[Trilinos-Users] Deterministic messaging?

[Bartlett, Roscoe A]

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
> 
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