diff --git a/dnn/scripts/gen_flatbuffers_schema.py b/dnn/scripts/gen_flatbuffers_schema.py
index 3c43561b4f80a1902b539a17219764c01036fba6..9794c7565e899f19726f7411b80d40ecbaa54bc5 100755
--- a/dnn/scripts/gen_flatbuffers_schema.py
+++ b/dnn/scripts/gen_flatbuffers_schema.py
@@ -52,14 +52,11 @@ class FlatBuffersWriter(IndentWriterBase):
             name = p + e
             e = self._enums[(p, e)]
             self._write_doc(e.name)
-            self._write("enum %s%s : uint {", p, e.name, indent=1)
+            attribute = "(bit_flags)" if e.combined else ""
+            self._write("enum %s%s : uint %s {", p, e.name, attribute, indent=1)
             for idx, member in enumerate(e.members):
                 self._write_doc(member)
-                if e.combined:
-                    self._write("%s=%d,", scramble_enum_member_name(str(member)),
-                            1<<idx)
-                else:
-                    self._write("%s,", scramble_enum_member_name(str(member)))
+                self._write("%s,", scramble_enum_member_name(str(member)))
             self._write("}\n", indent=-1)
 
     def _write_doc(self, doc):
@@ -97,8 +94,11 @@ class FlatBuffersWriter(IndentWriterBase):
             return
         self._write_doc(e.name)
         self._used_enum.add(key)
-        self._write("%s:%s%s = %s;", e.name_field, p.name, e.name,
-                    scramble_enum_member_name(str(e.members[e.default])))
+        if e.combined:
+            default = e.compose_combined_enum(e.default)
+        else:
+            default = scramble_enum_member_name(str(e.members[e.default]))
+        self._write("%s:%s%s = %s;", e.name_field, p.name, e.name, default)
 
     def _resolve_const(self, v):
         while v in self._cur_const_val:
@@ -120,9 +120,12 @@ class FlatBuffersWriter(IndentWriterBase):
             return
         self._used_enum.add((e.src_class, e.src_name))
         enum_name = e.src_class + e.src_name
-        self._write(
-            "%s:%s = %s;", e.name_field, enum_name,
-            scramble_enum_member_name(str(e.src_enum.members[e.get_default()])))
+        s = e.src_enum
+        if s.combined:
+            default = s.compose_combined_enum(e.get_default())
+        else:
+            default = scramble_enum_member_name(str(s.members[e.get_default()]))
+        self._write("%s:%s = %s;", e.name_field, enum_name, default)
 
     def _get_fb_default(self, cppdefault):
         if not isinstance(cppdefault, str):
diff --git a/dnn/scripts/gen_param_defs.py b/dnn/scripts/gen_param_defs.py
index 47f58af04ca5c1512cf81abd2a6ffb106d63850f..dff1cc85cb82429e1b40b71f08e08af40e60441a 100755
--- a/dnn/scripts/gen_param_defs.py
+++ b/dnn/scripts/gen_param_defs.py
@@ -73,11 +73,21 @@ class member_defs:
         """define an enum; the result would contain both an enum class def and its
         corresponding data field
 
-        :param default: index of default member value
+        :param default:
+            for normal enum class: index of default member value
+            for bit combined class: tuple of index of default member value
+
+            For example, following representations of the default value for bit
+            combined class are all equivalent:
+                Enum(members=('a', 'b', 'c'), default=('a', 'b'), ...)
+                Enum(members=('a', 'b', 'c'), default=(0, 1), ...)
+                Enum(members=('a', 'b', 'c'), default=(1 << 0) | (1 << 1), ...)
 
         :attr name_field: name of the data field of this enum in the param
             struct
-        :attr member_alias: list of (member, alias) pairs
+        :attr member_alias:
+            for normal enum class: list of (member, alias) pairs
+            for bit combined class: list of (tuple of members, alias) paris
         """
         __slots__ = ['name', 'name_field', 'members', 'default',
                      'member_alias', 'combined']
@@ -90,17 +100,11 @@ class member_defs:
             name = member_defs.Doc.make(name)
             assert name.id[0].isupper()
             members = tuple(map(member_defs.Doc.make, members))
-            if isinstance(default, str):
-                if default not in name_field:
-                    raise ValueError(
-                        "Default value '{}' does not exist.".format(default))
-                default = name_field.index(default)
-            assert isinstance(default, int)
             self.name = name
             self.combined = combined
             self.name_field = self.get_name_field(name.id, name_field)
             self.members = members
-            self.default = default
+            self.default = self.normalize_enum_value(default)
 
             self.all_enums[(param_name, name.id)] = self
 
@@ -114,6 +118,43 @@ class member_defs:
             assert isinstance(name_field, str)
             return name_field
 
