Update

Author: odow

ext/KNITROMathOptInterfaceExt.jl

@@ -676,14 +676,18 @@ end
 
 function MOI.add_constraint(model::Optimizer, x::MOI.VariableIndex, ::MOI.ZeroOne)
     MOI.throw_if_not_valid(model, x)
-    lb, ub = nothing, nothing
+    fx, lb, ub = nothing, nothing, nothing
     p = Ref{Cdouble}(NaN)
     info = model.variable_info[x.value]
-    if info.has_lower_bound || info.is_fixed
+    if info.is_fixed
+        KNITRO.@_checked KNITRO.KN_get_var_fxbnd(model.inner, _c_column(x), p)
+        fx = p[]
+    end
+    if info.has_lower_bound
         KNITRO.@_checked KNITRO.KN_get_var_lobnd(model.inner, _c_column(x), p)
         lb = max(0.0, p[])
     end
-    if info.has_upper_bound || info.is_fixed
+    if info.has_upper_bound
         KNITRO.@_checked KNITRO.KN_get_var_upbnd(model.inner, _c_column(x), p)
         ub = min(1.0, p[])
     end
@@ -694,6 +698,9 @@ function MOI.add_constraint(model::Optimizer, x::MOI.VariableIndex, ::MOI.ZeroOn
     )
     # Calling `set_var_type` resets variable bounds in KNITRO. To fix, we need
     # to restore them after calling `set_var_type`.
+    if fx !== nothing
+        KNITRO.@_checked KNITRO.KN_set_var_fxbnd(model.inner, _c_column(x), fx)
+    end
     if lb !== nothing
         KNITRO.@_checked KNITRO.KN_set_var_lobnd(model.inner, _c_column(x), lb)
     end

test/MOI_wrapper.jl

@@ -65,8 +65,6 @@ function test_MOI_Test_cached()
         model,
         config;
         exclude=Union{String,Regex}[
-            # TODO(odow): this fails in Linux and Windows
-            r"^test_linear_Semiinteger_integration$",
             # This is an upstream issue in MOI with bridges and support
             # comparing VectorNonlinear and VectorQuadratic
             r"^test_basic_VectorNonlinearFunction_GeometricMeanCone$",