[MPIWG Fortran] MPI-3 ticket 349: Fortran question
Rolf Rabenseifner
rabenseifner at hlrs.de
Fri Dec 20 05:04:07 CST 2013
Hi Jim,
> I don't think that the proposal is in conflict with sections 2.5.6 or
> 4.1.5. These sections are talking about addresses and not
> specifically about how one can use the MPI_Aint type. We mean to
> address only the latter item -- correct usage of the MPI address
> integer type.
I also do not see a conflict.
But I see that the new concept must be explained within these sections.
This is about consistency of the whole MPI document.
> In terms of where to put the proposed text in the chapter, I suggest
> we make that a separate discussion, once the technical issues have
> been resolved.
As you mentioned below,
technically there are two solutions:
A. require that disp=addr2-addr1 and addr2=addr1+disp can be
calculated with the intrinsic arithmetic operations - and +.
This would require:
128 bit MPI_Aint on a system that
- uses full 64 bit absolute addresses, AND
- does not have one-s complement arithmetic AND
- MPI_BOTTOM is not defined in the middle
B. require that disp=addr2-addr1 and addr2=addr1+disp
is calculated with your two new functions to guarantee
that always 64 bits signed MPI_Aint are enough
to store any 64 bit unsigned absolute addresses.
If we decide A, then only an advice to implementers would be fine.
If we decide B, then several "corrections" are needed.
> I do have a concern, in particular, about section 4.1.12, "Correct
> use of Addresses", which seems to suggest that one should be able to
> do arithmetic directly on absolute addresses stored in address
> integers. The only way that this could be supported on some
> platforms (e.g. one's complement integers) is to make the MPI_Aint
> an integer that is larger than an address, so that
> overflow/underflow cannot occur. Because of Fortran's dynamic
> MPI_BOTTOM, address integers on such a platform would have to be
> 128-bits to ensure that there can be no overflow.
>
> What's your take on that section?
The notations MPI-3.0 page 115 lines 42 and 47 v+i and u-v
need not to be interpreted as C and Fortran + and -.
One could say that there is a lack of not having defined
these operations.
I principle, you are right when you expect (as all MPI-readers so far)
that + and - on these lines are C and Fortran + and -,
and therefore, solution A is required.
Note that solution A is not the worst because our systems have IEEE
data representation which has one's complements and therefore no Need
for doubling the size of MPI_Aint, especially on the pure 32-bit Blue-Gene
Systems.
If one wants to go with B (and this is a free Forum decision)
then one should add text to
> MPI-3.0 Sect. 2.5.6, page 16 lines 30-37 and
> MPI-3.0 Sect. 4.1.5, page 102 lines 28-35
and also to
- MPI 3.0 Sect. 4.1.12, page 115 line 48, e.g.,
"Note that v+i and u-v need to be calculated
with MPI_AINT_ADD and MPI_AINT_DIFF."
And the two new routines after page 103 line 46.
My mails only try to help that proposal B is fully complete
and consistent.
They are not about whether I would like to have A or B.
Because A continues to stay a work-around for B,
I would be happy with B.
Best regards
Rolf
----- Original Message -----
> From: "Jim Dinan" <james.dinan at gmail.com>
> To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> Cc: "MPI-WG Fortran working group" <mpiwg-fortran at lists.mpi-forum.org>, "longb" <longb at cray.com>
> Sent: Thursday, December 19, 2013 9:55:42 PM
> Subject: Re: [MPIWG Fortran] MPI-3 ticket 349: Fortran question
>
>
> Hi Rolf,
>
>
> I don't think that the proposal is in conflict with sections 2.5.6 or
> 4.1.5. These sections are talking about addresses and not
> specifically about how one can use the MPI_Aint type. We mean to
> address only the latter item -- correct usage of the MPI address
> integer type.
>
>
> In terms of where to put the proposed text in the chapter, I suggest
> we make that a separate discussion, once the technical issues have
> been resolved.
>
>
> I do have a concern, in particular, about section 4.1.12, "Correct
> use of Addresses", which seems to suggest that one should be able to
> do arithmetic directly on absolute addresses stored in address
> integers. The only way that this could be supported on some
> platforms (e.g. one's complement integers) is to make the MPI_Aint
> an integer that is larger than an address, so that
> overflow/underflow cannot occur. Because of Fortran's dynamic
> MPI_BOTTOM, address integers on such a platform would have to be
> 128-bits to ensure that there can be no overflow.
>
>
> What's your take on that section?
>
>
> ~Jim.
>
>
>
> On Fri, Dec 13, 2013 at 9:11 AM, Rolf Rabenseifner <
> rabenseifner at hlrs.de > wrote:
>
>
> Jim,
>
>
> > Could you provide a list of the specific changes that you feel are
> > needed on these tickets?
