Fix get RelativeGap when problem is not a mixed-integer problem (#421)

odow · web-flow · commit 636daf2e4fed · 2023-02-14T17:05:43.000+13:00
diff --git a/src/MOI/MOI_wrapper.jl b/src/MOI/MOI_wrapper.jl
@@ -3206,6 +3206,9 @@ function MOI.get(model::Optimizer, attr::MOI.RelativeGap)
     _throw_if_optimize_in_progress(model, attr)
     p = Ref{Cdouble}()
     ret = CPXgetmiprelgap(model.env, model.lp, p)
+    if ret == CPXERR_NOT_MIP
+        throw(MOI.GetAttributeNotAllowed(attr, "Not a mixed-integer problem."))
+    end
     _check_ret(model, ret)
     return p[]
 end
diff --git a/test/MathOptInterface/MOI_wrapper.jl b/test/MathOptInterface/MOI_wrapper.jl
@@ -216,6 +216,15 @@ function test_PassNames()
     return
 end
 
+function test_relative_gap_GetAttributeNotAllowed()
+    model = CPLEX.Optimizer()
+    x = MOI.add_variable(model)
+    MOI.add_constraint(model, x, MOI.GreaterThan(1.0))
+    MOI.optimize!(model)
+    @test_throws MOI.GetAttributeNotAllowed MOI.get(model, MOI.RelativeGap())
+    return
+end
+
 end  # module TestMOIwrapper
 
 TestMOIwrapper.runtests()
