Dear All,

I am trying to solve a mixed-integer optimization problem in `JuMP`

and `Gurobi`

. I have a variable x_{i,j} over i,j \in \{1,2,\ldots,n\}, where n is a fairly large number. However, for this particular problem, over an index set

P=\{(i,j) \mid (i,j) \textrm{ satisfying some property}\},

I have x_{i,j} = 0 for all i,j \in P.

Because there are other constraints involving x_{i,j}, it is more convenient if I set those values over P to zero through `JuMP`

rather than hard coding them. I see there are two ways I can do that in `JuMP`

, one is via `fix`

and the other one is through `@constraint`

macro, e.g.,

```
for i,j in P
@constraint(model_name, x[i,j] == 0.0)
end
```

or

```
for i, j in P
fix(x[i,j], 0.0; force = true)
end
```

For better performance, which one would be more suitable? Any tips/suggestions will be much appreciated!