Re: [boost] Confused about serialization

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-08-26 15:31:42

Hmm - this raises a couple of questions in my mind.  I would guess this is 
because I don't kow what the meserenne twister does.

First a slight cosmetic change just to avoid a confusing/ugly cast;

 template<class Archive>
 inline void save (Archive &ar, const unsigned int) const {
    for (int j = 0; j < state_size; ++j) {
        const UIntType x = compute (j);
        ar << boost::serialization::make_nvp("item", x);
    }
}

But I'm intrigued about one thing.  It seems to me that if you have an 
instance of the  class meserenne twister and serialize it to a file then 
load it back to another instance - the two wont be equal unless compute(j) 
== j ?

What am I missing here?

Neal Becker wrote:
> I think this is OK now.  Here is addition to mersenne_twister.hpp:
>  friend class boost::serialization::access;
>
>  template<class Archive>
>  inline void save (Archive &ar, const unsigned int) const {
>    for (int j = 0; j < state_size; ++j) {
>      UIntType x = compute (j);
>      ar << boost::serialization::make_nvp("item", const_cast<const
> UIntType&>(x));
>    }
>  }
>
>  template<class Archive>
>  inline void load (Archive &ar, const unsigned int) {
>    for (int j = 0; j < state_size; ++j) {
>      ar >> boost::serialization::make_nvp ("item", x[j]);
>    }
>    i = state_size;
>  }
>
>  template<class Archive>
>  void serialize(Archive & ar, const unsigned int file_version) {
>    boost::serialization::split_member(ar, *this, file_version);
>  }
>
> Also:
> #include <boost/serialization/split_member.hpp>
> #include <boost/serialization/nvp.hpp>
>
> Here is a simple test that passes:
>
> #include <boost/archive/text_oarchive.hpp>
> #include <boost/archive/text_iarchive.hpp>
> #include <boost/random.hpp>
>
> typedef  boost::mt19937 rng_t;
>
>
> int main() {
>  rng_t rng1;
>
>  std::ostringstream os;
>  boost::archive::text_oarchive oa(os);
>  oa << const_cast<const rng_t&>(rng1);
>
>  std::string st (os.str());
>  std::istringstream is (st);
>  boost::archive::text_iarchive ia (is);
>  rng_t rng2;
>  ia >> rng2;
>
>  //  std::cout << rng2;
>  assert (rng1 == rng2);
> }
>
>
> _______________________________________________
> Unsubscribe & other changes:
> http://lists.boost.org/mailman/listinfo.cgi/boost