[mpiwg-rma] RMA Errata

[Jeff Hammond]

I don't see why it matters which process allocated the memory.  These
are synchronization operations we are talking about and the notion of
synchronization on the memory in a shared memory window should be
valid in all the synchronization modes we have specified.  I think
it's reasonable for Rolf to want PSCW to make sense for shared memory
windows.  Imagine there is hardware with a point-to-point memory fence
between processes (some of the new instructions in AArch64 have this
feel to them, btw).

And it is absolutely clear in MPI-3 that shared memory is associated
with a particular process.  See the rank argument in
http://www.mpich.org/static/docs/v3.1/www3/MPI_Win_shared_query.html.
This function takes process rank as an _input_, which means that there
is a well-defined notion of memory associated with a particular
process.

Jeff

On Sun, Jan 25, 2015 at 11:19 AM, William Gropp <wgropp at illinois.edu> wrote:
> I think this is simply more evidence that the shared memory access should
> entirely be through the valid language-specified mechanisms, including
> interaction with other routines and threads that may access the same memory.
>
> I most definitely do not think that the load/store access to shared memory
> is intended to be associated only with memory that was somehow “allocated”
> by a particular process.  I’m not even sure how I’d define that without
> referring to a particular implementation.
>
> Bill
>
> On Jan 22, 2015, at 2:30 AM, Rolf Rabenseifner <rabenseifner at hlrs.de> wrote:
>
> #1 -- The effective target rank of load/store operations is currently not
> defined on shared memory windows.  That statement may seem like nonsense.
> However, it is important for situations where load/store operations interact
> with RMA operations that do have an explicit target rank (e.g.
> lock/unlock).  I believe this was an oversight, and we intended that the
> load/store operations target the rank that allocated the memory.
>
>
>
> _______________________________________________
> mpiwg-rma mailing list
> mpiwg-rma at lists.mpi-forum.org
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma



-- 
Jeff Hammond
jeff.science at gmail.com
http://jeffhammond.github.io/