On Dec 14, 2011, at 4:39 PM, Matthew Knepley wrote: > On Wed, Dec 14, 2011 at 3:13 PM, Mark F. Adams <mark.adams at columbia.edu> > wrote: > > On Dec 14, 2011, at 3:44 PM, Barry Smith wrote: > > > > > On Dec 14, 2011, at 12:45 PM, Mark F. Adams wrote: > > > >> I have a nonlinear problem and am finding the the convergence test for the > >> interior PETSc linear solver is apparently testing against the norm of the > >> first linear solve (see appended). > > > > No it is || r = b - Ax ||/|| b|| with a B in there if left > > preconditioned > > > > It has nothing to do with the "first linear solve". Each linear solve is > > self contained and it does not use anything from a previous linear solve to > > determine convergence of a later linear solve. > > > > Matts suggestion -ksp_converged_use_initial_residual_norm did the trick. > > >> This is clearly not what anyone would want, > > > > Why not? > > > > OK, I should say I don't know why anyone would want this and if you pop a KSP > into a nonlinear loop, which is a very common thing to do obviously, then you > get behavior that is probably not what you want. Namely, an approximate > Newton where the outer nonlinear tolerance is much smaller than the inner > linear tolerance. Just my perspective. > > We put it in because there is a very common case, where you give an initial > guess, its great > say 10^-7, and you really do not want to iterate to 10^-12. I think what you > really want is
OK, I'll buy that, > something like EW since it is meaningfully connected to the nonlinear > tolerance, which is > physical. > What is EW. What I am doing is classic inexact Newton (or it looks like these folks are doing Picard). Mark > Matt > > > Mark > > > Barry > > > > > >> is this the intended semantics? > > > > > >> Is there perhaps a method to reset rtol? > >> > >> Mark > >> > >> Picard iteration 0 max(resid) = 781020 > >> 0 KSP Residual norm 2.499264167662e+07 > >> 1 KSP Residual norm 6.330915810095e+06 > >> 2 KSP Residual norm 1.856999435466e+06 > >> 3 KSP Residual norm 3.967325725053e+05 > >> 4 KSP Residual norm 9.037332775808e+04 > >> 5 KSP Residual norm 1.826960320400e+04 > >> Linear solve converged due to CONVERGED_RTOL iterations 5 > >> Picard iteration 1 max(resid) = 727577 ------- Rate = 1.07345 > >> 0 KSP Residual norm 6.885328126772e+06 > >> 1 KSP Residual norm 2.150319244570e+06 > >> 2 KSP Residual norm 2.297759417371e+05 > >> 3 KSP Residual norm 3.321819214451e+04 > >> 4 KSP Residual norm 4.155970071625e+03 > >> Linear solve converged due to CONVERGED_RTOL iterations 4 > >> Picard iteration 2 max(resid) = 486788 ------- Rate = 1.49465 > >> 0 KSP Residual norm 2.987417661953e+06 > >> 1 KSP Residual norm 5.046119985008e+05 > >> 2 KSP Residual norm 3.882757664605e+04 > >> 3 KSP Residual norm 4.106091678345e+03 > >> Linear solve converged due to CONVERGED_RTOL iterations 3 > >> Picard iteration 3 max(resid) = 137348 ------- Rate = 3.54418 > >> 0 KSP Residual norm 7.285359985607e+05 > >> 1 KSP Residual norm 9.132700545850e+04 > >> 2 KSP Residual norm 6.834608381922e+03 > >> Linear solve converged due to CONVERGED_RTOL iterations 2 > >> Picard iteration 4 max(resid) = 25082.7 ------- Rate = 5.47582 > >> 0 KSP Residual norm 1.207523847817e+05 > >> 1 KSP Residual norm 1.286174706329e+04 > >> Linear solve converged due to CONVERGED_RTOL iterations 1 > >> Picard iteration 5 max(resid) = 5723.21 ------- Rate = 4.38264 > >> 0 KSP Residual norm 2.211945822133e+04 > >> Linear solve converged due to CONVERGED_RTOL iterations 0 > >> > > > > > > > > > -- > 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20111214/0ed19a68/attachment.html>