[mpiwg-rma] same_op_no_op

[Jeff Hammond]

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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>> 
>> 
>> -- 
>> Jeff Hammond
>> jeff.science at gmail.com
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