Expose VarDesc::persistable to Python (#4911)

paddle/framework/var_desc.h

@@ -79,6 +79,10 @@ class VarDescBind {
 
   void SetType(VarDesc::VarType type) { desc_.set_type(type); }
 
+  bool Persistable() const { return desc_.persistable(); }
+
+  void SetPersistable(bool persistable) { desc_.set_persistable(persistable); }
+
  private:
   const TensorDesc &tensor_desc() const;
   TensorDesc *mutable_tensor_desc();

paddle/pybind/protobuf.cc

@@ -202,7 +202,8 @@ void BindVarDsec(py::module &m) {
       .def("set_lod_level", &VarDescBind::SetLoDLevel)
       .def("type", &VarDescBind::GetType)
       .def("set_type", &VarDescBind::SetType)
-      .def("serialize_to_string", [](VarDescBind &var_desc) -> py::bytes {
+      .def("serialize_to_string",
+           [](VarDescBind &var_desc) -> py::bytes {
              const VarDesc *desc = var_desc.Proto();
              PADDLE_ENFORCE(desc->IsInitialized(),
                             "VarDesc has not been initialized.");
@@ -211,7 +212,9 @@ void BindVarDsec(py::module &m) {
                  desc->SerializeToString(&res),
                  "Serialize VarDesc Error. This could be a bug of Paddle.");
              return res;
-      });
+           })
+      .def("persistable", &VarDescBind::Persistable)
+      .def("set_persistable", &VarDescBind::SetPersistable);
 
   py::enum_<VarDesc::VarType>(var_desc, "VarType", "")
       .value("LOD_TENSOR", VarDesc::LOD_TENSOR)

python/paddle/v2/framework/framework.py

@@ -15,6 +15,7 @@ class Variable(object):
                  shape=None,
                  dtype=None,
                  lod_level=None,
+                 persistable=False,
                  **kwargs):
         self.block = block
 
@@ -70,6 +71,17 @@ class Variable(object):
                                      "lod_level is {2}. They are not "
                                      "matched".format(self.name, self.lod_level,
                                                       lod_level))
+        if persistable is not None:
+            if is_new_var:
+                self.desc.set_persistable(persistable)
+            else:
+                if persistable != self.persistable:
+                    raise ValueError(
+                        "Variable {0} has been created before."
+                        "The previous persistable is {1}; the new "
+                        "persistable is {2}. They are not matched".format(
+                            self.name, self.persistable, persistable))
+
         self.block.vars[name] = self
         self.op = None
 
@@ -80,6 +92,10 @@ class Variable(object):
 
     __repr__ = __str__
 
+    @property
+    def persistable(self):
+        return self.desc.persistable()
+
     @property
     def name(self):
         return self.desc.name()
@@ -445,7 +461,9 @@ class Parameter(Variable):
             if each < 0:
                 raise ValueError("Parameter shape should not be related with "
                                  "batch-size")
-        Variable.__init__(self, block, shape=shape, dtype=dtype, **kwargs)
+
+        Variable.__init__(
+            self, block, persistable=True, shape=shape, dtype=dtype, **kwargs)
         self.trainable = kwargs.get('trainable', True)
         self.init_attr = kwargs.get('initialize_attr', {
             'type': 'uniform_random',