[Mpi3-rma] Draft Plenary Presentation for MPI RMA
dinan at mcs.anl.gov
Fri Feb 4 14:45:42 CST 2011
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.
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