+        def normalize_enum_value(self, value):
+            def normalize(v):
+                if isinstance(v, str):
+                    if v not in self.members:
+                        raise ValueError(
+                            "enum member '{}' does not exist.".format(v))
+                    v = self.members.index(v)
+                assert isinstance(v, int)
+                return v
+            if self.combined:
+                if isinstance(value, int):
+                    value = self.decompose_combined_enum(value)
+                assert isinstance(value, tuple)
+                value = tuple(normalize(i) for i in value)
+                return value
+            else:
+                return normalize(value)
+
+        @staticmethod
+        def decompose_combined_enum(v):
+            """Integer => tuple of the indexes of the enum members"""
+            assert isinstance(v, int)
+            idx = 0
+            members = []
+            while v > 0:
+                if v & 1:
+                    members.append(idx)
+                idx += 1
+                v >>= 1
+            return tuple(members)
+
+        def compose_combined_enum(self, v):
+            """tuple of members => Integer"""
+            assert self.combined and isinstance(v, tuple)
+            norm_v = self.normalize_enum_value(v)
+            return sum(1 << i for i in norm_v)
+
     class Field(Base):
         """define a normal data field"""
         __slots__ = ['name', 'dtype', 'default']
@@ -146,6 +187,10 @@ class member_defs:
                 src_name = name
             self.src_name = src_name
             self.default = default
+            # TODO: remove this assertion if needed; adding mock param_defs in
+            # current testing framework is too complicated, and currently we
+            # only allow aliasing of normal enum
+            assert not self.src_enum.combined
 
         @property
         def src_enum(self):
@@ -157,7 +202,7 @@ class member_defs:
             set"""
             if self.default is None:
                 return self.src_enum.default
-            return self.default
+            return self.src_enum.normalize_enum_value(self.default)
 
 
 class ParamDef:
@@ -198,7 +243,7 @@ class ParamDef:
             self.name.id, name, name_field, members, default, member_alias))
         return self
 
-    def add_bit_combination_enum(self, name, *members, default=0,
+    def add_bit_combination_enum(self, name, *members, default=tuple(),
                  name_field=None, member_alias=[]):
         self.members.append(member_defs.Enum(
             self.name.id, name, name_field, members, default, member_alias, True))
@@ -322,11 +367,13 @@ class PyWriter(IndentWriterBase):
             '       for idx, v in enumerate(pdata):\n'
             '           if isinstance(v, _EnumBase):\n'
             '               pdata[idx] = _enum_member2num[id(v)]\n'
+            '           elif isinstance(v, _BitCombinedEnumBase):\n'
+            '               pdata[idx] = v._value_\n'
             '       return tag + self._packer.pack(*pdata)\n'
             '\n'
         )
-        self._write(
-            'class _EnumBase(enum.Enum):\n'
+        # it's hard to mix custom implemention into enum, just do copy-paste instead
+        classbody = (
             '   @classmethod\n'
             '   def __normalize(cls, val):\n'
             '       if isinstance(val, str):\n'
@@ -349,6 +396,12 @@ class PyWriter(IndentWriterBase):
             '       return super()._missing_(value)\n'
             '\n'
         )
+        self._write(
+            'class _EnumBase(enum.Enum):\n' + classbody
+        )
+        self._write(
+            'class _BitCombinedEnumBase(enum.Flag):\n' + classbody
+        )
         if not self._imperative:
             self._write(
                 'def _as_dtype_num(dtype):\n'
@@ -464,30 +517,42 @@ class SerializedDType(_ParamDefBase):
     def _on_member_enum(self, e):
         qualname = '{}.{}'.format(self._cur_param_name, e.name)
 
-        self._write('class %s(_EnumBase):', e.name, indent=1)
+        if e.combined:
+            self._write('class %s(_BitCombinedEnumBase):', e.name, indent=1)
+        else:
+            self._write('class %s(_EnumBase):', e.name, indent=1)
+
         self._write_doc(e.name)
 
         for idx, emem in enumerate(e.members):
-            self._write('%s = "%s"', emem, emem)
-            self._write_doc(emem)
             if e.combined:
-                self._enum_member2num.append('id({}.{}):{}'.format(
-                    qualname, emem, 1<<idx))
+                self._write('%s = 1 << %d', emem, idx)
+                self._write_doc(emem)
             else:
+                self._write('%s = "%s"', emem, emem)
+                self._write_doc(emem)
                 self._enum_member2num.append('id({}.{}):{}'.format(
                     qualname, emem, idx))
 
