Search found 337 matches

by bussieck
2 months ago
Forum: Modeling
Topic: Load Flow of 33 buses distribution system, current in between buses equal zero
Replies: 1
Views: 128

Re: Load Flow of 33 buses distribution system, current in between buses equal zero

You might want to attached a working model, so we can see what is going on. But most likely, your model was reported infeasible and that's why you don't get meaningful values in your reported variables.

-Michael
by bussieck
2 months ago
Forum: Modeling
Topic: stochastic programming
Replies: 1
Views: 190

Re: stochastic programming

Have slack variables with high costs to make the second stage problem always feasible.

-Michael
by bussieck
2 months ago
Forum: Syntax
Topic: Maximizing a maximum
Replies: 1
Views: 183

Re: Maximizing a maximum

What about, eq(t,i).. power(t)=g=p(i,t) If the model wants to have minimum of power (because of cost or so) the equality for for i will happen automatically. If that's not the case, you need to introduce binary variables that make sure at least one of the constraints is fulfilled with equality. Thes...
by bussieck
2 months ago
Forum: Syntax
Topic: Endogenous function in lag operation
Replies: 1
Views: 123

Re: Endogenous function in lag operation

This restriction exists because that is not allowed in mathematical programming. Endogenous variables can't be used model types like LP, MIP, NLP or MINLP. These type of operators can be easily used in local search and other methods, but GAMS is not a good language for this.

-Michael
by bussieck
2 months ago
Forum: Syntax
Topic: Set multiplication
Replies: 1
Views: 170

Re: Set multiplication

I really did not get what you try to accomplish here. Write your model in mathematical notation and then the translation to GAMS is easy.

-Michael
by bussieck
2 months ago
Forum: Syntax
Topic: Set optimal solution
Replies: 1
Views: 141

Re: Set optimal solution

Unfortunately, there is no simple way to do that, but a complicated one with GAMS/Cplex. You need to tell GAMS/Cplex to report all solutions found and to be reported to a "callback" program (userincbicall). This GAMS program can check if the stopping criterion is met (e.g. if the solution value is s...
by bussieck
2 months ago
Forum: Syntax
Topic: GAMS indexing issues
Replies: 1
Views: 166

Re: GAMS indexing issues

If you need a second i index in your equation logic use ALIAS. There were lots of other compilation errors, but this one compiles and produces an optimum solution. Not sure if this is what you had in mind. BTW, for code there a nice code section syntax. -Michael Set i 'regions' / A, B /; Parameter T...
by bussieck
2 months ago
Forum: Syntax
Topic: Minos Run Error
Replies: 2
Views: 294

Re: Minos Run Error

You have specified Cplex options in a Minos option file. Minos does not know what to do with these... Options don't help with models that can be evaluated at bad points. Use bounds to keep the variables away from regions that can't be evaluated, e.g. x.lo=1e-6; for algebra with sqrt(x).

-Michael
by bussieck
2 months ago
Forum: Syntax
Topic: Parameter of Variabe
Replies: 1
Views: 159

Re: Parameter of Variabe

No parameter are know entities. Variables are determined by the solver subject to the equations and the objective.

-Michael
by bussieck
2 months ago
Forum: Syntax
Topic: why is the elapsed seconds smaller than the total seconds
Replies: 1
Views: 94

Re: why is the elapsed seconds smaller than the total seconds

I would not worry about this. This is probably a rounding error in routines that measure time somewhat independently.

-Michael