function [x,FVAL,MAXFVAL,EXITFLAG,OUTPUT,LAMBDA] = fminimax(FUN,x,A,B,Aeq,Beq,LB,UB,NONLCON,options,varargin)
%FMINIMAX Finds a minimax solution of a function of several variables.
%   FMINIMAX solves the following problem:
%   min (max {FUN(X} )  where FUN and X can be vectors or matrices.
%    X 
% 
%   X=MINIMAX(FUN,X0) starts at X0 and finds a minimax solution X to 
%   the functions described in FUN (usually an M-file: FUN.M). FUN
%   should return the values F, at X, of the functions to be minimized 
%   when called with feval: F = feval(FUN,X).
%
%   X=FMINIMAX(FUN,X0,A,B) solves the minimax problem subject to the
%   linear inequalities A*X <= B.
%
%   X=FMINIMAX(FUN,X0,A,B,Aeq,Beq) solves the minimax problem
%   subject to the linear equalities Aeq*X = Beq as well.  (Set A=[] and B=[] 
%   if no inequalities exist.)
%
%   X=FMINIMAX(FUN,X0,A,B,Aeq,Beq,LB,UB) defines a set of lower 
%   and upper bounds on the design variables, X, so that the solution is 
%   in the range LB <= X <= UB. You may use empty matrices for LB and UB
%   if no bounds exist. Set LB(i) = -Inf if X(i) is unbounded below; 
%   set UB(i) = Inf if X(i) is unbounded above.
%   
%   X=FMINIMAX(FUN,X0,A,B,Aeq,Beq,LB,UB,NONLCON) subjects the 
%   goal attainment problem to the constraints defined in NONLCON (usually an 
%   M-file: NONLCON.m). The function NONLCON should return the vectors
%   C and Ceq, representing the nonlinear inequalities and equalities 
%   respectively, when called with feval: [C, Ceq] = feval(NONLCON,X). FMINIMAX 
%   optimizes such that C(X)<=0 and Ceq(X)=0.
%
%   X=FMINIMAX(FUN,X0,A,B,Aeq,Beq,LB,UB,NONLCON,OPTIONS) minimizes with the 
%   default optimization parameters replaced by values in the structure 
%   OPTIONS, an argument created with the OPTIMSET function.  See OPTIMSET 
%   for details.  Used options are Display, TolX, TolFun, TolCon, 
%   DerivativeCheck, GradObj, GradConstr, MaxFunEvals, MaxIter, MeritFunction, 
%   MinAbsMax, Diagnostics, DiffMinChange and DiffMaxChange. Use the GradObj 
%   option to specify that FUN may be called with two output arguments where 
%   the second, G, is the partial derivatives of the function df/dX, at the 
%   point X: [F,G] = feval(FUN,X). Use the GradConstr option to specify that 
%   NONLCON may be called with four output arguments: 
%   [C,Ceq,GC,GCeq] = feval(NONLCON,X) where GC is the partial derivatives of 
%   the constraint vector of inequalities C an GCeq is the partial derivatives 
%   of the constraint vector of equalities Ceq. Use OPTIONS = [] as a place 
%   holder if no options are set.
%
%   X=FMINIMAX(FUN,X0,A,B,Aeq,Beq,LB,UB,NONLCON,OPTIONS,P1,P2,...)
%   passes the problem-dependent parameters P1,P2,... directly to the 
%   functions FUN and NONLCON: feval(FUN,X,P1,P2,...) and 
%   feval(NONLCON,X,P1,P2,...). Pass empty matrices for A, B, Aeq, Beq, LB, UB, 
%   NONLCON and OPTIONS to use the default values.
%
%   [X,FVAL]=FMINIMAX(FUN,X0,...) returns the value of the objective 
%   functions at the solution X: FVAL=feval(FUN,X).
%
%   [X,FVAL,MAXFVAL]=FMINIMAX(FUN,X0,...) returns MAXFVAL = max { FUN(X) } 
%   at the solution X.
%
%   [X,FVAL,MAXFVAL,EXITFLAG]=FMINIMAX(FUN,X0,...) returns a string EXITFLAG  
%   that describes the exit condition of FMINIMAX.  
%   If EXITFLAG is:
%      > 0 then FMINIMAX converged to a solution X.
%      0   then the maximum number of function evaluations was reached.
%      < 0 then FMINIMAX did not converge to a solution.
%   
%   [X,FVAL,MAXFVAL,EXITFLAG,OUTPUT]=FMINIMAX(FUN,X0,...) returns a structure
%   OUTPUT with the number of iterations taken in OUTPUT.iterations, the number
%   of function evaluations in OUTPUT.funcCount, and the algorithm used in 
%   OUTPUT.algorithm.  
%
%   [X,FVAL,MAXFVAL,EXITFLAG,OUTPUT,LAMBDA]=FMINIMAX(FUN,X0,...) returns the 
%   Lagrange multipliers at the solution X: LAMBDA.lower for LB, LAMBDA.upper 
%   for UB, LAMBDA.ineqlin is for the linear inequalities, LAMBDA.eqlin is for 
%   the linear equalities, LAMBDA.ineqnonlin is for the nonlinear inequalities, 
%   and LAMBDA.eqnonlin is for the nonlinear equalities.
%
%   See also OPTIMSET, OPTIMGET.

