dfft2i

NAME

dfft2i - initialize the array WSAVE, which is used in both the forward and backward transforms.

SYNOPSIS

  SUBROUTINE DFFT2I( M, N, WORK)
  INTEGER M, N
  DOUBLE PRECISION WORK(*)
 
  SUBROUTINE DFFT2I_64( M, N, WORK)
  INTEGER*8 M, N
  DOUBLE PRECISION WORK(*)

F95 INTERFACE

  SUBROUTINE FFT2I( M, N, WORK)
  INTEGER :: M, N
  REAL(8), DIMENSION(:) :: WORK
 
  SUBROUTINE FFT2I_64( M, N, WORK)
  INTEGER(8) :: M, N
  REAL(8), DIMENSION(:) :: WORK

C INTERFACE

#include <sunperf.h>

void dfft2i(int m, int n, double *work);

void dfft2i_64(long m, long n, double *work);

ARGUMENTS

* M (input): Number of rows to be transformed. M >= 0.
* N (input): Number of columns to be transformed. N >= 0.
* WORK (input/output): On entry, an array of dimension (M + 2*N + MAX(M, 2*N) + 30) or greater. DFFT2I needs to be called only once to initialize array WORK before calling DFFT2F and/or DFFT2B if M, N and WORK 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.