Fixing issues from @zoq's review

src/mlpack/core/optimizers/sgd/sgd.hpp

@@ -146,7 +146,7 @@ class SGD
   bool& ResetPolicy() { return resetPolicy; }
 
   //! Get the update policy.
-  UpdatePolicyType UpdatePolicy() const { return updatePolicy; }
+  const UpdatePolicyType& UpdatePolicy() const { return updatePolicy; }
   //! Modify the update policy.
   UpdatePolicyType& UpdatePolicy() { return updatePolicy; }
 

src/mlpack/methods/ann/layer/cross_entropy_error_impl.hpp

@@ -47,10 +47,10 @@ void CrossEntropyError<InputDataType, OutputDataType>::Backward(
 template<typename InputDataType, typename OutputDataType>
 template<typename Archive>
 void CrossEntropyError<InputDataType, OutputDataType>::Serialize(
-    Archive& /* ar */,
+    Archive& ar,
     const unsigned int /* version */)
 {
-  // Nothing to do here.
+  ar & data::CreateNVP(eps, "eps");
 }
 
 } // namespace ann