Add support for getting objective

Author: odow

src/MOI_wrapper/MOI_multi_objective.jl

@@ -138,6 +138,21 @@ function MOI.set(
     return
 end
 
+function MOI.get(
+    model::Optimizer,
+    ::MOI.ObjectiveFunction{MOI.VectorAffineFunction{Float64}},
+)
+    env = GRBgetenv(model)
+    F = MOI.ScalarAffineFunction{Float64}
+    f = F[]
+    for i in 1:MOI.get(model, NumberOfObjectives())
+        ret = GRBsetintparam(env, "ObjNumber", i - 1)
+        _check_ret(env, ret)
+        push!(f, _get_affine_objective(model; is_multiobjective = true))
+    end
+    return MOI.Utilities.operate(vcat, Float64, f...)
+end
+
 function MOI.supports(
     model::Optimizer,
     ::MOI.ObjectiveFunction{MOI.VectorAffineFunction{Float64}},

src/MOI_wrapper/MOI_wrapper.jl

@@ -1150,19 +1150,11 @@ function MOI.set(
     return
 end
 
-function MOI.get(
-    model::Optimizer,
-    ::MOI.ObjectiveFunction{MOI.ScalarAffineFunction{Float64}},
-)
-    if model.objective_type == _SCALAR_QUADRATIC
-        error(
-            "Unable to get objective function. Currently: " *
-            "$(model.objective_type).",
-        )
-    end
+function _get_affine_objective(model::Optimizer; is_multiobjective::Bool)
     _update_if_necessary(model)
     dest = zeros(length(model.variable_info))
-    ret = GRBgetdblattrarray(model, "Obj", 0, length(dest), dest)
+    name = is_multiobjective ? "ObjN" : "Obj"
+    ret = GRBgetdblattrarray(model, name, 0, length(dest), dest)
     _check_ret(model, ret)
     terms = MOI.ScalarAffineTerm{Float64}[]
     for (index, info) in model.variable_info
@@ -1171,11 +1163,25 @@ function MOI.get(
         push!(terms, MOI.ScalarAffineTerm(coefficient, index))
     end
     constant = Ref{Cdouble}()
-    ret = GRBgetdblattr(model, "ObjCon", constant)
+    name = is_multiobjective ? "ObjNCon" : "ObjCon"
+    ret = GRBgetdblattr(model, name, constant)
     _check_ret(model, ret)
     return MOI.ScalarAffineFunction(terms, constant[])
 end
 
+function MOI.get(
+    model::Optimizer,
+    ::MOI.ObjectiveFunction{MOI.ScalarAffineFunction{Float64}},
+)
+    if model.objective_type == _SCALAR_QUADRATIC
+        error(
+            "Unable to get objective function. Currently: " *
+            "$(model.objective_type).",
+        )
+    end
+    return _get_affine_objective(model; is_multiobjective = false)
+end
+
 function MOI.set(
     model::Optimizer,
     ::MOI.ObjectiveFunction{F},