Search found 214 matches

by dirkse
2 years ago
Forum: Modeling
Topic: constraint variables in set
Replies: 2
Views: 1527

Re: constraint variables in set

Nebu, I assume that the batteries are partitioned into clusters (i.e. each battery is in exactly one cluster). A little bit of GAMS code could check this and abort if false: this prevents a lot of head-scratching about infeasible models in case of data errors. You could just have a variable P(cluste...
by dirkse
2 years ago
Forum: Modeling
Topic: conditional constraint using alias
Replies: 1
Views: 1584

Re: conditional constraint using alias

Hello gams_learner58, The scheme you've chosen to represent your network seems to be a difficult one. I suggest you looks at the GAMS Tutorial: https://www.gams.com/latest/docs/UG_Tutorial.html This will explain many useful things about GAMS. As an added bonus, it includes a convenient and powerful ...
by dirkse
2 years ago
Forum: Solvers
Topic: CPLEX presolve would not turn off
Replies: 1
Views: 2431

Re: CPLEX presolve would not turn off

Ali,

Interesting question. If you attach the entire .log file from your run to a post that will allow people to search for clues to explain this behavior.

-Steve
by dirkse
2 years ago
Forum: Syntax
Topic: EMP syntax error: key expected: is the key min
Replies: 2
Views: 2152

Re: EMP syntax error: key expected: is the key min

Hi, The dualEqu keyword is something I would use to modify a single-agent optimization model whose objective is specified in the GAMS model statement. By default all equations in such a model are constraints on the agent (i.e. normal constraints) but dualEqu says that some equations move away from t...
by dirkse
2 years ago
Forum: Modeling
Topic: Finding 'Equilibria' using EMP equilibrium
Replies: 2
Views: 2252

Re: Finding 'Equilibria' using EMP equilibrium

Hello, As I understand it, you have 3 follower agents, each of whom solves their own optimization model, and one leader agent, also with an optimization model. You can do this in EMP: you formulate the model as a bilevel program. https://www.gams.com/37/docs/UG_EMP_Bilevel.html https://www.gams.com/...
by dirkse
2 years ago
Forum: Syntax
Topic: Negative exponential
Replies: 11
Views: 6604

Re: Negative exponential

Alexanre, You wrote: I have a condition that I need to test, if the transport occurs from the node (n) to the (np), or the opposite (np,n). One of this 2 situations will occurs. The other will be zero, or not occurs. If on of them occurs (Q>0), so, use the equation so ( min >"ir"> max ); i...
by dirkse
2 years ago
Forum: Modeling
Topic: How can a three-way equality constraint be defined in GAMS?
Replies: 3
Views: 2391

Re: How can a three-way equality constraint be defined in GAMS?

Teo, Your primary question was about how to write A == B == C. You are correct in supposing that the way to write this is to use two equations: f1.. A =E= B; f2.. B =E= C; I have some additional comments about how you might use auxiliary variables. Your formulations included several sums that you us...
by dirkse
2 years ago
Forum: Syntax
Topic: upper/lower bound vs restriction
Replies: 1
Views: 2622

Re: upper/lower bound vs restriction

Pitters, In most cases, the two items you mention (x.up = 50 or x =L= 50) are identical. For example, most LP solvers include a presolve step that converts singleton equations like x =L= 50 into the equivalent explicit upper bound. Usually it is best to just set the variable upper bound explicitly i...
by dirkse
2 years ago
Forum: Syntax
Topic: compile-time variable/Parameter
Replies: 2
Views: 4292

Re: compile-time variable/Parameter

Iman, A compile-time variable is a mechanism for text substitution. For example, your GAMS code can look like this: set I; $gdxin data_%CASENAME% $load I $gdxin blah blah blah solve m using nlp min z; execute_unlload 'results_%CASENAME%', blah, blah, blah; and you can run the GAMS model like this ga...
by dirkse
2 years ago
Forum: Solvers
Topic: MOSEK: Problem becomes infeasible when I change the objective function
Replies: 4
Views: 3759

Re: MOSEK: Problem becomes infeasible when I change the objective function

Hello,

If you suspect that there is a bug in GAMS you should contact GAMS support with a minimal reproducible example. Be clear about what you consider wrong, and what you expect instead, and how to reproduce the wrong behavior. Send .log and .lst files illustrating the wrong behavior.

-Steve