>
> I expected that you are doining this.
> I only want to mention the locations.
>
> Your new model differentiates beween
> - absolute addresses generated from locations with MPI_GET_ADDRESS
> - relative displacements as differences of two absolute addresses
> and the needed arithmetic
> - relative displacements with normal + - * arithmetic
> - absolute addresses and displacments with
> MPI_AINT_ADD and MPI_AINT_DIFF arithmetic
>
> Therefore:
> MPI-3.0 Sect. 2.5.6, page 16 lines 30-37 and
> MPI-3.0 Sect. 4.1.5, page 102 lines 28-35
> should reflect this differentiation.
>
> The proposed rationale in #349 may go at the end of page 102 lines
> 28-35.
> After MPI-3.0 Sect. 4.1.5, page 103 line 46, you should add
> MPI_AINT_ADD and MPI_AINT_DIFF.
>
>
> Best regards
> Rolf
>
>
>
> ----- Original Message -----
> > From: "Jim Dinan" < james.dinan at gmail.com >
> > To: "Rolf Rabenseifner" < rabenseifner at hlrs.de >
> > Cc: "MPI-WG Fortran working group" <
> > mpiwg-fortran at lists.mpi-forum.org >, "longb" < longb at cray.com >
>
>
> > Sent: Friday, December 13, 2013 1:35:13 PM
> > Subject: Re: [MPIWG Fortran] MPI-3 ticket 349: Fortran question
> >
> >
> > Rolf,
> >
> >
> > Could you provide a list of the specific changes that you feel are
> > needed on these tickets? For reference, and to bring in feedback
> > from others on the cc, we are discussing:
> >
> >
> > MPI_Aint_add --
> > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/349
> > Linked list example updates --
> > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/402
> > MPI_Aint_diff --
> > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/404
> >
> >
> > Let's solve the technical issues first to see where things stand,
> > and
> > then come back to the issue of how to handle voting on these
> > changes.
> >
> >
> > Thank you for helping to improve these tickets!
> >
> >
> > Best,
> > ~Jim.
> >
> >
> >
> > On Thu, Dec 12, 2013 at 12:34 PM, Rolf Rabenseifner <
> > rabenseifner at hlrs.de > wrote:
> >
> >
> > Dear Jim,
> >
> > I would like to disagree.
> > Looking at #349, I see wording like "base address" etc.
> > whereas MPI-3.0 p102.29 uses "absolute address".
> >
> > And, the ticket does not show the location of the new text,
> > nor all the needed background info.
> >
> > MPI is a standard document and the proposed change
> > (absolute addresses can no longer be used in
> > normal arithmetic) should be well prepared.
> >
> > The current text is not ready.
> >
> > You start to differentiate between "absolute addresses"
> > and "relative displacements" and their use of MPI_Aint.
> >
> > Please have a look at 2.5.6 on page 16.
> > This section should be clarified.
> >
> > Please try to produce one proposal that is complete
> > and fits to the standard.
> > Voting in small pieces (several tickets) is not the best.
> >
> >
> > Best regards
> > Rolf
> >
> > ----- Original Message -----
> > > From: "Jim Dinan" < james.dinan at gmail.com >
> > > To: "Rolf Rabenseifner" < rabenseifner at hlrs.de >
> > > Cc: "MPI-WG Fortran working group" <
> > > mpiwg-fortran at lists.mpi-forum.org >, "longb" < longb at cray.com >,
> > > "Jim Dinan"
> > > < dinan at mcs.anl.gov >
> >
> >
> > > Sent: Thursday, December 12, 2013 5:51:30 PM
> > > Subject: Re: [MPIWG Fortran] MPI-3 ticket 349: Fortran question
> > >
> > >
> > > Hi Rolf,
> > >
> > >
> > > Thanks for the corrections -- I apologize, what I had sent was a
> > > very
> > > rough draft of the proposal. I applied your changes to the
> > > proposal, cleaned some things up, and added the datatypes
> > > examples
> > > corrections. Could you take another look when you get a chance?
> > >
> > >
> > > In terms of proposal logistics, I would like to let MPI_Aint add
> > > and
> > > diff tickets progress independently. I agree that they need to
> > > be
> > > together, and I think we can rely on the chapter committee to
> > > handle
> > > that if add/diff end up split between two versions of the
> > > standard.
> > > MPI_Aint_diff should be ready for a reading at the next meeting
> > > and
> > > MPI_Aint_add will be ready for a first vote. Given the
> > > discussion
> > > about MPI 3.x/4.0 timeline yesterday, I think the risk of these
> > > not
> > > being in the same release of the spec is very low. Since the
> > > Forum
> > > has already done all of the work required to move MPI_Aint_add to
> > > a
> > > vote, I would prefer not to rewind this process by merging it
> > > with
> > > the diff ticket.
