Name

sfft_init, dfft_init, cfft_init, zfft_init − Initialization step for fast fourier transform in one dimension

FORMAT

status = {S,D,C,Z}FFT_INIT (n, fft_struct, stride_1_flag)

Arguments

ninteger∗4
Specifies the number of values to be transformed, that is, the length of the array to be transformed; n > 0. For real operations, n must be even. 

fft_structrecord /dxml$s_fft_structure/ for single-precision real operations
record /dxml$d_fft_structure/ for double-precision real operations
record /dxml$c_fft_structure/ for single-precision complex operations
record /dxml$z_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.

stride_1_flaglogical
Specifies the allowed distance between consecutive elements in the input and output arrays:

TRUE: Stride must be 1. 

FALSE: Stride is at least 1. 

Description

The _FFT_INIT 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. 

Use the initialization routine that is appropriate for the data format. Then use the corresponding application and exit routines to complete the transform.  For example, use SFFT_INIT for the internal data structures used by SFFT_APPLY and end with the SFFT_EXIT routine. 

Return Values

0DXML$_SUCCESS()

4(real transforms only)
DXML$_ILL_N_IS_ODD()

8DXML$_ILL_N_RANGE()

12DXML$_INS_RES()