[mpich-discuss] MPI-IO issue

Wei-keng Liao wkliao at ece.northwestern.edu
Thu Feb 16 17:37:27 CST 2012 

Matt,

Can you show us the codes you use to create the derived data type?
Are you using MPI_ORDER_FORTRAN in MPI_Type_create_subarray()?
I am suspecting maybe the order is not set correctly.


ROMIO has a test program named coll_test.c under src/mpi/romio/test.
It uses MPI_Type_create_darray() to create the new data type for
a subarray accesses similar to your case. It only writes once, though.

Please run that test to see if it passes. If not, then it might be
the ROMIO source code. Also, there have been several updates since
1.2.1p1. Give the latest a try. Maybe it solves the problem all at once.

Wei-keng


On Feb 16, 2012, at 2:41 PM, Grismer, Matthew J Civ USAF AFMC AFRL/RBAT wrote:

> Wei-keng,
> 
> Ok, I went back and removed my derived type, and use
> MPI_Type_create_subarray.  I checked the extents of the created types, and
> they are correct on all processors.  I also verified that size (ie*je*ke) of
> the subarray type I created matched the amount of data I am requesting each
> processor to read in MPI_File_read_all.  The data is still being read
> incorrectly.  After the first MPI_File_read_all for x, I used
> MPI_File_get_position on each processor to see if they are in the correct
> location (the upper bound extent).  Only processor 0 shows the correct
> location, the other 7 processes are all at the wrong location far short of
> the upper extent (processor 0 correctly shows 513000, the others are showing
> 81000 or 84000).
> 
> I forgot to mention I am using version 1.2.1p1 built on Mac OS X 10.6 with
> Intel compilers.  Would it be worth upgrading to the latest version (I
> didn't realize how far I had fallen behind)?
> 
> Matt
> 
> -----Original Message-----
> From: mpich-discuss-bounces at mcs.anl.gov
> [mailto:mpich-discuss-bounces at mcs.anl.gov] On Behalf Of Wei-keng Liao
> Sent: Monday, February 13, 2012 5:13 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: Re: [mpich-discuss] MPI-IO issue
> 
> Hi Matt,
> 
> Could you please try MPI_Type_create_subarray() to see if
> the same error happens, so we can rule out the possibility
> that the error is from your derived datatype?
> 
> Wei-keng
> 
> 
> On Feb 13, 2012, at 5:08 AM, Matthew J. Grismer wrote:
> 
>> Wei-keng,
>> 
>> Yes, that is exactly what I set the lowerbound and extent to for the
> derived
>> type on each of the processors.  And then I went back and checked that the
>> values were set correctly with MPI_Type_get_extent.  Then the view and
> reads
>> are as in my first example in the original post, reading x, then y, then z
>> in separate reads.
>> 
>> Matt
>> 
>> 
>> On 2/10/12 6:07 PM, "Wei-keng Liao" <wkliao at ece.northwestern.edu> wrote:
>> 
>>> Matt,
>>> 
>>> Based on the way you use the new derived datatype in MPI_FILE_SET_VIEW,
>>> the lowerbound and extent should be 0 and ie*je*ke*8, respectively.
>>> 8 byte is the bytes for real*8 type. Can you verify those values?
>>> 
>>> Wei-keng
>>> 
>>> 
>>> On Feb 10, 2012, at 4:25 PM, Grismer, Matthew J Civ USAF AFMC AFRL/RBAT
> wrote:
>>> 
>>>> Thanks for the info, I was not aware of the extent of the derived type.
> I
>>>> used MPI_Type_create_resized to change the lower bound and extent of the
>>>> derived types on each processor to cover the entire array, not just the
>>>> sub-blocks I wanted.  Now x reads correctly on each processor, but then
> y
>>>> and z are still wrong.  After the MPI_File_read_all command for x, I
> used
>>>> the MPI_File_get_position command to see where each processors file
> pointer
>>>> was.  Only on processor 0 has the file pointer moved to the correct
> location
>>>> in the file, on all the other processors it is different and far short
> of
>>>> the correct location.  I'm defining the derived types and extents the
> same
>>>> way on all the processors, and even check the extents after I set them
> to
>>>> verify they are correct.  Any other thoughts on what I am missing?
> Thanks.
>>>> 
>>>> Matt
>>>> 
>>>> -----Original Message-----
>>>> From: mpich-discuss-bounces at mcs.anl.gov
>>>> [mailto:mpich-discuss-bounces at mcs.anl.gov] On Behalf Of Wei-keng Liao
>>>> Sent: Wednesday, February 08, 2012 7:33 PM
>>>> To: mpich-discuss at mcs.anl.gov
>>>> Subject: Re: [mpich-discuss] MPI-IO issue
>>>> 
>>>> Hi,
>>>> 
>>>> I am guessing the problem is the datatype you created.
