[Mpi-22] MPI-2.1 ambiguity?
William Gropp
wgropp at [hidden]
Thu Jul 17 11:41:55 CDT 2008
I don't think that text will work. Specifically, what is the type of
MPI_INT in Fortran? It may be something other than a Fortran
INTEGER. So, either these values need to already be converted into
the language-of-the-headerfile, or we need a new datatype for Fortran
that can contain a C or a C++ Datatype (e.g., something like INTEGER
(KIND=MPI_DATATYPE_C_HANDLE) ). That's why I think that they must be
presented by the implementation with the values that you would get by
taking making use of the conversion functions. Of course, an
application must then be careful not to apply MPI_Type_c2f to the
Fortran version of MPI_INT ...
There's another option. Drop the requirement that all of the
predefined datatypes are predefined in all languages, but specify
that they may be used (with the appropriate handle conversion) as
input to any routine where it makes sense. For datatypes, this
includes the datatype construction routines but not the communication
routines (don't use MPI_INT when sending INTEGERs with Fortran).
This is what the Opaque Objects text expects.
Bill
On Jul 17, 2008, at 10:01 AM, Rolf Rabenseifner wrote:
> My primary oal is:
> We should make clarifications which state that
> each predefined handle must be available in every
> language binding.
> People may be confused by current wording in several places:
>
> - MPI-2.1 (June 23, 2008) Section 16.3.6 MPI Opaque Objects,
> page 483, lines 46-47:
> "All predefined datatypes can be used in datatype constructors
> in any language."
>
> - MPI-2.1 (June 23, 2008) Section 16.3.9 Constants,
> page 488, lines 33-35:
> "MPI constants have the same value in all languages,
> unless specified otherwise. This does not
> apply to constant handles (MPI_INT, MPI_COMM_WORLD,
> MPI_ERRORS_RETURN, MPI_SUM, etc.) These handles need
> to be converted, as explained in Section 16.3.4."
>
> - MPI-2.1 (June 23, 2008) Annex A.1.1 Defined Constants,
> page 491, lines 22-23:
> "The C and Fortran name is listed in the left column and the
> C++ name is listed in the middle or right column."
>
> Proposal:
> =========
>
> MPI-2.1 p. 488, lines 33-35 reads:
> "MPI constants have the same value in all languages,
> unless specified otherwise. This does not
> apply to constant handles (MPI_INT, MPI_COMM_WORLD,
> MPI_ERRORS_RETURN, MPI_SUM, etc.) These handles need
> to be converted, as explained in Section 16.3.4."
>
> but should read:
> "MPI constants have the same value in all languages,
> unless specified otherwise. This does not
> apply to constant handles (MPI_INT, MPI_COMM_WORLD,
> MPI_ERRORS_RETURN, MPI_SUM, etc.)
> Although these handles (e.g. predefined datatypes)
> must exist in all language bindings, their values
> may be different in each language binding.
> If one wants to use a constant handle from one language binding
> (e.g., MPI_DOUBLE from mpi.h) in a call to an MPI function in
> another language binding (e.g., in Fortran MPI_SEND), then
> these handles need
> to be converted, as explained in Section 16.3.4."
>
> Does this help?
>
> Best regards
> Rolf
>
>
> On Thu, 17 Jul 2008 09:03:35 -0500
> William Gropp <wgropp_at_[hidden]> wrote:
>> To make this perfectly clear, should the standard state that the
>> values of the predefined datatypes from another language are exactly
>> the same as the value produced by the handle conversion function?
>> E.g., in Fortran, the value of MPI_INT is what you would get from
>> MPI_TYPE_C2F( MPI_INT ) (where MPI_INT is the C version). It
>> should also state that just because Fortran defines MPI_LONG_LONG,
>> that does not imply that Fortran support an integer type that
>> corresponds to the C long long type.
>>
>> Bill
>>
>> On Jul 17, 2008, at 4:03 AM, Rolf Rabenseifner wrote:
>>
>>> Hi all,
>>>
>>> The argument-chain was:
>>>
>>>>>> William Gropp wrote:
>>>>>>> One piece of relevant text in MPI 2.0 is in section 4.12.6 (in
>>>>>>> MPI-2.0) says that "All predefined datatypes can be used in
>>>>>>> datatype constructors in any language."
