function [oo_, maxerror] = perfect_foresight_solver_core(M_, options_, oo_)
%function [oo_, maxerror] = simulation_core(M_, options_, oo_)

% Copyright (C) 2015 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/>.

if options_.linear_approximation && ~(isequal(options_.stack_solve_algo,0) || isequal(options_.stack_solve_algo,7))
    error('perfect_foresight_solver: Option linear_approximation is only available with option stack_solve_algo equal to 0.')
end

if options_.linear && isequal(options_.stack_solve_algo,0)
    options_.linear_approximation = 1;
end

if options_.block
    if options_.bytecode
        try
            [info, tmp] = bytecode('dynamic', oo_.endo_simul, oo_.exo_simul, M_.params, repmat(oo_.steady_state,1,options_.periods+2), options_.periods);
        catch
            info = 0;
        end
        if info
            oo_.deterministic_simulation.status = false;
        else
            oo_.endo_simul = tmp;
            oo_.deterministic_simulation.status = true;
        end
        if options_.no_homotopy
            mexErrCheck('bytecode', info);
        end
    else
        oo_ = feval([M_.fname '_dynamic'], options_, M_, oo_);
    end
else
    if options_.bytecode
        try
            [info, tmp] = bytecode('dynamic', oo_.endo_simul, oo_.exo_simul, M_.params, repmat(oo_.steady_state,1,options_.periods+2), options_.periods);
        catch
            info = 0;
        end
        if info
            oo_.deterministic_simulation.status = false;
        else
            oo_.endo_simul = tmp;
            oo_.deterministic_simulation.status = true;
        end
        if options_.no_homotopy
            mexErrCheck('bytecode', info);
        end
    else
        if M_.maximum_endo_lead == 0 % Purely backward model
            oo_ = sim1_purely_backward(options_, M_, oo_);
        elseif M_.maximum_endo_lag == 0 % Purely forward model
            oo_ = sim1_purely_forward(options_, M_, oo_);
        else % General case
            if options_.stack_solve_algo == 0
                if options_.linear_approximation
                    oo_ = sim1_linear(options_, M_, oo_);
                else
                    oo_ = sim1(M_, options_, oo_);
                end
            elseif options_.stack_solve_algo == 6
                oo_ = sim1_lbj(options_, M_, oo_);
            elseif options_.stack_solve_algo == 7
                periods = options_.periods;
                if ~isfield(options_.lmmcp,'lb')
                    [lb,ub,pfm.eq_index] = get_complementarity_conditions(M_,options_.ramsey_policy);
                    options_.lmmcp.lb = repmat(lb,periods,1);
                    options_.lmmcp.ub = repmat(ub,periods,1);
                end
                y = oo_.endo_simul;
                y0 = y(:,1);
                yT = y(:,periods+2);
                z = y(:,2:periods+1);
                illi = M_.lead_lag_incidence';
                [i_cols,junk,i_cols_j] = find(illi(:));
                illi = illi(:,2:3);
                [i_cols_J1,junk,i_cols_1] = find(illi(:));
                i_cols_T = nonzeros(M_.lead_lag_incidence(1:2,:)');
                if options_.linear_approximation
                    y_steady_state = oo_.steady_state;
                    x_steady_state = transpose(oo_.exo_steady_state);
                    ip = find(M_.lead_lag_incidence(1,:)');
                    ic = find(M_.lead_lag_incidence(2,:)');
                    in = find(M_.lead_lag_incidence(3,:)');
                    % Evaluate the Jacobian of the dynamic model at the deterministic steady state.
                    model_dynamic = str2func([M_.fname,'_dynamic']);
                    [d1,jacobian] = model_dynamic(y_steady_state([ip; ic; in]), x_steady_state, M_.params, y_steady_state, 1);
                    % Check that the dynamic model was evaluated at the steady state.
                    if max(abs(d1))>1e-12
                        error('Jacobian is not evaluated at the steady state!')
                    end
                    nyp = nnz(M_.lead_lag_incidence(1,:)) ;
                    ny0 = nnz(M_.lead_lag_incidence(2,:)) ;
                    nyf = nnz(M_.lead_lag_incidence(3,:)) ;
                    nd = nyp+ny0+nyf; % size of y (first argument passed to the dynamic file).
                    jexog = transpose(nd+(1:M_.exo_nbr));
                    jendo = transpose(1:nd);
                    z = bsxfun(@minus,z,y_steady_state);
                    x = bsxfun(@minus,oo_.exo_simul,x_steady_state);
                    [y,info] = dynare_solve(@linear_perfect_foresight_problem,z(:), options_, ...
                                            jacobian, y0-y_steady_state, yT-y_steady_state, ...
                                            x, M_.params, y_steady_state, ...
                                            M_.maximum_lag, options_.periods, M_.endo_nbr, i_cols, ...
                                            i_cols_J1, i_cols_1, i_cols_T, i_cols_j, ...
                                            M_.NNZDerivatives(1),jendo,jexog);
                else
                    [y,info] = dynare_solve(@perfect_foresight_problem,z(:),options_, ...
                                            str2func([M_.fname '_dynamic']),y0,yT, ...
                                            oo_.exo_simul,M_.params,oo_.steady_state, ...
                                            M_.maximum_lag,options_.periods,M_.endo_nbr,i_cols, ...
                                            i_cols_J1, i_cols_1, i_cols_T, i_cols_j, ...
                                            M_.NNZDerivatives(1));
                end
                if all(imag(y)<.1*options_.dynatol.f)
                    if ~isreal(y)
                        y = real(y);
                    end
                else
                    info = 1;
                end
                if options_.linear_approximation
                    oo_.endo_simul = [y0 bsxfun(@plus,reshape(y,M_.endo_nbr,periods),y_steady_state) yT];
                else
                    oo_.endo_simul = [y0 reshape(y,M_.endo_nbr,periods) yT];
                end
                if info == 1
                    oo_.deterministic_simulation.status = false;
                else
                    oo_.deterministic_simulation.status = true;
                end
            end
        end
    end
end

if nargout>1
    y0 = oo_.endo_simul(:,1);
    yT = oo_.endo_simul(:,options_.periods+2);
    yy  = oo_.endo_simul(:,2:options_.periods+1);
    if ~exist('illi')
        illi = M_.lead_lag_incidence';
        [i_cols,junk,i_cols_j] = find(illi(:));
        illi = illi(:,2:3);
        [i_cols_J1,junk,i_cols_1] = find(illi(:));
        i_cols_T = nonzeros(M_.lead_lag_incidence(1:2,:)');
    end
    if options_.block && ~options_.bytecode
        maxerror = oo_.deterministic_simulation.error;
    else
        if options_.bytecode
            [chck, residuals, junk]= bytecode('dynamic','evaluate', oo_.endo_simul, oo_.exo_simul, M_.params, oo_.steady_state, 1);
        else
            residuals = perfect_foresight_problem(yy(:),str2func([M_.fname '_dynamic']), y0, yT, ...
                                                  oo_.exo_simul,M_.params,oo_.steady_state, ...
                                                  M_.maximum_lag,options_.periods,M_.endo_nbr,i_cols, ...
                                                  i_cols_J1, i_cols_1, i_cols_T, i_cols_j, ...
                                                  M_.NNZDerivatives(1));
        end
        maxerror = max(max(abs(residuals)));
    end
end