NLP infeasibility problem on a MINLP
Posted: Mon Jul 21, 2008 9:32 pm
Hi my name is Daniel, and I'm new using GAMS. I had to learn the
program because I'm developing a model for synthetise Heat Exchangers
Networks as a master thesis.
Well, I'm writting in this forum because I've a problem with DICOPT.
The model developed is parametrized with a variable called DTmin, and
what I do is make an optimization Loop with a pool of values for this
particular variable. In some cases there is an optimal MINLP solution,
but in other cases DICOPT reports the following sentence: "Too many
infeasible NLP subproblems consider the use of infeasder option"
when I analize the Log file it shows something that I think is a clue,
but I can't understand.
when DICOPT is running shows:
** Feasible Solution. Value of objetive = 45800 (or something like
that), this value is closer to the optimal solution reached for som
values of DTmin.
After this, the program search the solution during 3 iterations (in
phase =3) and then says:
** Loss of feasibility while tightening tolerances - Return to phase
0
the solver iterate once, and find the same old value (45800) and the
problem repeats until MAXCYCICLES gets to the maximum value.
¿What can I do for the convergence of my problem?
¿Is a good posibility change the infeasder option?, and if is ¿How can
I do this?
thanks and best regards!!
PS: I'm using as a solvers
CPLEX: LP
CONOPT: NLP
DICOPT: MINLP
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