add clear_model interface in fleetwrapper (PaddlePaddle#18815)

* dump slot

* test

* proto

* dump slot

* test

* proto

* code style

* code style

* code style

* style

* add delete after unseen days

* add unseen days

* code style

* conflict solve
test=develop

* add clear model

* code style
test=develop

* code style
test=develop

Author: Thunderbrook

paddle/fluid/framework/fleet/fleet_wrapper.cc

@@ -521,6 +521,15 @@ void FleetWrapper::ShrinkSparseTable(int table_id) {
 #endif
 }
 
+void FleetWrapper::ClearModel() {
+#ifdef PADDLE_WITH_PSLIB
+  auto ret = pslib_ptr_->_worker_ptr->clear();
+  ret.wait();
+#else
+  VLOG(0) << "FleetWrapper::ClearModel does nothing when no pslib";
+#endif
+}
+
 void FleetWrapper::ShrinkDenseTable(int table_id, Scope* scope,
                                     std::vector<std::string> var_list,
                                     float decay, int emb_dim) {

paddle/fluid/framework/fleet/fleet_wrapper.h

@@ -148,6 +148,7 @@ class FleetWrapper {
   // mode = 1, save delta feature, which means save diff
   void SaveModel(const std::string& path, const int mode);
 
+  void ClearModel();
   void ShrinkSparseTable(int table_id);
   void ShrinkDenseTable(int table_id, Scope* scope,
                         std::vector<std::string> var_list, float decay,

paddle/fluid/pybind/fleet_wrapper_py.cc

@@ -49,6 +49,7 @@ void BindFleetWrapper(py::module* m) {
       .def("init_model", &framework::FleetWrapper::PushDenseParamSync)
       .def("save_model", &framework::FleetWrapper::SaveModel)
       .def("load_model", &framework::FleetWrapper::LoadModel)
+      .def("clear_model", &framework::FleetWrapper::ClearModel)
       .def("stop_server", &framework::FleetWrapper::StopServer)
       .def("gather_servers", &framework::FleetWrapper::GatherServers)
       .def("gather_clients", &framework::FleetWrapper::GatherClients)

python/paddle/fluid/incubate/fleet/parameter_server/pslib/__init__.py

@@ -264,6 +264,21 @@ def shrink_dense_table(self, decay, emb_dim=11, scope=None, table_id=None):
                                                    decay, emb_dim)
         self._role_maker._barrier_worker()
 
+    def clear_model(self):
+        """
+        clear_model() will be called by user. It will clear sparse model.
+
+        Examples:
+            .. code-block:: python
+
+              fleet.clear_model()
+
+        """
+        self._role_maker._barrier_worker()
+        if self._role_maker.is_first_worker():
+            self._fleet_ptr.clear_model()
+        self._role_maker._barrier_worker()
+
     def load_one_table(self, table_id, model_path, **kwargs):
         """
         load pslib model for one table or load params from paddle model