Hi,I’m a beginner with JuMP and have some problems using the IPOPT solver.

When using the IPOPT solver, there is no way to create an integer variable, an error occurs.

Can someone help me？？？Thanks a lot.

using JuMP

using Ipopt

model = Model(Ipopt.Optimizer)

@variable(model, z , Int)

LoadError: `MOI.SingleVariable`

-in-`MOI.Integer`

constraints are not supported and cannot be bridged into supported constrained variables and constraints. See details below:

[1] constrained variables in `MOI.Integer`

are not supported because no added bridge supports bridging it.

Cannot add free variables and then constrain them because:

(1) `MOI.SingleVariable`

-in-`MOI.Integer`

constraints are not supported

(1) `MOI.SingleVariable`

-in-`MOI.Integer`

constraints are not supported because:

Cannot use `MOIB.Constraint.ScalarFunctionizeBridge{Float64,MOI.Integer}`

because:

(2) `MOI.ScalarAffineFunction{Float64}`

-in-`MOI.Integer`

constraints are not supported

(2) `MOI.ScalarAffineFunction{Float64}`

-in-`MOI.Integer`

constraints are not supported because:

Cannot use `MOIB.Constraint.ScalarSlackBridge{Float64,MOI.ScalarAffineFunction{Float64},MOI.Integer}`

because:

[1] constrained variables in `MOI.Integer`

are not supported