANK, DIMS, HOWMANY_RANK, HOWMANY_DIMS, IN, OUT, FLAGS);

RES = KML_FFTF_PLAN_GURU_DFT_R2C(RANK, DIMS, HOWMANY_RANK, HOWMANY_DIMS, IN, OUT, FLAGS);

Return Value

The function returns a structure pointer of the kml_fft(f)_plan type. This object is used as a parameter in the kml_fft(f)_execute function to perform FFT on the current input and output. In addition, the object may also be added into the kml_fft(f)_execute_dft_r2c function as a parameter to perform FFT on the new input and output.

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

Parameters

Parameter	Data Type	Description	Input/Output
rank	int	Dimension of a single FFT sequence. Constraint: 1 <= rank <= 3	Input
dims	Double precision: const kml_fft_iodim* Single precision: const kml_fftf_iodim*	dims is a structure array whose size is rank. dims[i] contains the following members: int n: FFT length of the i-th dimension. int is: interval between successive elements of the i-th dimensional FFT input sequence. int os: interval between successive elements of the i-th dimensional FFT output sequence. Constraint: dims[i].n >= 1, for i in 0 to rank - 1	Input
howmany_rank	int	The memory allocation between multiple rank-dimension FFTs is described by the howmany_dims array of the howmany_rank dimension. howmany_rank indicates the number of dimensions required by the memory access mode of the start address of each rank-dimension FFT to be calculated. Constraint: 0 <= howmany_rank <= 3	Input
howmany_dims	Double precision: const kml_fft_iodim* Single precision: const kml_fftf_iodim*	howmany_dims is a structure array whose size is howmany_rank. howmany_dims[i] contains the following members: int n: number of pending FFTs in the i-th dimension of the howmany_rank dimension space. int is: interval between successive FFT input sequences of the i-th dimension. int os: interval between successive FFT output sequences of the i-th dimension.	Input
in	Double precision: double* Single precision: float*	Inputs the data to be transformed.	Input
out	Double precision: kml_fft_complex* Single precision: kml_fftf_complex*	Outputs the data generated using FFT.	Output
flags	unsigned int	A planning option, not in use.	Input

Dependencies

C: "kfft.h"

Fortran: "kfft.f03"

Examples

C interface:

    int rank = 2; 
    kml_fft_iodim *dims; 
    dims = (kml_fft_iodim*)kml_fft_malloc(sizeof(kml_fft_iodim) * rank); 
    dims[0].n = 2; 
    dims[0].is = 3; 
    dims[0].os = 2; 
    dims[1].n = 3; 
    dims[1].is = 1; 
    dims[1].os = 1; 
    int howmany_rank = 1; 
    kml_fft_iodim *howmany_dims; 
    howmany_dims = (kml_fft_iodim*)kml_fft_malloc(sizeof(kml_fft_iodim) * howmany_rank); 
    howmany_dims[0].n = 2; 
    howmany_dims[0].is = 2 * 3; 
    howmany_dims[0].os = 2 * 2; 
    double init[12] = {120, 8, 0, 0, 0, -8, -8, -8, -16, 0, -40, -8}; 
    double *in; 
    in = (double*)kml_fft_malloc(sizeof(double) * 12); 
    for (int i = 0; i < 12; i++) { 
        in[i] = init[i]; 
    } 
    kml_fft_complex *out; 
    out = (kml_fft_complex*)kml_fft_malloc(sizeof(kml_fft_complex) * 8); 
    kml_fft_plan plan; 
    plan = kml_fft_plan_guru_dft_r2c(rank, dims, howmany_rank, howmany_dims, in, out, KML_FFT_ESTIMATE); 
    kml_fft_execute_dft_r2c(plan, in, out); 
 
    kml_fft_destroy_plan(plan); 
    kml_fft_free(howmany_dims); 
    kml_fft_free(dims); 
    kml_fft_free(in); 
    kml_fft_free(out); 
 
