zffti

NAME

zffti - initialize the array WSAVE, which is used in both ZFFTF and ZFFTB.

SYNOPSIS

  SUBROUTINE ZFFTI( N, WSAVE)
  INTEGER N
  DOUBLE PRECISION WSAVE(*)
 
  SUBROUTINE ZFFTI_64( N, WSAVE)
  INTEGER*8 N
  DOUBLE PRECISION WSAVE(*)

F95 INTERFACE

  SUBROUTINE ZFFTI( N, WSAVE)
  INTEGER :: N
  REAL(8), DIMENSION(:) :: WSAVE
 
  SUBROUTINE ZFFTI_64( N, WSAVE)
  INTEGER(8) :: N
  REAL(8), DIMENSION(:) :: WSAVE

C INTERFACE

#include <sunperf.h>

void zffti(int n, double *wsave);

void zffti_64(long n, double *wsave);

ARGUMENTS

* N (input): Length of the sequence to be transformed. N >= 0.
* WSAVE (input/output): On entry, an array of dimension (4 * N + 15) or greater. ZFFTI needs to be called only once to initialize array WORK before calling ZFFTF and/or ZFFTB 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.