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Hi all,
Many many thanks to all of you for your time, sincere help, useful tips and
advices.
I have solved that problem. I just removed the gcc flag -O3 from my compile
script and the error vanished. However the speed of my code is also reduced
to 50 iterations/minute from 70 iterations/minute, still not bad.
Is there any alternative to -O3 flag?
I tried -O2 too but this also gives errors.
I know this is now a non-openmpi problem but I know this is the forum of
experienced programmers so I hope you people would tolerate me and would
help me.
Cheers,
Asad
On Wed, Apr 28, 2010 at 4:59 AM, Gus Correa <gus_at_[hidden]> wrote:
> Hi Dave
>
>
> Dave Love wrote:
>
>> Gus Correa <gus_at_[hidden]> writes:
>>
>> Or run a serial version on the same set of machines,
>>> compiled in similar ways (compiler version, opt flags, etc)
>>> to the parallel versions, and compare results.
>>> If the results don't differ, then you can start blaming MPI.
>>>
>>
>> That wouldn't show that there's actually any OpenMPI-specific problem,
>> though -- the parallelism potentially introduces indeterminacy. [I
>> don't mean to imply Guy thinks otherwise, or that anyone has enough
>> information to guess what's actually happening.] General discussion of
>> numerical issues and scientific computing war stories must be way
>> off-topic here...
>>
>>
> You are right.
> Actually, on a case of an ocean model that I tested this way,
> exactly the opposite happened.
> The optimization flags were the main cause of changes in the results,
> as expected.
> Whether the code was compiled and run serial or parallel with MPI
> made little difference (although it might).
>
> Well, IMHO, this is not totally off topic.
> I don't think it hurts the list protocol to have a relatively
> lax criterion for what is on or off.
> After all, the original question and the following
> discussion was about whether MPI (OpenMPI in particular)
> can affect or not numerical accuracy.
>
> Regards,
> Gus Correa
>
> _______________________________________________
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>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>
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