Yeah, and also I didn't realize you were using snes. cat ~benkirk/codes/fins/trunk/examples/Make.common
There are some nice options in there to plot the linear solver convergence and nonlinear solution update - it can be informative. -Ben ----- Original Message ----- From: Andrea Hawkins <[email protected]> To: Kirk, Benjamin (JSC-EG311); libmesh-users <[email protected]> Sent: Wed Feb 24 10:18:46 2010 Subject: Re: [Libmesh-users] Time Stepping That wouldn't explain it working after restarts though, would it? Because with a restart, I'm seeding the initial condition with the previous solution. So, the linear solver should be using this as an initial guess, correct? Thanks, Andrea On Wed, Feb 24, 2010 at 10:14 AM, Kirk, Benjamin (JSC-EG311) <[email protected]> wrote: > Since you are rolling your own newton you might need to set the linear solver > initial guess to 0 (the newton delta) - by default the linear implicit system > uses the current solution as the krylov initial guess. > > Obviously this could be horribly wrong as you converge nonlinearly... > > -Ben > > > > ----- Original Message ----- > From: Andrea Hawkins <[email protected]> > To: libmesh-users <[email protected]> > Sent: Wed Feb 24 09:59:14 2010 > Subject: [Libmesh-users] Time Stepping > > Hello- > > I am running a nonlinear time-dependent simulation and am currently > attempting to implement the generalized alpha time stepping algorithm. > As default I use PETSc for my linear solves and updates, but this > method requires I write my own newton update. > > I had been setting those options outside of the time loop, but found > out that the PetscNonlinearSolver was getting cleared after every time > step so moving that into the time loop solved that problem. However, > I'm now seeing some very peculiar behavior... The first time step > things go fine. The second time step, things also seem to go fine, > however the newton solver actually ends up converging back to the same > solution it started with so that the third time step starts with the > same values as the second. I have actually gone into the newton solver > and seen that the first newton steps leave the initial values but > converge back. > > While this issue could be many things, I have double checked (at > length) with people familiar with this algorithm that I'm at least > attempting to implement the correct thing. > > Is there something else I should be concerned about getting reset > every time step? Because when I run it for only one time step and then > restart and repeat, I do not see this behavior. > > Thanks! > Andrea > > ------------------------------------------------------------------------------ > Download Intel® Parallel Studio Eval > Try the new software tools for yourself. Speed compiling, find bugs > proactively, and fine-tune applications for parallel performance. > See why Intel Parallel Studio got high marks during beta. > http://p.sf.net/sfu/intel-sw-dev > _______________________________________________ > Libmesh-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/libmesh-users > ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
