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function f=comp_idgt(coef,g,a,lt,phasetype,algns)
%-*- texinfo -*-
%@deftypefn {Function} comp_idgt
%@verbatim
%COMP_IDGT Compute IDGT
% Usage: f=comp_idgt(c,g,a,lt,phasetype);
%
% Input parameters:
% c : Array of coefficients.
% g : Window function.
% a : Length of time shift.
% lt : Lattice type
% phasetype : Type of phase
% Output parameters:
% f : Signal.
%
% Value of the algorithm chooser
%
% algns=0 : Choose the fastest algorithm
%
% algns=0 : Always choose multi-win
%
% algns=1 : Always choose shear
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/comp/comp_idgt.html}
%@end deftypefn
% Copyright (C) 2005-2016 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.3.1
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% AUTHOR : Peter L. Soendergaard.
M=size(coef,1);
N=size(coef,2);
W=size(coef,3);
L=N*a;
if lt(2)==1
f = comp_isepdgt(coef,g,L,a,M,phasetype);
else
if (algns==1) || (algns==0 && lt(2)<=2)
% FIXME : Calls non-comp function
if phasetype==1
coef=phaseunlock(coef,a,'lt',lt);
end;
% ----- algorithm starts here, split into sub-lattices ---------------
mwin=comp_nonsepwin2multi(g,a,M,lt,L);
% phase factor correction (backwards), for more information see
% analysis routine
E = exp(2*pi*i*a*kron(0:N/lt(2)-1,ones(1,lt(2))).*...
rem(kron(ones(1,N/lt(2)), 0:lt(2)-1)*lt(1),lt(2))/M);
coef=bsxfun(@times,coef,E);
% simple algorithm: split into sublattices and add the result from each
% sublattice.
f=zeros(L,W,assert_classname(coef,g));
for ii=0:lt(2)-1
% Extract sublattice
sub=coef(:,ii+1:lt(2):end,:);
f=f+comp_idgt(sub,mwin(:,ii+1),lt(2)*a,[0 1],0,0);
end;
else
g=fir2long(g,L);
[s0,s1,br] = shearfind(L,a,M,lt);
f=comp_inonsepdgt_shear(coef,g,a,s0,s1,br);
end;
end;
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