dffti

NAME

dffti - initialize the array WSAVE, which is used in both DFFTF and DFFTB.

SYNOPSIS

  SUBROUTINE DFFTI( N, WSAVE)
  INTEGER N
  DOUBLE PRECISION WSAVE(*)
 
  SUBROUTINE DFFTI_64( N, WSAVE)
  INTEGER*8 N
  DOUBLE PRECISION WSAVE(*)

F95 INTERFACE

  SUBROUTINE FFTI( N, WSAVE)
  INTEGER :: N
  REAL(8), DIMENSION(:) :: WSAVE
 
  SUBROUTINE FFTI_64( N, WSAVE)
  INTEGER(8) :: N
  REAL(8), DIMENSION(:) :: WSAVE

C INTERFACE

#include <sunperf.h>

void dffti(int n, double *wsave);

void dffti_64(long n, double *wsave);

ARGUMENTS

* N (input): Length of the sequence to be transformed. N >= 0.
* WSAVE (input): On entry, an array of dimension (2 * N + 15) or greater. DFFTI needs to be called only once to initialize array WORK before calling DFFTF and/or DFFTB if N and WSAVE remain unchanged between these calls. Thus, subsequent transforms or inverse transforms of same size can be obtained faster than the first since they do not require initialization of the workspace.