On Wednesday 27 of May 2009 8:35:49 pm Eugene Loh wrote: > George Bosilca wrote: > > This is a problem of numerical stability, and there is no solution > > for such a problem in MPI. Usually, preconditioning the input > > matrix improve the numerical stability. > > At the level of this particular e-mail thread, the issue seems to me to > be different. Results are added together in some arbitrary order and > there are variations on order of 10^-10. This is not an issue of > numerical stability, but just of bitwise floating-point reproducibility. > > And, given that one could fix the order (by using explicit source > processes instead of MPI_ANY_SOURCE), one could "fix" this particular > problem in MPI. > > Anyhow, I'm just picking nits here.
Eugene, I really do not understand why you insist on the order. Maybe there is something subtle about the order that I do not understand. Anyhow, I changed the code according to your suggestion. Thank you, Vasilis
