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constraintscplex

Constraint error with greater than operator

I'm ever in trouble with Cplex, I don't know why. So I attach a snippet of code:

 dvar int+ soglia[pazienti][giorni][slot];
 dvar int+ sogliar[pazienti][giorni][slot];
 dvar int+ soglial[pazienti][giorni][slot];

 forall(k in giornidue, w in slot)  sum(j in pazienti)(soglia[j,k,w]+sogliar[j,k,w]+soglial[j,k,w]) > sum(j in pazienti)(soglia[j,k-1,w]+sogliar[j,k-1,w]+soglial[j,k-1,w]);

And get this error:

Function operator >(dexpr int, dexpr int) not available in CPLEX context

I don't understand why i can not use > between int.

Solution

  • As mentioned in one of the comments to your answer, strict inequality is not supported in the theory of linear programming. However, since you know that both sides of your expression are integer,

    a > b

    is equivalent to

    a >= b + 1

    where the latter does not require strict inequality. Rewriting the constraint like this should work.