Fix serialization.

src/mlpack/core/dists/discrete_distribution.hpp

@@ -205,8 +205,24 @@ class DiscreteDistribution
   template<typename Archive>
   void Serialize(Archive& ar, const unsigned int /* version */)
   {
-    // We only need to save the probabilities, since that's all we hold.
-    ar & data::CreateNVP(probabilities, "probabilities");
+    // We serialize the vector manually since there seem to be some problems
+    // with some boost versions.
+    size_t dimensionality;
+    dimensionality = probabilities.size();
+    ar & data::CreateNVP(dimensionality, "dimensionality");
+
+    if (Archive::is_loading::value)
+    {
+      probabilities.clear();
+      probabilities.resize(dimensionality);
+    }
+
+    for (size_t i = 0; i < dimensionality; ++i)
+    {
+      std::ostringstream oss;
+      oss << "probabilities" << i;
+      ar & data::CreateNVP(probabilities[i], oss.str());
+    }
   }
 
  private: