Don't delete on free---DeleteVisitor() in FFN will do that.

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

@@ -72,11 +72,6 @@ class GRU
       const size_t outSize,
       const size_t rho = std::numeric_limits<size_t>::max());
 
-  /**
-   * Delete the GRU and the layers it holds.
-   */
-  ~GRU();
-
   /**
    * Ordinary feed forward pass of a neural network, evaluating the function
    * f(x) by propagating the activity forward through f.

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

@@ -76,17 +76,6 @@ GRU<InputDataType, OutputDataType>::GRU(
   gradIterator = outParameter.end();
 }
 
-template<typename InputDataType, typename OutputDataType>
-GRU<InputDataType, OutputDataType>::~GRU()
-{
-  boost::apply_visitor(deleteVisitor, input2GateModule);
-  boost::apply_visitor(deleteVisitor, output2GateModule);
-  boost::apply_visitor(deleteVisitor, outputHidden2GateModule);
-  boost::apply_visitor(deleteVisitor, inputGateModule);
-  boost::apply_visitor(deleteVisitor, forgetGateModule);
-  boost::apply_visitor(deleteVisitor, hiddenStateModule);
-}
-
 template<typename InputDataType, typename OutputDataType>
 template<typename eT>
 void GRU<InputDataType, OutputDataType>::Forward(