Using -ksp_type preonly -pc_type lu didn't change the number of required newton iterations.
I don't understand what you mean by "then backoff". Thanks Hesam ----- Original Message ----- From: "Matthew Knepley" <[email protected]> To: "petsc-maint" <petsc-maint at mcs.anl.gov>, "Hesameddin Ilatikhameneh" <hilatikh at purdue.edu> Cc: "For users of the development version of PETSc" <petsc-dev at mcs.anl.gov> Sent: Tuesday, December 11, 2012 4:09:46 PM Subject: Re: [petsc-maint #143637] SNES takes 50 newton iterations On Tue, Dec 11, 2012 at 1:02 PM, Hesameddin Ilatikhameneh <hilatikh at purdue.edu> wrote: > Hello, > > I want to minimize a simple energy equation (E = E(x0,x1,...,xN)) using > nonlinear solver SNES. This way SNES equation F(x) = dE/dxi = 0 and jacobian > is J = dF/dx = d2E/dx2. I have attached a report explaining the problem and > how I implemented it. > > The energy is related to 1D chain of balls connected with springs and the > final answer is that all balls spaced equal to ideal distance. > > My problem is that SNES takes near 30-50 newton iterations to converge which > seems to be too much for such a simple problem. > I have also attached the code and appreciate your help on this. Start with -ksp_type preonly -pc_type lu, and then backoff. This gives you the true Newton convergence rate. Matt > Thanks > Hesam > -- 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
