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 >
