Re: [mpiwg-rma] Problems with RMA synchronization in combination with load/store shared memory accesses
Errata and changes to the documents are separate. Errata take effect when passed. Bill William Gropp Director, Parallel Computing Institute Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Jun 1, 2014, at 9:06 PM, Jeff Hammond wrote:
For MPI-3.1?
On Sunday, June 1, 2014, William Gropp <[email protected]> wrote: We can always do errata.
Bill
William Gropp Director, Parallel Computing Institute Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign
On Jun 1, 2014, at 8:51 PM, Jim Dinan wrote:
I tend to agree with Jeff. On some architectures different operations are requires to make my operations visible to others versus making operations performed by others visible to me.
Is this meeting the last call for errata, or is it the September meeting?
~Jim.
On Sat, May 31, 2014 at 4:44 PM, Jeff Hammond <[email protected]> wrote: Remote load-store cannot be treated like local load-store from a sequential consistency perspective. If a process does local load-store, it is likely that no memory barrier will be required to see a consistent view of memory. When another process does load-store, this changes dramatically.
Jeff
On Sat, May 31, 2014 at 3:31 PM, Rajeev Thakur <[email protected]> wrote:
I think before ticket 429 (https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/429) is put up for a vote as errata, the RMA working group needs to decide whether remote loads/stores to shared memory windows are treated as local loads and stores or as put/get operations (for the purpose of the assert definitions). The text will be different depending on that.
If remote loads/stores to shared memory windows are considered as local loads/stores they will be covered under MPI_MODE_NOSTORE; if considered as put/get operations, they will be covered under MPI_MODE_NOPRECEDE, MPI_MODE_NOSUCCEED, and MPI_MODE_NOPUT.
Ticket 429 says they should be considered as local loads/stores.
Rajeev
On May 27, 2014, at 1:25 PM, Jim Dinan <[email protected]> wrote:
Hi Rolf,
MPI_MODE_NOSTORE applies to local updates that should be made visible to other processes following the end of the access epoch. I believe that visibility of updates made by other processes were intended to be incorporated into the NOPRECEDE/NOSUCCEED assertions. I think that Hubert's proposal may be the right approach -- that remote load/store accesses to the shared memory window should be treated as "RMA" (e.g. analogous to get/put) operations.
~Jim.
On Mon, May 19, 2014 at 1:16 PM, Rolf Rabenseifner <[email protected]> wrote: Jim and RMA WG,
There are now two questions:
Jim asked:
Question to WG: Do we need to update the fence assertions to better define interaction with local load/store accesses and remote stores?
Rolf asked:
Additionally, I would recommend that we add after MPI-3.0 p451:33
Note that in shared memory windows (allocated with MPI_WIN_ALLOCATE_SHARED), there is no difference between remote store accesses and local store accesses to the window.
This would help to understand that "the local window was not updated by stores" does not mean "by local stores", see p452:1 and p452:9.
For me, it is important to understand the meaning of the current assertions if they are used in a shared memory window. Therefore my proposal above as erratum to MPI-3.0.
In MPI-3.1 and 4.0, you may want to add additional assertions.
Your analysis below, will also show that mpich implements Post-Start-Complete-Wait synchronization in a wrong way, if there are no calls to RMA routines.
Best regards Rolf
----- Original Message -----
From: "Jim Dinan" <[email protected]> To: "MPI WG Remote Memory Access working group" <[email protected]>
-- Jeff Hammond [email protected] http://jeffhammond.github.io/ _______________________________________________ mpiwg-rma mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma
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William Gropp