vdfftb(3P) Sun Performance Library vdfftb(3P)NAMEvdfftb - compute a periodic sequence from its Fourier coefficients.
The VDFFT operations are normalized, so a call of VDFFTF followed by a
call of VDFFTB will return the original sequence.
SYNOPSIS
SUBROUTINE VDFFTB(M, N, X, XT, MDIMX, WSAVE)
INTEGER M, N, MDIMX
DOUBLE PRECISION X(MDIMX,*), XT(MDIMX,*), WSAVE(*)
SUBROUTINE VDFFTB_64(M, N, X, XT, MDIMX, WSAVE)
INTEGER*8 M, N, MDIMX
DOUBLE PRECISION X(MDIMX,*), XT(MDIMX,*), WSAVE(*)
F95 INTERFACE
SUBROUTINE FFTB([M], [N], X, XT, [MDIMX], WSAVE)
INTEGER :: M, N, MDIMX
REAL(8), DIMENSION(:) :: WSAVE
REAL(8), DIMENSION(:,:) :: X, XT
SUBROUTINE FFTB_64([M], [N], X, XT, [MDIMX], WSAVE)
INTEGER(8) :: M, N, MDIMX
REAL(8), DIMENSION(:) :: WSAVE
REAL(8), DIMENSION(:,:) :: X, XT
C INTERFACE
#include <sunperf.h>
void vdfftb(int m, int n, double *x, double *xt, int mdimx, double
*wsave);
void vdfftb_64(long m, long n, double *x, double *xt, long mdimx, dou‐
ble *wsave);
ARGUMENTS
M (input) The number of sequences to be transformed. M >= 0.
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. For VDFFTF, a real two-dimensional array X(M,N)
whose rows contain the sequences to be transformed.
XT (workspace)
A real two-dimensional work array with dimensions of (MDIMX x
N).
MDIMX (input)
Leading dimension of the arrays X and XT as specified in a
dimension or type statement. MDIMX >= M.
WSAVE (input)
On entry, an array of dimension (N+15) or greater initialized
by VDFFTI.
6 Mar 2009 vdfftb(3P)