%   Copyright (c) 1990-98 by The MathWorks, Inc.
%   $Revision: 1.15 $  $Date: 1998/10/22 19:28:40 $
%   Andy Grace 7-9-90.


defaultopt = optimset('display','final',...
   'TolX',1e-6,'TolFun',1e-6,'TolCon',1e-6,'DerivativeCheck','off',...
   'Diagnostics','off',...
   'GradObj','off','GradConstr','off','MaxFunEvals','100*numberOfVariables',...
   'MaxIter',400,...
   'DiffMaxChange',1e-1,'DiffMinChange',1e-8, 'MeritFunction','multiobj',...
   'MinAbsMax', 0);
% If just 'defaults' passed in, return the default options in X
if nargin==1 & nargout <= 1 & isequal(FUN,'defaults')
   x = defaultopt;
   return
end

caller='fminimax';

if nargin < 10, options = [];
   if nargin < 9, NONLCON = [];
      if nargin < 8, UB = [];
         if nargin < 7, LB = [];
            if nargin < 6, Beq = [];
               if nargin < 5, Aeq = [];
                  if nargin < 4, B = [];
                     if nargin < 3, A = [];
                        if nargin < 2, error('fminimax requires two input arguments'); 
                        end,end,end,end,end,end,end,end,end 
                        

xnew=[x(:); 0 ];

numberOfVariablesplus1 = length(xnew);
numberOfVariables = numberOfVariablesplus1 - 1;

diagnostics = isequal(optimget(options,'diagnostics','off'),'on');
options = optimset(defaultopt,options);
switch optimget(options,'display')
case {'off','none'}
   verbosity = 0;
case 'iter'
   verbosity = 2;
case 'final'
   verbosity = 1;
otherwise
   verbosity = 1;
end

% Set to column vectors
B = B(:);
Beq = Beq(:);

[xnew(1:numberOfVariables),l,u,msg] = checkbounds(xnew(1:numberOfVariables),LB,UB,numberOfVariables);
if ~isempty(msg)
   EXITFLAG = -1;
   [FVAL,MAXFVAL,OUTPUT,LAMBDA] = deal([]);
   x(:) = xnew(1:numberOfVariables);
   if verbosity > 0
      disp(msg)
   end
   return
end

neqgoals = optimget(options, 'minabsmax');

% meritFunctionType is 1 unless changed by user to fmincon merit function;
% formerly options(7)
% 0 uses the fmincon single-objective merit and Hess; 1 is the default
meritFunctionType = strcmp(optimget(options,'meritfunction'),'multiobj');
lenVarIn = length(varargin);
% goalgra and goalfun also take: neqgoals,funfcn,gradfcn,WEIGHT,GOAL,x
goalargs = 6; 

usergradflag = strcmp(optimget(options,'GradObj'),'on');
usergradconstflag = strcmp(optimget(options,'GradConstr'),'on');
userhessflag = strcmp(optimget(options,'Hessian'),'on');
if userhessflag
   warning('FMINIMAX does not use user-supplied Hessian.')
   userhessflag = 0;
end

