Originally posted by: NaomiLearnCplex

Hello,

I found some information from website indicating that cplex support "indicator constraints" which allow variables in the conditions. That suits my needs to set up conditions for binary variables f_ij, in particular, f_ij=1 when x_ij>0, and f_ij=0 when x_ij=0. f_ij and x_ij are decision variables.

However, when I use implication operator "->" or "==>", there are always errors. Can someone help me with this question? 

Below are some of my scripts:

// define decision variables

dvar int+ x[Sites][Days]; 

dvar boolean f[Sites][Days]; 

// define objective

dexpr float SiteAllocation = sum(i in Sites,t in Days)x[i][t]*(0.5*Parameter[i]);
maximize SiteAllocation;

subject to {

Constr01:

forall (i in Sites, t in Days)

f[i][t]==0 -> x[i][t]==0;

f[i][t]==1 -> x[i][t]>0

Constr02:

forall(i in Sites, t in Days_less)
   f[i][t]+f[i][t+1]+f[i][t+2]+f[i][t+3]+f[i][t+4] <= 1;

}
  

Originally posted by: BoJensen

This question belongs to the OPL forum please ask it there, thank you.

Originally posted by: VincentBeraudier

You have to use => to set logical constraints.

So your code becomes:

forall (i in Sites, t in Days){

f[i][t]==0 => x[i][t]==0;

f[i][t]==1 => x[i][t]>=1;

}

> is not a valid operator for integer variable in OPL, so you have to use >=

(You have to use {} if you want to share the same generator for a list of constraints.

Originally posted by: NaomiLearnCplex

Hi Vincent,

It helps, thank you!