The text you pinpoint is clear about the target: the MPI bindings. The
question here is not about bindings, but about a predefined datatype, a
case where I don't think the text applies.
George.
On Tue, Feb 9, 2016 at 6:17 PM, Jeff Hammond <jeff.scie...@gmail.com> wrote:
> "MPI-3.0 (and later) compliant Fortran bindings are not only a property of
> the MPI library itself, but rather a property of an MPI library together
> with the Fortran compiler suite for which it is compiled." (MPI 3.1 Section
> 17.1.7).
>
> Of course, implementations can provide support in excess of the minimum
> required by the standard, provided that support remains compliant with the
> standard.
>
> Jeff
>
>
> On Mon, Feb 8, 2016 at 9:21 PM, George Bosilca <bosi...@icl.utk.edu>
> wrote:
> >
> > Sorry to spoil the fun here, but this proposal is a very bad idea. It is
> mandated by the MPI standard, page 25 line 27 (v3.1), not only to provide
> all predefined datatypes, but to have support for them. There are optional
> datatypes, but MPI_DOUBLE_PRECISION (which is explicitly the base
> predefined datatype for MPI_2DOUBLE_PRECISION) is not one of them.
> >
> > Now we can argue if DOUBLE PRECISION in Fortran is a double in C. As
> these languages are interoperable, and there is no explicit conversion
> function, it is safe to assume this is the case. Thus, is seems to me
> absolutely legal to provide the MPI-required support for DOUBLE PRECISION
> despite the fact that Fortran support is not enabled.
> >
> > Now taking a closer look at the op, I see nothing in the standard the
> would require to provide the op if the corresponding language is not
> supported. While it could be nice (as a convenience for the users and also
> because there is no technical reason not to) to enable the loc op, on non
> native datatypes, this is not mandatory. Thus, the current behavior exposed
> by Open MPI is acceptable from the standard perspective.
> >
> > George.
> >
> >
> > On Mon, Feb 8, 2016 at 4:35 PM, Jeff Squyres (jsquyres) <
> jsquy...@cisco.com> wrote:
> >>
> >> Awesome; thanks Gilles.
> >>
> >>
> >> > On Feb 8, 2016, at 9:29 AM, Gilles Gouaillardet <
> gilles.gouaillar...@gmail.com> wrote:
> >> >
> >> > ok, will do
> >> >
> >> > Cheers,
> >> >
> >> > Gilles
> >> >
> >> > On Monday, February 8, 2016, Jeff Squyres (jsquyres) <
> jsquy...@cisco.com> wrote:
> >> > I like your suggestion better -- if we can somehow report during the
> compile/link that the reason for the error is because Open MPI was not
> compiled with Fortran support, that would definitely be preferable.
> >> >
> >> > FWIW: my suggestion was because I wanted to convey the *reason* for
> the error (i.e., that OMPI has no Fortran support), and a pragma-based
> solution didn't occur to me. I didn't want to follow Gilles' suggestion of
> just removing the symbols, because that will lead to other confusion (e.g.,
> "Hey, Open MPI is not compliant because it doesn't have Fortran datatypes
> available in C!").
> >> >
> >> > Gilles: do you want to poke around and see if you can make any of
> Jeff's suggestions work out nicely? (i.e., give some kind of compile/link
> error that states that Open MPI was not built with Fortran support?)
> >> >
> >> >
> >> > On Feb 8, 2016, at 8:55 AM, Jeff Hammond <jeff.scie...@gmail.com>
> wrote:
> >> > >
> >> > > Waiting until runtime to issue this error is a terrible idea,
> because then the PETSc team (among others) will disparage you for allowing
> a user to successfully build against an unusable library. They are
> on-record numerous times in the past as to the evils of e.g. no-op symbols
> in MPI or other runtime libraries, since this means that compile- and
> link-based tests pass, even though nothing good will happen when the user
> employs them in an application.
> >> > >
> >> > > The right thing to do is what Gilles proposed: do not define the
> types in mpi.h so that it is impossible to compile C code with Fortran
> datatypes, if Fortran datatypes are not supported. There are more and less
> effective ways to do this, in terms of letting the user know what is
> happening. For example, you can just not define them, which might confuse
> novices who don't know how to read error messages (HPC users are frequent
> offenders).
