vdffti

NAME

vdffti - initialize the array WSAVE, which is used in both VRFFTF and VRFFTB.

SYNOPSIS

  SUBROUTINE VDFFTI( N, WSAVE)
  INTEGER N
  DOUBLE PRECISION WSAVE(*)
 
  SUBROUTINE VDFFTI_64( N, WSAVE)
  INTEGER*8 N
  DOUBLE PRECISION WSAVE(*)

F95 INTERFACE

  SUBROUTINE VFFTI( N, WSAVE)
  INTEGER :: N
  REAL(8), DIMENSION(:) :: WSAVE
 
  SUBROUTINE VFFTI_64( N, WSAVE)
  INTEGER(8) :: N
  REAL(8), DIMENSION(:) :: WSAVE

C INTERFACE

#include <sunperf.h>

void vdffti(int n, double *wsave);

void vdffti_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 (N + 15) or greater. VRFFTI needs to be called only once to initialize WSAVE before calling VRFFTF and/or VRFFTB 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.