[Mpi-22] Another MPI-2.2 attribute ambiguity?

Tue May 19 12:16:17 CDT 2009

MPICH2 passes the value of the extra_state that was saved in the  
internal storage to the callback routine, which is case 2 (the copy is  
implicit as the value is passed to the routine and C semantics ensures  
that the value isn't changed).

Bill

On May 18, 2009, at 10:24 AM, Jeff Squyres wrote:

> I'm most curious to know what current MPI implementations do in this
> scenario.
>
>
> On May 14, 2009, at 1:05 PM, Jeff Squyres wrote:
>
>> Another question about this issue...
>>
>> Since all fortran values are passed by reference, does the MPI care
>> if the callback function changes the EXTRA_STATE value?  I see 2
>> choices:
>>
>> 1. The MPI copies the value of extra_state when MPI_*_CREATE_KEVAL
>> is invoked to internal storage.  This internal storage is passed to
>> all the callbacks when invoked.  If any of the callbacks change the
>> value, then subsequent invocations of the callback get the changed
>> value.
>>
>> 2. The MPI copies the value of extra_state when MPI_*_CREATE_KEVAL
>> is invoked to internal storage.  This internal storage is copied any
>> time a callback is invoked; the copy is passed to the callback (and
>> freed when the callback returns).  In this way, the same EXTRA_STATE
>> value that was originally passed to the keyval constructor will
>> always be passed to any callbacks.
>>
>> What do current MPI implementations do?
>>
>> OMPI's development trunk has been updated to do #1; I'm wondering if
>> it should do #2.
>>
>>
>>
>> On Apr 17, 2009, at 10:21 AM, Jeff Squyres (jsquyres) wrote:
>>
>>> Ok, I'll file an MPI-3 ticket for this.
>>>
>>> (for everyone else on the 2.2 list wondering why you just got
>>> blitzkrieged with a whole pile of emails on this topic: the
>>> listserver
>>> sent all these mails to moderation because of the lengthy CC list.
>>> IU
>>> just approved all the mails to go through this morning)
>>>
>>>
>>> On Apr 17, 2009, at 9:40 AM, William Gropp wrote:
>>>
>>>> Yes, this is worth an ATI - the fact that we traded this much
>>> mail on
>>>> it is proof of that :)
>>>>
>>>> Thanks, Jeff.
>>>>
>>>> Bill
>>>>
>>>> On Apr 17, 2009, at 8:14 AM, Jeff Squyres wrote:
>>>>
>>>>> Someone pointed out to me this morning that there's no
>>> restriction
>>>> on
>>>>> the value of EXTRA_STATE when CREATE_KEYVAL is invoked -- it may
>>>> be an
>>>>> expression, for example.  I think that pretty much seals the deal
>>>> that
>>>>> #2 is the correct way.
>>>>>
>>>>> I think that this is worth an ATI in the text; does anyone
>>> disagree?
>>>>> I volunteer to write it up/make a 3.0 ticket (hey, first ticket
>>> for
>>>>> the Misc WG! :-) ) if no one disagrees.
>>>>>
>>>>>
>>>>> On Apr 17, 2009, at 8:59 AM, Supalov, Alexander wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Intel MPI (and most likely other MPICH2 derivatives) appears
>>> to use
>>>>>> method #2.
>>>>>>
>>>>>> Best regards.
>>>>>>
>>>>>> Alexander
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Jeff Squyres [mailto:jsquyres_at_[hidden]]
>>>>>> Sent: Thursday, April 16, 2009 4:19 PM
>>>>>> To: MPI 2.2; Rajeev Thakur; William Gropp; Rolf Rabenseifner;
>>>> Hubert
>>>>>> Ritzdorf; Terry Dontje; Dave Goodell; Darius Buntinas; Pavan
>>>> Balaji;
>>>>>> Supalov, Alexander; Bronis de Supinski; David Solt; Hans
>>> Westgaard
>>>>>> Ry; Håkon Bugge
>>>>>> Subject: Another MPI-2.2 attribute ambiguity?
>>>>>>
>>>>>> This is related to -- but different from -- MPI 2.2 ticket #55
>>>>>> ("MPI-2.1 Cross-language attribute example is wrong").
>>> Explicitly
>>>>>> adding all the #55 CC members to this mail, plus a few others.
>>>>>>
>>>>>> I cannot find any text in MPI-2.1 (e.g., p223-225) describing
>>>>>> specific
>>>>>> behavior regarding the EXTRA_STATE arguments passed to the
>>> Fortran
>>>>>> keyval copy and delete functions (both the ADDRESS_KIND and
>>>>>> deprecated
>>>>>> flavors).  I see two choices:
>>>>>>
>>>>>> 1. pass the user's original EXTRA_STATE argument by reference to
>>>> the
>>>>>> callbacks, or
>>>>>> 2. copy the user's original EXTRA_STATE into internal MPI
>>> storage
>>>> and
>>>>>> pass *that* value by reference to the callbacks
>>>>>>
>>>>>> ==> Open MPI currently does #1.  What do other implementations
>>> do?
>>>>>>
>>>>>> I raise this issue because the text does not indicate which
>>> way is
>>>>>> right.  And I just ran across an old Sun test that assumed
>>> #2.  But
>>>>>> our internal copy of the Intel MPI tests assume #1 (to be
>>> fair: I
>>>>>> have
>>>>>> no idea if the Intel tests originally assumed #2 and we changed
>>>> them
>>>>>> to #1 over time).  Indeed, #2 is actually in-line with the
>>>> philosophy
>>>>>> of storing attribute values in internal MPI storage.  E.g.:
>>>>>>
>>>>>>  INTEGER foo = 4
>>>>>>  INTEGER bar
>>>>>>  CALL MPI_COMM_SET_ATTR(comm, keyval, foo, ierr)
>>>>>>  foo = 5
>>>>>>  CALL MPI_COMM_GET_ATTR(comm, keyval, bar, flag, ierr)
>>>>>>
>>>>>> bar should equal 4, not 5 (right?).
>>>>>>
>>>>>> So what does that mean (or imply) about the EXTRA_STATE value
>>>> passed
>>>>>> to the Fortran callbacks?
>>>>>>
>>>>>> --
>>>>>> Jeff Squyres
>>>>>> Cisco Systems
>>>>>>
>>>>>>
>>>>
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>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Jeff Squyres
>>>>> Cisco Systems
>>>>>
>>>>
>>>> William Gropp
>>>> Deputy Director for Research
>>>> Institute for Advanced Computing Applications and Technologies
>>>> Paul and Cynthia Saylor Professor of Computer Science
>>>> University of Illinois Urbana-Champaign
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>> Jeff Squyres
>>> Cisco Systems
>>>
>>>
>>> _______________________________________________
>>> mpi-22 mailing list
>>> mpi-22_at_[hidden]
>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>
>>
>> -- 
>> Jeff Squyres
>> Cisco Systems
>>
>>
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>> mpi-22 mailing list
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>
>
> -- 
> Jeff Squyres
> Cisco Systems
>
>
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William Gropp
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign