function [ys,params,info] = evaluate_steady_state(ys_init,M,options,oo,steadystate_check_flag)
% function [ys,params,info] = evaluate_steady_state(ys_init,M,options,oo,steadystate_check_flag)
% Computes the steady state
%
% INPUTS
%   ys_init                   vector           initial values used to compute the steady
%                                                 state
%   M                         struct           model structure
%   options                   struct           options
%   oo                        struct           output results
%   steadystate_check_flag    boolean          if true, check that the
%                                              steadystate verifies the
%                                              static model
%
% OUTPUTS
%   ys                        vector           steady state (in declaration order)
%   params                    vector           model parameters possibly
%                                              modified by user steadystate
%                                              function
%   info                      2x1 vector       error codes
%
% SPECIAL REQUIREMENTS
%   none

% Copyright (C) 2001-2020 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/>.

info = 0;
check = 0;

steadystate_flag = options.steadystate_flag;
params = M.params;
exo_ss = [oo.exo_steady_state; oo.exo_det_steady_state];

if length(M.aux_vars) > 0 && ~steadystate_flag && M.set_auxiliary_variables
    h_set_auxiliary_variables = str2func([M.fname '.set_auxiliary_variables']);
    ys_init = h_set_auxiliary_variables(ys_init,exo_ss,params);
end

if options.ramsey_policy
    if steadystate_flag
        % explicit steady state file
        [ys,params,info] = evaluate_steady_state_file(ys_init,exo_ss,M, ...
                                                      options,steadystate_check_flag);
        %test whether it solves model conditional on the instruments
        resids = evaluate_static_model(ys,exo_ss,params,M,options);
        n_multipliers=M.ramsey_eq_nbr;
        nan_indices=find(isnan(resids(n_multipliers+1:end)));

        if ~isempty(nan_indices)
            if options.debug
                fprintf('\nevaluate_steady_state: The steady state file computation for the Ramsey problem resulted in NaNs.\n')
                fprintf('evaluate_steady_state: The steady state was computed conditional on the following initial instrument values: \n')
                for ii = 1:size(options.instruments,1)
                    fprintf('\t %s \t %f \n',options.instruments{ii},ys_init(strmatch(options.instruments{ii},M.endo_names,'exact')))
                end
                fprintf('evaluate_steady_state: The problem occured in the following equations: \n')
                fprintf('\t Equation(s): ')
                for ii=1:length(nan_indices)
                    fprintf('%d, ',nan_indices(ii));
                end
                skipline()
                fprintf('evaluate_steady_state: If those initial values are not admissable, change them using an initval-block.\n')
                skipline(2)
            end
            info(1) = 84;
            info(2) = resids'*resids;
            return
        end

        if any(imag(ys(n_multipliers+1:end)))
            if options.debug
                fprintf('\nevaluate_steady_state: The steady state file computation for the Ramsey problem resulted in complex numbers.\n')
                fprintf('evaluate_steady_state: The steady state was computed conditional on the following initial instrument values: \n')
                for ii = 1:size(options.instruments,1)
                    fprintf('\t %s \t %f \n',options.instruments{ii},ys_init(strmatch(options.instruments{ii},M.endo_names,'exact')))
                end
                fprintf('evaluate_steady_state: If those initial values are not admissable, change them using an initval-block.\n')
                skipline(2)
            end
            info(1) = 86;
            info(2) = resids'*resids;
            return
        end

        if max(abs(resids(n_multipliers+1:end))) > options.solve_tolf %does it solve for all variables except for the Lagrange multipliers
            if options.debug
                fprintf('\nevaluate_steady_state: The steady state file does not solve the steady state for the Ramsey problem.\n')
                fprintf('evaluate_steady_state: Conditional on the following instrument values: \n')
                for ii = 1:size(options.instruments,1)
                    fprintf('\t %s \t %f \n',options.instruments{ii},ys_init(strmatch(options.instruments{ii},M.endo_names,'exact')))
                end
                fprintf('evaluate_steady_state: the following equations have non-zero residuals: \n')
                for ii=n_multipliers+1:M.endo_nbr
                    if abs(resids(ii)) > options.solve_tolf
                        fprintf('\t Equation number %d: %f\n',ii-n_multipliers, resids(ii))
                    end
                end
                skipline(2)
            end
            info(1) = 85;
            info(2) = resids'*resids;
            return
        end
    end
    if options.debug
        infrow=find(isinf(ys_init));
        if ~isempty(infrow)
            fprintf('\nevaluate_steady_state: The initial values for the steady state of the following variables are Inf:\n');
            for iter=1:length(infrow)
                fprintf('%s\n',M.endo_names{infrow(iter)});
            end
        end
        nanrow=find(isnan(ys_init));
        if ~isempty(nanrow)
            fprintf('\nevaluate_steady_state: The initial values for the steady state of the following variables are NaN:\n');
            for iter=1:length(nanrow)
                fprintf('%s\n',M.endo_names{nanrow(iter)});
            end
        end
    end
    %either if no steady state file or steady state file without problems
    [ys,params,info] = dyn_ramsey_static(ys_init,M,options,oo);
    if info
        return
    end
    %check whether steady state really solves the model
    resids = evaluate_static_model(ys,exo_ss,params,M,options);

