[MPICH] disp argument in MPI_File_set_view() in Fortran

[Wei-keng Liao]

Mmm...  I did remember I have seen it somewhere. Thanks, Rajeev.

Wei-keng


On Sun, 28 Jan 2007, Rajeev Thakur wrote:

> The problem is that if you just pass 0 in Fortran, the Fortran compiler will
> pass it as a pointer to a 4-byte integer (assuming integers are 4 bytes on
> your system), whereas file offsets and displacements on the same system are
> 8 bytes, and the MPI library is expecting a pointer to an 8-byte integer.
> This is one of the common user errors that I mention in an MPI or MPI-IO
> tutorial.
>
> Rajeev
>
>
>> -----Original Message-----
>> From: owner-mpich-discuss at mcs.anl.gov
>> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Wei-keng Liao
>> Sent: Sunday, January 28, 2007 2:19 AM
>> To: mpich-discuss at mcs.anl.gov
>> Subject: [MPICH] disp argument in MPI_File_set_view() in Fortran
>>
>>
>> I am testing a Fortran MPI I/O code. I found that when
>> setting the file
>> view, if I used "0" directly for the disp argument in
>> MPI_File_set_view()
>> call, then MPI_File_write() or MPI_File_write_at() will fail.
>>
>> But if I used a variable of type
>> integer(KIND=MPI_OFFSET_KIND) and set it
>> to 0 and used it in the disp argument, everything works fine.
>> I also can
>> see all Fortran test codes in ROMIO test directory written in
>> this way.
>>
>> I looked into ADIO implementation, in particular, ad_nfs_write.c and
>> ad_pvfs_write.c. I put a print statement to print the offset
>> value passed
>> into functions ADIOI_NFS_WriteContig() and
>> ADIOI_PVFS_WriteContig() and I
>> got a very large number, like 85899346160, although it should be very
>> small or 0 in my test code. I believe there is something
>> fishy in type
>> casting when passing the offset variable among functions in ROMIO.
>> However, C seems not having this problem.
>>
>> I am using mpich2-1.0.5 on a Linux cluster running athlon
>> i386 and RedHat
>> 2.4.21-32.0.1.EL. MPICH is compiled with gcc, gfortran 4.0.0.
>>
>> Wei-keng
>>
>>
>>
>