"Zou (Non-US), Ling" <[email protected]> writes: > Hi Jed, > > I was searching a topic on preconditioning in the mail list and found this > email. > > > On Wed, Oct 10, 2012 at 2:55 PM, Jed Brown <[email protected]> wrote: > >> Then you aren't using a matrix-free method at all. > > > In case of using SNESDefaultComputeJacobianColor to compute Jacobian matrix > and mf_operator command, is this exactly what you are describing ('aren't > using a matrix-free method at all')? > > The SNESDefaultComputeJacobianColor I found in lines 149-155 from > http://www.mcs.anl.gov/petsc/petsc-2.3.3/src/snes/examples/tutorials/ex5.c.html
1. Please upgrade PETSc. I don't think we have any links to these antique man pages, so I assume you specifically changed the version number back rather than landing there accidentally. 2. It is NOT a matrix-free method because coloring is used to assemble the matrix. It usually doesn't make sense to assemble a matrix using coloring, but then not use it to apply the matrix (-snes_mf_operator only uses the assembled matrix for preconditioning).
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