[Trilinos-Users] Deterministic messaging?

[John R Cary]

Mike,

Thanks for your response.  This helps, as we will now go back
to searching for our uninitialized memory.

Re Roscoe's comments, the scenario concerning me
was the use of waitany when an MPI process might
receive from any of a number of other ranks.  I
think that in this case, there can be no guarantee
of order, and so the non commutativity of numerical
arithmetic gets one.

Thanks to everyone for your responses.

John


On 6/15/11 9:49 AM, Heroux, Michael A wrote:
> John,
>
> As long as you are running on the same number of MPI processes on the same
> machine, without threading (for example in Epetra), you should see bit-wise
> identical results from Trilinos.
>
> Mike
>
>
> On 6/15/11 9:30 AM, "Roscoe Bartlett"<rabartl at sandia.gov>  wrote:
>
>> John,
>>
>> I thought that bit-wise reproducibility with singe thread-per-process MPI was
>> guaranteed on a homogeneous machine (and is given by the MPI implementation of
>> global reduction operations).  On a heterogeneous machine I am not sure this
>> is true but you will have to talk to the MPI implementation people about this,
>> not Trilinos developers.  As long as MPI race conditions don't exist, I don't
>> think this is a Trilinos problem.
>>
>> Moving to multi-core (multiple threads, etc.) changes all of this ...
>>
>> -Ross
>>
>>
>>> -----Original Message-----
>>> From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-
>>> users-bounces at software.sandia.gov] On Behalf Of Willenbring, James M
>>> Sent: Wednesday, June 15, 2011 7:42 AM
>>> To: John R Cary; Trilinos Users
>>> Subject: Re: [Trilinos-Users] Deterministic messaging?
>>>
>>> John,
>>>
>>> We have discussed this a few times at developer meetings.  The
>>> consensus has been that bit-level reproducibility is prohibitively
>>> expensive.  Are you able to modify the test to have some tolerance?
>>> This seems to be the most common way to avoid needing bit-level
>>> reproducibility.
>>>
>>> Jim
>>>
>>> -----Original Message-----
>>> From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-
>>> users-bounces at software.sandia.gov] On Behalf Of John R Cary
>>> Sent: Wednesday, June 15, 2011 6:33 AM
>>> To: Trilinos Users
>>> Subject: [Trilinos-Users] Deterministic messaging?
>>>
>>> We have a regression test that uses a trilinos solver.
>>> It seems to drift a bit (numerical errors) when run in
>>> parallel but not serial.
>>>
>>> Is the messaging when using trilinos solvers deterministic
>>> so that one can have bit-level reproducibility?
>>>
>>> Can it be made so?
>>>
>>> Thx....John
>>>
>>> _______________________________________________
>>> Trilinos-Users mailing list
>>> Trilinos-Users at software.sandia.gov
>>> http://software.sandia.gov/mailman/listinfo/trilinos-users
>>>
>>> _______________________________________________
>>> Trilinos-Users mailing list
>>> Trilinos-Users at software.sandia.gov
>>> http://software.sandia.gov/mailman/listinfo/trilinos-users
>>
>> _______________________________________________
>> Trilinos-Users mailing list
>> Trilinos-Users at software.sandia.gov
>> http://software.sandia.gov/mailman/listinfo/trilinos-users
>
>
>