[n,c,wsave]=cfftb(n,c,wsave);

function [n,c,wsave]=cfftb(n,c,wsave);
persistent iw1 iw2 ; 

if isempty(iw1), iw1=0; end;
if isempty(iw2), iw2=0; end;
%***BEGIN PROLOGUE  CFFTB
%***SUBSIDIARY
%***PURPOSE  Compute the unnormalized inverse of CFFTF.
%***LIBRARY   SLATEC (FFTPACK)
%***CATEGORY  J1A2
%***TYPE      COMPLEX (RFFTB-S, CFFTB-C)
%***KEYWORDS  FFTPACK, FOURIER TRANSFORM
%***AUTHOR  Swarztrauber, P. N., (NCAR)
%***DESCRIPTION
%
%  ********************************************************************
%  *   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   NOTICE   *
%  ********************************************************************
%  *                                                                  *
%  *   This routine uses non-standard Fortran 77 constructs and will  *
%  *   be removed from the library at a future date.  You are         *
%  *   requested to use CFFTB1.                                       *
%  *                                                                  *
%  ********************************************************************
%
%  subroutine CFFTB computes the backward complex discrete Fourier
%  transform (the Fourier synthesis).  Equivalently, CFFTB computes
%  a complex periodic sequence from its Fourier coefficients.
%  The transform is defined below at output parameter C.
%
%  A call of CFFTF followed by a call of CFFTB will multiply the
%  sequence by N.
%
%  The array WSAVE which is used by subroutine CFFTB must be
%  initialized by calling subroutine CFFTI(N,WSAVE).
%
%  Input Parameters
%
%  N       the length of the complex sequence C.  The method is
%          more efficient when N is the product of small primes.
%
%  C       a complex array of length N which contains the sequence
%
%  WSAVE   a real work array which must be dimensioned at least 4*N+15
%          in the program that calls CFFTB.  The WSAVE array must be
%          initialized by calling subroutine CFFTI(N,WSAVE), and a
%          different WSAVE array must be used for each different
%          value of N.  This initialization does not have to be
%          repeated so long as N remains unchanged.  Thus subsequent
%          transforms can be obtained faster than the first.
%          The same WSAVE array can be used by CFFTF and CFFTB.
%
%  Output Parameters
%
%  C       For J=1,...,N
%
%              C(J)=the sum from K=1,...,N of
%
%                 C(K)*EXP(I*(J-1)*(K-1)*2*PI/N)
%
%                         where I=SQRT(-1)
%
%  WSAVE   contains initialization calculations which must not be
%          destroyed between calls of subroutine CFFTF or CFFTB
%
%***REFERENCES  P. N. Swarztrauber, Vectorizing the FFTs, in Parallel
%                 Computations (G. Rodrigue, ed.), Academic Press,
%                 1982, pp. 51-83.
%***ROUTINES CALLED  CFFTB1
%***REVISION HISTORY  (YYMMDD)
%   790601  DATE WRITTEN
%   830401  Modified to use SLATEC library source file format.
%   860115  Modified by Ron Boisvert to adhere to Fortran 77 by
%           changing dummy array size declarations (1) to (*).
%   861211  REVISION DATE from Version 3.2
%   881128  Modified by Dick Valent to meet prologue standards.
%   891214  Prologue converted to Version 4.0 format.  (BAB)
%   900131  Routine changed from user-callable to subsidiary
%           because of non-standard Fortran 77 arguments in the
%           call to CFFTB1.  (WRB)
%   920501  Reformatted the REFERENCES section.  (WRB)
%***end PROLOGUE  CFFTB
c_shape=size(c);c=reshape(c,1,[]);
wsave_shape=size(wsave);wsave=reshape(wsave,1,[]);
%***FIRST EXECUTABLE STATEMENT  CFFTB
if( n==1 )
c_shape=zeros(c_shape);c_shape(:)=c(1:numel(c_shape));c=c_shape;
wsave_shape=zeros(wsave_shape);wsave_shape(:)=wsave(1:numel(wsave_shape));wsave=wsave_shape;
return;
end;
iw1 = fix(n + n + 1);
iw2 = fix(iw1 + n + n);
[n,c,wsave,dumvar4,dumvar5]=cfftb1(n,c,wsave,wsave(sub2ind(size(wsave),max(iw1,1)):end),wsave(sub2ind(size(wsave),max(iw2,1)):end));   dumvar4i=find((wsave(sub2ind(size(wsave),max(iw1,1)):end))~=(dumvar4));dumvar5i=find((wsave(sub2ind(size(wsave),max(iw2,1)):end))~=(dumvar5));   wsave(iw1-1+dumvar4i)=dumvar4(dumvar4i); wsave(iw2-1+dumvar5i)=dumvar5(dumvar5i); 
c_shape=zeros(c_shape);c_shape(:)=c(1:numel(c_shape));c=c_shape;
wsave_shape=zeros(wsave_shape);wsave_shape(:)=wsave(1:numel(wsave_shape));wsave=wsave_shape;
end
%DECK CFFTF1