    n_multipliers=M.ramsey_eq_nbr;
    nan_indices_multiplier=find(isnan(resids(1:n_multipliers)));
    nan_indices=find(isnan(resids(n_multipliers+1:end)));

    if ~isempty(nan_indices)
        if options.debug
            fprintf('\nevaluate_steady_state: The steady state computation for the Ramsey problem resulted in NaNs.\n')
            fprintf('evaluate_steady_state: The steady state computation resulted in the following instrument values: \n')
            for i = 1:size(options.instruments,1)
                fprintf('\t %s \t %f \n',options.instruments{i},ys(strmatch(options.instruments{i},M.endo_names,'exact')))
            end
            fprintf('evaluate_steady_state: The problem occured in the following equations: \n')
            fprintf('\t Equation(s): ')
            for ii=1:length(nan_indices)
                fprintf('%d, ',nan_indices(ii));
            end
            skipline()
        end
        info(1) = 82;
        return
    end

    if ~isempty(nan_indices_multiplier)
        if options.debug
            fprintf('\nevaluate_steady_state: The steady state computation for the Ramsey problem resulted in NaNs in the auxiliary equations.\n')
            fprintf('evaluate_steady_state: The steady state computation resulted in the following instrument values: \n')
            for i = 1:size(options.instruments,1)
                fprintf('\t %s \t %f \n',options.instruments{i},ys(strmatch(options.instruments{i},M.endo_names,'exact')))
            end
            fprintf('evaluate_steady_state: The problem occured in the following equations: \n')
            fprintf('\t Auxiliary equation(s): ')
            for ii=1:length(nan_indices_multiplier)
                fprintf('%d, ',nan_indices_multiplier(ii));
            end
            skipline()
        end
        info(1) = 83;
        return
    end

    if max(abs(resids)) > options.solve_tolf %does it solve for all variables including the auxiliary ones
        if options.debug
            fprintf('\nevaluate_steady_state: The steady state for the Ramsey problem could not be computed.\n')
            fprintf('evaluate_steady_state: The steady state computation stopped with the following instrument values:: \n')
            for i = 1:size(options.instruments,1)
                fprintf('\t %s \t %f \n',options.instruments{i},ys(strmatch(options.instruments{i},M.endo_names,'exact')))
            end
            fprintf('evaluate_steady_state: The following equations have non-zero residuals: \n')
            for ii=1:n_multipliers
                if abs(resids(ii)) > options.solve_tolf/100
                    fprintf('\t Auxiliary Ramsey equation number %d: %f\n',ii, resids(ii))
                end
            end
            for ii=n_multipliers+1:M.endo_nbr
                if abs(resids(ii)) > options.solve_tolf/100
                    fprintf('\t Equation number %d: %f\n',ii-n_multipliers, resids(ii))
                end
            end
            skipline(2)
        end
        info(1) = 81;
        info(2) = resids'*resids;
        return
    end
elseif steadystate_flag
    % explicit steady state file
    [ys,params,info] = evaluate_steady_state_file(ys_init,exo_ss,M, options,steadystate_check_flag);
    if size(ys,2)>size(ys,1)
        error('STEADY: steady_state-file must return a column vector, not a row vector.')
    end
    if info(1)
        return
    end
elseif ~options.bytecode && ~options.block
    if ~options.linear
        % non linear model
        static_model = str2func([M.fname '.static']);
        [ys,check] = dynare_solve(@static_problem,...
                                  ys_init,...
                                  options, exo_ss, params,...
                                  M.endo_nbr,...
                                  static_model);
        if check && options.debug
            [ys,check,fvec,fjac] = dynare_solve(@static_problem,...
                                                ys_init,...
                                                options, exo_ss, params,...
                                                M.endo_nbr,...
                                                static_model);
            [infrow,infcol]=find(isinf(fjac) | isnan(fjac));
            if ~isempty(infrow)
                fprintf('\nSTEADY:  The Jacobian at the initial values contains Inf or NaN. The problem arises from: \n')
                display_problematic_vars_Jacobian(infrow,infcol,M,ys_init,'static','STEADY: ')
            end
            problematic_equation = find(~isfinite(fvec));
            if ~isempty(problematic_equation)
                fprintf('\nSTEADY:  numerical initial values or parameters incompatible with the following equations\n')
                disp(problematic_equation')
                fprintf('Please check for example\n')
                fprintf('   i) if all parameters occurring in these equations are defined\n')
                fprintf('  ii) that no division by an endogenous variable initialized to 0 occurs\n')
            end
        end
    else
        % linear model
        fh_static = str2func([M.fname '.static']);
        [fvec,jacob] = fh_static(ys_init,exo_ss, ...
                                 params);