> > >
> > >
> > > ~Jim.
> > >
> > >
> > >
> > > On Thu, Dec 12, 2013 at 9:14 AM, Rolf Rabenseifner <
> > > rabenseifner at hlrs.de > wrote:
> > >
> > >
> > > Jim and all,
> > >
> > > MPI_Get_address((char *) addr1 - (char *) addr2, &result)
> > >
> > > This is really wrong, because (char *) addr1 - (char *) addr2
> > > is not an address and cannot be used as input to MPI_Get_address.
> > >
> > > (char *) addr1 - (char *) addr2 is a displacement.
> > >
> > > Both tickets 349 and 404 need to be together, because they
> > > are based on a clear distinguishing between
> > > - Location in memory (input of MPI_GET_ADDRESS), e.g. x, y
> > > - absolute addresses (output of MPI_GET_ADDRESS), e.g., addr_x,
> > > addr_y
> > > - relative displacements (diff of two absolute addresses), e.g.
> > > dist_xy
> > >
> > > Your new statement is that calculations like
> > > dist_xy = addr_y - addr_x
> > > addr_y = addr_x + dist_xy
> > > need to be done by subroutine calls or functions,
> > > because absolute addresses are stored in MPI_Aint variables
> > > through some (unknown/strange) mapping,
> > > wheras relative displacements are normal unsigned integers
> > > that can be used for normal arithmetic.
> > >
> > > The one ticket must show this clearly and must be integrated into
> > > section 4.1.5
> > >
> > >
> > > Best regards
> > > Rolf
> > >
> > >
> > > ----- Original Message -----
> > >
> > >
> > > > From: "Jim Dinan" < james.dinan at gmail.com >
> > > > To: "Rolf Rabenseifner" < rabenseifner at hlrs.de >
> > > > Cc: "MPI-WG Fortran working group" <
> > > > mpiwg-fortran at lists.mpi-forum.org >, "longb" < longb at cray.com
> > > > >,
> > > > "Jim Dinan"
> > > > < dinan at mcs.anl.gov >
> > > > Sent: Thursday, December 12, 2013 3:20:41 PM
> > > > Subject: Re: [MPIWG Fortran] MPI-3 ticket 349: Fortran question
> > > >
> > > >
> > > > Hi Rolf,
> > > >
> > > >
> > > > Thank you very much for the feedback! Sorry if I forgot to
> > > > respond;
> > > > the comments definitely were not ignored. We discussed the
> > > > Aint
> > > > difference calculation in the working group and decided to
> > > > create
> > > > an
> > > > additional ticket for MPI_Aint_disp. We did not see a clean
> > > > way
> > > > to
> > > > handle this in MPI_Aint_add, because both arguments need to be
> > > > handled as unsigned in the arithmetic.
> > > >
> > > >
> > > > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/404
> > > >
> > > >
> > > >
> > > > I have a list of fixes the to the datatypes examples that I'll
> > > > post
> > > > to the ticket soon.
> > > >
> > > >
> > > > Jeff Squyres is also helping us move the MPI_Aint arithmetic
> > > > routines
> > > > to functions in the Fortran bindings. Should be done today.
> > > >
> > > >
> > > > Were there any other concerns that we missed?
> > > >
> > > >
> > > > Thanks,
> > > > ~Jim.
> > > >
> > > >
> > > >
> > > > On Thu, Dec 12, 2013 at 1:42 AM, Rolf Rabenseifner <
> > > > rabenseifner at hlrs.de > wrote:
> > > >
> > > >
> > > > Jeff and Bill,
> > > >
> > > > <
> > > > https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/349#comment:22
> > > > >
> > > > was ignored.
> > > > The answer seems to be yes and the clear implication is that
> > > > we need also a routine to calculate disp := addr2-addr1
> > > >
> > > > About the Fortran Interfaces:
> > > > We should keep the old style without INTENT, because for the
> > > > old-style
> > > > the implementor has the freedom to add INTENT as he/she wants
> > > > and it is still compliant with the outcome of the definition.
> > > >
> > > > I do not see, why we have a function in C and a subroutine
> > > > in Fortran.
> > > > Like MPI_Wtime, in all three languages (C, new and old
> > > > Fortran),
> > > > we should do the same.
