VecView and MPI IO

Shao-Ching Huang schuang at
Fri Feb 6 18:27:49 CST 2009


I am getting a zero-sized file "" when I write a vector, say
"my_vec", to disk file "foo":

   MPI_Comm comm;
   PetscViewer viewer;
   Vec my_vec;
   PetscViewerBinaryOpen(comm, "foo", FILE_MODE_WRITE, &viewer);
   VecView(my_vec, viewer);

My questions are:
1. Can I safely ignore the .info file? (Is it useful?)
2. How can I prevent the .info file from being generated?



Matthew Knepley wrote:
> On Thu, Feb 5, 2009 at 7:48 PM, Shao-Ching Huang <schuang at> 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

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