Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] ROMIO bug reading darrays
From: Richard Shaw (jrs65_at_[hidden])
Date: 2014-05-07 16:10:58


Thanks Rob. I'll keep track of it over there. How often do updated versions
of ROMIO get pulled over from MPICH into OpenMPI?

On a slightly related note, I think I heard that you had fixed the 32bit
issues in ROMIO that were causing it to break when reading more than 2 GB
(i.e. http://www.open-mpi.org/community/lists/users/2012/07/19762.php).
Have those been pulled into OpenMPI? I've been staying clear of ROMIO for a
while (in favour of OMPIO), to avoid those issues.

Thanks,
Richard

On 7 May 2014 12:36, Rob Latham <robl_at_[hidden]> wrote:

>
>
> On 05/05/2014 09:20 PM, Richard Shaw wrote:
>
>> Hello,
>>
>> I think I've come across a bug when using ROMIO to read in a 2D
>> distributed array. I've attached a test case to this email.
>>
>
> Thanks for the bug report and the test case.
>
> I've opened MPICH bug (because this is ROMIO's fault, not OpenMPI's
> fault... until I can prove otherwise ! :>)
>
> http://trac.mpich.org/projects/mpich/ticket/2089
>
> ==rob
>
>
>> In the testcase I first initialise an array of 25 doubles (which will be
>> a 5x5 grid), then I create a datatype representing a 5x5 matrix
>> distributed in 3x3 blocks over a 2x2 process grid. As a reference I use
>> MPI_Pack to pull out the block cyclic array elements local to each
>> process (which I think is correct). Then I write the original array of
>> 25 doubles to disk, and use MPI-IO to read it back in (performing the
>> Open, Set_view, and Real_all), and compare to the reference.
>>
>> Running this with OMPI, the two match on all ranks.
>>
>> > mpirun -mca io ompio -np 4 ./darr_read.x
>> === Rank 0 === (9 elements)
>> Packed: 0.0 1.0 2.0 5.0 6.0 7.0 10.0 11.0 12.0
>> Read: 0.0 1.0 2.0 5.0 6.0 7.0 10.0 11.0 12.0
>>
>> === Rank 1 === (6 elements)
>> Packed: 15.0 16.0 17.0 20.0 21.0 22.0
>> Read: 15.0 16.0 17.0 20.0 21.0 22.0
>>
>> === Rank 2 === (6 elements)
>> Packed: 3.0 4.0 8.0 9.0 13.0 14.0
>> Read: 3.0 4.0 8.0 9.0 13.0 14.0
>>
>> === Rank 3 === (4 elements)
>> Packed: 18.0 19.0 23.0 24.0
>> Read: 18.0 19.0 23.0 24.0
>>
>>
>>
>> However, using ROMIO the two differ on two of the ranks:
>>
>> > mpirun -mca io romio -np 4 ./darr_read.x
>> === Rank 0 === (9 elements)
>> Packed: 0.0 1.0 2.0 5.0 6.0 7.0 10.0 11.0 12.0
>> Read: 0.0 1.0 2.0 5.0 6.0 7.0 10.0 11.0 12.0
>>
>> === Rank 1 === (6 elements)
>> Packed: 15.0 16.0 17.0 20.0 21.0 22.0
>> Read: 0.0 1.0 2.0 0.0 1.0 2.0
>>
>> === Rank 2 === (6 elements)
>> Packed: 3.0 4.0 8.0 9.0 13.0 14.0
>> Read: 3.0 4.0 8.0 9.0 13.0 14.0
>>
>> === Rank 3 === (4 elements)
>> Packed: 18.0 19.0 23.0 24.0
>> Read: 0.0 1.0 0.0 1.0
>>
>>
>>
>> My interpretation is that the behaviour with OMPIO is correct.
>> Interestingly everything matches up using both ROMIO and OMPIO if I set
>> the block shape to 2x2.
>>
>> This was run on OS X using 1.8.2a1r31632. I have also run this on Linux
>> with OpenMPI 1.7.4, and OMPIO is still correct, but using ROMIO I just
>> get segfaults.
>>
>> Thanks,
>> Richard
>>
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
> --
> Rob Latham
> Mathematics and Computer Science Division
> Argonne National Lab, IL USA
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>