[mpiwg-rma] MPI_Win_create on unmapped memory?

[William Gropp]

Yes.  The r and l values must remain valid until the free.

Bill

William Gropp
Director and Chief Scientist, NCSA
Thomas M. Siebel Chair in Computer Science
University of Illinois Urbana-Champaign






> On Jan 2, 2018, at 2:52 PM, Nathan Hjelm <hjelmn at mac.com> wrote:
> 
> I would expect that the intent is also that the memory should not be freed/unmapped before the matching call to MPI_Win_free() correct?
> 
> -Nathan
> 
> On Jan 02, 2018, at 01:19 PM, William Gropp <wgropp at illinois.edu> wrote:
> 
>> It was certainly the intent that the memory be allocated.  Specifically, if a is the pointer and the region is of length L, then (assuming char *a and ) a[0] … a[L-1] must be valid r and l values at the point of the call.
>> 
>> Bill
>> 
>> William Gropp
>> Director and Chief Scientist, NCSA
>> Thomas M. Siebel Chair in Computer Science
>> University of Illinois Urbana-Champaign
>> 
>>> On Jan 2, 2018, at 1:52 PM, Jeff Hammond <jeff.science at gmail.com <mailto:jeff.science at gmail.com>> wrote:
>>> If a user passes a (base,size) pair that corresponds to a range of addresses that are not allocated and/or mapped, is that a correct MPI program?
>>> 
>>> The only text I can find that implies that buffers passed to MPI_Win_create have to be allocated is the following, assuming that one interprets "existing memory" this way.  
>>> 
>>> "Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of comm." (MPI 3.1 11.2.1)
>>> 
>>> The Fortran-specific text is similarly suggestive, but it only says that a user can pass a simply contiguous array, not that such a thing is required.
>>> 
>>> "In Fortran, one can pass the first element of a memory region or a whole array, which must be ‘simply contiguous’"
>>> 
>>> Thanks,
>>> 
>>> Jeff
>>> 
>>> --
>>> Jeff Hammond
>>> jeff.science at gmail.com <mailto:jeff.science at gmail.com>
>>> http://jeffhammond.github.io/ <http://jeffhammond.github.io/>_______________________________________________
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