        ii = find(~isfinite(fvec));
        if ~isempty(ii)
            ys=fvec;
            check=1;
            disp(['STEADY:  numerical initial values or parameters incompatible with the following' ...
                  ' equations'])
            disp(ii')
            disp('Check whether your model is truly linear. Put "resid(1);" before "steady;" to see the problematic equations.')
        elseif isempty(ii) && max(abs(fvec)) > 1e-12
            ys = ys_init-jacob\fvec;
            resid = evaluate_static_model(ys,exo_ss,params,M,options);
            if max(abs(resid)) > 1e-6
                check=1;
                fprintf('STEADY: No steady state for your model could be found\n')
                fprintf('STEADY: Check whether your model is truly linear. Put "resid(1);" before "steady;" to see the problematic equations.\n')
            end
        else
            ys = ys_init;
        end
        if options.debug
            if any(any(isinf(jacob) | isnan(jacob)))
                [infrow,infcol]=find(isinf(jacob) | isnan(jacob));
                fprintf('\nSTEADY:  The Jacobian contains Inf or NaN. The problem arises from: \n\n')
                for ii=1:length(infrow)
                    fprintf('STEADY:  Derivative of Equation %d with respect to Variable %s  (initial value of %s: %g) \n',infrow(ii),deblank(M.endo_names(infcol(ii),:)),deblank(M.endo_names(infcol(ii),:)),ys_init(infcol(ii)))
                end
                fprintf('Check whether your model is truly linear. Put "resid(1);" before "steady;" to see the problematic equations.\n')
            end
        end
    end
else
    % block or bytecode
    [ys,check] = dynare_solve_block_or_bytecode(ys_init,exo_ss, params, options, M);
end

if check
    info(1)= 20;
    %make sure ys contains auxiliary variables in case of problem with dynare_solve
    if length(M.aux_vars) > 0 && ~steadystate_flag
        if M.set_auxiliary_variables
            ys = h_set_auxiliary_variables(ys,exo_ss,params);
        end
    end
    resid = evaluate_static_model(ys,exo_ss,params,M,options);
    info(2) = resid'*resid ;
    if isnan(info(2))
        info(1)=22;
    end
    return
end

% If some equations are tagged [static] or [dynamic], verify consistency
if M.static_and_dynamic_models_differ
    % Evaluate residual of *dynamic* model using the steady state
    % computed on the *static* one
    z = repmat(ys,1,M.maximum_lead + M.maximum_lag + 1);
    zx = repmat([exo_ss'], M.maximum_lead + M.maximum_lag + 1, 1);
    if options.bytecode
        [r, ~]= bytecode('dynamic','evaluate', z, zx, params, ys, 1);
    elseif options.block
        [r, oo.dr] = feval([M.fname '.dynamic'], z', zx, params, ys, M.maximum_lag+1, oo.dr);
    else
        iyv = M.lead_lag_incidence';
        iyr0 = find(iyv(:));
        xys = z(iyr0);
        r = feval([M.fname '.dynamic'], z(iyr0), zx, params, ys, M.maximum_lag + 1);
    end
    % Fail if residual greater than tolerance
    if max(abs(r)) > options.solve_tolf
        info(1) = 25;
        return
    end
end

if ~isreal(ys)
    info(1) = 21;
    info(2) = sum(imag(ys).^2);
    ys = real(ys);
    return
end

if ~isempty(find(isnan(ys)))
    info(1) = 22;
    info(2) = NaN;
    return
end

function [resids,jac] = static_problem(y,x,params,nvar,fh_static_model)
[r,j] = fh_static_model(y,x,params);
resids = r(1:nvar);
jac = j(1:nvar,1:nvar);