id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
3306	Bug in serializing MPI datatypes/classes with arrays	jayesh@…	Matthias Troyer	"Hi,
 We received a bug report from a user using BOOST_MPI + MPICH2 on windows. On further investigation we found that the bug seems to be in the boost MPI serialization code. The code in 1.39.0 does not handle serialization of arrays (for MPI datatypes) correctly. The following change in the boost header file ""boost\mpi\detail\mpi_datatype_primitive.hpp"" is required for programs that serialize arrays to behave correctly. The fix below is a *quick-fix*. You can integrate the following patch or fix the bug *correctly*. I replaced the save_array() member function (line 61-66 in mpi_datatype_primitive.hpp @ 1.39.0) with the code below to get my test case working, 

{{{

    // fast saving of arrays of MPI types
    template<class T>
    void save_array(serialization::array<T> const& x, unsigned int /* version */)
    {
      BOOST_ASSERT (addresses.size() > 0);
      BOOST_ASSERT (types.size() > 0);
      BOOST_ASSERT (lengths.size() > 0);
      // We don't need the array size. Pop it !
      addresses.pop_back();
      types.pop_back();
      lengths.pop_back();

      if (x.count())
        save_impl(x.address(), boost::mpi::get_mpi_datatype(*x.address()), x.count());
    }

}}}

 I used the code below (Run it with 1 MPI process, mpiexec -n 1 foo.exe) for my testing, 

{{{

 #include <iostream>
 #include <boost/mpi/environment.hpp>
 #include <boost/mpi/communicator.hpp>

 #include <boost/serialization/array.hpp>
 #include <boost/serialization/base_object.hpp>
 #include <boost/serialization/utility.hpp>
 
 using namespace std;
 namespace mpi = boost::mpi;

 class TFoo
 {
private: 
    friend class boost::serialization::access;

    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & a_;
        ar & d_;
        ar & f_;
        ar & foo_arr;
    }

    int      a_;
    double   d_;
    float    f_;
    int      foo_arr[5];
 public:
     TFoo(): a_(0), d_(0.0),f_(0.0){
         for(int i=0; i<5; i++){
             foo_arr[i] = i;
         }
     }
     TFoo(int a, double d, float f): a_(a),d_(d),f_(f){
         for(int i=0; i<5; i++){
             foo_arr[i] = i;
         }
     }
     TFoo(const TFoo &foo){
         a_ = foo.a_;
         d_ = foo.d_;
         f_ = foo.f_;
         for(int i=0; i<5; i++){
             foo_arr[i] = foo.foo_arr[i];
         }
     }
     void print(void ){
         std::cout << a_ << "" , "" << d_ << "" , "" << f_ << endl;
         for(int i=0; i<5; i++){
             std::cout << foo_arr[i] << "" , "";
         }
         std::cout << std::endl;
     }
     void printAddresses(void){
         std::cout << &a_ << "" , "" << &d_ << "" , "" << &f_ << endl;
     }
 };

BOOST_IS_MPI_DATATYPE(TFoo)

 class TBar
 {
private: 
    friend class boost::serialization::access;

    int  h_[2];
    TFoo q_[2];

    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & h_;
        ar & q_;
    }
 public:
     TBar(){
         h_[0] = 0; h_[1] = 0;
     }
     TBar(int h_0, int h_1, TFoo q_0, TFoo q_1){
         h_[0] = h_0;
         h_[1] = h_1;
         q_[0] = q_0;
         q_[1] = q_1;
     }
     void print(void ){
         cout << h_[0] << "" , "" << h_[1] << endl;
         q_[0].print(); q_[1].print();
     }
     void printAddresses(void ){
         std::cout << "" &h_ = "" << &h_ << "" &q_ = "" << &q_  << std::endl;
         std::cout << &h_[0] << "" , "" << &h_[1] << std::endl;
         q_[0].printAddresses(); q_[1].printAddresses();
     }
 };

BOOST_IS_MPI_DATATYPE(TBar)

 int main(int argc, char* argv[])
 {
    int i=0;
    mpi::environment env(argc, argv);
    mpi::communicator world;
    std::cout << ""I am process "" << world.rank() << "" of "" << world.size()
              << ""."" << std::endl;

    TFoo foo(1234, 3.14, 3.14f);
    TFoo foo_next(5678, 4.12, 4.12f);
    TBar bar(1234, 1234, foo, foo_next);

    try{
        if (world.rank() == 0)
        {
            TFoo foo1;
            TBar bar1;

            world.isend(0, 0, foo);//AV here!!!
            world.isend(0, 0, bar);//AV here!!!

            world.recv(0, 0, foo1);
            world.recv(0, 0, bar1);
            std::cout << ""FOO ======================"" << std::endl;
            foo1.print();
            std::cout << ""BAR ======================"" << std::endl;
            bar1.print();
        }
    }catch(mpi::exception &exception){
        cout << ""Error :"" << exception.what();
    }

    return 0;
 }

}}}

 We recommended the user to contact BOOST MPI devs regarding the *correct* fix.

Regards,

Jayesh Krishna
MPICH2 team
"	Bugs	closed	Boost 1.40.0	mpi	Boost 1.39.0	Problem	fixed