Re: [Boost-users] [mpi] - why this code hangs on gather?

Subject: Re: [Boost-users] [mpi] - why this code hangs on gather?
From: tomasz jankowski (tomasz_jacek_at_[hidden])
Date: 2009-10-28 06:04:15

Dnia 27-10-2009 o godz. 13:49 Matthieu Brucher napisa³(a):
> Hi,
> 
> If I understood your code correctly, you are sending every piece of
> data through rank 0 and then it waits for the completion of the
> operations. Then, every rank receives data, as well as the first rank.
> But the first rank is waiting for ots own receive to finish, which can
> never happen. You should put the wait all after the receptions.

at last I have found:

code done by rest of ranks (non 0) should be closed in brace parenthesis

> >  if( world.rank() == 0 ){
> >
> >    mpi::request reqs[nProcs-1];
> >
> >    for(unsigned int i=1;i<nProcs;++i){
> >      std::vector<molecule> sendmol;
> >        unsigned int pos=extraBits+i*chunkSize;
> >
> >      for(unsigned int j=0;j<chunkSize;++j){
> >        sendmol.push_back(data[pos]);
> >        pos++;
> >      }
> >
> >     reqs[i-1] = world.isend(i, 0, sendmol);
> >      std::cout<<"msg sended to "<< i <<std::endl;std::cout.flush();
> >    }
> >
> >    for(unsigned int i=0;i<chunkSize + extraBits;++i){
> >      molecule tmp = data[i];
> >      tmp.x_ *= uni_real();
> >      tmp.y_ *= uni_real();
> >      tmp.z_ *= uni_real();
> >      tmp.message_ = "from process: " +
> > boost::lexical_cast<std::string>(world.rank());
> >      res.push_back(tmp);
> >    }
> >
> >    mpi::wait_all(reqs, reqs + nProcs - 1);
> >    std::cout<<"calculation finished in 0 "<<std::endl;std::cout.flush();
> >
> >  }

//here should be
else{

> >
> >
> >
> >
> >   std::vector<molecule> recvmol;
> >   mpi::request recv;
> >   recv = world.irecv(0, 0, recvmol);
> >   recv.wait();
> >   std::cout<<"receiving finished
> > "<<world.rank()<<std::endl;std::cout.flush();
> >
> >
> >  for(unsigned int i=0;i<recvmol.size();++i){
> >    molecule tmp = recvmol[i];
> >    tmp.x_ *= uni_real();
> >    tmp.y_ *= uni_real();
> >    tmp.z_ *= uni_real();
> >    tmp.print();
> >    tmp.message_ =  "from process: " +
> > boost::lexical_cast<std::string>(world.rank());
> >    res.push_back(tmp);
> >  }
> >      std::cout<<"calculation finished in
> > "<<world.rank()<<std::endl;std::cout.flush();

//here block should be closed
}

> >  //wysylanie wynikow ze wszystkich procesow mpi do procesu 0
> >  if( world.rank() == 0 ){
> >    gather(world,res,allRes,0);
> >  std::cout<<"gather finished "<<world.rank()<<std::endl;std::cout.flush();
> >
> >  } else {
> >    gather(world,res,0);
> >  std::cout<<"gather finished"<<world.rank()<<std::endl;std::cout.flush();
> >
> >  }
> >
> >  // output
> >  if(world.rank()==0){
> >    for(unsigned int i=0;i<static_cast<unsigned int>(world.size());++i){
> >      std::cout<<"results from process "<<i<<": "<<std::endl;
> >
> >      for(int k=0; k<allRes[i].size();k++){
> >        allRes[i][k].print();
> >      }
> >      std::cout<<std::endl;
> >
> >    }
> >  std::cout<<"making output finished
> > "<<world.rank()<<std::endl;std::cout.flush();
> >
> >  }
> >
> >  return 0;
> > }

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