Dear support team,

I was trying to solve a scheduling model using GAMS/Gurobi. The snippet code is:

```
Binary variable x(i,k);
Equations c1,c2;
c1(k).. sum(i, x(i,k)) =e= 1;
c2(i).. sum(k, x(i,k)) =e= 1;
```

Using the binary variables, the model has solved optimally.

I have used SOS type_1 variables instead of binary variables and run the model.

```
SOS1 variable x(i,k);
Equations c1,c2;
c1(k).. sum(i, x(i,k)) =e= 1;
c2(i).. sum(k, x(i,k)) =e= 1;
```

The model has solved optimally and the results are the same as previous.

AKAIK, the SOS type_1 constraint says that at most one of the variables must be non-zero. the equation is:

```
x1 + x2 + ... + xn <= 1 for n=1...N
```

I’m working on the coding my model in the GUROBI software using Java API. While I have defined the SOS type_1 constraint in the model and run it, I get the zero solution for all assignment variables. I negotiated to GUROBI support team and they mentioned that:

the all-zero solution is feasible.

Would you say that do I have a mistake to implement GAMS code, please?

Regards

Omidi. A