diff --git a/deepes/include/torch/es_agent.h b/deepes/include/torch/es_agent.h
index 76a456c3199a0c6fae78a04fad9a1841118ea723..486b74e207ac939c27339dd60ef9eb23ce2285b2 100644
--- a/deepes/include/torch/es_agent.h
+++ b/deepes/include/torch/es_agent.h
@@ -161,8 +161,17 @@ public:
   
 
 private:
-  std::shared_ptr<T> _sampling_model;
+  int64_t _calculate_param_size() {
+    auto params = _model->named_parameters();
+    for (auto& param: params) {
+      torch::Tensor tensor = param.value().view({-1});
+      _param_size += tensor.size(0);
+    }
+    return _param_size;
+  }
+
   std::shared_ptr<T> _model;
+  std::shared_ptr<T> _sampling_model;
   bool _is_sampling_agent;
   std::shared_ptr<SamplingMethod> _sampling_method;
   std::shared_ptr<Optimizer> _optimizer;
@@ -171,15 +180,6 @@ private:
   // malloc memory of noise and neg_gradients in advance.
   float* _noise;
   float* _neg_gradients;
-
-  int64_t _calculate_param_size() {
-    auto params = _model->named_parameters();
-    for (auto& param: params) {
-      torch::Tensor tensor = param.value().view({-1});
-      _param_size += tensor.size(0);
-    }
-    return _param_size;
-  }
 };
 
 }