> found that running the same source code on these OS, with the same
> versions of of gcc and open-mpi installed on them, gives different
> results than Fedora and Ubuntu after a few hundred iterations. The first
> few hundered iterations are exactly similar to that of Fedora and
> Ubuntu but then it starts giving different results.
Are you also using the same hardware? Different hardware platforms may
exhibit different rounding behaviour. After some dependent interations
such effects might indeed sum up and yield different results. The issue
is called numeric (in)stability and is not specifically related to openmpi.