[mpiwg-rma] same_op_no_op

[Balaji, Pavan]

MPI-2 defines atomicity only for the same operation, not any operation for MPI_ACCUMULATE.

  — Pavan

On Mar 10, 2014, at 11:22 PM, Jeff Hammond <jeff.science at gmail.com> wrote:

> So MPI-2 denied compatibility between replace and not-replace?
> 
> Jeff
> 
> Sent from my iPhone
> 
>> On Mar 11, 2014, at 12:06 AM, "Balaji, Pavan" <balaji at anl.gov> wrote:
>> 
>> 
>> It doesn’t break backward compatibility.  The info argument is still useful when you don’t want to use replace.  I don’t see anything wrong with it.
>> 
>>> On Mar 10, 2014, at 11:01 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>>> 
>>> Does this or does this not break BW compatibility w.r.t. MPI-2.2 and
>>> did we do it intentionally?  Unless we did so intentionally and
>>> explicitly, I will argue that the WG screwed up and the info key+val
>>> is invalid.
>>> 
>>> Jeff
>>> 
>>>> On Mon, Mar 10, 2014 at 11:03 PM, Balaji, Pavan <balaji at anl.gov> wrote:
>>>> 
>>>> If a hardware can implement MPI_SUM, it should be able to implement MPI_SUM with 0 as well.
>>>> 
>>>> But that’s not a generic solution.
>>>> 
>>>> Jeff: at some point you were planning to bring in a ticket which does more combinations of operations than just same_op and no_op.  Maybe it’s worthwhile bringing that up again?
>>>> 
>>>> — Pavan
>>>> 
>>>>> On Mar 10, 2014, at 9:26 PM, Jim Dinan <james.dinan at gmail.com> wrote:
>>>>> 
>>>>> Maybe there's a loophole that I'm forgetting?
>>>>> 
>>>>> 
>>>>> On Mon, Mar 10, 2014 at 9:43 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>>>>> How the hell can I do GA or SHMEM then? Roll my own mutexes and commit perf-suicide?
>>>>> 
>>>>> Jeff
>>>>> 
>>>>> Sent from my iPhone
>>>>> 
>>>>>> On Mar 10, 2014, at 8:32 PM, Jim Dinan <james.dinan at gmail.com> wrote:
>>>>>> 
>>>>>> You can't use replace and sum concurrently at a given target address.
>>>>>> 
>>>>>> ~Jim.
>>>>>> 
>>>>>> On Mon, Mar 10, 2014 at 4:30 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>>>>>> Given the following, how do I use MPI_NO_OP, MPI_REPLACE and MPI_SUM
>>>>>> in accumulate/atomic operations in a standard-compliant way?
>>>>>> 
>>>>>> accumulate_ops — if set to same_op, the implementation will assume
>>>>>> that all concurrent accumulate calls to the same target address will
>>>>>> use the same operation. If set to same_op_no_op, then the
>>>>>> implementation will assume that all concurrent accumulate calls to the
>>>>>> same target address will use the same operation or MPI_NO_OP. This can
>>>>>> eliminate the need to protect access for certain operation types where
>>>>>> the hardware can guarantee atomicity. The default is same_op_no_op.
>>>>>> 
>>>>>> We discuss this before and the resolution was not satisfying to me.
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> Jeff
>>>>>> 
>>>>>> --
>>>>>> Jeff Hammond
>>>>>> jeff.science at gmail.com
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>>>>> 
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>>> 
>>> 
>>> -- 
>>> Jeff Hammond
>>> jeff.science at gmail.com
>>> _______________________________________________
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>>> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpiwg-rma
>> 
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