> >> > >
> >> > > You could use e.g.:
> >> > >
> >> > > #define MPI_DOUBLE_PRECISION choke me No Fortran support when
> library was compiled!
> >> > >
> >> > > Unfortunately, Clang colorized output emphasizes the wrong problem
> here, and ICC doesn't even echo the message at all in its error message.
> GCC issues the same error four times, and makes it relatively hard to miss
> the message.
> >> > >
> >> > > If the following GCC extension is supported, along with C99/C++11,
> you could do this:
> >> > >
> >> > > #define MPI_DOUBLE_PRECISION _Pragma("GCC error \"MPI was not
> compiled with Fortran support\"")
> >> > >
> >> > > For the _functions_ that require Fortran support, you can use e.g.
> __attribute__((error("no Fortran"))) on the function declaration, although
> neither ICC nor Clang support this, and it ends up throwing two error
> messages when compiled (only one - the right one - when only preprocessed),
> which might confuse the same folks that it is trying to help.
> >> > >
> >> > > Best,
> >> > >
> >> > > Jeff
> >> > >
> >> > > On Mon, Feb 8, 2016 at 5:14 AM, Jeff Squyres (jsquyres) <
> jsquy...@cisco.com> wrote:
> >> > > The issue at hand is trying to help the user figure out that they
> have an open MPI built without fortran support.
> >> > >
> >> > > Perhaps we should improve the error reporting at run time to
> display something about the fact that you used a fortran data type but have
> an OMPI that was compiled without fortran support.
> >> > >
> >> > > Sent from my phone. No type good.
> >> > >
> >> > > On Feb 8, 2016, at 4:00 AM, Gilles Gouaillardet <
> gilles.gouaillar...@gmail.com> wrote:
> >> > >
> >> > >> That being said, should we remove these fortran types from include
> files and libs when ompi is configure'd without fortran support ?
> >> > >>
> >> > >> Cheers,
> >> > >>
> >> > >> Gilles
> >> > >>
> >> > >> Jeff Hammond <jeff.scie...@gmail.com> wrote:
> >> > >>
> >> > >> > BTW: is there a reason you don't want to just use the C
> datatypes? The fundamental output of the index is an integer value --
> casting it to a float of some flavor doesn't fundamentally change its value.
> >> > >>
> >> > >> The code in question is not mine. I have suggested to the
> developers that they should use the correct C types. The reason I became
> aware of this issue is that one of my colleagues compiled and ran this code
> on a system where OpenMPI was built without Fortran support and the code
> started failing with errors from MPI which were not seen on other systems.
> >> > >>
> >> > >>
> >> > >> If you use an MPI library compiled without Fortran support, you
> should expect precisely nothing related to Fortran to work. You might get
> more than this because the universe is being nice to you, but you should
> treat it as serendipity when something works, not a bug when something
> doesn't.
> >> > >>
> >> > >> Jeff
> >> > >>
> >> > >>
> >> > >> --
> >> > >> Jeff Hammond
> >> > >> jeff.scie...@gmail.com
> >> > >> http://jeffhammond.github.io/
> >> > >> _______________________________________________
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> >> > >> Link to this post:
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> >> > >
> >> > > _______________________________________________
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> >> > >
> >> > >
> >> > >
> >> > > --
> >> > > Jeff Hammond
> >> > > jeff.scie...@gmail.com
> >> > > http://jeffhammond.github.io/
> >> > > _______________________________________________
> >> > > users mailing list
> >> > > us...@open-mpi.org
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> >> > > Link to this post:
> http://www.open-mpi.org/community/lists/users/2016/02/28461.php
> >> >
> >> >
> >> > --
> >> > Jeff Squyres
> >> > jsquy...@cisco.com
> >> > For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
> >> >
> >> > _______________________________________________
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> >>
> >>
> >> --
> >> Jeff Squyres
> >> jsquy...@cisco.com
> >> For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
> >>
> >> _______________________________________________
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> >
> >
> >
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>
>
>
>
> --
> Jeff Hammond
> jeff.scie...@gmail.com
> http://jeffhammond.github.io/
>
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>