>>> [....]
>>>
>>> This text is supported also by:
>>> MPI-2.0 Chap. 10.1.6 page 276 and
>>> MPI-2.0 Annex B.2, page 344 define for all Fortran predefined
>>> datatype handles as C++ counter-part.
>>>
>>> In the meeting, there was a consensus (?) that it is a bug
>>> if an MPI implementation does not support, e.g. MPI_INT
>>> in the mpif.h Fortran header file.
>>> (This bug can be found, e.g., in MPICH-2 and will be fixed,
>>> when I understood correctly)
>>>
>>> The value (not the name!!) of MPI_INT in mpif.h and mpi.h may be
>>> different, as stated already in MPI-2.0, Sect. 4.12.9.
>>> MPI_INT from C mpi.h cannot be used in a Fortran CALL MPI_SEND(...).
>>> You need to convert, or you must use MPI_INT from Fortran mpif.h.
>>>
>>> (I.e. one may distiguish between mixed languages in
>>> one MPI executable [addressed by MPI-2.0 Section 4.12.9],
>>> and sending a message from a Fortran MPI executable to a C MPI
>>> executable and vice versa [see MPI 2.0 Section 4.12.6].)
>>>
>>> Because this is already "clearly" defined in MPI-2.0,
>>> you will not find any remark about this in the Change-Log
>>> of MPI-2.1.
>>>
>>> MPI-2.2 may make it more clear in the revisiting of datatypes.
>>>
>>> Best regards
>>> Rolf
>>>
>>> On Thu, 17 Jul 2008 10:20:28 +0200
>>> Hubert Ritzdorf <ritzdorf_at_it.neclab.eu> wrote:
>>>> No, we didn't have them. The request to provide all C datatypes in
>>>> Fortran was specified in one of the last meetings. When I remember
>>>> correctly, it was specified in the last meeting in Chicago or
>>>> the meeting before (I think it was specified together with item 33
>>>> of the change log). I implemented it together with the changes
>>>> for MPI 2.1 since I assumed that it was contained also in the
>>>> change log. After your mail, I recognized that it is only
>>>> implicitly
>>>> mentioned by item 33.
>>>>
>>>> Hubert
>>>>
>>>> Jeff Squyres wrote:
>>>>> What does NEC MPI do -- do you have MPI_INT and MPI_FLOAT
>>>>> (etc.) in
>>>>> mpif.h?
>>>>>
>>>>>
>>>>> On Jul 16, 2008, at 12:57 PM, Hubert Ritzdorf wrote:
>>>>>
>>>>>> What's about the C++ datatypes for complex ?
>>>>>> MPI_COMPLEX and MPI_Double_Complex are already defined for
>>>>>> Fortran
>>>>>> datatypes. The complex Fortran datatypes within C++ have a
>>>>>> special
>>>>>> name in order to avoid a name collision.
>>>>>>
>>>>>> Hubert
>>>>>>
>>>>>> William Gropp wrote:
>>>>>>> One piece of relevant text in MPI 2.0 is in section 4.12.6 (in
>>>>>>> MPI-2.0) says that "All predefined datatypes can be used in
>>>>>>> datatype
>>>>>>> constructors in any language." However, the example uses
>>>>>>> MPI_Type_f2c ton convert the Fortran handle to the C version
>>>>>>> before
>>>>>>> passing it into the MPI_Type_create_struct routine, so this text
>>>>>>> could be interpreted as allowing the use of those datatypes
>>>>>>> through
>>>>>>> the handle conversion mechanism without requiring them to be
>>>>>>> defined
>>>>>>> in each languages header file. Presumably the requirement is
>>>>>>> that
>>>>>>> they be predefined with the value that you'd get from the handle
>>>>>>> conversion function?
>>>>>>>
>>>>>>> Bill
>>>>>>>
>>>>>>> On Jul 16, 2008, at 8:18 AM, Hubert Ritzdorf wrote:
>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> when I remember correctly, it was decided to provide the C MPI
>>>>>>>> datatypes
>>>>>>>> in Fortran since
>>>>>>>> the Fortran datatypes are supported in C and C++.
