CFFTI/CFFTF/CFFTB

DCL:MATH2:FFTLIB: Fast Fourier Transformation: Explanation of Subroutines

2.3.7 CFFTI/CFFTF/CFFTB

1.

Functions

Performs Fourier transformation on cyclic complex data: CFFTI initializes; CFFTF performs forward Fourier transformation; and CFFTB performs inverse Fourier transformation.

2.

Definitions

Below, it is assumed that .

Forward transformation is defined as follows.

Inverse transformation is defined as follows.

　

3.

Call

CALL CFFTI(N,WSAVE)
CALL CFFTF(N,C,WSAVE)
CALL CFFTB(N,C,WSAVE)

4.

Explanation of Parameters

N (I) Length of data to process.

WSAVE (R) Working array: must have length of at least 4N+15.

C (C) Complex array to process. It is both the input and output parameter. (See above definition.)

5.

Notes

(a): This transformation does not involve normalization. In other words, when CFFTF and CFFTB are called successively, then the value of the original value multiplied by a factor of N is returned.

`N`	`(I)`	Length of data to process.
`WSAVE`	`(R)`	Working array: must have length of at least 4`N`+15.
`C`	`(C)`	Complex array to process. It is both the input and output parameter. (See above definition.)