if isempty(NONLCON)
   userconstflag = 0;
else
   userconstflag = 1;
end

line_search = strcmp(optimget(options,'largescale','off'),'off'); % 0 means trust-region, 1 means line-search
if ~line_search
   warning('Large-scale algorithm not currently available for this problem type.')
   line_search = 1;
end

constflag = 1;  % always goal constraints
gradflag = 1; % always can compute gradient of goalfun since based on x
hessflag = 0;
% If (user) nonlinear constraints exist, need 
%  either both function and constraint gradients, or not

if userconstflag
   if usergradflag & usergradconstflag
      gradconstflag = 1;
   elseif usergradflag & ~usergradconstflag
      usergradflag = 0;
      gradconstflag = 0;
   elseif ~usergradflag & usergradconstflag
      usergradconstflag = 0;
      gradconstflag = 0;
   else
      gradconstflag = 0;
   end
else % No user nonlinear constraints
   if usergradflag
      gradconstflag = 1;
   else
      gradconstflag = 0;
   end
end

   

% Convert to inline function as needed
if ~isempty(FUN)  % will detect empty string, empty matrix, empty cell array
   [funfcn, msg] = optimfcnchk(FUN,'goalcon',length(varargin),usergradflag,userhessflag);
else
   errmsg = sprintf('%s\n%s', ...
      'FUN must be a function name, valid string expression, or inline object;', ...
      ' or, FUN may be a cell array that contains these type of objects.');
   error(errmsg)
end
% We can always compute gradient since based only on xnew
[ffun, msg] = optimfcnchk('goalfun','fminimax',lenVarIn+goalargs,gradflag);


if userconstflag % NONLCON is non-empty
   [confcn, msg] = ...
      optimfcnchk(NONLCON,'goalcon',length(varargin),usergradconstflag,0,1);
else
   confcn{1} = '';
end
[cfun, msg]= optimfcnchk('goalcon','fminimax',lenVarIn+goalargs,gradconstflag,0,1); 

lenvlb=length(l);
lenvub=length(u);
CHG = 1e-7*abs(xnew)+1e-7*ones(numberOfVariablesplus1,1);
i=1:lenvlb;
lindex = xnew(i)<l(i);
if any(lindex),
   xnew(lindex)=l(lindex)+1e-4; 
end
i = 1:lenvub;
uindex = xnew(i)>u(i);
if any(uindex)
   xnew(uindex)=u(uindex);
   CHG(uindex)=-CHG(uindex);
end
x(:) = xnew(1:end-1);

% Evaluate user function to get number of function values at x, not xnew!
switch funfcn{1}
case 'fun'
   user_f = feval(funfcn{3},x,varargin{:});
case 'fungrad'
   user_f = feval(funfcn{3},x,varargin{:});
   
case 'fungradhess'
   user_f = feval(funfcn{3},x,varargin{:});
   
case 'fun_then_grad'
   user_f = feval(funfcn{3},x,varargin{:}); 
case 'fun_then_grad_then_hess'
   user_f = feval(funfcn{3},x,varargin{:}); 
otherwise
   error('Undefined calltype in FMINIMAX');
end
user_f = user_f(:);
len_user_f = length(user_f);

WEIGHT = ones(len_user_f,1);
GOAL = zeros(len_user_f,1);

GRAD=zeros(numberOfVariablesplus1,1);
HESS = [];
extravarargin= {neqgoals,funfcn,confcn,WEIGHT,GOAL,x,varargin{:}}; 
% Evaluate goal function
switch ffun{1}
case 'fun'
   f = feval(ffun{3},xnew,extravarargin{:});
case 'fungrad'
   [f,GRAD] = feval(ffun{3},xnew,extravarargin{:});
  
case 'fungradhess'
   [f,GRAD,HESS] = feval(ffun{3},xnew,extravarargin{:});

case 'fun_then_grad'
   f = feval(ffun{3},xnew,extravarargin{:}); 
   GRAD = feval(ffun{4},xnew,extravarargin{:});
  
case 'fun_then_grad_then_hess'
   f = feval(ffun{3},xnew,extravarargin{:}); 
   GRAD = feval(ffun{4},xnew,extravarargin{:});
   HESS = feval(ffun{5},xnew,extravarargin{:});
   
