[mpich-discuss] MPI_set_view, for offset larger than an integer

[Jeff Hammond]

The MPI standard, which is the only official documentation about the
function syntax of MPI_File_set_view, says this:

int MPI_File_set_view(MPI_File fh, MPI_Offset disp, MPI_Datatype etype,
             MPI_Datatype filetype, const char *datarep, MPI_Info info)

The size of the disp type is specified as follows:

13.6.7 MPI_Offset Type

MPI_Offset is an integer type of size sufficient to represent the size
(in bytes) of the largest file supported by MPI. Displacements and
offsets are always specified as values of type MPI_Offset.

Thus, it should not be possible to overflow this value if you're
accessing the file in a correct way.

Jeff

On Wed, Mar 13, 2013 at 10:28 AM, Ana María Sánchez
<krazorange at gmail.com> wrote:
> Hi all,
>
>     I need to read a file, using MPI_set_view. The problem occurs when the
> file is so large that the offset that I need to provide to the MPI_set_view
> is larger than the maximum value for an integer.  For example I need to set
> the offset to 3826145886. In some documentation I've read the offset is a
> long, but in other it indicates its an integer.
>
>  Is there any possible work around this? Could the offset be set to
> negative, and if so, will it start at the end of the file?
>
>  I have installed  mpich2-1.3.1.
>
> Thank you,
>
>
>
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-- 
Jeff Hammond
Argonne Leadership Computing Facility
University of Chicago Computation Institute
jhammond at alcf.anl.gov / (630) 252-5381
http://www.linkedin.com/in/jeffhammond
https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond