dfftb
dfftb - compute a periodic sequence from its Fourier coefficients. The DFFT operations
are unnormalized, so a call of DFFTF followed by a call of DFFTB will multiply the
input sequence by N.
SUBROUTINE DFFTB( N, X, WSAVE)
INTEGER N
DOUBLE PRECISION X(*), WSAVE(*)
SUBROUTINE DFFTB_64( N, X, WSAVE)
INTEGER*8 N
DOUBLE PRECISION X(*), WSAVE(*)
SUBROUTINE FFTB( [N], X, WSAVE)
INTEGER :: N
REAL(8), DIMENSION(:) :: X, WSAVE
SUBROUTINE FFTB_64( [N], X, WSAVE)
INTEGER(8) :: N
REAL(8), DIMENSION(:) :: X, WSAVE
#include <sunperf.h>
void dfftb(int n, double *x, double *wsave);
void dfftb_64(long n, double *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)
-
On entry, WSAVE must be an array of dimension (2 * N + 15) or greater and
must have been initialized by DFFTI.