On Thu, Aug 17, 2017 at 12:22 AM, Matthew Knepley <[email protected]> wrote:
> On Wed, Aug 16, 2017 at 10:14 AM, Mark Adams <[email protected]> wrote: > >> I just want to check the interpretation of snes_type test. Is this pretty >> conclusively good? >> > > It looks right, but the entires in the Jacobian are crazy. You should > non-dimensionalize first. > This is non-dimensionalize and it is 2D FE 2nd order equation so everything should be O(1), that is, there is no 1/h like term. And the domain is (1) and the grid is small so h is O(1) anyway. > > Matt > > >> Testing hand-coded Jacobian, if the ratio is >> O(1.e-8), the hand-coded Jacobian is probably correct. >> Run with -snes_test_display to show difference >> of hand-coded and finite difference Jacobian. >> Norm of matrix ratio 1.38299e-16, difference 1.11738 (user-defined state) >> Norm of matrix ratio 9.50529e-09, difference 7.67972e+07 (constant state >> -1.0) >> Norm of matrix ratio 1.07438e-08, difference 8.68036e+07 (constant state >> 1.0) >> >> > > > -- > 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 > > http://www.caam.rice.edu/~mk51/ >
