Hello Matt, On Jan 17, 2012, at 12:53 PM, Matthew Knepley wrote:
> On Tue, Jan 17, 2012 at 2:51 PM, Xuefei (Rebecca) Yuan <xyuan at lbl.gov> > wrote: > Hello all, > > I have a piece of code that need to store the RHS vector b of the ksp object > via vecview. > > However, the routine is like: > > > ierr = DMMGSetSNESLocal(dmmg, FormFunctionLocal, > FormJacobianLocal,0,0);CHKERRQ(ierr); > ierr = DMMGSolve(dmmg);CHKERRQ(ierr); > > The rhs evaluation is in FormFunctionLocal(), how could store the rhs vector > b? > > 1) In your nonlinear problem, what do you mean by b? > This b is refer to the linear problem's rhs, i.e., for the nonlinear problem F(u)=0 is the residual evaluation in FormFunctionLocal, and for the linear solver, Ax=b, this rhs vector b is -F(u^{k]), k is the iteration number for the nonlinear solver. I want to separate the Jacobian matrix and the rhs vector from the very beginning for testing some linear solver: ******* start solving for time = 0.50000 at time step = 1****** 0 SNES Function norm 1.242539468950e-02 start saving jacobian Linear solve converged due to CONVERGED_ITS iterations 1 1 SNES Function norm 3.341795546738e-05 Linear solve converged due to CONVERGED_ITS iterations 1 2 SNES Function norm 1.329755764187e-08 Linear solve converged due to CONVERGED_ITS iterations 1 3 SNES Function norm 3.067585609727e-12 Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE The jacobian matrix was saved before calling the linear solver provided by PETSc, and I need to get the corresponding rhs vector b with this jacobian matrix. > 2) Don't use DMMG, use petsc-dev with regular SNES and SNESSetDM() > I will look into that later. > Matt > Thanks very much! Best regards, Rebecca > Thanks very much! > > Cheers, > > Rebecca > > > > > > > -- > 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-users/attachments/20120117/3b5436f2/attachment-0001.htm>