Bill, Rajeev, and all other RMA WG members, Hubert and Torsten discussed already in 2012 the meaning of the MPI one-sided synchronization routines for MPI-3.0 shared memory. This question is still unresolved in the MPI-3.0 + errata. Does the term "RMA Operation" include "a remote load/store from an origin process to the window Memory on a target"? Or not? The ticket #435 expects "not". In this case, MPI_Win_fence and post-start-complete-wait cannot be used for synchronizing the sending process of data with the receiving process of data that use only local and remote load/stores on shared memory windows. Ticket 435 extends the meaning of MPI_Win_fence and post-start-complete-wait that they provide sender-Receiver synchronization between processes that use local and remote load/stores on shared memory windows. I hope that all RMA working group members, agree that - currently the behavior of these sync-routines for shared memory remote load/stores is undefined due to the undefined definition of "RMA Operation" - and that we need an errata that resolves this problem. What is your opinion about the solution provided in https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/435 ? Best regards Rolf PS: Ticket 435 is the result of a discussion of Pavan, Hubert and I at ISC2014. ----- Original Message -----

From: Hubert Ritzdorf Sent: Tuesday, September 11, 2012 7:26 PM To: [email protected] Subject: MPI_Win_allocate_shared and synchronization functions

Hi,

it's quite unclear what Page 410, Lines 17-19

A consistent view can be created in the uni?fied memory model (see Section 11.4) by utilizing the window synchronization functions (see Section 11.5)

really means. Section 11.5 doesn't mention any (load/store) access to shared memory. Thus, must

(*) RMA communication calls and RMA operations be interpreted as RMA communication calls (MPI_GET, MPI_PUT, ...) and ANY load/store access to shared window (*) put call as put call and any store to shared memory (*) get call as get call and any load from shared memory (*) accumulate call as accumulate call and any load or store access to shared window ?

Example: Assertion MPI_MODE_NOPRECEDE

Does

the fence does not complete any sequence of locally issued RMA calls

mean for windows created by MPI_Win_Allocate_shared ()

the fence does not complete any sequence of locally issued RMA calls or any load/store access to the window memory ?

It's not clear to me. I will be probably not clear for the standard MPI user. RMA operations are defined only MPI functions for window objects (as far as I can see). But possibly I'm totally wrong and the synchronization functions synchronize only the RMA communication calls (MPI_GET, MPI_PUT, ...).

Hubert

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Wednesday, September 12, 2012 11:37 AM

Hubert,

This is what I was referring to. I'm in favor of this proposal.

Torsten

-- Dr. Rolf Rabenseifner . . . . . . . . . .. email [email protected] High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307)