-        for emem, emem_alis in e.member_alias:
-            self._write('%s = %s', emem_alis, emem)
+        for emem, emem_alias in e.member_alias:
+            if e.combined:
+                self._write('%s = %s', emem_alias, e.compose_combined_enum(emem))
+            else:
+                self._write('%s = %s', emem_alias, emem)
 
         self._unindent()
         self._write('')
 
+        if e.combined:
+            default = e.compose_combined_enum(e.default)
+        else:
+            default = "'{}'".format(e.members[e.default])
+
         self._cur_fields.append(self.FieldDef(
             name=e.name_field,
             cvt='{}.convert({})'.format(qualname, e.name_field),
             fmt='I',
-            default="'{}'".format(e.members[e.default]),
+            default=default,
             type=qualname,
             doc=None))
 
@@ -495,11 +560,16 @@ class SerializedDType(_ParamDefBase):
         self._write('%s = %s.%s', e.name, e.src_class, e.src_name)
         s = e.src_enum
         qualname = '{}.{}'.format(e.src_class, e.src_name)
+
+        if s.combined:
+            default = s.compose_combined_enum(e.get_default())
+        else:
+            default = "'{}'".format(s.members[e.get_default()])
         self._cur_fields.append(self.FieldDef(
             name=e.name_field,
             cvt='{}.convert({})'.format(qualname, e.name_field),
             fmt='I',
-            default="'{}'".format(s.members[e.get_default()]),
+            default=default,
             type=qualname,
             doc=None))
 
@@ -639,14 +709,19 @@ class CPPWriter(IndentWriterBase):
                 v += ','
             self._write(v)
         for mem, alias in e.member_alias:
-            self._write('%s = %s,', alias, mem)
+            if e.combined:
+                self._write('%s = %s,', alias, e.compose_combined_enum(mem))
+            else:
+                self._write('%s = %s,', alias, mem)
         self._write('};', indent=-1)
         self._non_static_members.append(e)
         self._write('static MEGDNN_CONSTEXPR uint32_t %s_NR_MEMBER = %d;',
                     str(e.name).upper(), len(e.members))
-        self._add_ctor_args(e.name,
-                            '{}::{}'.format(e.name, e.members[e.default]),
-                            e.name_field)
+        if e.combined:
+            default = 'static_cast<{}>({})'.format(e.name, e.compose_combined_enum(e.default))
+        else:
+            default = '{}::{}'.format(e.name, e.members[e.default])
+        self._add_ctor_args(e.name, default, e.name_field)
 
     def _on_member_enum_alias(self, e):
         s = e.src_enum
@@ -654,10 +729,11 @@ class CPPWriter(IndentWriterBase):
         self._non_static_members.append(e)
         self._write('static MEGDNN_CONSTEXPR uint32_t %s_NR_MEMBER = %d;',
                     str(e.name).upper(), len(s.members))
-        self._add_ctor_args(e.name,
-                            '{}::{}'.format(e.name,
-                                            s.members[e.get_default()]),
-                            e.name_field)
+        if s.combined:
+            default = 'static_cast<{}>({})'.format(e.name, s.compose_combined_enum(e.default))
+        else:
+            default = '{}::{}'.format(e.name, s.members[e.get_default()])
+        self._add_ctor_args(e.name, default, e.name_field)
 
     def _on_member_field(self, f):
         self._non_static_members.append(f)
diff --git a/dnn/scripts/gen_tablegen.py b/dnn/scripts/gen_tablegen.py
index 8322058b9fc9f001752484595727d91d91be23e2..fa032c20e44c88ed30594efaefbe9935fa4bcf0b 100755
--- a/dnn/scripts/gen_tablegen.py
+++ b/dnn/scripts/gen_tablegen.py
@@ -106,7 +106,12 @@ class ConverterWriter(IndentWriterBase):
             return
 
