[mpiwg-rma] Questions about multiple overlapped windows

Tatsuya Abe abetatsuya at gmail.com
Sun Dec 7 18:57:25 CST 2014

Dear all,

I am interested in memory consistency models, and studying program
verification with memory consistency models.  I started to read MPI
3.0 document (and Dr. Torsten Hoefler's tutorial slides).

I am wondering if you could give replys to my questions.
I have two questions about multiple overlapped windows:

1. (Assume that I create two overlapped windows.)  What happens if I
   do MPI_Put through one window and MPI_Get through the other window?

2. I am wondering what are multiple overlapped windows for.

1. I can find no description about the first question in MPI 3.0

   I found Torsten's slides (credit by RMA Working Group, MPI Forum),
   which explicitly showed relations between operations (Load, Store,
   Get, Put, and Acc) on pp.82--84.  But, it seems an explaination
   when exactly one window is created,

   For example, page 83 of the slide seems to claim that Put and
   Get are allowed when they are not NOVL (non-overlapped)
   through one window in separate semantics.

   One of my questions is ``are Put and Get allowed when they are
   not NOVL (non-overlapped) through *two* *overlapped* windows
   in separate semantics?''  I would like to get such table about
   multiple windows.

2. I can find no example about multiple overlapped windows except
   Figure 11.1 in MPI 3.0 document. Also, I suspect that Put and Get
   are allowed when they are not NOVL (non-overlapped) through two
   overlapped windows in separate semantics.

   I cannot come up with any useful example code.  Why are multiple
   *and* overlapped windows allowed to be active?


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