Using OR in a Gurobi Expression

[TR]

Is there a ways in Gurobi to add an OR in the expression?

a1, b1,  c1,  d1 are Binary decision variables.

A constraint: a1 + b1 + c1 + d1 <= an integer

Would like to modify the above constraint as

    a1 + b1 + (c1 OR d1) <= an integer

Of course this can be done by adding another decision variable, which will make the model size to increase.

Thanks GUROBI.

[Michael Winkler]

You need to add an extra constraint for this, namely c1 + d1 <= 1. (As a result you have two constraints, a1 + b1 + c1 + d1 <= some integer, and  c1 + d1 <= 1.)

Best,

Michael

[Dr Michael F]

I suggest two constraints:

a1+b1+c1<= an integer
a1+b1+d1<= an integer