On Mon, Jul 06, 2009 at 11:39:59AM +0200, Manuel Holtgrewe wrote: > do I understand the MPI-2 Parallel I/O correctly (C++)? > > After opening a file with MPI::File::Open, I can use Read_at on the > returned file object. I give offsets in bytes and I can perform random > access reads from any process at any point of the file without > violating correctness (although the performance might/should/will be > better using views): > > MPI::File f = MPI::File::Open(MPI::COMM_WORLD, filename, MPI::MODE_RDONLY, > MPI::INFO_NULL); > // ... > MPI::Offset pos_in_file = ...; > // ... > f.Read_at(pos_in_file, buffer, local_n + 1, MPI::INTEGER); > // ... > f.Close();
why the +1 ? what's local_n in the first place? > I have some problems with the program reading invalid data and want to > make sure I am actually using parallel I/O the right way. I think you're OK here. What are you seeing? Is this NFS? ==rob -- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA
