[Ipopt] Best and free way of interacting with IPOPT on Linux

[Edson Cordeiro do Valle]

              Hello all
         Well just to revival an old list topic, but I think it's an 
important tip for Ipopt users.
  One of the free tools (but not open source) to interact with Ipopt 
it's the EMSO simulator (http://www.enq.ufrgs.br/trac/alsoc).
Its a project leaded by Prof. Argimiro Secchi and Phd Rafael Pelegrini 
Soares at Chemical Eng. Department at Federal Univ. of Rio Grande do Sul 
( a South Brazilian University).
EMSO is an equation-oriented dynamic and steady-state simulator and 
optimizer, it uses a high-level modeling language.  This software 
provides a set of sparse algebra and automatic differentiation 
functionalities that evaluate a NLA (Non-Linear Algebraic Equations) 
system in a fast and efficient way. Some NLP solvers (OPT++, Ipopt and a 
complex implementation) were interfaced with the software. In EMSO, the 
optimization problem can be easily described as bellow (HS71 problem):

Optimization hs71
     VARIABLES
          x1 as Real(Default=1, Lower=1, Upper=5);
          x2 as Real(Default=5, Lower=1, Upper=5);
          x3 as Real(Default=5, Lower=1, Upper=5);
          x4 as Real(Default=1, Lower=1, Upper=5);
     MINIMIZE
          x1*x4*(x1+x2+x3) + x3;    
     EQUATIONS
          x1*x2*x3*x4 > 25;    
          x1*x1 + x2*x2 + x3*x3 + x4*x4 = 40;    
     OPTIONS
          NLPSolver = "ipopt_emso";
          NLPSolveNLA = 1;
          relativeAccuracy = 1e-6;
 end

Since EMSO uses an object oriented approach, the code is highly 
reusable. Although it was  designed to chemical eng. problems,  it's 
possible to  use  it to model any kind of problem. The work of our team 
in Emso developing and all other features will be presented an EngOPT ( 
a Optimization congress that will be held in Rio de Janeiro - Brazil, 
next month, see: http://www.engopt.org/en/introduction.php). Of course 
it does not have all language features as Gams or Ampl, but is a free 
and robust alternative.

Note that due to some license issues, it can only be used for academic 
purposes.
                                                                      
enjoy EMSO

-- 
                                                  Edson C. do Valle
                                                edsoncv at enq.ufrgs.br
                                                   Skype: edson.cv