On Tue, Jul 12, 2022 at 7:39 AM Pierre Jolivet <pie...@joliv.et> wrote:
> > > On 12 Jul 2022, at 2:32 PM, Matthew Knepley <knep...@gmail.com> wrote: > > On Mon, Jul 11, 2022 at 1:17 PM Pierre Jolivet <pie...@joliv.et> wrote: > >> Hello, >> Could anyone help me understand what is going on in the following >> example, please? >> I have a VecNest. >> I either: a) initialize all values to 0.0, then set a specific part of >> the vector to nonzero or b) initialize a part of the vector to 0.0 and set >> the other part to nonzero. >> I don’t see why a) and b) produce different results. >> >> $ ./ex1111 -pc_type fieldsplit -ksp_monitor_true_residual >> -ksp_converged_reason -fieldsplit_pc_type jacobi -ksp_pc_side right >> -ksp_view_final_residual -nest_subvec true >> 0 KSP unpreconditioned resid norm 8.375635517980e-01 true resid norm >> 8.375635517980e-01 ||r(i)||/||b|| 1.000000000000e+00 >> 1 KSP unpreconditioned resid norm 4.748816884247e-01 true resid norm >> 4.748816884247e-01 ||r(i)||/||b|| 5.669798875623e-01 >> 2 KSP unpreconditioned resid norm 4.713006778679e-01 true resid norm >> 4.713006778679e-01 ||r(i)||/||b|| 5.627043784990e-01 >> 3 KSP unpreconditioned resid norm 7.092979927129e-02 true resid norm >> 7.092979927129e-02 ||r(i)||/||b|| 8.468587144106e-02 >> 4 KSP unpreconditioned resid norm 1.457836310255e-02 true resid norm >> 1.457836310255e-02 ||r(i)||/||b|| 1.740567992870e-02 >> 5 KSP unpreconditioned resid norm 1.625040500524e-14 true resid norm >> 1.633468028779e-14 ||r(i)||/||b|| 1.950261595401e-14 >> Linear solve converged due to CONVERGED_RTOL iterations 5 >> KSP final norm of residual 1.63347e-14 >> $ ./ex1111 -pc_type fieldsplit -ksp_monitor_true_residual >> -ksp_converged_reason -fieldsplit_pc_type jacobi -ksp_pc_side right >> -ksp_view_final_residual -nest_subvec false >> 0 KSP unpreconditioned resid norm 0.000000000000e+00 true resid norm >> 8.375635517980e-01 ||r(i)||/||b|| inf >> Linear solve converged due to CONVERGED_ATOL iterations 0 >> KSP final norm of residual 0.837564 >> > > I find if I assemble the vector, I get the same answers. Will try to > figure out what assembly is doing. > > > It’s probably reseting all these values > https://petsc.org/main/src/vec/vec/interface/rvector.c.html#line511, > which I believe are being used in VecNorm() inside VecNormalize(). > I guess any call to VecNestSubVec() should invalidate those as well, > otherwise we get wrong cached norms. > I will give this a go. > I believe the bug is the following: You change values in a subvector, which does StateIncrease on the subvector, but not StateIncrease on the nest vector, so it has its cached norm I am not sure what to do about this, since how can the parent know you pulled out the subvector? Will think. Matt > Thanks, > Pierre > > Thanks, > > Matt > > >> Thanks, >> Pierre >> >> > > -- > 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 > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> > > > -- 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 https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>