How to formulate that once binary variable equals 1 then other one equals zero forever?

[dunyayigezerken]

I need to choose objective function under some circumstances.

obj_select = obj1*var1 + obj2*var2
.
.
.
obj.. z =e= obj_select

I need to decide var1 and var2 binary variable values. Conditions;

When var1 = 1 for a condition then var2 =0 no matter it became 1 before, the model just select the obj1 to optimize
When var2 = 1 for a condition then var1 =0 no matter it became 1 before, the model just select the obj1 to optimize

to sum up, I need to choose one objective according to the some conditions in the dataset.

Is there any idea?

[abhosekar]

if var1 and var2 are binary, you can do this by using the constraint
var1 + var2=e= 1;

However, you would be introducing nonlinearities/nonconvexities in your problem by such a formulation that uses obj1*var1. If var1 depends ‘only’ on data, it would be advisable to calculate it beforehand and use it as a parameter instead.
Also, I don’t understand what you mean by ‘irrespective of it became 1 before’. Are you solving your problem multiple times? You won’t have a value assigned to a variable until you solve it.

• Atharv

[dunyayigezerken]

if var1 and var2 are binary, you can do this by using the constraint
var1 + var2=e= 1;

However, you would be introducing nonlinearities/nonconvexities in your problem by such a formulation that uses obj1*var1. If var1 depends ‘only’ on data, it would be advisable to calculate it beforehand and use it as a parameter instead.
Also, I don’t understand what you mean by ‘irrespective of it became 1 before’. Are you solving your problem multiple times? You won’t have a value assigned to a variable until you solve it.

• Atharv

Thanks for answer, actually, I want to code Particle Swarm Opt. in GAMS, so probably I have to run the code iteratively but I dont know that is it possible or not in GAMS? So, I try to be ready for diffculties such as nonlinearity etc.