Originally posted by: valkiri

Hello.

 If i have two variables  IloIntVar var(env,0,10);  IloIntVar  b(env,0,1);

I want to implement this constraint :  if var is upper than 5 variable b must take 1 and must take 0 else.

Thanks.

You cannot do exactly what you want. Your choices are: to say var > 5 => b = 1, var < 5 => b = 0 and var == 5 is ambiguous (b could take either value); or to say var >= 5 + epsilon => b = 1, var <= 5 => b = 0 and 5 < var < 5 + epsilon is forbidden (for some small but not too small choice of epsilon); or do the second version but with the "forbidden zone" 5 - epsilon < var < 5.

Try searching for "indicator constraint" in the CPLEX documentation.

Paul, note that these are IloIntVar instances, so "upper than 5" is actually >=6. So I think this can be modeled as

model.add(IloIfThen(env, var >= 6, b == 1));
model.add(IloIfThen(env, var <= 5, b == 0));

Oops, you are of course correct. I thought 'var' was IloNumVar. Should have read the question more closely.

Originally posted by: valkiri

Thanks  DanielJunglas 

Thanks PaulRubin

Its work perfectly.

Valkiri.