On Thu, Feb 5, 2009 at 7:48 PM, Shao-Ching Huang <schuang at ats.ucla.edu> wrote: > Hi, > > I am trying to create restart/check-pointing files for a time-stepping > simulation (by writing out vectors to files). > > 1. Does VecView always use the MPI collective I/O? > > The HTML documentation of PetscViewerBinaryOpen says: "For writing > files it only opens the file on processor 0 in the communicator."
You must run with -viewer_binary_mpiio. However, I recommend very very strongly that you profile this first. We have not need to use MPI/IO below several thousand processors. > 2. Do I have to set anything to enable MPI I/O when configuring PETSc? > (My MPI library has MPI I/O.) This should happen automatically. Matt > Thank you. > > Shao-Ching -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
