On Wednesday 28 April 2010, Joshua R. Tepper wrote: > Hi all, > I am trying to use Valgrind to debug an MPI application, but things don't > seem to work. I understand that Valgrind explicitly implements wrapper > functions for MPI calls and uses the PMPI interface. To the best of my > understanding, when called in the context of MPI, valgrind should somehow > check MPI calls, yes > avoid giving "garbage" output from the underlying mpi > libraries, no (but see below) > and suppress the printing of a separate output for each node. no (how did you infer that?)
Re the garbage, debugging MPI apps is problematic because the NIC I/O and control buffers are mapped directly into memory, and memcheck doesn't have a way to detect state changes in them. One option is to use the --ignore-ranges= flag, if you can figure out what the relevant NIC addresses are. Another is to tell your MPI stack to not map cards into memory, but just to use TCP/IP via normal syscalls to communicate. That is (or at least, used to be) possible with OpenMPI with the mpirun args --mca btl tcp,self, for example. If you are using OpenMPI you might want to ask the OpenMPI devs for advice. They are pretty Memcheck-aware, afaik. J ------------------------------------------------------------------------------ _______________________________________________ Valgrind-users mailing list Valgrind-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-users