>>>>>>>>
>>>>>>>> Hubert
>>>>>>>>
>>>>>>>> Jeff Squyres wrote:
>>>>>>>>> I will file a proposal about this if there is a problem, but I
>>>>>>>>> wanted
>>>>>>>>> to ask the group before I did so. In the changelog for
>>>>>>>>> MPI-2.1:
>>>>>>>>>
>>>>>>>>> 2. Section 3.2.2 on page 27, Section 16.1.6 on page 453, and
>>>>>>>>> Annex
>>>>>>>>> A.1
>>>>>>>>> on page 491.
>>>>>>>>> MPI_LONG_LONG_INT, MPI_LONG_LONG (as synonym),
>>>>>>>>> MPI_UNSIGNED_LONG_LONG,
>>>>>>>>> MPI_SIGNED_CHAR, and MPI_WCHAR are moved from optional to
>>>>>>>>> official
>>>>>>>>> and they
>>>>>>>>> are therefore deï¬ned for all three language bindings.
>>>>>>>>>
>>>>>>>>> Note that it says that these C datatype names must be in all
>>>>>>>>> three
>>>>>>>>> language bindings.
>>>>>>>>>
>>>>>>>>> Are C MPI datatypes supposed to be available in Fortran? I
>>>>>>>>> looked
>>>>>>>>> in
>>>>>>>>> mpif.h for Open MPI, MPICH2, HP MPI, and Intel MPI, and I
>>>>>>>>> didn't
>>>>>>>>> see C
>>>>>>>>> MPI datatypes in there (e.g., MPI_INT and MPI_FLOAT).
>>>>>>>>>
>>>>>>>>> So:
>>>>>>>>>
>>>>>>>>> - is there language somewhere in MPI that says that C
>>>>>>>>> datatypes are
>>>>>>>>> not supposed to be in mpif.h? (and therefore the MPI-2.1
>>>>>>>>> changelog
>>>>>>>>> is
>>>>>>>>> wrong)
>>>>>>>>>
>>>>>>>>> or
>>>>>>>>>
>>>>>>>>> - are all 4 of the above MPI's wrong for not including the C
>>>>>>>>> datatypes
>>>>>>>>> in mpif.h?
>>>>>>>>>
>>>>>>>>> --Jeff Squyres
>>>>>>>>> Cisco Systems
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> mpi-22 mailing list
>>>>>>>>> mpi-22_at_[hidden] <mailto:mpi-22_at_[hidden]>
>>>>>>>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>>>>>>>>
>>>>>>>>> <smime.p7s><ATT00001.txt>
>>>>>>>
>>>>>>> William Gropp
>>>>>>> Paul and Cynthia Saylor Professor of Computer Science
>>>>>>> University of Illinois Urbana-Champaign
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ----------------------------------------------------------------
>>>>>>> --
>>>>>>> ------
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> mpi-22 mailing list
>>>>>>> mpi-22_at_[hidden]
>>>>>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>>>>>>
>>>>>> _______________________________________________
>>>>>> mpi-22 mailing list
>>>>>> mpi-22_at_[hidden]
>>>>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>>>>
>>>>>
>>>>> --Jeff Squyres
>>>>> Cisco Systems
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> mpi-22 mailing list
>>>>> mpi-22_at_[hidden]
>>>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>>>>
>>>
>>> Dr. Rolf Rabenseifner . . . . . . . . . .. email
>>> rabenseifner_at_[hidden]
>>> High Performance Computing Center (HLRS) . phone
>>> ++49(0)711/685-65530
>>> University of Stuttgart . . . . . . . . .. fax ++49(0)711 /
>>> 685-65832
>>> Head of Dpmt Parallel Computing . . .
>>> www.hlrs.de/people/rabenseifner
>>> Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)
>>> _______________________________________________
>>> mpi-22 mailing list
>>> mpi-22_at_[hidden]
>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
>>
>> William Gropp
>> Paul and Cynthia Saylor Professor of Computer Science
>> University of Illinois Urbana-Champaign
>>
>>
>>
>
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner_at_[hidden]
> High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530
> University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832
> Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner
> Nobelstr. 19, D-70550 Stuttgart, Germany . (Office: Allmandring 30)
> _______________________________________________
> mpi-22 mailing list
> mpi-22_at_[hidden]
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-22
William Gropp
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign
*
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