         # wrapped with default value
-        default_val = "static_cast<{}::{}>({})".format(fullname, e.name, e.default)
+        if e.combined:
+            default_val = "static_cast<{}::{}>({})".format(
+                    fullname, e.name, e.compose_combined_enum(e.default))
+        else:
+            default_val = "{}::{}::{}".format(fullname, e.name, e.members[e.default])
+
         wrapped = self._wrapped_with_default_value(td_class, default_val)
 
         self._current_tparams.append("{}:${}".format(wrapped, e.name_field))
@@ -124,7 +129,13 @@ class ConverterWriter(IndentWriterBase):
         self._write("def {} : {};".format(td_class, enum_def))
 
         # wrapped with default value
-        default_val = "static_cast<{}::{}>({})".format(fullname, e.name, e.get_default())
+        s = e.src_enum
+        if s.combined:
+            default_val = "static_cast<{}::{}>({})".format(
+                    fullname, e.name, s.compose_combined_enum(e.get_default()))
+        else:
+            default_val = "{}::{}::{}".format(fullname, e.name, s.members[e.get_default()])
+
         wrapped = self._wrapped_with_default_value(td_class, default_val)
 
         self._current_tparams.append("{}:${}".format(wrapped, e.name_field))
diff --git a/imperative/python/src/ops.cpp b/imperative/python/src/ops.cpp
index 8eb2c5a9b726406c743e177dbbc7ee5ae1ac4974..f34975fcc50870f242dc0980f683a6924f997b91 100644
--- a/imperative/python/src/ops.cpp
+++ b/imperative/python/src/ops.cpp
@@ -87,9 +87,13 @@ struct pyobj_convert_generic {
     }
 };
 
+template<typename T, typename SFINAE=void>
+struct EnumTrait;
+
 template <typename T>
-struct EnumTrait {
+struct EnumTrait<T, std::enable_if_t<std::is_enum_v<T>>> {
     static constexpr bool is_bit_combined = false;
+    static constexpr std::underlying_type_t<T> max = 0;
 };
 
 template <typename T>
@@ -264,18 +268,25 @@ struct BitCombinedEnumWrapper {
             return ret;
         }
     }
-    static PyObject* py_new_combined_enum(PyTypeObject* type, PyObject*, PyObject*) {
-        PyObject* obj = type->tp_alloc(type, 0);
-        reinterpret_cast<BitCombinedEnumWrapper*>(obj)->value = static_cast<T>(1);
-        return obj;
-    }
-    static int py_init(PyObject* self, PyObject* args, PyObject*) {
-        int input = 1;
-        if (PyArg_ParseTuple(args, "|i", &input)){
-            reinterpret_cast<BitCombinedEnumWrapper*>(self)->value =
-                    static_cast<T>(input);
+    static PyObject* py_new_combined_enum(PyTypeObject* type, PyObject* args, PyObject*) {
+        if (!PyTuple_Size(args)) {
+            PyObject* obj = type->tp_alloc(type, 0);
+            reinterpret_cast<BitCombinedEnumWrapper*>(obj)->value = T();
+            return obj;
+        }
+        else {
+            PyObject* input;
+            if (!PyArg_ParseTuple(args, "|O", &input)) {
+                return nullptr;
+            }
+            T value;
+            try {
+                value = pyobj_convert_generic<T>::from(input);
+            } CATCH_ALL(nullptr);
+            PyObject* obj = type->tp_alloc(type, 0);
+            reinterpret_cast<BitCombinedEnumWrapper*>(obj)->value = value;
+            return obj;
         }
-        return 0;
     }
     static PyObject* py_repr(PyObject* self) {
         return pyobj_convert_generic<std::string>::to(
@@ -325,6 +336,12 @@ struct pyobj_convert_generic<T,
     static T from(PyObject* obj) {
         if (PyObject_TypeCheck(obj, &Wrapper::type)) {
             return reinterpret_cast<Wrapper*>(obj)->value;
+        } else if(PyLong_Check(obj)) {
+            auto value = pyobj_convert_generic<std::underlying_type_t<T>>::from(obj);
+            mgb_throw_if(value > EnumTrait<T>::max, mgb::MegBrainError,
+                    "out of range, cannot convert %zu to %s",
+                    static_cast<uint32_t>(value), Wrapper::name);
+            return static_cast<T>(value);
         }
         // try as string
         // TODO: type checkcd
diff --git a/imperative/tablegen/targets/python_c_extension.cpp b/imperative/tablegen/targets/python_c_extension.cpp
index 1de71a858a43684f14550c0cdbd30052e1f505f3..130962e0eb3886e97b60ee50510d7e04957d4410 100644
--- a/imperative/tablegen/targets/python_c_extension.cpp
+++ b/imperative/tablegen/targets/python_c_extension.cpp
@@ -90,10 +90,12 @@ void EnumAttrEmitter::emit_tpl_spl() {
                 "template<> PyNumberMethods "
                 "$enumTpl<$opClass::$enumClass>::number_methods={};\n",
                 &ctx);
-        os << tgfmt(
-                "template<> struct EnumTrait<$opClass::$enumClass> {  static constexpr "
-                "bool is_bit_combined = true;};\n",
-                &ctx);
+        os << tgfmt(R"(
+template<> struct EnumTrait<$opClass::$enumClass> {
+    static constexpr bool is_bit_combined = true;
+    static constexpr std::underlying_type_t<$opClass::$enumClass> max = (1llu << $0) - 1;
+};
+)", &ctx, attr->getEnumMembers().size());
     }
 
