Hi All,<br>I have the following output from -snes_view with the default snes setting., but I don't know what the KSPPREONLY does on the coarse grid. Can anyone provide some hints on this?<br><br>Assuming:<br>A_{coarse} * e_{coarse} =r _{coarse} <br>
<br><br>Thanks a lot,<br><br>Yan<br><br><br>------------------------------------------------------------------------------<br>SNES Object:<br> type: ls<br> line search variant: SNESLineSearchCubic<br> alpha=0.0001, maxstep=1e+08<br>
maximum iterations=50, maximum function evaluations=10000<br> tolerances: relative=1e-08, absolute=1e-50, solution=1e-08<br> total number of linear solver iterations=32<br> total number of function evaluations=5<br> KSP Object:<br>
type: fgmres<br> GMRES: restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization with no iterative refinement<br> GMRES: happy breakdown tolerance 1e-30<br> maximum iterations=10000, initial guess is zero<br>
tolerances: relative=1e-05, absolute=1e-50, divergence=10000<br> right preconditioning<br> PC Object:<br> type: mg<br> MG: type is FULL, levels=2 cycles=v<br> Coarse gride solver -- level 0 presmooths=1 postsmooths=1 -----<br>
KSP Object:(mg_coarse_)<br> type: preonly<br> maximum iterations=1, initial guess is zero<br> tolerances: relative=1e-05, absolute=1e-50, divergence=10000<br> left preconditioning<br> PC Object:(mg_coarse_)<br>
type: lu<br> LU: out-of-place factorization<br> matrix ordering: nd<br> LU: tolerance for zero pivot 1e-12<br> LU: factor fill ratio needed 5.02244<br> Factored matrix follows<br>
Matrix Object:<br> type=seqaij, rows=4096, cols=4096<br> package used to perform factorization: petsc<br> total: nonzeros=401152, allocated nonzeros=401152<br> using I-node routines: found 1024 nodes, limit used is 5<br>
linear system matrix = precond matrix:<br> Matrix Object:<br> type=seqaij, rows=4096, cols=4096<br> total: nonzeros=79872, allocated nonzeros=79872<br> using I-node routines: found 1024 nodes, limit used is 5<br>
Down solver (pre-smoother) ......<br><br>