fix bug

test=develop

python/paddle/fluid/trainer_desc.py

@@ -78,7 +78,7 @@ class MultiTrainer(TrainerDesc):
     def _gen_trainer_desc(self):
         super(MultiTrainer, self)._gen_trainer_desc()
         self.proto_desc.class_name = "MultiTrainer"
-        self._device_worker._set_infer(self.infer_)
+        self._device_worker._set_infer(self._infer)
         self._device_worker._gen_worker_desc(self.proto_desc)
 
 
@@ -96,6 +96,6 @@ class DistMultiTrainer(TrainerDesc):
         self.proto_desc.class_name = "DistMultiTrainer"
         if self._program == None:
             raise RuntimeError("None Program")
-        self._device_worker._set_infer(self.infer_)
-        self._device_worker._set_program(self.program_)
+        self._device_worker._set_infer(self._infer)
+        self._device_worker._set_program(self._program)
         self._device_worker._gen_worker_desc(self.proto_desc)