function [dr,info]=resol(ys,check_flag)
% function [dr,info]=resol(ys,check_flag)
% Computes first and second order approximations
%
% INPUTS
%    ys:             vector of variables in steady state
%    check_flag=0:   all the approximation is computed
%    check_flag=1:   computes only the eigenvalues
%
% OUTPUTS
%    dr:             structure of decision rules for stochastic simulations
%    info=1:         the model doesn't determine the current variables '...' uniquely
%    info=2:         MJDGGES returns the following error code'
%    info=3:         Blanchard Kahn conditions are not satisfied: no stable '...' equilibrium
%    info=4:         Blanchard Kahn conditions are not satisfied:'...' indeterminacy
%    info=5:         Blanchard Kahn conditions are not satisfied:'...' indeterminacy due to rank failure
%    info=6:         The jacobian evaluated at the steady state is complex.
%    info=20:        can't find steady state info(2) contains sum of sqare residuals
%    info=30:        Variance can't be computed
%
% SPECIAL REQUIREMENTS
%    none

% Copyright (C) 2001-2008 Dynare Team
%
% This file is part of Dynare.
%
% Dynare 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.
%
% Dynare 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 Dynare.  If not, see <http://www.gnu.org/licenses/>.

global M_ options_ oo_ bayestopt_
global it_

jacobian_flag = 0; 

options_ = set_default_option(options_,'jacobian_flag',1);
info = 0;

it_ = M_.maximum_lag + 1 ;

if M_.exo_nbr == 0
  oo_.exo_steady_state = [] ;
end

% check if ys is steady state
tempex = oo_.exo_simul;
oo_.exo_simul = repmat(oo_.exo_steady_state',M_.maximum_lag+M_.maximum_lead+1,1);
if M_.exo_det_nbr > 0 
  tempexdet = oo_.exo_det_simul;
  oo_.exo_det_simul = repmat(oo_.exo_det_steady_state',M_.maximum_lag+M_.maximum_lead+1,1);
end
dr.ys = ys;
check1 = 0;
% testing for steadystate file
fh = str2func([M_.fname '_static']);
if options_.steadystate_flag
  [dr.ys,check1] = feval([M_.fname '_steadystate'],dr.ys,...
			 [oo_.exo_steady_state; oo_.exo_det_steady_state]);
else
  % testing if ys isn't a steady state or if we aren't computing Ramsey policy
  if  options_.ramsey_policy == 0
      if options_.linear == 0
          % nonlinear models
          if max(abs(feval(fh,dr.ys,[oo_.exo_steady_state; ...
                    oo_.exo_det_steady_state], M_.params))) > options_.dynatol
              [dr.ys,check1] = dynare_solve(fh,dr.ys,options_.jacobian_flag,...
                                            [oo_.exo_steady_state; ...
		    oo_.exo_det_steady_state], M_.params);
          end
      else
          % linear models
          [fvec,jacob] = feval(fh,dr.ys,[oo_.exo_steady_state;...
		    oo_.exo_det_steady_state], M_.params);
          if max(abs(fvec)) > 1e-12
              dr.ys = dr.ys-jacob\fvec;
          end
    end
  end
end
% testing for problem
if check1
  info(1)= 20;
  if options_.steadystate_flag
      resid = check1 ;
  else
      resid = feval(fh,ys,oo_.exo_steady_state, M_.params);
  end   
  info(2) = resid'*resid ; % penalty...
  return
end

dr.fbias = zeros(M_.endo_nbr,1);
if(options_.model_mode==1)
    [dr,info,M_,options_,oo_] = dr1_sparse(dr,check_flag,M_,options_,oo_);
else
    [dr,info,M_,options_,oo_] = dr1(dr,check_flag,M_,options_,oo_);
end
if info(1)
  return
end

if M_.exo_det_nbr > 0
  oo_.exo_det_simul = tempexdet;
end
oo_.exo_simul = tempex;
tempex = [];

% 01/01/2003 MJ added dr_algo == 1
% 08/24/2001 MJ uses Schmitt-Grohe and Uribe (2001) constant correction
%               in dr.ghs2 
% 05/26/2003 MJ added temporary values for oo_.exo_simul