otherwise
   error('Undefined calltype in FMINIMAX');
end



% Evaluate goal constraints
switch cfun{1}
case 'fun'
   [ctmp,ceqtmp] = feval(cfun{3},xnew,extravarargin{:});
   c = ctmp(:); ceq = ceqtmp(:);
   cGRAD = zeros(numberOfVariablesplus1,length(c));
   ceqGRAD = zeros(numberOfVariablesplus1,length(ceq));
case 'fungrad'
   [ctmp,ceqtmp,cGRAD,ceqGRAD] = feval(cfun{3},xnew,extravarargin{:});
   c = ctmp(:); ceq = ceqtmp(:);
  
case 'fun_then_grad'
   [ctmp,ceqtmp] = feval(cfun{3},xnew,extravarargin{:});
   c = ctmp(:); ceq = ceqtmp(:);
   [cGRAD,ceqGRAD] = feval(cfun{4},xnew,extravarargin{:});
   
case ''
   c=[]; ceq =[];
   cGRAD = zeros(numberOfVariablesplus1,length(c));
   ceqGRAD = zeros(numberOfVariablesplus1,length(ceq));
otherwise
   error('Undefined calltype in FMINIMAX');
end

non_eq = length(ceq);
non_ineq = length(c);
[lin_eq,Aeqcol] = size(Aeq);
[lin_ineq,Acol] = size(A);
[cgrow, cgcol]= size(cGRAD);
[ceqgrow, ceqgcol]= size(ceqGRAD);

eq = non_eq + lin_eq;
ineq = non_ineq + lin_ineq;

if ~isempty(Aeq) & Aeqcol ~= numberOfVariables
   error('Aeq has the wrong number of columns.')
end
if ~isempty(A) & Acol ~= numberOfVariables
   error('A has the wrong number of columns.')
end
if  cgrow~=numberOfVariables & cgcol~=non_ineq
   error('Gradient of the nonlinear inequality constraints is the wrong size.')
end
if ceqgrow~=numberOfVariables & ceqgcol~=non_eq
   error('Gradient of the nonlinear equality constraints is the wrong size.')
end

just_user_constraints = non_ineq - len_user_f - neqgoals;

OUTPUT.algorithm = 'minimax SQP, Quasi-Newton, line_search';
if diagnostics > 0
   % Do diagnostics on information so far
   msg = diagnose('fminimax',OUTPUT,usergradflag,userhessflag,userconstflag,usergradconstflag,...
      line_search,options,xnew(1:end-1),non_eq,...
      just_user_constraints,lin_eq,lin_ineq,l,u,funfcn,confcn,f,GRAD,HESS, ...
      c(1:just_user_constraints),ceq,cGRAD(1:just_user_constraints,:),ceqGRAD);
end


% add extra column to account for extra xnew component
A =[A,zeros(lin_ineq,1)];
Aeq =[Aeq,zeros(lin_eq,1)];

[xnew,MAXFVAL,lambda,EXITFLAG,OUTPUT]=...
   nlconst(ffun,xnew,l,u,full(A),B,full(Aeq),Beq,cfun,options, ...
   verbosity,gradflag,gradconstflag,hessflag,meritFunctionType,...
   CHG,f,GRAD,HESS,c,ceq,cGRAD,ceqGRAD,neqgoals,funfcn,confcn,WEIGHT,GOAL,x,varargin{:});
just_user_constraints = length(lambda.ineqnonlin) - len_user_f - neqgoals;
lambda.ineqnonlin = lambda.ineqnonlin(1:just_user_constraints);
LAMBDA=lambda;

OUTPUT.algorithm = 'minimax SQP, Quasi-Newton, line_search';  % override nlconst output

% compute FVAL since it is lambda instead of F(x)
% Evaluate user function to get number of function values at x, not xnew!
x(:)=xnew(1:end-1);
switch funfcn{1}
case 'fun'
   user_f = feval(funfcn{3},x,varargin{:});
case 'fungrad'
   user_f = feval(funfcn{3},x,varargin{:});
   
case 'fungradhess'
   user_f = feval(funfcn{3},x,varargin{:});
   
case 'fun_then_grad'
   user_f = feval(funfcn{3},x,varargin{:}); 
case 'fun_then_grad_then_hess'
   user_f = feval(funfcn{3},x,varargin{:}); 
otherwise
   error('Undefined calltype in FMINIMAX');
end
FVAL = user_f;