    /* 
     * out = {{1.200000e+02, 0.000000e+00}, {1.200000e+02, -1.385641e+01}, 
     *        {1.360000e+02, 0.000000e+00}, {1.120000e+02, 0.000000e+00}, 
     *        {-8.000000e+01, 0.000000e+00}, {2.800000e+01, 2.078461e+01}, 
     *        {1.600000e+01, 0.000000e+00}, {-2.000000e+01, -3.464102e+01}} 
     */

Fortran interface:

    INTEGER(C_INT) :: RANK = 2 
    INTEGER(C_INT) :: HOWMANY_RANK = 1 
    TYPE(KML_FFT_IODIM), POINTER :: DIMS(:), HOWMANY_DIMS(:) 
    REAL(C_DOUBLE), DIMENSION(12) :: INIT 
    TYPE(C_DOUBLE), POINTER :: IN(:) 
    TYPE(KML_FFT_COMPLEX), POINTER :: OUT(:) 
    TYPE(C_PTR) :: PIN, POUT, PDIMS, PHOWMANY_DIMS 
    INTEGER(C_SIZE_T) :: SIZE1, SIZE2, SIZE3, SIZE4 
    SIZE1 = 8 * 12 
    SIZE2 = 16 * 8 
    SIZE3 = 12 * RANK 
    SIZE4 = 12 * HOWMANY_RANK 
    PDIMS = KML_FFT_MALLOC(SIZE3) 
    PHOWMANY_DIMS = KML_FFT_MALLOC(SIZE4) 
    PIN = KML_FFT_MALLOC(SIZE1) 
    POUT = KML_FFT_MALLOC(SIZE2) 
    CALL C_F_POINTER(PIN, IN, SHAPE=[12]) 
    CALL C_F_POINTER(POUT, OUT, SHAPE=[8]) 
    CALL C_F_POINTER(PDIMS, DIMS, SHAPE=[RANK]) 
    CALL C_F_POINTER(PHOWMANY_DIMS, HOWMANY_DIMS, SHAPE=[HOWMANY_RANK]) 
     
    DIMS(0)%N = 2 
    DIMS(0)%IS = 3 
    DIMS(0)%OS = 2 
    DIMS(1)%N = 3 
    DIMS(1)%IS = 1 
    DIMS(1)%OS = 1 
    HOWMANY_DIMS(0)%N = 2 
    HOWMANY_DIMS(0)%IS = 2 * 3 
    HOWMANY_DIMS(0)%OS = 2 * 3 
    DATA INIT/120, 8, 0, 0, 0, -8, -8, -8, -16, 0, -40, -8/ 
    INTEGER :: I 
    DO WHILE(I <= 12) 
        IN(I) = INIT(I) 
    END DO 
    TYPE(C_PTR) :: PLAN 
    PLAN = KML_FFT_PLAN_GURU_DFT_R2C(RANK, DIMS, HOWMANY_RANK, HOWMANY_DIMS, IN, OUT, KML_FFT_ESTIMATE) 
    CALL KML_FFT_EXECUTE_DFT_R2C(PLAN, IN, OUT) 
 
    CALL KML_FFT_DESTROY_PLAN(PLAN) 
    CALL KML_FFT_FREE(PHOWMANY_DIMS) 
    CALL KML_FFT_FREE(PDIMS) 
    CALL KML_FFT_FREE(PIN) 
    CALL KML_FFT_FREE(POUT) 
    ! 
    ! OUT = /1.200000E+02, 0.000000E+00, 1.200000E+02, -1.385641E+01, 
    !        1.360000E+02, 0.000000E+00, 1.120000E+02, 0.000000E+00, 
    !        -8.000000E+01, 0.000000E+00, 2.800000E+01, 2.078461E+01, 
    !        1.600000E+01, 0.000000E+00, -2.000000E+01, -3.464102E+01/ 
    !

Parent topic: R2C Transforms