kml_fft(f)_plan_many_dft_r2c

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_many_dft_r2c(int rank, const int *n, int howmany, double *in, const int *inembed, int istride, int idist, kml_fft_complex *out, const int *onembed, int ostride, int odist, unsigned flags);

kml_fftf_plan kml_fftf_plan_many_dft_r2c(int rank, const int *n, int howmany, float *in, const int *inembed, int istride, int idist, kml_fftf_complex *out, const int *onembed, int ostride, int odist, unsigned flags);

Fortran interface:

RES = KML_FFT_PLAN_MANY_DFT_R2C(RANK, N, HOWMANY, IN, INEMBED, ISTRIDE, IDIST, OUT, ONEMBED, OSTRIDE, ODIST, FLAGS);

RES = KML_FFTF_PLAN_MANY_DFT_R2C(RANK, N, HOWMANY, IN, INEMBED, ISTRIDE, IDIST, OUT, ONEMBED, OSTRIDE, ODIST, 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 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
howmany	int	howmany indicates how many multi-dimensional FFTs are needed.	Input
in	Double precision: double* Single precision: float*	Inputs the data to be transformed.	Input
inembed	const int*	inembed is an array whose size is rank or NULL. This array indicates the size of each dimension of a larger space for input FFT data storage. Constraint: inembed[i] ≥ n[i] for i in 0, rank-1. Or if inembed == NULL, inembed is equal to n.	Input
istride	int	Interval between successive elements of the i-th dimensional FFT input sequence.	Input
idist	int	idist indicates the interval between FFT input sequences.	Input
out	Double precision: kml_fft_complex* Single precision: kml_fftf_complex*	Outputs the data generated using FFT.	Output
onembed	const int*	onembed is an array whose size is rank or NULL. This array indicates the size of each dimension of a larger space for output FFT data storage. Constraint: onembed[i] ≥ n[i] for i in 0, rank-1. Or if onembed == NULL, onembed is equal to n.	Input
ostride	int	Interval between successive elements of the i-th dimensional FFT output sequence.	Input
odist	int	odist indicates the interval between FFT output sequences.	Input
flags	unsigned int	A planning option, not in use.	Input

Dependencies

C: "kfft.h"

Fortran: "kfft.f03"

Examples

C interface:

    int rank = 1; 
    int *n; 
    n = (int*)kml_fft_malloc(sizeof(int) * rank); 
    n[0] = 4; 
    int howmany = 3; 
    int istride = 1; 
    int ostride = 1; 
    int idist = 4; 
    int odist = n[0] / 2 + 1; 
    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) * (n[0] / 2 + 1) * howmany); 
    kml_fft_plan plan; 
    plan = kml_fft_plan_many_dft_r2c(rank, n, howmany, in, NULL, istride, idist, out, NULL, ostride, odist, KML_FFT_ESTIMATE); 
    kml_fft_execute_dft_r2c(plan, in, out); 
 
    kml_fft_destroy_plan(plan); 
    kml_fft_free(n); 
    kml_fft_free(in); 
    kml_fft_free(out); 
 
    /* 
     * out = {{1.280000e+02, 0.000000e+00}, {1.200000e+02, -8.000000e+00}, 
     *        {1.120000e+02, 0.000000e+00}, {-2.400000e+01, 0.000000e+00}, 
     *        {8.000000e+00, -0.000000e+00}, {8.000000e+00, 0.000000e+00}, 
     *        {-6.400000e+01, 0.000000e+00}, {2.400000e+01, -8.000000e+00}, 
     *        {-4.800000e+01, 0.000000e+00}} 
     */

Fortran interface:

    INTEGER(C_INT) :: RANK = 1 
    INTEGER(C_INT) :: N(1) 
    REAL(C_DOUBLE), DIMENSION(12) :: INIT 
    TYPE(C_DOUBLE), POINTER :: IN(:) 
    TYPE(KML_FFT_COMPLEX), POINTER :: OUT(:) 
    INTEGER, POINTER :: INEMBED(:), ONEMBED(:) 
    TYPE(C_PTR) :: PIN, POUT 
    INTEGER(C_INT) :: HOWMANY = 3 
    INTEGER(C_INT) :: ISTRIDE = 1 
    INTEGER(C_INT) :: OSTRIDE = 1 
    INTEGER(C_INT) :: IDIST = 4 
    INTEGER(C_INT) :: ODIST = 3 
    INTEGER(C_SIZE_T) :: RSIZE, CSIZE 
    RSIZE = 8 * 12 
    CSIZE = 16 * 9 
    PIN = KML_FFT_MALLOC(RSIZE) 
    POUT = KML_FFT_MALLOC(CSIZE) 
    CALL C_F_POINTER(PIN, IN, SHAPE=[12]) 
    CALL C_F_POINTER(POUT, OUT, SHAPE=[9]) 
    CALL C_F_POINTER(C_NULL_PTR, INEMBED, SHAPE=[0]) 
    CALL C_F_POINTER(C_NULL_PTR, ONEMBED, SHAPE=[0]) 
    N(1) = 4 
    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_MANY_DFT_R2C(RANK, N, HOWMANY, IN, INEMBED, ISTRIDE, IDIST, OUT, ONEMBED, OSTRIDE, ODIST, KML_FFT_ESTIMATE); 
    CALL KML_FFT_EXECUTE_DFT_R2C(PLAN, IN, OUT); 
 
    CALL KML_FFT_DESTROY_PLAN(PLAN) 
    CALL KML_FFT_FREE(PIN) 
    CALL KML_FFT_FREE(POUT) 
    ! 
    ! OUT = /1.280000E+02, 0.000000E+00, 1.200000E+02, -8.000000E+00, 
    !        1.120000E+02, 0.000000E+00, -2.400000E+01, 0.000000E+00, 
    !        8.000000E+00, -0.000000E+00, 8.000000E+00, 0.000000E+00, 
    !        -6.400000E+01, 0.000000E+00, 2.400000E+01, -8.000000E+00, 
    !        -4.800000E+01, 0.000000E+00/ 
    !

Parent topic: R2C Transforms