Fix check for NumVars when there is a ScalarNonlinearFunction (#633)

Author: odow

src/MOI_wrapper/MOI_multi_objective.jl

@@ -29,7 +29,11 @@ function MOI.set(
     attr::MultiObjectiveFunction,
     f::MOI.ScalarAffineFunction,
 )
-    num_vars = length(model.variable_info)
+    _update_if_necessary(model)
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    num_vars = pInt[]
     obj = zeros(Float64, num_vars)
     for term in f.terms
         column = _info(model, term.variable).column

src/MOI_wrapper/MOI_wrapper.jl

@@ -1201,7 +1201,11 @@ end
 ###
 
 function _zero_objective(model::Optimizer)
-    num_vars = length(model.variable_info)
+    _update_if_necessary(model)
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    num_vars = pInt[]
     obj = zeros(Float64, num_vars)
     ret = GRBdelq(model)
     _check_ret(model, ret)
@@ -1275,7 +1279,11 @@ function MOI.set(
         ret = GRBdelq(model)
         _check_ret(model, ret)
     end
-    num_vars = length(model.variable_info)
+    _update_if_necessary(model)
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    num_vars = pInt[]
     obj = zeros(Float64, num_vars)
     for term in f.terms
         obj[column(model, term.variable)] += term.coefficient
@@ -1292,9 +1300,13 @@ end
 
 function _get_affine_objective(model::Optimizer; is_multiobjective::Bool)
     _update_if_necessary(model)
-    dest = zeros(length(model.variable_info))
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    num_vars = pInt[]
+    dest = zeros(num_vars)
     name = is_multiobjective ? "ObjN" : "Obj"
-    ret = GRBgetdblattrarray(model, name, 0, length(dest), dest)
+    ret = GRBgetdblattrarray(model, name, 0, num_vars, dest)
     _check_ret(model, ret)
     terms = MOI.ScalarAffineTerm{Float64}[]
     for (index, info) in model.variable_info
@@ -1330,7 +1342,11 @@ function MOI.set(
     affine_indices, affine_coefficients, I, J, V =
         _indices_and_coefficients(model, f)
     # We need to zero out any existing linear objective.
-    obj = zeros(length(model.variable_info))
+    _update_if_necessary(model)
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    obj = zeros(pInt[])
     for (i, c) in zip(affine_indices, affine_coefficients)
         obj[i+1] = c
     end
@@ -1354,8 +1370,12 @@ function MOI.get(
     ::MOI.ObjectiveFunction{MOI.ScalarQuadraticFunction{Float64}},
 )
     _update_if_necessary(model)
-    dest = zeros(length(model.variable_info))
-    ret = GRBgetdblattrarray(model, "Obj", 0, length(dest), dest)
+    pInt = Ref{Cint}(0)
+    ret = GRBgetintattr(model, "NumVars", pInt)
+    _check_ret(model, ret)
+    num_vars = pInt[]
+    dest = zeros(num_vars)
+    ret = GRBgetdblattrarray(model, "Obj", 0, num_vars, dest)
     _check_ret(model, ret)
     terms = MOI.ScalarAffineTerm{Float64}[]
     for (index, info) in model.variable_info
@@ -3448,6 +3468,7 @@ function MOI.set(model::Optimizer, attr::MOI.Name, name::String)
 end
 
 MOI.get(model::Optimizer, ::MOI.NumberOfVariables) = length(model.variable_info)
+
 function MOI.get(model::Optimizer, ::MOI.ListOfVariableIndices)
     return sort!(collect(keys(model.variable_info)), by = x -> x.value)
 end

test/MOI/MOI_wrapper.jl

@@ -1641,6 +1641,23 @@ function test_objbound_errors_when_GRB_INFINITY()
     return
 end
 
+function test_set_nonlinear_objective_twice()
+    if !Gurobi._supports_nonlinear()
+        return
+    end
+    model =
+        MOI.Bridges.full_bridge_optimizer(Gurobi.Optimizer(GRB_ENV), Float64)
+    MOI.set(model, MOI.Silent(), true)
+    x, _ = MOI.add_constrained_variable(model, MOI.Interval(2.0, 3.0))
+    MOI.set(model, MOI.ObjectiveSense(), MOI.MIN_SENSE)
+    f = MOI.ScalarNonlinearFunction(:exp, Any[x])
+    MOI.set(model, MOI.ObjectiveFunction{typeof(f)}(), f)
+    MOI.set(model, MOI.ObjectiveFunction{typeof(f)}(), f)
+    MOI.optimize!(model)
+    @test isapprox(MOI.get(model, MOI.ObjectiveValue()), exp(2.0); atol = 1e-4)
+    return
+end
+
 end  # TestMOIWrapper
 
 TestMOIWrapper.runtests()