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

Rajeev Thakur thakur at mcs.anl.gov
Wed Mar 13 11:04:15 CDT 2013


And if you are using Fortran, you have to define the offset variable as integer (kind=MPI_OFFSET_KIND).

On Mar 13, 2013, at 10:57 AM, Jeff Hammond wrote:

> 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
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