> > > 1) Grid sequencing: This is easy if you use a DMDA. You just use > > > -snes_grid_sequence > > > and its automatic. Since you report that smaller grids converge, > > this > > > is usually enough. > > Unfortunately, no. > Isn't this a 1D problem with no geometry? You should use DMDA. It would make > it easier.
I think you misunderstood my too-short-a-comment. What I meant was unfortunately -snes_grid_sequence was not enough to make it converge. I went up to -snes_grid_sequence 10. I always use DMDA and yes, the only geometry in the problem is a straight line of points from -X to +X, where preferably X = infinity, but numerically of course not. > > I'm not sure what you mean here. Do you mean I should run normal newton > > line > > search snes with SNESSetNPC(snes_of_type_gs)? > Yes. Will do that once I get back to this next week. > > I wish it was so easy: I did try all the snes types before posting the > > first > > post. Also all KSP types. Except those that need things I don't have, of > > course. > Not sure what you mean here. To use FAS, you can either use DMDA, or provide > interpolation operators between grids. Yes, but FAS does not converge either. Neither does any other snes type except ngs, and changing to any other KSP type makes no difference either – though why would it as the KSP seems to converge nicely anyway. I have also tried all snes LS types, to no avail. A correction: funnily enough, newtontr claims it converges, but it does not really. It ends up with the same "solution" as almost everything else does and thinks it is a solution (CONVERGED_SNORM_RELATIVE) whereas I know full well it is not a solution, not even close. But I always found newtontr fiddly anyway: it tends to be too trigger happy to shout "convergence" and finding the right parameters to make it not-so-trigger-happy is hard. Cheers, Juha -- ----------------------------------------------- | Juha Jäykkä, ju...@iki.fi | | http://koti.kapsi.fi/~juhaj/ | -----------------------------------------------
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