On Tue, Apr 29, 2014 at 2:09 PM, Xiangdong <epsco...@gmail.com> wrote:
> It turns out to a be a bug in my FormFunctionLocal(DMDALocalInfo > *info,PetscScalar **x,PetscScalar **f,AppCtx *user). I forgot to initialize > the array f. Zero the array f solved the problem and gave consistent result. > > Just curious, why does not petsc initialize the array f to zero by default > inside petsc when passing the f array to FormFunctionLocal? > If you directly set entires, you might not want us to spend the time writing those zeros. > I have another quick question about the array x passed to > FormFunctionLocal. If I want to know the which x is evaluated, how can I > output x in a vector format? Currently, I created a global vector vecx and > a local vector vecx_local, get the array of vecx_local_array, copy the x to > vecx_local_array, scatter to global vecx and output vecx. Is there a quick > way to restore the array x to a vector and output? > I cannot think of a better way than that. Matt > Thank you. > > Best, > Xiangdong > > > > On Mon, Apr 28, 2014 at 10:28 PM, Barry Smith <bsm...@mcs.anl.gov> wrote: > >> >> On Apr 28, 2014, at 3:23 PM, Xiangdong <epsco...@gmail.com> wrote: >> >> > Hello everyone, >> > >> > When I run snes program, >> >> ^^^^ what SNES program”? >> >> > it outputs "SNES Function norm 1.23456789e+10". It seems that this norm >> is different from residue norm (even if solving F(x)=0) >> >> Please send the full output where you see this. >> >> > and also differ from norm of the Jacobian. What is the definition of >> this "SNES Function Norm”? >> >> The SNES Function Norm as printed by PETSc is suppose to the 2-norm of >> F(x) - b (where b is usually zero) and this is also the same thing as the >> “residue norm” >> >> Barry >> >> > >> > Thank you. >> > >> > Best, >> > Xiangdong >> >> > -- 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
