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

20 Oct 2011


      on Wed Oct 19 2011, Matthias Troyer  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 
#include 
#include 
#include 
int
main( int argc, char * argv [] )
{
  boost::mpi::environment env(argc, argv);
  boost::mpi::communicator world;
if(world.rank()==0){
      std::mapstd::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::mapstd::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?

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com