cfftf

NAME

cfftf - compute the Fourier coefficients of a periodic sequence. The FFT operations are unnormalized, so a call of CFFTF followed by a call of CFFTB will multiply the input sequence by N.

SYNOPSIS

  SUBROUTINE CFFTF( N, X, WSAVE)
  COMPLEX X(*)
  INTEGER N
  REAL WSAVE(*)
 
  SUBROUTINE CFFTF_64( N, X, WSAVE)
  COMPLEX X(*)
  INTEGER*8 N
  REAL WSAVE(*)

F95 INTERFACE

  SUBROUTINE FFTF( [N], X, WSAVE)
  COMPLEX, DIMENSION(:) :: X
  INTEGER :: N
  REAL, DIMENSION(:) :: WSAVE
 
  SUBROUTINE FFTF_64( [N], X, WSAVE)
  COMPLEX, DIMENSION(:) :: X
  INTEGER(8) :: N
  REAL, DIMENSION(:) :: WSAVE

C INTERFACE

#include <sunperf.h>

void cfftf(int n, complex *x, float *wsave);

void cfftf_64(long n, complex *x, float *wsave);

ARGUMENTS

* N (input): Length of the sequence to be transformed. These subroutines are most efficient when N is a product of small primes. N >= 0.
* X (input): On entry, an array of length N containing the sequence to be transformed.
* WSAVE (input): On entry, WSAVE must be an array of dimension (4 * N + 15) or greater and must have been initialized by CFFTI.