zfftb
zfftb - compute a periodic sequence from its Fourier coefficients. 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(*)
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
#include <sunperf.h>
void zfftb(int n, doublecomplex *x, double *wsave);
void zfftb_64(long n, doublecomplex *x, double *wsave);
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* N (input)
-
Length of the sequence to be transformed. These subroutines are most efficient when N is a product of small primes. N >= 0.
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* X (input)
-
On entry, an array of length N containing the sequence to be transformed.
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* WSAVE (input/output)
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On entry, WSAVE must be an array of dimension (4 * N + 15) or greater and
must have been initialized by ZFFTI.