[KNITRO] Add support for retrieving variable domain (metab0t#81)

* feat: add get_variable_domain method to KNITRO.

* feat: add variable domain test

* doc: add variable domain get.

Author: eminyouskn

docs/source/attribute/knitro.md

@@ -83,7 +83,7 @@
     - ✅
     - ✅
 *   - Domain
-    - ❌
+    - ✅
     - ✅
 *   - PrimalStart
     - ❌

include/pyoptinterface/knitro_model.hpp

@@ -22,16 +22,15 @@
 	B(KN_new);                          \
 	B(KN_free);                         \
 	B(KN_update);                       \
+	B(KN_solve);                        \
 	B(KN_get_param_id);                 \
 	B(KN_get_param_type);               \
 	B(KN_set_int_param);                \
 	B(KN_set_char_param);               \
 	B(KN_set_double_param);             \
 	B(KN_get_int_param);                \
 	B(KN_get_double_param);             \
-	B(KN_add_vars);                     \
 	B(KN_add_var);                      \
-	B(KN_add_cons);                     \
 	B(KN_add_con);                      \
 	B(KN_set_var_lobnd);                \
 	B(KN_set_var_upbnd);                \
@@ -43,7 +42,6 @@
 	B(KN_get_var_name);                 \
 	B(KN_set_con_lobnd);                \
 	B(KN_set_con_upbnd);                \
-	B(KN_set_con_eqbnd);                \
 	B(KN_get_con_lobnd);                \
 	B(KN_get_con_upbnd);                \
 	B(KN_set_con_name);                 \
@@ -54,10 +52,8 @@
 	B(KN_add_obj_constant);             \
 	B(KN_del_obj_constant);             \
 	B(KN_add_obj_linear_struct);        \
-	B(KN_del_obj_linear_struct);        \
 	B(KN_del_obj_linear_struct_all);    \
 	B(KN_add_obj_quadratic_struct);     \
-	B(KN_del_obj_quadratic_struct);     \
 	B(KN_del_obj_quadratic_struct_all); \
 	B(KN_chg_obj_linear_term);          \
 	B(KN_add_con_constant);             \
@@ -71,7 +67,6 @@
 	B(KN_set_cb_grad);                  \
 	B(KN_set_cb_hess);                  \
 	B(KN_del_obj_eval_callback_all);    \
-	B(KN_solve);                        \
 	B(KN_get_var_primal_value);         \
 	B(KN_get_var_dual_value);           \
 	B(KN_get_con_value);                \
@@ -324,6 +319,21 @@ inline int knitro_var_type(VariableDomain domain)
 	}
 }
 
+inline VariableDomain knitro_variable_domain(int var_type)
+{
+	switch (var_type)
+	{
+	case KN_VARTYPE_CONTINUOUS:
+		return VariableDomain::Continuous;
+	case KN_VARTYPE_INTEGER:
+		return VariableDomain::Integer;
+	case KN_VARTYPE_BINARY:
+		return VariableDomain::Binary;
+	default:
+		throw std::runtime_error("Unknown variable type");
+	}
+}
+
 inline int knitro_obj_goal(ObjectiveSense sense)
 {
 	switch (sense)
@@ -423,6 +433,7 @@ class KNITROModel : public OnesideLinearConstraintMixin<KNITROModel>,
 	std::string get_variable_name(const VariableIndex &variable) const;
 	void set_variable_name(const VariableIndex &variable, const std::string &name);
 	void set_variable_domain(const VariableIndex &variable, VariableDomain domain);
+	VariableDomain get_variable_domain(const VariableIndex &variable) const;
 	double get_variable_rc(const VariableIndex &variable) const;
 	std::string pprint_variable(const VariableIndex &variable) const;
 

lib/knitro_model.cpp

@@ -290,6 +290,13 @@ void KNITROModel::set_variable_domain(const VariableIndex &variable, VariableDom
 	_mark_dirty();
 }
 
+VariableDomain KNITROModel::get_variable_domain(const VariableIndex &variable) const
+{
+	KNINT indexVar = _variable_index(variable);
+	int var_type = _get_value<KNINT, int>(knitro::KN_get_var_type, indexVar);
+	return knitro_variable_domain(var_type);
+}
+
 double KNITROModel::get_variable_rc(const VariableIndex &variable) const
 {
 	_check_dirty();

lib/knitro_model_ext.cpp

@@ -64,6 +64,7 @@ NB_MODULE(knitro_model_ext, m)
 		BIND_F(get_variable_name)
 		BIND_F(set_variable_name)
 		BIND_F(set_variable_domain)
+		BIND_F(get_variable_domain)
 		BIND_F(get_variable_rc)
 		BIND_F(delete_variable)
 	    // clang-format on

src/pyoptinterface/_src/knitro.py

@@ -106,6 +106,7 @@ def autoload_library():
     VariableAttribute.LowerBound: lambda model, v: model.get_variable_lb(v),
     VariableAttribute.UpperBound: lambda model, v: model.get_variable_ub(v),
     VariableAttribute.Name: lambda model, v: model.get_variable_name(v),
+    VariableAttribute.Domain: lambda model, v: model.get_variable_domain(v),
     VariableAttribute.ReducedCost: lambda model, v: model.get_variable_rc(v),
 }
 

tests/test_knitro.py

@@ -484,20 +484,32 @@ def test_variable_attribute_primal_start():
 
 
 def test_variable_attribute_domain():
-    """Test setting variable domain."""
+    """Test getting and setting variable domain."""
     model = knitro.Model()
     x = model.add_variable(lb=0.0, ub=10.0)
 
+    # Default domain should be Continuous
+    domain = model.get_variable_attribute(x, poi.VariableAttribute.Domain)
+    assert domain == poi.VariableDomain.Continuous
+
+    # Set to Integer and verify
     model.set_variable_attribute(
         x, poi.VariableAttribute.Domain, poi.VariableDomain.Integer
     )
+    domain = model.get_variable_attribute(x, poi.VariableAttribute.Domain)
+    assert domain == poi.VariableDomain.Integer
 
     model.set_objective(x, poi.ObjectiveSense.Minimize)
     model.add_linear_constraint(x, poi.ConstraintSense.GreaterEqual, 2.5)
     model.optimize()
 
     assert model.get_value(x) == approx(3.0)
 
+    # Test Binary domain
+    y = model.add_variable(domain=poi.VariableDomain.Binary)
+    domain = model.get_variable_attribute(y, poi.VariableAttribute.Domain)
+    assert domain == poi.VariableDomain.Binary
+
 
 def test_constraint_attribute_name():
     """Test getting and setting constraint name."""