[MPI3 Fortran] Fwd: Serious problem/bug in MPI libraries with the alignment of MPI_DOUBLE_PRECISION

Wed Sep 28 01:40:06 CDT 2011

For the case that somebody missed the email,
here again the attachment mpi_alignment.f90 

----- Original Message -----
> From: "Alexander Supalov" <alexander.supalov at intel.com>
> To: "MPI-3 Fortran working group" <mpi3-fortran at lists.mpi-forum.org>
> Sent: Wednesday, September 28, 2011 5:37:21 AM
>
> Subject: Re: [MPI3 Fortran] Fwd: Serious problem/bug in MPI libraries with the alignment of MPI_DOUBLE_PRECISION
> PS. Please redistribute the test program that was contained in Rolf's
> original email.
> 
> -----Original Message-----
> From: Supalov, Alexander
> Sent: Wednesday, September 28, 2011 12:21 AM
> To: MPI-3 Fortran working group
> Subject: RE: [MPI3 Fortran] Fwd: Serious problem/bug in MPI libraries
> with the alignment of MPI_DOUBLE_PRECISION
> Importance: High
> 
> Hi,
> 
> I'm surprised to see no Intel MPI on the list below. Both Intel MPI
> and MS MPI are based on MPICH2. Please add me (for Intel MPI) to this
> kind of announcement from now on. We also make Intel compiler, so it
> makes a lot of sense to ask at the source rather than elsewhere.
> 
> Best regards.
> 
> Alexander
> 
> -----Original Message-----
> From: mpi3-fortran-bounces at lists.mpi-forum.org
> [mailto:mpi3-fortran-bounces at lists.mpi-forum.org] On Behalf Of Rolf
> Rabenseifner
> Sent: Tuesday, September 27, 2011 5:22 PM
> To: MPI-3 Fortran working group
> Subject: [MPI3 Fortran] Fwd: Serious problem/bug in MPI libraries with
> the alignment of MPI_DOUBLE_PRECISION
> 
> For your info:
> I informed the providers of independent MPI libraries with Fortran
> bindings about a serious problem with the definition of Fortran
> datatypes.
> 
> My apologies if I missed some of the independent MPI libraries.
> 
> In this case, please also run the program and please send the result
> to me.
> 
> Best regards
> Rolf
> 
> ----- Forwarded Message -----
> From: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> To: "Richard Treumann" <treumann at us.ibm.com>, "Rajeev Thakur"
> <thakur at mcs.anl.gov>, "Jeff Squyres" <jsquyres at cisco.com>, "Shinji
> Sumimoto" <s-sumi at labs.fujitsu.com>, "Hubert Ritzdorf"
> <hubert.ritzdorf at emea.nec.com>, "Fab Tillier" <ftillier at microsoft.com>
> Sent: Tuesday, September 27, 2011 5:15:15 PM
> Subject: Serious problem/bug in MPI libraries with the alignment of
> MPI_DOUBLE_PRECISION
> 
> Dear all,
> 
> as far as I know, you represent some MPI libraries that are not
> directly based on another one in the list:
> - mpich2: Rajeev
> - OpenMPI: Jeff
> - IBM: Rich Treumann
> - NEC: Hubert
> - Fujitsu: Shinji Sumimoto
> - Microsoft: Fab
> (Which independent library is missing on this list?) (Who of the list
> uses already mich2 or OpenMPI as bases or does not provide a Fortran
> binding, and can be therefore removed from this list?)
> 
> The problem is simple and has at the end only three numbers:
> 
> Aligments of:
> - DOUBLE PRECISION within a SEQUENCE derived type = 4 (e.g. with
> Intel)
> - DOUBLE PRECISION within a BIND(C) derived type = 8
> - MPI_DOUBLE_PRECISION (= k_i in MPI-2.2 p.78:45) = 4 or 8
> 
> The details:
> Which is the alignment of Fortran DOUBLE PRECISION according to k_i on
> MPI-2.2, page 78 line 45 and page 96 line 42.
> 
> Since 1977 (Fortran 77) in Fortran COMMON blocks and 1990 (Fortran 90)
> in Fortran SEQUENCE derived types (which have the same memory layout
> according to the SEQUENCE-rules), the MPI alignment and the Fortran
> alignment in such constructs should be the same, e.g., the Intel
> compiler has alignment 4 !!!
> 
> This may be significantly different to C, where Intel uses alignment
> 8!
> 
> With Fortran 2003, we got the Fortran BIND(C) derived types.
> Here, a Fortran DOUBLE PRECISION has with Intel's compiler the
> aligment 8.
> 
> As far as I understand, mpich2 and Cray produce following results with
> an Intel compiler:
> 
> Aligments of:
> - DOUBLE PRECISION within a SEQUENCE derived type = 4
> - DOUBLE PRECISION within a BIND(C) derived type = 8
> - MPI_DOUBLE_PRECISION (= k_i in MPI-2.2 p.78:45) = 8
> 
> This is definitely wrong compared to MPI-1.1 and MPI-2.0 but may be
> helpful for MPI-3.0 when we like to switch to a definition that is
> based on BIND(C).
> 
> Question:
> What is the output of the attached test program when running with
> - your MPI library
> - and your compiler
> - and with Intel's compiler
> 
> Please can you send me the output of such mpiruns?
> 
> Thanks in advance and best regards
> Rolf
> 
> PS: We need not to care about 8/8/8.
> Only 4/8/x causes problems:
> If all those have x=8 then I'll propose to
> adopt the MPI-3.0 to the reality.
> If we have some implementations with 4/8/8 and
> others with 4/8/4 then we have a serious problem
> because only one answer can be correct,
> and the question would be whether the historical
> answer (x=4) or the modern answer (x=8)
> should be chosen.
> 
> --
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> 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)
> 
> --
> Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
> 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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-- 
Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de
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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