dfftb (3p)

Name

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.

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);

Description

Oracle Solaris Studio Performance Library                            dfftb(3P)



NAME
       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.


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.




                                  7 Nov 2015                         dfftb(3P)