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 <g...@ldeo.columbia.edu> wrote: > Hi Dave > > > Dave Love wrote: > >> Gus Correa <g...@ldeo.columbia.edu> 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 > > _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users >> > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- "Statistical thinking will one day be as necessary for efficient citizenship as the ability to read and write." - H.G. Wells
