Search found 6 matches

by Sisco
4 years ago
Forum: Modeling
Topic: Complementarity constraints or sigmoid ?
Replies: 1
Views: 1953

Complementarity constraints or sigmoid ?

Hello, as I'm writing an NLP problem, I understand there are two possibilities to smoothly model a valve-like behaviour (0/1) : Sigmoids Complementarity constraints What are the advantages and drawbacks of each methods ? Do solvers prefer one or the other ? As I understand it, complementarity constr...
by Sisco
4 years ago
Forum: Solvers
Topic: *** Failure calling solver: CONOPT4 (rc=1). What does it mean?
Replies: 6
Views: 6596

Re: *** Failure calling solver: CONOPT4 (rc=1). What does it mean?

Hello, some days ago, I got the latest version of GAMS (28.2.0) along with CONOPT4. And I got the same error than above. FATAL SYSTEM ERROR Number 55668 Failure Calling Conopt4 (rc=1) Hasn't this error been fixed yet ? My (small) problem runs perfectly with Conopt. I took Conopt4 to be able to solve...
by Sisco
4 years ago
Forum: Solvers
Topic: Feasible with CONOPT3, Infeasible with CONOPT4
Replies: 0
Views: 2306

Feasible with CONOPT3, Infeasible with CONOPT4

Hello everyone, lately I bought the latest version of GAMS along with CONOPT4 so as to be able to solve a large NLP problem for which CONOPT3 was taking way too long. So I tested CONOPT4 on a small problem at first but it was unable to find a feasible solution while CONOPT3 did find one. I can see C...
by Sisco
5 years ago
Forum: Modeling
Topic: Communication between resolution loop and model ?
Replies: 0
Views: 1752

Communication between resolution loop and model ?

Hello everyone, my model is based on meteorological conditions (coming from an Excel file) which act like perturbations. It is hard to find an initialization point good enough to solve everything but I have a resolution loop than can do the trick. First I use flat conditions and solve. Then, I use t...
by Sisco
5 years ago
Forum: Syntax
Topic: Is it possible to use sets and variables this way ?
Replies: 2
Views: 2586

Re: Is it possible to use sets and variables this way ?

Yes I know this one. The requirement comes from a discretization method called "orthogonal collocation on finite elements". I have E elements in time and N collocation points in each element. The problem is at the bounds between elements. I could write my variables this way : T(E,N). But T...
by Sisco
5 years ago
Forum: Syntax
Topic: Is it possible to use sets and variables this way ?
Replies: 2
Views: 2586

Is it possible to use sets and variables this way ?

Hi, I would like a variable T to be defined in such a way that it takes the following values : T(1) to T(10) The thing is, my problem requires using two sets in a specific way : Is it possible to use sets B (1 to 4) and C (1 to 3) so that I can write something like T( B+3*(C-1) ) and finally have T(...