Contents
zfftb - compute a periodic sequence from its Fourier coeffi-
cients. The FFT operations are unnormalized, so a call of
ZFFTF followed by a call of ZFFTB will multiply the input
sequence by N.
SUBROUTINE ZFFTB(N, X, WSAVE)
DOUBLE COMPLEX X(*)
INTEGER N
DOUBLE PRECISION WSAVE(*)
SUBROUTINE ZFFTB_64(N, X, WSAVE)
DOUBLE COMPLEX X(*)
INTEGER*8 N
DOUBLE PRECISION WSAVE(*)
F95 INTERFACE
SUBROUTINE FFTB([N], X, WSAVE)
COMPLEX(8), DIMENSION(:) :: X
INTEGER :: N
REAL(8), DIMENSION(:) :: WSAVE
SUBROUTINE FFTB_64([N], X, WSAVE)
COMPLEX(8), DIMENSION(:) :: X
INTEGER(8) :: N
REAL(8), DIMENSION(:) :: WSAVE
C INTERFACE
#include <sunperf.h>
void zfftb(int n, doublecomplex *x, double *wsave);
void zfftb_64(long n, doublecomplex *x, double *wsave);
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/output)
On entry, WSAVE must be an array of dimension (4 *
N + 15) or greater and must have been initialized
by ZFFTI.