Dear Matt, The initial guess was zero for all cases of SNES solvers. The initial jacobian was identity for all cases. The system is small and is ran sequentially. I have to add that I use FDColoring routine for the jacobian as well.
Regards, Ray On Monday, May 4, 2015, Matthew Knepley <knep...@gmail.com> wrote: > On Mon, May 4, 2015 at 5:41 PM, Reza Yaghmaie <reza.yaghma...@gmail.com > <javascript:_e(%7B%7D,'cvml','reza.yaghma...@gmail.com');>> wrote: > >> >> Dear Matt, >> >> Actually the initial jacobian was identity. Regular SNES converges in 48 >> iterations, GMRES in 19, NCG in 67,... >> Do you think SNESQN with the basiclineseach was the problem for >> divergence? >> If I use SNESQN by default should not it converge with initial identity >> jacobian? >> > > Do you mean that you used an initial guess of the identity, or that the > Actual Jacobian was the identity at your > initial guess? > > Matt > > >> Best regards, >> Reza >> >> >> >> >> On Monday, May 4, 2015, Matthew Knepley <knep...@gmail.com >> <javascript:_e(%7B%7D,'cvml','knep...@gmail.com');>> wrote: >> >>> On Mon, May 4, 2015 at 2:11 PM, Reza Yaghmaie <reza.yaghma...@gmail.com> >>> wrote: >>> >>>> >>>> Dear PETSC representatives, >>>> >>>> I am solving a nonlinear problem with SNESNGMRES and it converges >>>> faster with less iterations compared to otehr SNES methods. Any idea why >>>> that is the case? >>>> >>> >>> It is impossible to tell with this information. >>> >>> >>>> Also SNESQN diverges quickly. I tried to use SNESLINESEARCHBASIC for >>>> the linesearch option and nothing changes. >>>> >>> >>> This can happen, especially if your matrix is far from the identity. >>> >>> >>>> I presume it is using the default SNESQN method. Btw, there are three >>>> options for QN, as "SNES_QN_LBFGS, SNES_QN_BROYDEN, SNES_QN_BADBROYEN" >>>> in teh manual. I tried to associate them with SNES however it seems these >>>> hyphened names don't work there. What am I missing? >>>> >>> >>> -snes_qn_scale_type <lbfgs,broyden,badbroyden> >>> >>> from >>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/SNESQNSetType.html >>> >>> Thanks, >>> >>> Matt >>> >>> Best regards, >>>> Ray >>>> >>> >>> >>> >>> -- >>> 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 >>> >> > > > -- > 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 >
