[mpich-discuss] Error with MPI_Register_datarep

[Eric Chamberland]

Le 2016-03-13 16:22, Thakur, Rajeev a écrit :
> In the 19 years since the MPI-2 standard was released, you may be the first one requesting this functionality :-). I am curious what are you using it for?
Here is the reason....

In 2012, when I read your book about MPI-2, I wrote all our I/O 
functions to use collective MPI I/O calls with "native" as datarep. I 
knew it would not be portable "as is" but the main usage is 64bits 
native format... then I told myself "It will be ok when I will want to 
read/write from 32 bits architectures or different endian style, since 
there is that user defined datarep possibility, as illustrated in chapet 
9.1 of the book...", but unfortunately for me, I didn't _tested_ the 
functionality in 2012... :/

So we moved all our file formats (meshes, results, etc) to be aligned 
with the output of "native" datarep into a 64bits standard linux x86 
architecture...  That means we have produced, for example, 1200 
validations tests with input/output files into that format...

That is, of course, excluding all user data since 4 years..

No I am in the phase of porting the code to fully support 32bits 
architecture (we have an 32bit ubuntu running here, and working on 
windows port).

So, I did test for the first time the datarep functionality to be able 
to convert 64 bits "long int" from/to 32 bits "long int" for 
writing/reading in respect to existing file format...

It was all an easy task in my mind with the user datarep functionality 
just as it is in the standard..

But it appears I am the only one in the world (wow...) to request a way 
to have his files portable with MPI... without performance losses for 
the "main" usage which is 64bits...

Maybe there is another simple way to do this?

Anyway, I am now expecting that you will tell me it will never be 
implemented _just for me_... :/

Maybe I can contribute? :)

Thanks,

Eric

>
> Rajeev
>
>
>> On Mar 13, 2016, at 1:51 PM, Eric Chamberland <Eric.Chamberland at giref.ulaval.ca> wrote:
>>
>> Le 2016-03-10 18:04, Thakur, Rajeev a écrit :
>>> Support for user-defined data representations has not been added to MPICH yet. There has not been much demand for it.
>> Thanks for your answer...
>>
>> Is it a "big" task?
>>
>> Should it be scheduled so it may appear in a forthcoming version?
>>
>> Thanks,
>>
>> Eric
>>
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