     auto str2type = [&](auto&& i) -> std::string {
@@ -138,7 +140,6 @@ void $0(PyTypeObject& py_type) {
             // others should always use singleton
             os << tgfmt(R"(
     e_type.tp_new = $enumTpl<$opClass::$enumClass>::py_new_combined_enum;
-    e_type.tp_init = $enumTpl<$opClass::$enumClass>::py_init;
     auto& number_method = $enumTpl<$opClass::$enumClass>::number_methods;
     number_method.nb_or = $enumTpl<$opClass::$enumClass>::py_or;
     number_method.nb_and = $enumTpl<$opClass::$enumClass>::py_and;
diff --git a/src/opr/impl/dnn/dnn.oprdecl b/src/opr/impl/dnn/dnn.oprdecl
index 16d6e3ff17c8b781156f468d83c8f96e8a24f033..c511ed496eee6eedc36ec75f3aba851bb5b60562 100644
--- a/src/opr/impl/dnn/dnn.oprdecl
+++ b/src/opr/impl/dnn/dnn.oprdecl
@@ -6,7 +6,7 @@ decl_opr('Convolution',
                      'convolution kernel in '
                      '(out channel, in channel, kern row, kern col) format')],
          params=[('param', 'ConvolutionV0'),
-                 ('execution_polity', 'ExecutionPolicy')],
+                 ('execution_polity', 'ExecutionPolicyV0')],
          desc='batched convolution on channeled 2D images')
 
 decl_opr('Convolution',
@@ -28,7 +28,7 @@ decl_opr('ConvolutionBackwardData',
                      'convolution kernel in '
                      '(out channel, in channel, kern row, kern col) format')],
          params=[('param', 'ConvolutionV0'),
-                 ('execution_polity', 'ExecutionPolicy')],
+                 ('execution_polity', 'ExecutionPolicyV0')],
          body=[
              'a, b = all_inputs',
              'all_inputs = [b, a]'
@@ -201,7 +201,7 @@ decl_opr('ConvBiasForward',
              Doc('bias', 'bias'),
          ],
          params=[('param', 'ConvBiasV1'),
-                 ('execution_policy', 'ExecutionPolicy')],
+                 ('execution_policy', 'ExecutionPolicyV0')],
          desc=('activation(convolution(src, filter) + bias) with specified '
                'dtype'),
          has_out_dtype=True)
diff --git a/tools/param_defs/mgb_opr_param_defs.py b/tools/param_defs/mgb_opr_param_defs.py
index d8fd2026e242be0a281a25c833590ec2cb314722..cd46edd2a82fba2b1e9b83335b14b040fee7c513 100644
--- a/tools/param_defs/mgb_opr_param_defs.py
+++ b/tools/param_defs/mgb_opr_param_defs.py
@@ -42,7 +42,12 @@ pdef('PersistentOutputStorage').add_fields(
               'when profile or heuristic algo selection it require the algos'
               'must be reproducible'),
           Doc('OPTMIZED',
-              'profile require algos are optmized to achieve fast-profile')).
+              'profile require algos are optmized to achieve fast-profile'),
+          default=('HEURISTIC',),
+          member_alias=[(('HEURISTIC', 'REPRODUCIBLE'), 'HEURISTIC_REPRODUCIBLE'),
+                        (('PROFILE', 'REPRODUCIBLE'), 'PROFILE_REPRODUCIBLE'),
+                        (('PROFILE', 'HEURISTIC'), 'PROFILE_HEURISTIC'),
+                        ]).
  add_fields('uint64',
             Doc('workspace_limit', 'workspace limit in bytes'),
             str(2**64-1)+'ull'))