Originally posted by: Zak86

Hi Guys,

I have declared an array variable IloNumVar [ ] x = ... .

I have constraint in which x[i] must be equal to 1 so i write cplex.addEq(x[i], 1)

and another constraint in which x[s] must be different from 0 . How can i write this constraint of " NOT EQUAL" please ?

Thank you in advance,

Zak

Short answer: you cannot. With CPOptimizer (constraint programming), not-equal is a legal constraint. With CPLEX (LP/MIP), it is not.

Longer answer: you can adapt the solution I posted to a related problem, by replacing the 'x' variable in my solution with zero.

Originally posted by: Zak86

Dear Pr Rubin,

Thank you for the quick reply.

However, please, as i'm a beginner in Mathematical programming. Your post seems a little bit complicated for me as it's well detailed :-) Or may be my case is very simple compared to it :-).

Indeed, i work on JAVA with the package of CPLEX what i want to do is :

I have a positive continuos array variable x[i]  >= 0 , where i is in [1 .. N ] and simply i want that, for a specific value of i ( for exmaple i = 3 ) , x[3] must be Not null ( x[3] <> 0),  .

How to write that please according to your method ?

I mean,  is the variable 'y' ( in your solution ) equal to x[3], 'L' = 0 and 'U' = POSITIVE_INFINITY ?

What do variables " m " , "U" , "L" and "Epsilon" refer to in my case please ? 

Note that if there is a  method to write a strict inequality on x[3] in CPLEX , ( x[3] > 0 ) , instead of ( x[3] <> 0 ) , it will also OK for me .

Sorry for this repetitive ask.

Thank you,

Zak