On 11 February 2010 15:06, George Bosilca wrote:
> This is absolutely not true. Open MPI supports zero length collective
> operations (all of them actually), but if their arguments are correctly
> shaped.
>
OK, you are right here ...
> What you're asking for is a free ticket to write MPI calls
This is absolutely not true. Open MPI supports zero length collective
operations (all of them actually), but if their arguments are correctly shaped.
What you're asking for is a free ticket to write MPI calls that do not follow
the MPI requirements when a special value for count is given.
While
Jeff Squyres wrote:
There's no synchronization *guarantee* in MPI collectives except for
MPI_BARRIER. [...] BCAST *can* synchronize; I'm not saying it has to.
I fully agree with Jeff and would even go a step further.
As has already been noted, there are also some implicit data
dependencies
On 11 February 2010 12:04, George Bosilca wrote:
>
> Therefore, we can argue as much as you want about what the correct arguments
> of a reduce call should be, a reduce(count=0) is one of the meaningless MPI
> calls and as such should not be tolerated.
>
Well, I have to disagree... I understand
On Feb 11, 2010, at 10:04 AM, George Bosilca wrote:
>> I misparsed your reply. Yes, bcast(1) *can* sync if it wants to. I don't
>> have a spec handy to check if bcast(0) is defined or not (similar to
>> reduce). If it is, then sure, it could sync as well.
>
> I have to disagree here. There are
could sync as well.
My previous point was that barrier is the only collective that is
*required* to synchronize.
From: devel-boun...@open-mpi.org
To: de...@open-mpi.org
Sent: Thu Feb 11 07:04:59 2010
Subject: Re: [OMPI devel] failure
withzero-lengthReduce()andbothsbuf=rbuf
>
> From: devel-boun...@open-mpi.org
> To: de...@open-mpi.org
> Sent: Thu Feb 11 07:04:59 2010
> Subject: Re: [OMPI devel] failure
> withzero-lengthReduce()andbothsbuf=rbuf=NULL
>
> Where does bcast(1) synchronize?
>
> (Oops on typo - if reduce(1) wasn't defined
onize.
-jms
Sent from my PDA. No type good.
From: devel-boun...@open-mpi.org
To: de...@open-mpi.org
Sent: Thu Feb 11 07:04:59 2010
Subject: Re: [OMPI devel] failure withzero-lengthReduce()andbothsbuf=rbuf=NULL
Where does bcast(1) synchronize?
(Oops on typo
