[Mpi3-rma] Use cases for RMA

[Greg Lindahl]

Bronis,

I've had good success using a dedicated rank or ranks to hold the
table, and 2-sided MPI operations to access it.

-- greg

On Wed, Mar 03, 2010 at 07:45:41AM -0800, Bronis R. de Supinski wrote:
> 
> Bill:
> 
> One use case that I am familiar with at LLNL is to
> distribute large read-only (write-once) tables. We
> have libraries with this access pattern; the current
> method is to replicate the tables in all MPI processes.
> We have done a prototype implementation using GAs to
> distribute the table. We also need support for caching
> values locally. I think a good RMA implementation
> would allow us to build a generic implementation of
> the distribute and cache functionality...
> 
> Bronis
> 
> 
> On Wed, 3 Mar 2010, William Gropp wrote:
> 
> > I went through the mail that was sent out in response to our request
> > for use cases, and I must say it was underwhelming.  I've included a
> > short summary below; based on this, we aren't looking at the correct
> > needs.  I don't think that these are representative of *all* of the
> > needs of RMA, but without good use cases, I don't see how we can
> > justify any but the most limited extensions/changes to the current
> > design.  Please (a) let me know if I overlooked something and (b) send
> > me (and the list) additional use cases.  For example, we haven't
> > included any of the issues needed to implement PGAS languages, nor
> > have we addressed the existing SHMEM codes.  Do we simply say that a
> > high-quality implementation will permit interoperation with whatever
> > OpenSHMEM is?  And what do we do about the RMI issue that one of the
> > two use cases that we have raises?
> >
> > Basically, I received two detailed notes for the area of Quantum
> > Chemistry.  In brief:
> >
> > MPI-2 RMA is already adequate for most parts, as long as the
> > implementation makes progress (as it is required to) on passive
> > updates.  Requires get or accumulate; rarely requires put.
> > Dynamic load balancing (a related but separate issue) needs some sort
> > of RMW.  (Thanks to Jeff Hammond)
> >
> > More complex algorithms and data structures appear to require remote
> > method invocation (RMI).  Sparse tree updates provide one example.
> > (Thanks to Robert Harrison)
> >
> > Bill
> >
> >
> > William Gropp
> > Deputy Director for Research
> > Institute for Advanced Computing Applications and Technologies
> > Paul and Cynthia Saylor Professor of Computer Science
> > University of Illinois Urbana-Champaign
> >
> >
> >
> >
> > _______________________________________________
> > mpi3-rma mailing list
> > mpi3-rma at lists.mpi-forum.org
> > http://*lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma
> >
> >
> _______________________________________________
> mpi3-rma mailing list
> mpi3-rma at lists.mpi-forum.org
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-rma