[petsc-users] A question on finite difference Jacobian

Zou (Non-US), Ling ling.zou at inl.gov
Tue Oct 6 15:29:59 CDT 2015

Hi All,

If the non-zero pattern of a finite difference Jacobian needs 20 colors to
color it (20 comes from MatFDColoringView, the non-zero pattern is
pre-determined from mesh connectivity), is it true that PETSc needs 40
functions evaluation to get the full Jacobian matrix filled? This is
because that a perturbation per color needs two function evaluation
according to PETSc manual (ver 3.6, page 123, equations shown in the middle
of the page).
But I only see 20 function evaluations. I probably have some
misunderstanding somewhere. Any suggestions?

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