Hi Giovani,

welcome to the world of Cplex, and good luck for your first steps.

To answer your question: it depends on how you interact with Cplex. If you use the API for Java, Python or C/C++, then you can formulate sigma-sums in one of these languages. There are multiple examples coming with the Cplex distribution in these programming languages. Let me suggest that you study these examples.

Another way is to use a modeling language, for example, AIMMS or AMPL. You can download them for free (as trial versions) from the vendor's internet-pages. In AMPL notation, for example, you write

set I := { 1,2,3 };

var x {I} >=0;

sum {i in I} x[i]

Armin Fügenschuh , thanks a lot for the response and recommendations Prof., really appreciate.