Priority in variable bridge

[blegat]

In the following model, Q is added as a constrained variable in the copy and it is then set as a parameter after. Because of this, it goes through the slack bridge which create a new variable that is a parameter and that is equal to Q[]. Then it fails saying that Mosek does not support quadratic constraints because it does not see Q[] as a parameter anymore.
During a copy, Parameter should have higher priority to be added as variable-wise constraint.

model = Model(() -> POI.Optimizer(Mosek.Optimizer()))
@variable(model, x)
@variable(model, Q[1:1, 1:1] in PSDCone())
@constraint(model, Q[] in Parameter(1.0))
@constraint(model, Q[] * x == 0)
optimize!(model)

[odow]

That's a messed up way to write the model! I don't know that I condone this approach. I would have done:

model = Model(() -> POI.Optimizer(Mosek.Optimizer()))
@variable(model, x)
@variable(model, Q[1:1, 1:1] in PSDCone())
@variable(model, p in Parameter(1.0))
@constraint(model, Q[1, 1] == p)
@constraint(model, p * x == 0)
optimize!(model)

[joaquimg]

I would write as @odow did. For me it is not surprising that Q[] * x is quadratic.

Maybe the user-proof solution is that the Parameter set should only be used in add_constrained_variable and never in add_constraint?

I still think that a @parameter macro would be very helpful to users, at least in POI.

[blegat]

@odow The way you write it is exactly the model after bridging Thinking more about it, I think the behavior makes sense. There could also be only part of the matrices that are set to parameters in which case what is done currently is definitely right.