[mpich-discuss] romio large array

[Rob Ross]

May be related to how we manage status?

-- Rob

On Apr 26, 2010, at 9:57 AM, Dave Goodell <goodell at mcs.anl.gov> wrote:

> On Apr 26, 2010, at 9:38 AM, Rob Latham wrote:
>
>> On Mon, Apr 26, 2010 at 08:05:41AM -0500, Dave Goodell wrote:
>>> [adding RobL]
>>>
>>> It looks like ROMIO is checking for reads of more data than INT_MAX
>>> bytes in a single call.  I'm guessing that this is defensive because
>>> some of the internal code in ROMIO may not be prepared to handle
>>> this case.  Rob can probably comment with less speculation.
>>
>> that's exactly what's going on.
>
> This is a stricter check than what the standard implies.  ROMIO is  
> checking that ((type_size*count)<=INT_MAX).  It really should only  
> need to check that (count<=INT_MAX) as long as all calculations are  
> internally handled with a larger (64-bit) type.  This would actually  
> permit the read in this user's instance.  Would it be hard to move  
> to the latter case?
>
>> Dave, I don't know if the forum is still talking about the MPI_COUNT
>> issue, but we get questions like this about once a year. People
>> definitely try to read more than 2GB of data at a time.
>
> It is under discussion.  But AFAIK all of the discussion is about  
> how to fix the "int count" parameters.
>
> -Dave
>
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