Name

sfft_init_grp, dfft_init_grp, cfft_init_grp, zfft_init_grp − Initialization step for group fast fourier transform in one dimension

FORMAT

status = {S,D,C,Z}FFT_INIT_GRP (n, fft_struct, grp_stride_1_flag, max_grp_size)

Arguments

ninteger∗4
Specifies the number of elements in the column within each one-dimensional data array; n > 0. For SFFT_INIT_GRP and DFFT_INIT_GRP, n must be even. 

fft_structrecord /dxml$s_grp_fft_structure/ for single-precision real operations
record /dxml$d_grp_fft_structure/ for double-precision real operations
record /dxml$c_grp_fft_structure/ for single-precision complex operations
record /dxml$z_grp_fft_structure/ for double-precision complex operations
You must include this argument but it needs no additional definitions. The argument is declared in the program before this routine. See <REFERENCE>(fft_struct_sec) for more information.

grp_stride_1_flaglogical
Specifies whether to allow a distance greater than 1 between elements.

TRUE: Group stride must be 1. 

FALSE: Group stride is at least 1. 

max_grp_sizeinteger∗4
Specifies the expected number of sets of data. If unknown, set max_grp_size = 0. 

Description

The _FFT_INIT_GRP functions build internal data structures needed to compute fast Fourier transforms of one-dimensional data.  These routines are the first step in a three-step procedure.  They create the internal data structures, using attributes defined in the file DXMLDEF.FOR. 

Return Values

0DXML$_SUCCESS()

4 (real transforms only)
DXML$_ILL_N_IS_ODD()

8DXML$_ILL_N_RANGE()

12DXML$_INS_RES()