Re: [Boost-users] [mpi/serialization] Potential bug or just library misunderstanding?

Subject: Re: [Boost-users] [mpi/serialization] Potential bug or just library misunderstanding?
From: Matthias Troyer (troyer_at_[hidden])
Date: 2011-11-10 18:00:23

On Oct 20, 2011, at 4:36 PM, Dave Abrahams wrote:

> 
> on Wed Oct 19 2011, Matthias Troyer <troyer-AT-phys.ethz.ch> wrote:
> 
>> On Sep 30, 2011, at 5:18 PM, Tim Jacobs wrote:
>> 
>>> I'm not sure why the following test-class produces this error:
>>> "MPI_Recv: MPI_ERR_TRUNCATE: message truncated"
>>> 
>>> If the std::map has only a single element (ie I remove one of the
>>> test[].push_back() lines) the error does not occur. Can someone
>>> verify that this is indeed a bug and not just novice misuse of the
>>> library?
>>> 
>>> Thanks,
>>> Tim
>>> 
>>> #include <boost/mpi.hpp>
>>> #include <boost/serialization/string.hpp>
>>> #include <boost/serialization/vector.hpp>
>>> #include <boost/serialization/map.hpp>
>>> 
>>> int
>>> main( int argc, char * argv [] )
>>> {
>>>  boost::mpi::environment env(argc, argv);
>>>  boost::mpi::communicator world;
>>> 
>>>  if(world.rank()==0){
>>>      std::map<int, std::vector<std::string> > test;
>>>      test[1].push_back("FOO");
>>>      test[50].push_back("BAR");
>>>      world.send(1, 1, boost::mpi::skeleton(test));
>>>      world.send(1, 1, boost::mpi::get_content(test));
>>>      std::cout << "sent" << std::endl;
>>>  }
>>>  else{
>>>      std::map<int, std::vector<std::string> > test;
>>>      world.recv(0,1,boost::mpi::skeleton(test));
>>>      world.recv(0,1,boost::mpi::get_content(test));
>>>  }
>>> }
>> 
>> The problem is that a std::map cannot be sent using the
>> skeleton&content approach, since the keys need to be known to build a
>> map.
> 
> I think, at least in principle, it should be possible to send a map that
> way *if* the keys never change... right?

Yes, in principle such a support could be added, but it would need a special serializition function for std::map

Matthias