#include <iostream>
#include <string>

#include <sys/utsname.h>

#include <boost/mpi.hpp>
#include <boost/optional.hpp>
#include <boost/serialization/access.hpp>
#include <boost/serialization/string.hpp>
namespace mpi = boost::mpi;


/// A very simple MPI message
class hello_msg {
  int rank_;
  std::string node_;
  std::string os_;
public:
  /// Ctor, using mpi::communicator instance to get rank no.
  hello_msg(const mpi::communicator& comm) {
    rank_ = comm.rank();
    // get nodename and os from uname(2)
    struct utsname uname_;
    uname(&uname_);
    node_ = uname_.nodename;
    os_ = uname_.sysname;
  };
  /// Default ctor, to use only just before serialization
  hello_msg() 
    : rank_(-1), node_("unknown"), os_("unknown")
  { };
  // print out the greeeting
  friend std::ostream& operator<< (std::ostream& o, hello_msg const& msg) {
    o << "Hello from MPI rank " << msg.rank_
      << " running on host " << msg.node_
      << " (" << msg.os_ <<")"
      << std::endl;
  };
protected:
  // provide serialization of this class, for MPI send/recv
  friend class boost::serialization::access;
  template<class Archive>
  void serialize(Archive& ar, const unsigned int version) {
    ar & rank_ & node_ & os_;
  };
};


int
main(int argc, char** argv)
{
  mpi::environment env(argc, argv);
  mpi::communicator world;

  // every MPI rank creates an "hello_msg" instance...
  hello_msg hello(world);

  // ...and sends it to rank 0
  world.send(0, 0, hello);
  
  // rank 0 prints out messages in the order they are received
  if (0 == world.rank()) {
    unsigned int n = world.size();
    while (n > 0) {
      mpi::status msg = world.probe();
      hello_msg greeting;
      world.recv(msg.source(), msg.tag(), greeting);
      std::cout << greeting;
      --n;
    };
  };

  return 0;
}