Re: [Mpi-22] MPI-2.1 ambiguity?
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
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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)
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