[mpi3-coll] Ticket 170, comment 9, both items

[Rolf Rabenseifner]

Torsten,

please comment on ticket 170 why the sentence

 The routine is called by all group members using 
 the same arguments for count, datatype, op and comm. 

should be wrong for MPI_SCAN and MPI_EXSCAN
while this sentence is true
for MPI_REDUCE and MPI_ALLREDUCE.

Without details, I would expect that this ticket 170 item
is absolutely correct and should be done as a ticket 0
change to clarify which rules are valid for the scan routines.
All other reductions are clear about this.

I do not expect that you want to allow that one
process uses MPI_FLOAT, another MPI_DOUBLE and both use MPI_SUM.
I'm not sure wether current text does not allow this.
Therefore clarifying wording is needed.

I would like to see the arguments and proposals in the comments to #170,
rather than only discussion at the meeting.

Best regards
Rolf


----- Original Message -----
> From: "Torsten Hoefler" <htor at illinois.edu>
> To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>
> Cc: "George Bosilca" <bosilca at eecs.utk.edu>
> Sent: Sunday, July 15, 2012 11:24:35 PM
> Subject: Re: Ticket 170, comment 9, both items
> Rolf,
> 
> This is in no way a ticket 0, it changes semantics and I know of a
> code
> that will break if we change this. I would at least like to see a
> discussion in the Forum.
> 
> Thanks,
> Torsten
> 
> On Sat, Jul 14, 2012 at 12:14:04PM +0200, Rolf Rabenseifner wrote:
> > Torsten and George,
> >
> > please commit attached coll.tex and inquiry.tex as soon as possible
> > with
> > (Torsten, please after the coll.tex in my previous Ticket 166 mail)
> >
> > Torsten:
> >   svn ci coll.tex 'Ticket 170, Item 1 - ticket-0-change marked with
> >   0.170'
> >
> > George:
> >   svn ci inquiry.tex 'Ticket 170, Item 2 - ticket-0-change marked
> >   with 0.170'
> >
> > Torsten, the added sentence is the same as for MPI_REDUCE (but
> > without root).
> > It is not needed in MPI_ALLREDUCE due to the very strong MPI-2.2
> > p175:42-43.
> > But in MPI_SCAN and EXSCAN it was missing and is now added.
> > It is ticket-0 because it does not hurt any implementation or
> > application
> > and it is needed because it is undefined in MPI-2.2.
> >
> > George, your change is done already partially a few lines above.
> > Also ticket-0.
> >
> > (I currently try to fix some overseen errors known for years.
> > Ticket 170 is one of these error lists.)
> >
> > Best regards
> > Rolf
> >
> >
> > --
> > 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)
> 
> 
> 
> --
> ### qreharg rug ebs fv crryF ------------- http://www.unixer.de/ -----
> Linux is like a wigwam: no Windows, no Gates, Apache inside.

-- 
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)