VecView and MPI IO

[Shao-Ching Huang]

Hi

I am getting a zero-sized file "foo.info" 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);
   PetscViewerDestroy(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?

Thanks,

Shao-Ching


Matthew Knepley wrote:
> 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