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