> On Oct 28, 2015, at 6:58 PM, Diego Avesani <diego.aves...@gmail.com> wrote:
>
> dear Damin,
> I wrote the solver by myself. I have not understood your answer.
Floating point addition is not associative. Doing a long sum in different
orders, as might happen when different numbers of nodes do local sums that are
then summed globally, will not get the same results. Even mpi global reduce
sum is not guaranteed by the standard to always get exactly the same answer
even with all the same arguments and number of tasks, it’s just recommended.
Noam
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Noam Bernstein
Center for Materials Physics and Technology
NRL Code 6390
noam.bernst...@nrl.navy.mil
phone: 703 683 2783
