I used -ksp_monitor_true_residual -ksp_monitor_true_solution -ksp_converged_reason
with MUMPS but it does not compute the true residual. Should I compute that myself? Below is a sample for a full log of MUMPS https://www.dropbox.com/s/fy5uknooxw77r19/log13Jun16_mumps?dl=0 Giang On Fri, Jul 15, 2016 at 2:52 AM, Mark Adams <[email protected]> wrote: > > > On Thu, Jul 14, 2016 at 7:29 PM, Matthew Knepley <[email protected]> > wrote: > >> On Thu, Jul 14, 2016 at 6:27 PM, Mark Adams <[email protected]> wrote: >> >>> >>>> >>>> Notice that there are 7 orders of magnitude between the apparent >>>> residual (using the preconditioner), and the actual residual, Ax - b. >>>> You are using Hypre, and this generally means the Hypre coarse grid >>>> operator is crap. Please >>>> >>>> >>> Huh?, this data looks fine, both the true and preconditioned residual >>> stay separated by about 9 orders of magnitude. This just tells you that the >>> norm of A (or is it A^-1) is 10^9. Am I misunderstanding this? >>> >> >> This is why Barry and I asked for a comparsion with MUMPS. If you are >> right, and its just the condition number, >> > > I said norm not condition number. I trust I'm missing something in this > thread. > > >> the LU >> will not be any more accurate. >> >> Matt >> >> -- >> What most experimenters take for granted before they begin their >> experiments is infinitely more interesting than any results to which their >> experiments lead. >> -- Norbert Wiener >> > >
