[mpiwg-rma] RMA Errata

Jeff Hammond jeff.science at gmail.com
Wed Jan 28 16:22:40 CST 2015

Thanks.  I understand that this isn't an easy issue.  We are trying to
use MPI-3 shared memory windows internally with PSCW-like
synchronization and I am inclined to just give up and use x86
intrinsics to do what I know is sufficient for our processors and
compilers, just to make it easy (and fast).


On Wed, Jan 28, 2015 at 1:43 PM, William Gropp <wgropp at illinois.edu> wrote:
> That’s a harder topic and I wanted to think more about it.  Here are the two
> issues with which I am most concerned:
> 1) We are defining the interaction of MPI with stuff that happens outside of
> MPI, in the programming language.  Yes, we always sort of did, but this is
> in an area where many skilled people have made mistakes, and the likelyhood
> of an error is much higher.  The lack of precision in these discussions
> reinforces my concern.
> 2) We are not considering the potential overhead that requiring other than a
> small set of RMA synchronization routines to guarantee some shared memory
> synchronization.  The sense that I get is that the Forum is unconcerned
> about this, which I think is a serious mistake, and one for which I have yet
> to see a compelling use case.
> Bill
> On Jan 28, 2015, at 7:46 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
> Fine, but it would be helpful if you would respond to my comments
> about allowing point-to-point _synchronization_ on shared memory using
> PSCW, since those were the more germane ones anyways.
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Jeff Hammond
jeff.science at gmail.com

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