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<p><font size="2" face="sans-serif">In order to ensure all nodes get the same memory segment, they all have to use the same "key". At least if this is implemented on Unix SysV or POSIX shmem. Then there's the possibility of some nodes allocing on a sub-comm first, etc. I think its just avoiding a lot of potential complications and don't see what the downside is.</font><br>
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<font size="2" face="sans-serif">_______________________________________________<br>
Douglas Miller BlueGene Messaging Development<br>
IBM Corp., Rochester, MN USA Bldg 030-2 A410<br>
dougmill@us.ibm.com Douglas Miller/Rochester/IBM</font><br>
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<img width="16" height="16" src="cid:1__=09BBFD61DFDF17A48f9e8a93df938@us.ibm.com" border="0" alt="Inactive hide details for "Ron Brightwell" ---12/07/2010 12:14:38 AM---On 12/06/2010 05:59 PM, James Dinan wrote:"><font size="2" color="#424282" face="sans-serif">"Ron Brightwell" ---12/07/2010 12:14:38 AM---On 12/06/2010 05:59 PM, James Dinan wrote:</font><br>
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<ul style="padding-left: 72pt"><font size="1" face="sans-serif"><b>"Ron Brightwell" <rbbrigh@sandia.gov></b></font><font size="1" face="sans-serif"> </font><br>
<font size="1" face="sans-serif">Sent by: mpi3-hybridpm-bounces@lists.mpi-forum.org</font>
<p><font size="1" face="sans-serif">12/07/2010 12:11 AM</font>
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mpi3-hybridpm@lists.mpi-forum.org</font></div></td></tr>
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<ul style="padding-left: 7pt"><font size="1" face="sans-serif">"mpi3-hybridpm@lists.mpi-forum.org" <mpi3-hybridpm@lists.mpi-forum.org></font></ul>
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<ul style="padding-left: 7pt"><font size="1" face="sans-serif">Re: [Mpi3-hybridpm] Hybrid WG meeting at the Forum</font></ul>
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<tt><font size="2">On 12/06/2010 05:59 PM, James Dinan wrote:<br>
> On 12/6/10 5:49 PM, Pavan Balaji wrote:<br>
>> Hi Doug,<br>
>><br>
>> On 12/06/2010 11:42 AM, Douglas Miller wrote:<br>
>>> Re: SHMEM ALLOC: I thought we were considering adding a "const char<br>
>>> *key" param so that shared memory allocations better match OS (e.g.<br>
>>> POSIX) shmem allocations and also to allow the call to be<br>
>>> non-synchronizing.<br>
>><br>
>> As I recalled, this was still being discussed. Did we decide on adding<br>
>> the key? Ron?<br>
>><br>
>> I'll add it in as a discussion item.<br>
><br>
> I think that the key is primarily helpful as a bootstrap mechanism for<br>
> processes to ensure they connect to the right shared segment. I think<br>
> the intent was to have shmem alloc be collective so this should be<br>
> extraneous.<br>
<br>
Right. I think you lose several important optimizations for shared <br>
memory if the call is not collective. It doesn't have to be synchronous, <br>
but it does have to be collective.<br>
<br>
-Ron<br>
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