>>>> Please check the type extent to see if it equals to the
>>>> size of entire array, using MPI_Type_extent(). If not,
>>>> the file pointer after the first read will not move to
>>>> the beginning of the second array you expected, which
>>>> leads to reading data from a wrong file location.
>>>> 
>>>> Also, if each process reads a block subarray, I suggest
>>>> to use MPI_Type_create_subarray to create the new datatype.
>>>> 
>>>> 
>>>> Wei-keng
>>>> 
>>>> 
>>>> On Feb 8, 2012, at 3:46 PM, Grismer, Matthew J Civ USAF AFMC AFRL/RBAT
>>>> wrote:
>>>> 
>>>>> I am attempting to use MPI-IO to read block, structured data from a
>>>>> file.  Three three-dimensional coordinate arrays are stored in the
> file,
>>>>> one after another with Fortran ordering and in binary (not Fortran
>>>>> unformatted):
>>>>> 
>>>>> header info
>>>>> (((x(i,j,k),i=1,ie),j=1,je),k=1,ke)
>>>>> (((y(i,j,k),i=1,ie),j=1,je),k=1,ke)
>>>>> (((z(i,j,k),i=1,ie),j=1,je),k=1,ke)
>>>>> 
>>>>> Each processor reads a block subset of the arrays, and I've defined a
>>>>> derived type using MPI_TYPE_INDEXED for the blocks that go to each
>>>>> processor.  MPI_TYPE_INDEXED takes as arguments the number of blocks,
>>>>> block size, and block displacement;  I created (and committed) the
>>>>> datatype with the number of blocks/displacements 3 times (i.e.
>>>>> subsetie*subsetje*subsetke*3) what I need for one variable above on a
>>>>> given processor.  Then I used the following to read the file across the
>>>>> processors:
>>>>> 
>>>>> count = subsetie*subsetje*subsetke
>>>>> call MPI_FILE_SET_VIEW ( fh, skipheader, mpi_real8, newdatatype,
>>>>> "native", mpi_info_null, ierror )
>>>>> call MPI_FILE_READ_ALL ( fh, x, count, mpi_real8, ierror )
>>>>> call MPI_FILE_READ_ALL ( fh, y, count, mpi_real8, ierror )
>>>>> call MPI_FILE_READ_ALL ( fh, z, count, mpi_real8, ierror )
>>>>> 
>>>>> The result from this is x is read correctly, y and z are not.  However,
>>>>> if I define one variable xyz(subsetie,subsetje,subsetke,3) and read all
>>>>> the data in one call:
>>>>> 
>>>>> count = subsetie*subsetje*subsetke*3
>>>>> call MPI_FILE_SET_VIEW ( fh, skipheader, mpi_real8, newdatatype,
>>>>> "native", mpi_info_null, ierror )
>>>>> call MPI_FILE_READ_ALL ( fh, xyz, count, mpi_real8, ierror )
>>>>> 
>>>>> everything is read correctly, which also verifies my derived type is
>>>>> correct.  Alternatively I can reset the view (with correct
>>>>> displacements) after each READ_ALL and read into the individual
>>>>> variables.
>>>>> 
>>>>> Is this the expected behavior?  If so I do not understand how to make
>>>>> successive collective reads from a file without resetting the view
>>>>> before every read, which will take a toll on performance when I
> continue
>>>>> to read many additional variables from the file.
>>>>> 
>>>>> Matt
>>>>> _______________________________________________
>>>>> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
>>>>> To manage subscription options or unsubscribe:
>>>>> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
>>>> 
>>>> _______________________________________________
>>>> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
>>>> To manage subscription options or unsubscribe:
>>>> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
>>>> _______________________________________________
>>>> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
>>>> To manage subscription options or unsubscribe:
>>>> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
>>> 
>>> _______________________________________________
>>> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
>>> To manage subscription options or unsubscribe:
>>> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
>> 
>> _______________________________________________
>> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
>> To manage subscription options or unsubscribe:
>> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
> 
> _______________________________________________
> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
> To manage subscription options or unsubscribe:
> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss
> _______________________________________________
> mpich-discuss mailing list     mpich-discuss at mcs.anl.gov
> To manage subscription options or unsubscribe:
> https://lists.mcs.anl.gov/mailman/listinfo/mpich-discuss

More information about the mpich-discuss mailing list