There is a bug in serialization which becomes apparent on 64-bit machines, such as an AMD Opteron: /asgard/home/phys/troyer/src/boost/boost/archive/ polymorphic_oarchive.hpp:66: error: `virtual void boost::archive::polymorphic_oarchive::save(int64_t)' and `virtual void boost::archive::polymorphic_oarchive::save(long int)' cannot be overloaded /asgard/home/phys/troyer/src/boost/boost/archive/ polymorphic_oarchive.hpp:67: error: `virtual void boost::archive::polymorphic_oarchive::save(uint64_t)' and `virtual void boost::archive::polymorphic_oarchive::save(long unsigned int)' cannot be overloaded long and int64_t are the same when using the gcc compiler on a 64-bit machine and this overload fails. Matthias