dear Damin, I wrote the solver by myself. I have not understood your answer.
Diego On 28 October 2015 at 23:09, Damien <dam...@khubla.com> wrote: > Diego, > > There aren't many linear solvers that are bit-consistent, where the answer > is the same no matter how many cores or processes you use. Intel's version > of Pardiso is bit-consistent and I think MUMPS 5.0 might be, but that's > all. You should assume your answer will not be exactly the same as you > change the number of cores or processes, although you should reach the same > overall error tolerance in approximately the same number of iterations. > > Damien > > > On 2015-10-28 3:51 PM, Diego Avesani wrote: > > dear Andreas, dear all, > The code is quite long. It is a conjugate gradient algorithm to solve a > complex system. > > I have noticed that when a do cycle is small, let's say > do i=1,3 > > enddo > > the results are identical. If the cycle is big, let's say do i=1,20, the > results are different and the difference increase with the number of > iterations. > > What do you think? > > > > Diego > > > On 28 October 2015 at 22:32, Andreas Schäfer <gent...@gmx.de> wrote: > >> On 22:03 Wed 28 Oct , Diego Avesani wrote: >> > When I use a single CPU a get a results, when I use 4 CPU I get another >> > one. I do not think that very is a bug. >> >> Sounds like a bug to me, most likely in your code. >> >> > Do you think that these small differences are normal? >> >> It depends on what small means. Floating point operations in a >> computer are generally not commutative, so parallelization may in deed >> lead to different results. >> >> > Is there any way to get the same results? is some align problem? >> >> Impossible to say without knowing your code. >> >> Cheers >> -Andreas >> >> >> -- >> ========================================================== >> Andreas Schäfer >> HPC and Grid Computing >> Department of Computer Science 3 >> Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany >> +49 9131 85-27910 >> PGP/GPG key via keyserver >> http://www.libgeodecomp.org >> ========================================================== >> >> (\___/) >> (+'.'+) >> (")_(") >> This is Bunny. Copy and paste Bunny into your >> signature to help him gain world domination! >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2015/10/27933.php >> > > > > _______________________________________________ > users mailing listus...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > > Link to this post: > http://www.open-mpi.org/community/lists/users/2015/10/27934.php > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2015/10/27935.php >