> > > >
> > > > Best regards
> > > > Rolf
> > > >
> > > > ----- Original Message -----
> > > > > From: "Jeff Squyres (jsquyres)" < jsquyres at cisco.com >
> > > > > To: "< longb at cray.com >" < longb at cray.com >, "MPI-WG Fortran
> > > > > working group" < mpiwg-fortran at lists.mpi-forum.org >
> > > > > Sent: Thursday, December 12, 2013 12:17:40 AM
> > > > > Subject: Re: [MPIWG Fortran] MPI-3 ticket 349: Fortran
> > > > > question
> > > > >
> > > > > Sounds good to me.
> > > > >
> > > > > Rolf -- is there any MPI reason we would not want to do this?
> > > > >
> > > > >
> > > > > On Dec 11, 2013, at 4:41 PM, Bill Long < longb at cray.com >
> > > > > wrote:
> > > > >
> > > > > >
> > > > > >
> > > > > > On 12/11/13 11:27 AM, Jeff Squyres (jsquyres) wrote:
> > > > > >> This ticket got a formal reading today at the Forum:
> > > > > >>
> > > > > >> http://svn.mpi-forum.org/trac/mpi-forum-web/ticket/349
> > > > > >> (as of this writing, there's still a BIND(C) in there,
> > > > > >> but
> > > > > >> it
> > > > > >> will be removed shortly)
> > > > > >>
> > > > > >> The function is basically intended to perform a
> > > > > >> mathematical
> > > > > >> operation. As such, I think that the 2 Fortran bindings
> > > > > >> should
> > > > > >> be FUNCTIONs, not SUBROUTINEs (a la MPI_WTICK/MPI_WTIME).
> > > > > >>
> > > > > >> Do you agree? If so, the ticket author (Jim Dinan) is
> > > > > >> amenable
> > > > > >> to
> > > > > >> changing the Fortran bindings to the following (and I'm
> > > > > >> assuming
> > > > > >> I have the syntax below correct, but feel free to correct
> > > > > >> me
> > > > > >> if
> > > > > >> they're wrong):
> > > > > >>
> > > > > >
> > > > > > Certainly it makes more sense for these to be functions in
> > > > > > Fortran.
> > > > > > Particularly if the programmer prefers supply an interface
> > > > > > and
> > > > > > call the C form directly. If the C and Fortran versions
> > > > > > are
> > > > > > both
> > > > > > functions, there is no change in the source code where the
> > > > > > function is used.
> > > > > >
> > > > > >> -----
> > > > > >> INTEGER(KIND=MPI_ADDRESS_KIND) MPI_Aint_add(base, disp)
> > > > > >> INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: base,
> > > > > >> disp
> > > > > >>
> > > > > >> INTEGER(KIND=MPI_ADDRESS_KIND) MPI_AINT_ADD(BASE, DISP)
> > > > > >> INTEGER(KIND=MPI_ADDRESS_KIND) BASE, DISP
> > > > > >
> > > > > > It is certainly an oddity that the spec has two forms like
> > > > > > this.
> > > > > > Any version of the Fortran standard that supports KIND= in
> > > > > > INTEGER also supports lower case names and INTENT()
> > > > > > attributes.
> > > > > > Maybe there could be some clean up of this in a future
> > > > > > revision.
> > > > > >
> > > > > > Cheers,
> > > > > > Bill
> > > > > >
> > > > > >
> > > > > >
> > > > > >> -----
> > > > > >>
> > > > > >
> > > > > > --
> > > > > > Bill Long
> > > > > > longb at cray.com
> > > > > > Fortran Technical Support & voice:
> > > > > > 651-605-9024
> > > > > > Bioinformatics Software Development fax:
> > > > > > 651-605-9142
> > > > > > Cray Inc./Cray Plaza, Suite 210/380 Jackson St./St. Paul,
> > > > > > MN
> > > > > > 55101
> > > > > >
> > > > > >
> > > > > > _______________________________________________
> > > > > > mpiwg-fortran mailing list
> > > > > > mpiwg-fortran at lists.mpi-forum.org
> > > > > > http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-fortran
> > > > >
> > > > >
> > > > > --
> > > > > Jeff Squyres
> > > > > jsquyres at cisco.com
> > > > > For corporate legal information go to:
> > > > > http://www.cisco.com/web/about/doing_business/legal/cri/
> > > > >
> > > > > _______________________________________________
> > > > > mpiwg-fortran mailing list
> > > > > mpiwg-fortran at lists.mpi-forum.org
> > > > > http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-fortran
> > > > >
> > > >
> > > > --
> > > > 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: Room
> > > > 1.307)
> > > >
> > > >
> > >
> > > --
> > > 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: Room
> > > 1.307)
> > >
> > >
> >
> > --
> > 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: Room
> > 1.307)
> >
> >
>
> --
> 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: Room 1.307)
>
>
--
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: Room 1.307)
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