dfftb(3P) Sun Performance Library dfftb(3P)NAMEdfftb - 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.
SYNOPSIS
SUBROUTINE DFFTB(N, X, WSAVE)
INTEGER N
DOUBLE PRECISION X(*), WSAVE(*)
SUBROUTINE DFFTB_64(N, X, WSAVE)
INTEGER*8 N
DOUBLE PRECISION X(*), WSAVE(*)
F95 INTERFACE
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
C INTERFACE
#include <sunperf.h>
void dfftb(int n, double *x, double *wsave);
void dfftb_64(long n, double *x, double *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/output)
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 (2 * N + 15) or
greater and must have been initialized by DFFTI.
6 Mar 2009 dfftb(3P)
