Fixing the value of some variables when defining it, not in the constraints

Specific Domains Optimization (Mathematical)
3

Hi @CactusHamster (I’m guessing you’re the same CactusHamster as modeling - Coding some parameters with index zero in Julia - Operations Research Stack Exchange :smile:).

To slightly elaborate on what @Henrique_Becker said,

for i=1:10, j=1:5
    @constraint(model, x[i, j] == 0)
end

will add 50 new linear constraints to your problem (rows to the constraint matrix). These should get pre-solved out by the solver, but it’s still work that needs to be done.

In contrast,

for i=1:10, j=1:5
    fix(x[i, j], 0.0)  # potentially with `; force = true` if there are other bounds
end

will set the lower and upper bounds of x[i, j] to 0.0. This will not add any new constraints so it might be a bit faster.

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