On Wed, Nov 30, 2016 at 8:54 PM, Justin Chang <[email protected]> wrote:
> Generally speaking, yes. But this is VIRS where I am enforcing maximum > principles. From what I have seen, the residual typically exhibit this > behavior if there are very few violations in the first place. > So you are saying that if you have some constraints, you can have a situation where you cannot satisfy F(u) = 0? This seems wrong to me, but maybe I do not understand something. > How would I "terminate on stagnation"? > This is what I do not want. Matt > On Wed, Nov 30, 2016 at 8:48 PM, Matthew Knepley <[email protected]> > wrote: > >> On Wed, Nov 30, 2016 at 8:38 PM, Justin Chang <[email protected]> >> wrote: >> >>> By manually terminating I meant setting -snes_max_it to 5 if I know >>> DIVERGED_LINE_SEARCH >>> occurs after 6 iterations. In a transient simulation I cannot do this >>> >> >> Let me elaborate. I mean that using DIVERGED_LINE_SEARCH as an indication >> of convergence is dicey. It may be that in the problem >> you looked at this was true, but I see no reason to believe its true in >> general. Why does your residual quit decreasing? >> >> Thanks, >> >> Matt >> >> >>> On Wed, Nov 30, 2016 at 8:35 PM, Matthew Knepley <[email protected]> >>> wrote: >>> >>>> On Wed, Nov 30, 2016 at 8:27 PM, Justin Chang <[email protected]> >>>> wrote: >>>> >>>>> Hi all, >>>>> >>>>> I am running some transient simulations using SNESVINEWTONRSLS. At >>>>> certain timesteps, I get a "DIVERGED_LINE_SEARCH" which essentially >>>>> "resets" my solution to zero and messes everything up. I notice that this >>>>> happens when the SNES Function norm no longer decreases, and if I were to >>>>> manually terminate the solver right before the final iteration I get the >>>>> answer I want. >>>>> >>>> >>>> Yes, its possible, however isn't that a dangerous way to terminate? >>>> Couldn't you terminate on stagnation? >>>> >>>> Thanks, >>>> >>>> Matt >>>> >>>> >>>>> Is there a way to "detect" this error and use the solution from the >>>>> previous non-failing iteration? Setting a fixed maximum iteration doesn't >>>>> seem reasonble because every time level will require different numbers of >>>>> iterations to converge. >>>>> >>>>> Thanks, >>>>> Justin >>>>> >>>> >>>> >>>> >>>> -- >>>> 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 >>>> >>> >>> >> >> >> -- >> 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 >> > > -- 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
