[Mpi3-rma] Draft Plenary Presentation for MPI RMA

[James Dinan]

Hi Torsten,

On 02/04/2011 12:35 PM, Torsten Hoefler wrote:
>> Slide 22: UPC doesn't allow sharing data on the stack, only heap data
>> can be shared.  In general, this is kind of an iffy thing, might
>> encounter some resistance to suggest doing this.  Linux is going to
>> initially map the stack to the zero page which is marked copy-on-write,
>> so beyond the parts you have used, the stack doesn't exist.
 >
> That's what registration is for. It has to be created then. Or am I
> missing something?

UPC doesn't allow shared variables on the stack and I can't think of any 
other PGAS model that does.  So, the argument of registering and 
exposing the stack doesn't seem like it holds water to me.

I believe Dan, et al.'s issue with MPI_Alloc_mem as a requirement is 
that *static* shared UPC objects could not be put into windows.  Static 
distributed shared arrays are one of the most common use cases in UPC. 
Adding win_register now allows you to register statically declared 
arrays and expose them in a window.

  ~Jim.